Taxonomy of finfish notes

Taxonomy of Finfish
Unit 1: General Introduction
Chapter 1: Principles of Taxonomy
Learning objective
This chapter deals with general introduction about finfish taxonomy. The students will
understand the importants of finfish taxonomy and need to study finfish taxonomy.
1.1.1 Introduction
Aquatic vertebrates that have gills throughout life and limbs, if any, in the shape of fins.
• Fishes constitute slightly more than one-half of the total number of approximately
48,170 recognized living vertebrate species.
• There are descriptions of an estimated 24,618 valid species of fishes.
• Number of extant fish species may be close to 28,500.
• Of the 482 fish families with living species recognized, the eight largest families,
each with over 400 species, contain approximately 33% of all species.
• These families, in the order of decreasing numbers of species are Cyprinidae,
Gobiidae, Cichlidae, Characidae, Loricariidae, Labridae, Belitoridae and
Serranidae.
• About 66% of the species in the eight largest families are freshwater fishes,
where as about 40% of all fishes occur in or almost always in freshwater.
Classification
It is the practice of arranging organisms into groups or categories.
Taxa (Taxon)
Groups of organisms recognized in a classification and given biological names (e.g.
Cypriniformes, Cyprinidae, and Cyprinus)
Category
The level or rank at which the taxon is placed (e.g. order, family and genus)
Systematics
• It is a biological science that discovers names, determines relationships,
classifies and studies evolution of living organisms.

• It is a synthesis of many kinds of knowledge, theory and method applied to all
kinds of classifications of organisms.
• It includes taxonomy.
• Our knowledge of biodiversity is incomplete. Only 1.70 million of the earth is
estimated 10-100 million sp have been scientifically erected, named and
classified. In the marine biota, 3,40,000 sp are known including many unnamed
species. It could be impossible to deal with the enormous diversity if it were not
ordered and classified.
• Systematic zoology solves this problem and develops many methods and
principles to make this task possible.
• It has a broader base than genetics, biochemistry and physiology.
Taxonomy
• The term ‘taxonomy’ is derived from the Greek word ‘taxis’ - arrangement and
‘nomos’ – law.
• The name taxonomy was first proposed by Candolle (1813)
• It is the theory and practice of classifying organisms based on the similarities and
differences by following certain internationally accepted principles, laws, rules
and regulations.
Identification
Placing the individual to each taxon by deductive procedure.
Classification
Ordering of animals into groups on the basis of their relationships.
1.1.2 Three stages of taxonomy
Alpha taxonomy
Description of new species and its arrangements in comprehensive genera.
Beta taxonomy
Relationships are worked out on the species level and on higher categories.
Gamma taxonomy
Studying the intraspecific variations and its evolutionary relationship.
1.1.3 Importance of Fish taxonomy
1. Reveals numerous interesting evolutionary phenomena in ichthyology.

2. Cultivates away of thinking and approaching of all biological problems needed for
the balance and well being of fish biology.
3. Produces catalogues, revisions, hand books, keys, monographs etc.
4. Avoids exotic species which may otherwise harm the habitats and native fauna.
5. Proper identification of fishes helps in museum development and maintenance.
6. Identification of fishes helps in the export of processed edible fishes as the
buyers are very conscious about the correct fish identification along with their
scientific and popular names.
7. Correct identification of a particular candidate finfish for aquaculture is very
important for successful culture practice.
8. Correct scientific name of any organism on which one is going to work is a
prerequisite for anyone before starting his biological research.
9. Correct scientific name is a functional label using which various spieces of
information concerning that organism can be retrieved.
1.1.4 Principal tasks of the taxonomists
Identification of Fish species
• When these are available, the description of the appropriate species should be
checked character by character with the keys and manuals available.
• Once this is over, the identifier has to compare with the type specimens
deposited in the established museums.
Taxonomical Revision
• For taxonomical revision of a family or genus, the investigator should study
specimens from various museums including the holotype and also fresh
specimens available in its native environment.
• While collecting fishes for revisional study there should not be any biased
population samples.
• Specimens of all stages and different sexes have to be collected with adequate
number of samples. Collections should cover all localities of the species.
• Sampling should be done in such a way as to provide study materials not only for
the species but also for the evolutionist.
• All the characters of a particular species for identification should be carefully
studied.
Study the evolutionary link

The taxonomist has to link the species from its ancestor. This well help to group the
organisms at higher taxon level.
• Chapter 2: Nomenclature, Types
Learning objective
This unit illustrates the general rules and regulation followed in naming of a fish
species. The students will understand the importance of binominal nomenclature to
name a fish.
1.2.1 International Commission on Zoological Nomenclature
The International Commission on Zoological Nomenclature (ICZN) provides and
regulates the system for ensuring that every animal has an unique and universally
accepted scientific name. Its financial and management affairs are handled by the
International Trust for Zoological Nomenclature (ICZN), a charity (not-for-proft company)
registered in the U.K.
This is essential to all areas of zoology including medical and veterinary science,
agriculature, horticulature, the environment and conservation and geology and
palaeontology. The maintenance of taxonomic standards and a consistent and universal
nomenclature are fundamental to current efforts to conserve biological diversity and it is
the unique role of the commission to maintain such international standards
nomenclature.
The commission was set up in 1895. It consists of 25 members from 20 countries. It
operates in two main ways. First, it publishes the International Code of Zoological
Nomenclature containing the rule universally accepted as governing the application of
scientific names to all organisms which are treated as animals. Secondly, it gives rulings
on individual nomenclatural problems brought to its attention, so as to achieve
internationally acceptable solutions. Several million species of animals are recognised
and more than 2000 new generic names and 15000 new specific names are added to
the zoological literature every year. With such a multiplicity of names, problems are
bound to occur. The commission operates through its quarterly journal, the Bulletin of
Zoological Nomenclature, in which problems needing a formal decision by the
commission are published for discussion by the zoological community.
The commission is under the auspices of the International Union of Biological Sciences
(IUBS). The American Association for Zoological Nomenclature and the European
Association for Zoological Nomenclature facilitate liaison between zoologists and the
ICZN and provide financial support for ICZN.

1.2.2 Nomenclature
The international code of zoological nomenclature is a system of rules and
recommendations authorized by the International Congresses of Zoology. It deals with a
set a regulations in zoological nomenclature. The object of “code is to promote stability
and universality in the scientific names of animals and ensure that each name is unique
and distinct. All its provisions are subservient to these ends” (Mayr, 1969). The valid
rules of zoological nomenclature are contained in a document entitled, ‘The
International Code of Zoological Nomenclature’.
Zoological Nomenclature is a system of scientific names applied to taxonomic units of
animals inclusive of both extant and extinct groups.
In finfish taxonomy, certain rules are to be strictly followed in establishing the validity of
a taxon. The Linnaean hierarchial system is followed in the classification of
finfishes. The Linnaean hierarchy is a structure of categorical ranks for taxa where each
category except the lowest includes one or more subordinate categories. The generally
accepted categories are as follows:
Kingdom
Phylum
Subphylum
Class
Subclass
Superorder
Order
Suborder
Superfamily
Family
Subfamily
Genus
Subgenus
Species
Subspecies
Normally, in the classification of finfishes the six categories namely, species, genus,
family, order, class and phylum are followed. In this hierarchial system, the higher

category or higher taxon includes kingdom to genus level, species and subspecies are
designated as lower taxon.
A finfish order always ends with’formes’ (e.g. Cypriniformes, Clupeiformes, etc.),
Superfamily has a standardized ending ‘oidea’ (e.g. Clupeoidea, etc.), Family of finfish
ends with ‘idea’ (e.g. Scombridae, Sciaenidae, etc.) and tribe ends with ‘ini’ (e.g.
Carangini, etc.).
The binomial nomenclature used for animals and plants is largely derived from Latin, as
are the names used for higher taxa such as families and orders. The words listed below
are the common adjectives and other modifiers that repeatedly occur in the systematic
names of many organisms. Not all the words or parts of words used in scientific names
for living things are derived from Latin. Some are derived from Greek, some from
languages local to the places where the organisms are found and many from the names
of the people who first described a species or other taxon. However, all are treated
grammatically as if they were Latin words. In particular, this means that to indicate
possession, the endings -a and -us turn into -ae and -i respectively and non-Latin
names of people add -i if male and -ii if female. This list of Latin and Greek words
commonly used in systematic names is intended to help those unfamiliar with classical
languages understand and remember the scientific names of organisms.
1.2.3 Naming with latin/ greek words
Latin/Greek word
or part word
Language L = Latin; G =
Greek; LG = similar in both
languages
English translation
albus L white
arcturus L northern
argentatus L silvery
australis L southern
bengalensis L Bengal, India
borealis L northern
brachy G short
carbo L coal
caulos G stem, stalk
caudatus L tailed

cephalus G head
chloro G green
-cola L -dweller
cristatus L Crested
cyano G blue-green
dactylus G finger or toe
deca G ten
dermis G skin
di- G two-
diplo- G double
dodeca G twelve
dolicho- G elongated
domesticus L domestic or house
dorsalis L back
dukhunensis L Deccan plateau, India
echinus G spine
ennea G ninety
erythro G red
familiaris L common
flora L flower
folius L leaf
fuscus L dark brown
fulvus L yellow
gaster G belly

glycis G sweet
halo G salt
hecta G hundred
hendeca G eleven
hepta G seven
heptaconta G seventy
hexa G six
hexaconta G sixty
hibernicus L Irish
horlensis L garden
icosa G twenty
indicus L Indian
lateralis L side
leucus G white
lineatus L lined or striped
ludovicani L Lewis’s
maculatus L spotted
major L greater
maximus L largest
melanus G black
minimus L smallest
minor L smaller
mono- G one-
montanus L mountains

morphos G shape
morph- G shape
mauro- G dark
niger L black
nona L nine
nothos G false, bastard
notos G southern
novaehollandiae L Australian
novaeselandiae L New Zealand
noveboracensis L New York
obscurus L dark
occidentalis L western
octa G eight
octacota G eighty
oeos- G tubular
officinalis L medicinal
orientalis L eastern
ortho- G straight
pachys G thick,stout
parvus L small
pedi- L feet
pelagius G oceanic
penta- G five-
pentaconta G fifty

petra G rocky,stony
phyllo G leaf
phyton G plant
platy G flat
protos G first
pteron G wing
punctatus L spotted
rhiza G root
rhytis G wrinked
rubra L red
-rostra- L beak
rufus L red
sativus L filling (food)
saurus G lizard
sinensis L Chinese
stoma G mouth, opening
striatus L striped
sylvi L forest, wild
letra- G four-
tetraconta G forty
tinctorius L dyeing
tomentosus L furry
tri- LG three-
trich-,thrix G hair

triconta G thirty
-ura G of the tail
uni L one
variabilis L variable
variegatus L variegated
ventrus L belly
verrucosus L rough skinned
viridis L green
volans L flying
vulgaris L common
1.2.4 Law of Priority
The valid name of the genus, species or subspecies must be the oldest name that fulfils
the requirements of the Law of Priority. This important rule was agreed upon in order to
avoid confusion in the application of scientific names and to eliminate duplication. In
general, names published earlier take precedence over the names of the same rank
published latter. If other names are subsequently published for the same taxon, they
become synonyms (invalid names). If more than one name for a single taxon or
identical names for different taxa are published simultaneously, it becomes the privilege
of the first reviser to select one of these names as the valid one and to place the others
in synonymy.
1.2.5 Binominal nomenclature
Like all other animals, the binomenclature system standardized by Linnaeus is followed
in scientific naming of finfishes. The binomen i.e. the scientific designation of the
species consisting of a generic and species name e.g. Thryssa malabarica. Thryssa is a
genus name and malabarica is species name. The genus name should start with capital
letter and the species name should be in small letter. Since the scientific names of the
species are italized, the genus and species name have to be underlined
separately. When a subgenus is used in combination with generic and species name in
classifying a species taxon, the subgenus should be placed in parenthesis between

genus and species. It should not be counted as one of the words in the binominal name
of species or trinominal name of a subspecies. E.g. Osteochilius (Osteochilichthys)
nashii (Day). If a subspecies is to be named, trinominal system has to be followed e.g.
Cirrhinus mrigala mrigala (Hamilton and Buchanan).
The generic group name must be in a noun in the nominative singular or be treated as
such. The species group must be a simple word of more than one letter, or a compound
word and must be or treated as (i) an adjective in a nominative singular agreeing in
gender with a generic with a generic name (e.g. Gasterosteus aculeatus); (ii) a noun in
the nominative singular standing in opposition to the generic name (e.g. Cichlasoma
maculicauda); (iii) a noun in the genitive singular such occurs in patronymic (e.g.
Trachinotus russelli, Epinephalus clarki, Mipterus peronii - Single ‘i’ relates to male while
double ‘ii’ relates to female), (iv) an adjective used as a substantive in the genitive case,
derived from the species name of an organism with which the animal in question is
associated, (v) name in genitive plural usually indicating something about the habitat
(e.g. Alepes djedaba, Solenostomus tuticorensis) and character of the species (e.g.
Eleutheronema tetradactylum, Nibea macultata). A species group name can also be
published in combination with genus group name but the latter need not be valid or
even available (e.g. Atropus atropus).
In naming a finfish family, a valid genus contained in the family should be given and
must be in the nominative plural e.g. Ariidae - genus Arius.
1.2.6 Authorship
The author (authors) of a scientific name is (are) the person (persons) who erect the
species of the first type. The names of author (authors), when cited follows the scientific
names of the species thus erected (e.g. Scomberoides commersonnianus Lacepede,
1802, Sardinella longiceps Valenciennes). Citing the original author (authors) not only
give credit to the individual (individuals) but also fixes responsibility for the name and
aids in locating the original description. If a species group taxon was described in a
given genus and latter transferred to another genus, the name of the author (authors) of
the species group name should be enclosed in parentheses [e.g. Arius sona (Hamilton,
1822) = Tachysurus sona (Hamilton, 1822); Amblygaster sirm (Walbaum, 1792) =
Sardinella sirm (Walbaum, 1792)].
If it is desried to cite the names of both the original author of a species group name and
of the reviser who transferred it to another genus, the names of the reviser should follow
in parentheses that enclose the original author (e.g. Scomberoides tala (Cuvier) Smith
Vaniz (1973).
1.2.7 Validity

Validity is a term that refers to the rights of names in relation to homonyms and
synonyms. Synonyms are different names used for the same species. Homonym is the
identity in spelling of available names denoting different species group taxa within the
same genus or objectively different taxa within the genus group or within the family
group. The earliest published synonym is referred as the senior synonym and latter
synonyms are junior synonyms.
Two kinds of synonyms-one consists of names that objectively refer to the same thing,
such as a new name for supposedly preoccupied name or names based on the same
specimen or illustration. These are called objective synonyms. In subjective synonyms,
the names are based on different materials.
1.2.8 Emendations
Any demonstrably intentional change in the original spelling of a name is emendation.
There are two types of emendations. In justified emendation, the correction of an
incorrect original spelling and the name thus emended takes the date and authorship of
the original spelling. In unjustified emendation, the name thus emended has status in
nomenclature with its own date and author.
1.2.9 History of Aquaculture in India
1. Holotype or type
The single specimen designated or indicated as ‘the type’ by the original author at the
time of publication of the original description.
2. Syntype
If there is no holotype, then all the specimens of the type series are syntypes. Syntypes
may include specimens not seen by the author but were based upon previously
published description or figures upon which he founded his taxon in whole or in part.
3. Paratype
After the holotype has been labelled, the remaining specimens of the type should be
labelled as ‘paratype’ in order to clearly identify the components of the original type
series.
4. Lectotype
It is one of the series of syntypes. Selection of lectotype should be undertaken only by a
specialist during revision work. It should never be done merely in order to add a type
specimen to the collection. If the description of a species is clearly based on particular
specimen, that specimen should be made the lectotype.
5. Neotype

A specimen selected on type subsequent to the original description in cases where the
original types are known to be destroyed and were suppressed by the commission.
6. Allotype
A paratype of opposite sex to the holotype.
7. Topotype
Specimen from the type locality collected there subsequent to the original description.
8. Paratopotype or Isotype
A specimen other than holotype taken at the same place as the holotype and included
in the original description.
1.2.10 Nomenclature change
Nomen nudum
A species name published without satisfying the condition of availability is generally
called as Nomen nudum.
Nomen dubium
The name of a nominal species for which available evidence is insufficient to permit
recognition of the zoological species to which it was applied.
Nomen oblitum
A name that has been remained unused as a senior synonym in the primary zoological
literature for more than fifty years is to be considered as forgotten name.
Nomen conservandum
A name preserved by the action of commission and placed on the appropriate official
list.
1.2.11 Periods of classification
1. First period
Even the primitive tribes were often excellent naturalists. Hippocrates (460 – 377 B.C)
enumerated different kinds of animals. Aristottle (383 – 322 B.C) was the Father of
Classification. He described that animals can be characterized according to their way of
living, their action, their habits and their bodily parts. However, he did not supply an
orderly, fully consistent classification of animals. Of all the preLinnaean authors, the one
who arrived at the most Natural Higher Classification was John Ray (1627 – 1705).

2. Second period (Linnaean and his contemporarian)
The great Swedish naturist Linnaeus (1707 – 1778) exerted such an important influene
on the entire subsequent development of classification of organisms. Hence, he was
called”Father of Taxonomy”. The binomial method of nomenclature was for the first time
applied by him to the animals in the 12th edition of his “Systema Naturae” (1758).
He followed Aristottle’s idea of the essential features of living things and his logic.
3. Third period (The empirical approach)
The hundred years between the 12th edition of his “Systema Naturae” and the
publication of “Darwin’s origin of species” was a period of subtle. Lamarek (1744 –
1829) who lived during this period had no visible influence on these developments
except for some purely practical contribution he made to the classification of
invertebrates. Cuvier (1789 – 1832) was far more influential during this period. A steady
and enormous increase in the number of known animals characterized this period.
Voyages all over the globe acquainted zoologists with the animals of Africa, Australia
and America.
4. Fourth period (Darwin and phylogeny)
Charles Darwin encountered so many phenomena of distribution, variation, structure
and adaptation during his voyage. Taxonomists began to accept evolution. The German
biologist Ernst Haeckel proposed the term ‘protista’. His phylogentic trees and
speculations greatly stimulated the taxonomy.
5. Fifth period (Population systematics)
Study of intraspecific variation was the objective of population systematics. It is not an
alternative to classical taxonomy but only an extension.
6. Sixth period
This period is characterized by renewed examination of whole theory of taxonomy and
development of biochemical and molecular markers to study the intraspecific variation.
1.2.12 Generic level identification
The purpose of a key is to facilitate identification of a taxon. This goal is achieved by
presenting appropriate diagnostic characters in a series of alternative choices. Keys

form a good tool for taxonomic analysis. In the preparation of keys, a taxonomist should
select and evaluate the diagnostic taxonomic characters. In this sense, keys are an
integral part of taxonomic procedure as well as means of presenting findings. A good
key should be dichotomous and should not offer more than two alternatives at any point.
The alternative should be clear cut and precise. The style of the key should be like
telegraphic code similar to taxonomic description of finfish species. The phrases should
be separated by semicolons. While preparing the key, the primary contrasting
characters of each couplet should be diagnostic and definitive. Supporting supplemental
characters should also be added.
Generally, two types of keys are used in taxonomy. They are:
i) Indented key and ii) Bracket key.
1.2.13 Indented key
A - Body normal, not tapering to a point; caudal fin forked.
B - No scutes before or behind pelvic fin base; maxilla tip blunt; anal fin origin well
behind last dorsal fin ray - Engraulis.
BB - Scutes present along belly, needle like; maxilla tip pointed; anal fin origin under
last dorsal fin ray.
C - Scutes needle like, present only before pelvic fin base - Stolephorus.
CC - Scutes present before and behind pelvic fin base - Thryssa.
AA - Body tapering to a point; caudal fin not forked - Coilia.
The indented key has an advantage that the relationship of various divisions can be
seen very quickly. But this key will be a very long key, alternatives may be widely
separated and it is wasteful of space.
1.2.14 Bracket key
The second type of key in most of the fish taxonomical studies is the bracket key. This
has the advantage that the couplets are composed of alternatives and are side by side
so that comparisons could be made easily. This key is also more economical and space
of because it is not indented. When properly constructed, this key will run forward or
backward with equal facility by following numbers indicating the path that the various

choices follow. The main disadvantage is that the relationship is not apparent to the
eye.
1. Body elongate, tail long and tapering; caudal fin not forked; upper
pectoral rays produced as long filaments.
Coilia
Body moderately long, caudal forked; pectoral rays normal. 2
2. Prominent silvery lateral stripe present. Stolephorus
No silvery lateral stripes. 3
3. Upper pectoral ray produced. Setipinna
Upper pectoral ray not produced. 4
4. No abdominal scutes in front of ventral fin. Thrissina
Abdominal scutes extends from isthmus to vent. Thryssa

Unit 2: Classical Taxonomy
Chapter 1: Morphological characters
2.1.1 Introduction
The nature of adipose eyelids, its development, extension of maxillae, position of
nostrils, nature of operculum whether serrated or not, presence of pores around the
mouth region and barbels, its numbers, type of mouth, the arching of lateral line, naked
area of breast region, pigments, bands on the lateral side, etc., are to be studied
carefully in large number of specimens covering different length groups.
Sometimes a morphological character attributed by a taxonomist as valid one for a
species at a given length, may prove to be invalid at larger length groups or at smaller
length groups. Hence, the taxonomists have to study the morphological characters at all
length groups covering large number of specimens .
The colour pattern in most of the fishes changes after death. Ichthyotaxonomists should
not give more importance to colouration. While studying colourations, the specimens
available at fish markets must not be studied and the colour pattern will also change
when the fish is preserved. Similarly the number of bands on the body, the spots and
pigmentation have to be studied only in fresh specimens.
2.1.2 Morphological charater use in ichthyotaxonomy
• To separate a family taxon, genus taxon in addition to their use in identifying species
taxon.
• To separate closely related genera and species
Example -1
The order, Pleuronectiformes includes six families and all these families could be
separated using the following morphological characters
1. Psettodidae – (i) Spiny rays present, (ii) eyes on left side or right side only, (iii)
dorsal fin origin well posterior to eye.
2. Pleuronectidae – (i) Pelvic without spine, (ii) eyes only on right side, (iii)
preopercle margin exposed, its hind margin free and visible.
3. Citharidae – (i) Eyes on one side (left or right), (ii) pelvic with one spine and five
rays.
4. Bothidae – (i) Eyes only on left side, (ii) edge of preopercle margin free and
visible, (iii) separate caudal fin.
5. Soleidae – (i) Pelvic without spine, (ii) preopercle margin exposed, its hind
margin hidden by skin, (iii) eyes only on right side.

6. Cynoglossidae – (i) No free preopercular margin, (ii) eyes on left side, (iii) caudal
fin
Example – 2
The genera in the family, Ariidae (marine catfishes) could be separated using the
following morphological characters.
1. Osteogeneosus – one pair of stiff and semiosseous maxillary barbells (mental
barbells absent)
2. Batrachocephalus – only 1 or 2 pairs of soft, minute rudimentary mental barbells
(maxillary barbells absent)
3. Arius – three pairs of slender barbells (one pair maxillary and 2 pairs mandibular)
Example – 3
• The presence of ventral scutes separate the closely related general such as
Stolephorus, Thryssa and Thryssina.
• If scutes are present between pectoral and pelvic fins, the species of such type
comes under the genus, Stolephorus.
• If the scutes are not present before the pectoral, such species are placed under
the genus. Thryssina and when scutes are present before and behind pelvic, fin,
such species are placed under the genus, Thryssa and Setipinna
• Species coming under the genus, Thryssa have the first pectoral fin ray normal,
whereas in the species coming under the genus, Setipinna, the first ray is
filamentous.
Example – 4
• Some morphological characters may also change in accordance to length
groups.
• In the genus, Atule of the family, Carangidae, the earlier authors while separating
this genus with closely related genera, Alepes emphasized the extension of
adipose eyelids.
• In the genus, Atule the adipose eyelid covers the entire eye except the central
slit.
• But in larger length groups, the ventral part of the eye is also covered with
adipose eyelids.
• Hence this character is applicable only in smaller specimens. In the genus,
Alepes the adipose eyelid covers three fourth of the eye on all length groups
2.1.3 Fish Diagnostics
Fish identification depends mostly on the external morphological characters of
the fish. Two main features are commonly used: morphometric and meristic

characters. Of these the first as the name indicates utilises the morphological or
external characters and the second the counts or the numbers. Depending upon
the group of fi"shesthese vary. For instance in the case of fish without scales the
number or counts of scales does not arise. H~ver the more commonly adopted
measurements are detailed below. These are the essential data one has to take
but many more can be added but their utility should be kept in mind.
2.1.4 Main Organs
The main organs in a fish are situated in the head region. The body carries the
fins, digestive, reproductive and other systems. Before explaining them it is better
to have an idea of. the body parts of a fish which are used in identification. Fish
may be with or without scales and spines but the major body configuration
remains the same.
2.1.5 Head Region
• 1. Snout. 2. Lips. 3. Mouth. 4. Jaws. 5. Teeth 6. Barbels. 7. Nostrils. 8. Eyes. 9.
Operculum, gills. 10.Median groove. 11. Pectoral girdle. 12. Occipital process.
• Depending upon the habits and habitats of the fish, variationsin structureand
shape are present in these organs:, These are detailed below.
2.1.5.1 Snout
The anterior most part of a fish, which in most cases is rounded or obtuse. Variations are (i).
Pointed and sharp (Eels Fig. 12 A). (ii). With a groove across on top. (Shismatorhynchos (Nukta)
nukta Fig. 12 B). Some as Garra nasuta have a proboscis developed (Fig. 12 C) (iii). Tubular
with jaws at tips. (Pipe fish. Fig. 12 D). (iv) Smooth in most cases covered with thin or thick skin
but in some tubercles may be present (Fig. 12E Gonoproktopterus,Barilius species) (v).
Overhanging the mouth (Fig. 12 F Engraulids).
Fig.12. Shape of snout. A. Pointed and sharp. Eel. B. With a groove across on top.
Schimatorhynchos (Nukta) nukta. C. With a well-developed proboscis Garra nasuta. D.
Tublar with jaws at tis. Pipe fish. E. With tubercles. F. Overhanging.

2.1.5.2 Lips
The premaxillary and maxillary bones of the upper jaw are covered by the upper lip and
the mandible on the lower jaw by the lower lip. Mostly these lips are thin smooth
membranes but in some theymay be with pores (Fig. 13A), stripes (Fig. 13B) as ni
Labeo dero and L. dyocheilus respectively or modified to form a sucker- like disc as in
Garro species (Fig. 13 E). In some as in the Mahseer the lower and upper lips are
continuous around the jaws and the labial fold (fold formed by the lips) is uninterrupted
by the isthmus (Fig. 13 C) or interrupted (Fig. 13D). The lower lip may evenable
prolonged as a flap called the mentum. In Tor progenius the upper lip is modified as a
fan shaped structure. (Fig. 13 F). Depending upon the position of the mouth the lips
may also be terminal or inferior as they are adherent to the jaws.
Fig. 13. Lip structure. A. Labeo dero with pores. B. Labeo dyocheilus with stripes. C.
Labial fold continuous with metum. D. Labial fold interrupted. (b=Upper lip) E. With a
suctorial disc on lower lip Garra. F. Upper lip with fan-shaped enlargement Tor
progenius.

2.1.5.3 Mouth
Mouth is the chief organ for feeding of the fish and based on the type of food it takes,
the shape, position, size and form vary. In most cases it is terminal or slightly below
sub-terminal (Fig. 14B). Surface swimmers as Danio, Puntius, and Rasbora species
have a terminal mouth (Fig. 14A). On the other hand hill stream fishes as ,) Balitora,
Bhavania, Garra specieshave their mouth narrow and placed in the ventral side of the
snout (Fig. 14 C) to suit their scratching of food from the rocks and boulders where they
live without being washed away by the surging waters. Species of Glyptothorax have
their mouth placed slightly inferior. In Belonidae (freshwaterGars) the mouth is superior
(Fig. 14 D), wide and the cleft extends to the border of the eyes (orbit).
Fig.14. Shape of mouth. A. Terminal (Danio, Rasbora, Putius). B. Sub-terminal. C.
Inferior (Balitora, Garra) D. Superior (Belontids).
2.1.5.4 Teeth
Teeth are borne on the jaws and palate. All fishes may not have teeth. Many as Chanos
chanos (Milk fish), Cyprinids are without teeth (called edendate). Siluroids have sharp
teeth. The teeth when present are mostly villiform (sharp) (Fig. 15 A), conical (Fig. 15
C), molariform (Fig. 15B Rita species), canine (Pseud apocryptes Goby). In Puffer fish
(Tetraodon species) the teeth are formed like a beak-like dental plate. In most fishes the
teeth on the lower jaw are in the form of a narrow or wide band, separated in the middle
where as on the upper jaw it is uninterrupted and continuous. On the palate they may
be in patches, discontinuous or continuous or as a single broad band. The band is
nearly curved and may extend deep into the corner of the mouth. The teeth are
essentially meant for crushing, scraping the food that the fish takes and accordingly
they are modified.

Fig. 15. Teeth. A. Villiform. B. Molariform (Rita). C. Conical (Gobies).
2.1.5.5 Jaws
As already stated the pre-maxillaries,maxillaries and mandiblebones fonn the upper and
lowerjaws. They are united by a symphysis Ooint) which enables them to open and
close the mouth. Thejaws bear the teeth described above and act as the frame for the
shape of the mouth.The palate teeth are borne by the vomer bone,which is not a part of
thejaw. Thejaws are essentiallymeantto capture,hold andswallow the prey and the teeth
help in munching, grinding andmaking it fit for passage through the gullet. In most fishes
thejaws aremore or less of equal length, but in somethe upperjaw is longer than the
lower (Fig. 16 A). In Clupeidae the lower jaw is longer than the upper (Fig. 16B). In
Engraulidae the upper jaw is projecting. In Ctenops species both the jaws are elongated
to form a some what pipe-shaped mouth. In Hyporhamphus species (Hemiramphidae)
the lower jaw in the adult is elongated as a long beak (Fig. 16 C). In Pipefishes
(Ichthyocampus species) both the jaws are produced as a beak. In puffer fishes both
jaws are divided by a median suture with a cutting edge and covered by ivory like
substance. In some the lower jaw may be having a horny covering as in Labeo fisheri
(Fig. 16D).

Fig.16. Jaws. A. Upper jaw longer than lower jaw (Engraulidae). B. Lower jaw longer
than upper jaw (Clupeidae. C. Lower jaw elongated (Hemiramphidae). D. Jaw ridge
horny (Labeo fisheri).
2.1.5.6 Barbels
Barbels are flexible tactile filaments under the chin surrounding the mouth, on the snout,
on the sides, on the ventral side and in between the nostrils. In catfishes they play a
very important role in identifying the food objects, locating the extent of the width in
crevices and also as a defense organ. Mystus bleekeri, the fiddler fish of Mysore, erects
its barbells in a threatening manner when disturbed. In the Ariid genus Osteogeniosus
the only pair of maxillary barbels are thick and semi-osseous (Fig. 17 B). Most siluroids
carry four pairs of barbels (Fig. 17 A), but it is not constant; it may be one, two or three.
The Cyprinids also have barbels but not as long as in the catfishes. In Nemacheilus the
barbells may be well developed and they are used as a sensory organ only (Fig. 17 C).
Fig. Barbels. A. Soft and muscular Clarias batrachus. B. Stiff and osseous
Osteogeniosus militaris. C. Simple hollow short tubes. Noemacheilus labeosus.

2.1.5.7 Nostrils
Nostrils are a pair of apertures or slits on the snout which are the openings for the smell
organs leading to the nasal canal on the skull. They are mostly small to medium and are
sunk in the snout, often covered by mucous especially in catfishes. A. pair of nasal
barbels is often seen, which may be long, short Orrudimentary and borne on the
posterior one. They are generally well separated (Fig. 18A) but in Sisoridae the nasal
barbels are closely placed one behind the other, slit-like but separated (Fig. 18 B). In
Heteropneustidae the anterior nostril is placed /' on the tip of the snout and produced as
short tube. In Ariidae they are closely placed and separated by a valve like structure
(Fig. 18C). In some Nemacheilines a flap separates them. In Oreonectes the anterior
nostril is prolonged as a long nasal barbel (Fig. 18 D). Whatever variations are seen the
nostrils are a vital part of the fish and useful in classification.
Fig 18. Nostrils. A. Placed wide apart Bagridae. B. Close together Sisoridae. C.
Separated by a valve Ariidae. D. With a barbel in-between Oreonectes (Oreonectes)
evezardi.
2.1.5.8 Eyes
Eyes mainly used for seeing food, enemies and predators are placed in most fishes
dorso- laterally (at the sides) along a mid-axis line of the body. However this position
may vary depending upon the habitat of the fish. It may be superior or inferior. Many

gobioid fishes have the eyes placed on the top of the" head. Species of Oxyurichthys.
Bathygobius. Boleophthalmus have the eyes placed on top ofthe head. Mugil corsula
has protruding eyes on the top (Fig. 19 A). In such cases the distance between the eyes
becomes short. Puffer fishes, gouramies also have such an arrangement. The eyes in
these cases are large. In some catfishes the eyes are placed low so that they are visible
from below the ventral surface. Chandramara chandramara (Fig. 19 B), Horabagrus
brachysoma, Ompok and Ailia species show this kind of placement. The catfishes
browse at the bottom and hence the eyes are situated at this level. The eyes are
generally large in size or moderate, but in the eels and hill-stream fishes they are, small;
the latter being denizens of fast powing shallow 'streams, with too much light
penetrating, larfe eyes would be a disadvantage. In Brachyamblyopui burmanicus (eel
like goby) the eyes are minute and hidden (Fig. 19 C) they are minute and hidden. The
eyes are subcutaneous and they may be circular, oval in shape. Some cave dwelling
fishes are totally blind.
Fig. 19. Eyes. A. Superior Mugil corsula. B. Inferior visible from below ventral surface
Chandramara chandramara. C. Minute reduced, hidden Brachyamblyopus burmanicus.
2.1.5.9 Operculum and Gills
Operculum and gills form part of the branchial apparatus. On either side of the fish the
gill slits are situated which may be wide (Fig. 20 A), narrow or even in the form of a
small aperture as in the case of the eels. In the snake eels (Ophichthyidae) the gill
openings are in the pharynx as wide slits (Fig. 20 B). On the other hand in Moray eels
(Muraenidae) they are small, round openings only (Fig. 20 D). In hill stream fishes they
are greatly restricted to the ventral side (Bhavania australis, Fig. 20 C). Where the
openings are wide they are covered by a group of flat thin opercular bones joined
together by the skin which covers the gills inside. On the ventral side of the head
numerous tiny thin bones are arranged fanwise from the lower side of the opercle.

These are branchiostegal rays (Fig. 20 F) covered by a thin membrane. Comb-like
plates, red on colour are seen on either side, which are the gills. The concave
pharyngeal margins of the branchial arches are fringed with a double series of either
cartilaginous or bony tubercles or filaments called the gill rakers. The anterior row of gill
rakers on each arch usually interdigitate with those of the posterio'r row on the
preceding arch and in this way the two rows form a sieve like mechanism to prevent any
solid particles entering the pharynx with the respiratory current of water and from
passing into the gill clefts and clogging it. The gill arches carry the gill lamellae and gill
rakers or branchiospines. The first branchial arch (the anterior- most one) (Fig. 20E)
carry rakers on the upper limb and filaments on the lower limb. Five gill arches are
placed on either side of the head region (Fig. 20 G). The rakers on the upper and lower
limb of the first arch are counted separately Usually the first gill arch alone is taken for
counts.

Fig. 20. Operculum and gills. a. Normal. B. Eel as a moderate slit in pharynx near base
of pectoral fin. C. Greatly restricted above base of pectoral fins Bhavania australis. D.
Round and lateral in pharynx Mureanidae. E. Structure of a gill. (u.l) Upper limb. (gf) Gill
filament. (ga) Gill arch. (ll). Lower limb. (gr) Gill rakers.
2.1.5.10 Median groove
Median longitudinal groove or fontanel are two longitudinal-externally visible long
depressions on the head and covered by skin in catfishes. They may be single or
double and are in the center of the head extending from near the snout to the base of
the occipital process. When single (Fig.21 A) it is a continuous depression without a
break. When double it is interrupted (Fig. 21 B) in the middle by a short bone. These
represent the passage for the cranial nerves in the skull. When covered with thick skin
its extent can be found by inserting a needle and dragging (Fig. 21 C).
Fig. 21 Median groove. A. Continuous. B. Interrupted as two fontanels. C. Extent and
identification of fontanel.
2.1.5.11 Pectoral girdle

These are paired bony structures on either side of the fish in the head region inserted
laterally in most cases. They bear the pectoral fin and pectoral spine in catfishes. These
articulate and are attached to the 'post-temporal bone of the cranium. Besides the spine
an elongated cleithral process (Fig. 22 A) is visible above the pectoral fin at the side in
catfishes. This may be rugose and prominent in some genera. The pectoral spines are
mostly stout, strong, serrated along the outer edge or smooth, but in most Cases they
are strong, with anteriorly directed (antrorse) serrations; in some both the inner and
outer edges are serrated, where the direction of the serrations are towards the posterior
end it is called retrorse. (Fig. 22 A) In Erethistes pussilus the spine serrations are
different; they are divergent (Fig. 22 B). Some fishes exhibit a long filament from the tip
of the pectoral spine.
Fig. 22. Pectoral girdle of Rita rita. A. Showing (PSP) pectoral spine with antrose teeth
on inner edge and retrorse teeth on outer edge. CL = Cleithrum. CLAM. = Upward
directed short narrow arm of Cleithum. CP = Cleithral process. O = Coracoid bone. TNL
= Tunnel. B. Divergent serrations along outer edge in Erethistes pussilus.

2.1.5.12 Occipital process
An arrow like conical bone with a broad base extending from the supra-occipital bone to
the basal bone of the dorsal fin (Fig. 23A) in catfishes. The junction with the basal bone
of the dorsal fin may be Interrupted (Fig. 23 B) by a short or long space which is helpful
on separating group of fishes. The bone may be interrupted by an inter-neural shield
(Fig. 23 C) as in Aorichthys aor and seenghala.
Fig. 23. Occipital process. Hara hara. A. Reaching basal bone of dorsal fin. B. Not
reaching. C. Inter neural shield.
2.1.6 Body

The Body of the fish carries the paired and unpaired fins, scales, lateral line and internal
organs as already started. The main features are 1. Paired fins. 2. Unpaired fins. 3.
Lateral line. 4. Scales.
2.1.6.1 Paired fins
The pectoral, pelvic fins are the paired fins since they are two in numbers placed side
by side. The pectoral fins- are inserted in most cases laterally but in some may be
horizontally (Psilorhynchidae, some Homalopterids) or even above the ventral profile
(perches, gobies) (Fig. 24 C). They bear the fin rays, simple and branched and in
catfishes the pectoral spine. In some cases the fin rays may be elongated as long
filaments (Fig. 24 D Ctenops nobilis). The shape of the pectoral fins vary differently.The
pelvic fins (some times called ventral fins), are inserted in most cases ventrally and are
placed with a distance in between them (Fig. 25 A), but in Gobiidae they are united. In
Sicyopterus they are united in the form of a cup (Fig. 25 B) shaped disc. The fins bear
the simple and branched rays.In Syngnathids they are much reduced. The fins are
absent in some (eels, Mastacembelidae, Puffer fishes). In perches the fins when
present may be thoracic (Fig. 24 A) or jugular (Fig. 24 B) in position and bear spines.
Fig. 24. Pelvic fin insertion. A. Thoracic. B. Jugular. C. Abdominal. D. with filaments
Ctenops nobilis.

Fig. 25. Pelvic fins: A. Free. B. United as a cup (Gobioids).
2.1.6.2 Unpaired fins
The dorsal, anal and caudal fins are unpaired in the sense that they are single and not
in pairs as the above. The dorsal fin in most fishes is single, concave in shape (Fig. 26
A) with smooth or serrated spine (Fig. 26 B), with simple (Fig. 26 D), and branched rays
(Fig. 26 F). The principal ray may be thickened (Fig. 26 E). There may be a procumbent
spine in some (Fig, 26 G Mystacoleucus). In Megalops cyprinoides the last ray is
prolonged as a filament (Fig. 26 H). In Perches there are two dorsal fins one after the
other with the first one separated either by a short or long gap from the second fin (Fig.
27 B) or may even be united (Fig. 27 A); both may bear spines and also soft and
branched rays. Generally the first fin is shorter than the second one but this may not
always be true. In mugils the first fin is with spines only, separated from the second one
by adistance. In Synbrachids (Swamp eels) the dorsal fin is vestigial in the form of
ridges only. In Mastacembelus the fin is in two parts; the first one with 32 to 40 short
depressible spines and 46 to 90 rays. In Sillaginopsis the second dorsal spine is
prolonged as a long filament(Fig. 26 C). The fin may be in different positions on the
dorsal profile, mostly at the center, but in many may be far posterior above the anal fin.
The fin may be free or even confluent with the caudal fin.
Fig 26 & 27 Added
An adipose dorsal fin is present in siluroids and salmons; it is generally smooth, free
(Fig. 28A) and not united with the rayed dorsal fin though the interspace between the
two may be long or short. In Sisor rhabdophorus the adipose fin is reduced in the form
of a spine (Fig. 28 C). In Chaca chaca and some other fishes it is confluent with the
caudal fin (Fig. 28 B).
Figure 28 Added

The anal fin is inserted on the ventral side and is with simple and branched rays.
Generally the fin is free (Fig. 29 A), short, but exceptions are there as in the case of
Horabagrus, Clarias, Heteropneustes, Schilbeids, Pangasids. Plotosids. In the latter the
fin is confluent with the caudal fin. (Fig. 29 B); whereas in Claridae and
Heteropneustidae though long, it is separated from the fin by a short distance. In
Horaichthys the fin is modified into two parts; the first six rays are separated as an
independent gonopodium. In Garnbusiaan intromittant organ i~present (Fig. 29 D). In
both cases Onlythe males show this adaptation. The perches (Fig. 29 C Dah1ioides
quadrifasciatus)may have spines in the anal fin.
Fig 29 Added
The caudal fin or the tail fin is the propeller for the fish and acts as a rudder. It is the
posterior most part of the fish body. It is of varying shapes and is always a single fin,
rounded. with or without margins (Fig. 30 C), truncate (Fig. 30 F), furcate or slightly
emarginate (Fig. 30 A), forked (Fig.30 B), lunate or lanceolate (Fig. 30 H), wedge or
paddle shaped (Fig. 30 D), notched (Fig. 30 E), rounded (Fig. 30 G) or ovate (Fig. 30 J)
etc. In most cases it is forked to varying degrees. The lobes may be equal or unequal
(Fig. 30 K) and sometimes filamentous extensions are also present (Sisor, Bagarius).
Fig 30 Added
2.1.6.3 Lateral line
The Lateral line is the sensory line formed along each side consisting of sensory pores
to tiny tubes in scales or skin. Most fishes have the lateral line, but in some it is absent
(Mugilidae) (Fig. 31 D). It is generally continuous (Fig. 31 A), but in some Cyprinids and
Perches it may be discontinuous (Fig. 31 B) or in two levels (Fig. 31 C). Generally it
stops at the base of the caudal fin but in Lates calcarifer it extends beyond into the
caudal fin (Fig.31 E). In Toxotes chatareus it is interrupted (see Fig. 10).
2.1.6.4 Scales
Scales are thin bony plates covering the whole ofpart of the body of the fish. They can
be microscopic as in the cobitids, small as in Chela, large as in Labeo and big as in
Mahseers. Their edges may be spinous (ctenoid Fig. 32 A, B Butis butis, Ophiocara
species of Eleotridae), or looth (cycloid Fig. 32 C, D). Most fishes have the latter variety.
The numbers Vary according to the size; it may even exceed 100 (Securicula), limited to
87 or even less than 20 Puntius titeya). Most are deciduous in that they fall off easily. In
some fishes the scales are in the form of bony plates (Puffer fishes).

The variations in the different body parts of the fish have been outlined mainly to
indicate that these are very helpful and often used in separating taxa.
Fig 32 Added
Abdomen
The Abdomen of a fish is mostly rounded except in flat fishes, hill stream fishes and
deep sea fishes where they are flat. In most Cyprinids the abdomen may be keeled with
no barbels (Fig. 33 A) or rounded with barbels (Fig. 33 B).
In CIupeids the ventral profile may be with serrations (Fig. 33 C). ,In the Sisorid fish
Glyptothorax an adhesive apparatus is developed (Fig. 33 D) in which the paired fins,
pectoral and pelvics, may be plaited (Fig. 33E).
Fig 33 Added

Chapter 2: Meristic characters
2.2.1 Meristics
Meristic characters which are countable have been widely used in studies of fish
population and species. Unlike the body proportions or colouration, meristic characters
are fixed usually at or before metamorphosis and remain constant throughout the life of
an individual.
All the meristic characters should be treated separately and the frequency distribution of
meristic characters must be given so as to find out any variation between species or
between population of a species.
The following abbreviations are used in fins, scales and gill rakers of a teleost:
D – Dorsal fin
A – Anal fin
P 1 – Pectoral fin
P 2 or V 2 – Ventral fin
C – Caudal fin
L1 – Lateral line scales
Ltr – Lateral transverse row of scales
O – Adipose dorsal fin
Gr – Gill rakers
Dorsal fin count and anal fin count includes spines and rays. Among two dorsals one
spinous and other ray type, then the formula may be given as D1 and DII where, DI
stands for spinous first dorsal and DII stands for rays of second dorsal fin. If 3 spines
and 7 branched rays are present in a single dorsal fin, then the formula may be given as
DIII, 7.
The anal fin count includes spines and rays. If two spines and 5 rays are present, the
formula may be given as AII, 5.
Pectoral fin count can be made on the left side. However, counts can be made on both
sides in a few number of specimens to permit estimation of bilateral variations.
Pelvic fin count includes both spines and rays if present.

Fin count formula is given as below:
D1, I, VII-VIII - This denotes first dorsal fin with one spine separated from the
rest of spines (VII-VIII).
D2, I, 15-16 - This denotes second dorsal fin with one spine followed by
15-16 rays.
AII, I, 10-15 - This denotes anal fin with two spines separated from one spine
followed by 10-15 rays.
Fig added (Meristic Character) (FAO Figure)
Gill raker counts are for lateral gill rakers on the first arch, normally on the left side. The
raker at the junction of the upper and lower limbs (epibranchial and ceratobranchial) is
included in the lower limb count as the major part of the base of the raker is over the
ceratobranchial. Rudimentary gill rakers, with the base width (lateral) of the raker equal
to, or less than the raker length, occur at the anterior ends of the upper and lower limbs
and these are included in the counts, though differentiated as ii, 7+19, iv=32.
Laterial line scales (L1) are scales along the lateral line from its origin to its posterior
most part of the lateral line. In some teleostean fishes as in clupeids lateral line is
absent. In such case scales will be counted along the row where the lateral line
normally would have been present.
Predorsal scales are scales on the midline in front of the dorsal fin origin. These scales
are counted as the scale rows which intersect the midline from the anterior point of the
dorsal fin to the orbit.
Scales above and below the lateral line (Ltr) – A transverse series below of scale rows;
below the lateral line scales are counted from the origin of the anal fin, not including the
median ventral scale row, along a forward diagonal to the lateral line; above lateral line
scales are counted from the origin of the dorsal fin, not including the median dorsal
scale row, on a diagonal backward to the lateral line; the lateral line row is not included
in these counts.
2.2.2 Orders of Fishes, with Selected Families
Class/subclass Order
Number
of
Families
Representative
families
Common
names
#
species
in order

Myxini Myxiniformes 1 Myxinidae hagfish 43
Cephalaspidomorphi Petromyzontiformes 1 Petromyzontidae lamprey 41
Chondrichythes
Holocephali Chimaeriformes 3 Chimaeridae chimaeras 31
Elasmo branchi i Heterodontiforrnes Heterodontidae
bullhead
sharks
8
Orectolobiformes 7 Rhincodontidae whale sharks 31
Carchiniformes 7 ground sharks 208
Lamniformes 7 Cetorhinidae
basking
sharks
16
Hexanchiformes 2 Hexanchidae cow sharks 5
Squaliformes 3 Squalidae dogfish 74
Squantiniforrnes 1 Squantinidae angel sharks 12
Pristiophoriormes 1 Pristiophoridae saw sharks 5
Raj iiformes 9 Rajidae skates, rays 456
Sarcopterygii
Coelocanthimorpha Coelacanthiformes 1 Latimeriidae coelacanth 1
Dipnoi Ceratodontiformes 1 Ceratodontidae
Australian
lungfish
1
Lepidosireniformes 2 Lepidosirenidae
S. Am.,
African
lungfish
5
Actinopterygii
Chondrostei Polypteriformes 1 Polypteridae
birchirs,
reedfish
10
Acipenseriformes 2 Acipenseridae
sturgeons,
paddlefish
26

Neopterygii Semionotoformes 1 Lepisosteidae gars 5
Amiiformes 1 Amiidae bowfin 1
Div. Teleostei 6 Hiodontidae mooneye 217
2 Megalopidae tarpon 8
3 Albulidae Bonefish 29
19 Anguillidae Eels 738
4
Swallowers,
gulpers
26
Clupeiformes 4 Clupeidae Herrings 357
Gonorynchiformes 4 Milkfish 35
Cypriniformes 6 Cyprinidae Carp, shiners 2,662
Catostomidae Suckers
Characiformes 10 Characidae Hatchetfish 1,343
Siluriformes 31 Ictaluridae Catfish 2,405
Gymnotiformes 6 Knifefish 62
Esociformes 2 Esocidae Pikes 5
Umbridae Mudminnows 5
Osmeriformes 13 Osmeridae Smelt 236
Salmoniformes 1 Salmonidae
Salmon, trout,
ciscoes
66
Whitefish,
chubs
Stomiiformes 9
Lightfish,
dragonfish
321
Ateleopodiformes 1 Ateleopodidae Jellynose fish 12

Aulopiformes 12 Lizardfish 219
Myctophiformes 2 Lanternfish 241
Lampridiformes 7
Ribbonfish,
oarfish
19
Polymixiiformes 1 Polymixiidae Beardfish 5
Percopsiformes 3 Percopsidae Trout-perch 9
Ophidiiformes 4 Cusk-eels 355
Gadiformes 12 Gadidae Cod,hake 482
Batrachoidiformes 17 Batrachoididae Toadfish 69
Lophiiformes 16 Lophidae Anglerfish 297
Ogvocephalidae Batfish
Mugiliformes 1 Mugilidae Mullets 80
Atheriniformes 5
Silversides,
grunion
285
Beloniformes 5
Needlefish,
flying fish
191
Cyprinodontiformes 13 Cyprinodontidae Livebearers 807
Pegasidae Seamoths
Syngnathidae
Pipefish,
seahorses
Indostomidae I. Paradoxus
Synbranchidormes 3 Synbranchidae Swamp eels 87
Scorpaeniformes 20 Cottidae
Scorpionfish,
sculpin
1,271
Dactylopteridae Flying gunards
Perciformes 128 Percichthyidae
Temperate
bass
9,293

Centrarchidae Sunfish
Percidae Perch, bass
Sciaenidae Drum
Mullidae Goatfishes
Cichlidae Cichlids
Mugilidae Mullets
Gobiidae Gobies
(also: bluefishes,
remoras, blennies,
mackerels,
dolphins,
snappers, tunas,
swardfish)
Pleuronectiformes 6 Pleuronectidae
Flounder,
flatfisehs
570
Tetraodontiformes 9 Balistidae Triggerfishes 339
Ostraciidae
Cowfish,
boxfish
Tetraodontidae Puffers
Molidae
Molas (ocean
sunfish)
Totals:5 classes 57 orders 478 families
~ 26,000
species
Chapter 3: Morphometric characters
2.3.1 Morphometrics
The morphometric characters are measurable features. These characters have been
helpful for separating closely related genera and species and even population within
species and are used in ichthyotaxonomical studies.

Measuring the linear dimension of whole or parts of finfish is probably the most widely
used technique in finfish taxnonomy. The commonly used length measurements in
finfishes are (i) total length, (ii) standard length and (iii) fork length. Of these, the most
frequently chosen one is total lengtth, because it is quick and easy to measure. Further,
total length has been related to many factors such as weight, age, fecundity, maturity,
etc. These parameters should be easily assessed in relation to total length.
Though total length is the easiest to measure, in larger species with a deeply forked
caudal fin, such as in scombrids, carangids, etc., fork length is preferred. Though
standard length is used by ichthyotaxonomists, in large specimens standard length is
not used because of the difficulty in ascertaining the posterior margin of the hypural
plate.
2.3.2 Methods of Measuring
Measurements are made with special measuring boards. Length measurements are
usually made with the fish lying on its right side snout to the left, on a measuring board
consisting essentially of a wooden or metal base carrying a centre scale and having a
headpiece (nose block) against which the snout is to be pressed (Holden and Rait,
1974). The mouth of the fish should be closed, the fish body and tail are straightened
along the mid-line and the readings are to be recorded from the scale. The
measurements should be recorded to the nearest 0.5 mm with a fine draftsman dividers
using a fresh fish in a near to relaxed condition as far as possible. Rays and other
dorso-ventrally flattened fishes may be measured by lying straight on their ventral
surface. Disc width rather than overall length is sometimes used as linear dimension of
rays. Large fishes could be measured with calipers or from point to point along the body
surface with a tape.
If a fish is to be measured in centimeter units, a board with 1 m long is sufficient. For a
larger specimen, an extension piece of 30 cm long can be clipped or hinged to the
board. For fish measured in half-centimeter units, a board of 50 cm long is usually
sufficient. The scale must correspond to the measurements being recorded. It is also
not possible to measure fish to the nearest centimeter below on a board ‘marked 2 cm
intervals’. Too many divisions in a scale will, either lead to mistake or waste time in
recording characters to the nearest division.
2.3.4 Definitions of Linear Measurements
Overall length measurements are made between perpendiculars along the median
longitudinal axis from the snout (U, the position of the maxillary symphysis).
Measurements from L are taken with the mouth closed. The other measurements to be
taken are:

1. Standard Length: Taken from U to the tip of the hypural bone (urostyle). This
varies from species to species.
2. Fork Length: Measured from U or L to the cartilaginous tip of shortest or median
caudal ray.
3. Total Length: Measured from U or L to the longest caudal fin ray, upper or lower,
or an average of both of them.
Longitudinal measurements other than overall length are also made between
perpendiculars using measuring board with, for example, a sliding cursor. When these
are made radially from point U, calipers are recommended. Point to point
measurements are sometimes made on big fishes such as tunas by tape. These would
be indicated by the word ‘surface’ as these are not generally recommended. All
measurements from LX to LM and also their ‘upper’ equivalents are grouped under the
general name ‘total length’ LT. LM has been called ‘bilobular length’ and ‘total auxiliary
length’. The word ‘Extreme’ is used in LX.
Fig No: Morphology and measurments of teleost
2.3.5 Definitions of Position
U Maxillary symphysis

L Mandibular symphysis
OO Anterior edge of orbit
O Posterior edge of orbit
J Posterior edge of mandible (buccal commissure)
Y Gill-cover notch
G’ Posterior bony edge of operculum
G Posterior membranous edge of gill cover
P Anterior point of insertion of the first pectoral fin ray
D1 Insertion of anterior dorsal (intersection of anterior margin of first dorsal spine,
fin held erect with the contour of the back)
D1’ Position of last ray of anterior dorsal
D2 Insertion of first ray of posterior dorsal
D2’ Position of last ray of posterior dorsal
Z Anterior edge of cloaca
A Insertion of first anal fin ray
A’ Position of last anal fin ray
B Insertion of dorsal lobe of caudal fin
S Posterior tip of urostyle (forward protuberance of hypural blade)
S’ Posterior edge of fleshy peduncle or of pigmented zone
S’’ Point of upper caudal keel
S’’’ Posterior limit of silvering (either last scale of the lateral line or the posterior zone
limit of the scale covered by the peduncle)
F Cartilaginous tip of shortest (median) caudal ray

F’ Membranous edge of caudal fin at fork
N Distal tip of the longest caudal fin ray with lobe normally extended
N’ Distal tip of the longest ventral fin ray with lobe normally extended
M Point where line NN’ intersects median longitudinal axis
M’ Mid point of line MN’
X Distal tip of longest dorsal caudal fin ray, with lobe brought to the median
longitudinal axis
X’ Distal tip of the longest ventral fin ray, with the lobe brought to the median
longitudinal axis
2.3.6 Overall Length Measurements
LT and UT Total length (any extreme or normal length)
LX Dorsal extreme length
LX’ Ventral extreme length
LX’’ Greater extreme length (LX or LX’, whichever is greater)
LN Dorsal normal length
LN’ Ventral normal length
LN’’ Greater normal length LN or LN’, whichever is greater
LM Median normal length
LM’ Mean normal length
LP Mid caudal length
LP’ Fork length
LS Standard length to urostyle

LS’ Standard length to peduncle
LS’’ Standard length to keel
LS’’’ Standard length to silvering
LB (Dorsal) Body length
2.3.7 Other Longitudinal Measurements
UJ Maxillary sheath length
LJ’ Mandibular length
UO Snout length
UY Upper head length
LG Opercular head length
LG’ Greatest head length
OO’ Orbital diameter
ID Longitudinal iris diameter
Ed Longitudinal pupil diameter
O’Y Postorbital dorsal distance
UDI Preanterior dorsal distance
UP Prepectoral distance
UV Preventral distance
UD2 Preposterior dorsal distance
D1D1’ Anterior dorsal fin base length
D2D2’ Posterior dorsal fin base length
UA Preanal distance

AA’ Anal fin base length
2.3.8 Vertical Measurements (Perpendicular Unless Otherwise Stated)
Oh Orbital depth (from orbital crest to lower edge of maxillary, passing
over middle of pupil)
Ih Perpendicular Iris Diameter.
Eh Perpendicular pupil diameter
YJ’ Head length
DIP Back depth (oblique)
DIV Anterior dorsal depth (or dorsoventral depth)
h Greatest depth
D2Z Posterior dorsal depth
D2A Dorsoanal depth (slightly oblique)
h’ Perpendicular anal depth
q (Least) peduncle depth
2.3.9 Lateral Measurements
PP Pectoral breadth
b Greatest breadth
OO Interorbital distance (at level of pupil centre)
2.3.10 Other Measurements
D1h Anterior dorsal height (distance from insertion to tip of longest spine)
D2h Posterior dorsal height (distance from insertion to tip of longest spine)
Ph Pectoral fin length

Vh Ventral fin length
Ah Anal fin height
Ch Dorsal caudal fin length
Ch’ Ventral caudal fin length
Ch’’ Greater caudal fin length
Ig Greatest iris diameter
Eg Greatest pupil diameter
g Greatest girth
VV Length of interventral flap
NN’ Spread caudal distance
All measurements should be taken in percent of standard length or fork length in mm.
For computation, a factor should be found out by dividing 100 with standard length.
Then this factor has to be multiplied with each morphometric character for a single
specimen to get percentage of standard length in millimeters (mm). The same
procedure has to be made for all the specimens of a species that are studied. From this
range, mean, standard deviation and standard error and confidence interval ranges can
be computed for each morphometric characters in a species. To obtain full information,
range of overlapping, overlapping ratio, range of extreme ratio and percentage of
overlapping ratio of all body proportions should be calculated in all combinations
(morphometric characters) for closely related species or species coming under same
genus.
2.3.11 Morphology and Morphometric Characters of Shark
The measurement of most of the morphometric characters are similar to bonyfish. As
sharks do not have spines or rays in fins, measurements of fins should be from the
origin of the fin to the respective fin lobe. The characters should be selected for sharks
from the one given for bonyfishes in accordance to its morphology. Length of claspers
and measurements of upper and lower lobes of caudal fin should be taken in addition to
the characters listed for bonyfishes.
Fig Added (FAO Figure-Morphology and Morphometric)

2.3.12 Morphology and morphometric measurements of rays
For rays, the following measurements should be recorded:
1. Preorbital length – Distance between snout to orbit
2. Postorbital length of disc – Distance between posterior part of orbit to anus
3. Body depth – Maximum distance across the body
4. Tail length – Distance between anus to the tip of posterior part of tail. The other
characters are similar to that of sharks and bony fishes.
2.3.13 Comparison of Sexes
5. The morphometric characters are to be taken separately for males and females.
To find out any difference for a character, least square method has to be
employed by taking standard length as ‘X’ and different morphometric characters
as ‘Y’. Analyses of co-variance (F-test) should be employed to find out any
significance. If there is any significance, the sexes should be treated separately.
• Chapter 4:Preservation and Cataloguing
Learning objectives
This part explains the importance of fish collection and preservation for taxonomical
works. The students will acquire knowledge to lable the specimen and how to store it.
2.4.1 Preservation
The finfishes collected from landing centre or from fish pond or from fish market should
be preserved in formalin. Commercial formalin is concentrated (about 40%) and so
must be diluted to 8-10%. When finfishes are collected from landing centres, colour
patterns, blotches, spots, stripes and other morphological characters are to be noted
carefully (in fresh condition) in the field note book. Preserved fishes should be packed
in plastic jars/bottles with the tail pointing upwards to avoid damage to the caudal
fin. The bottles should be neatly labelled. Labels should indicate serial number, exact
locality, date and time of collection, gear and craft employed, depth of the water and
sexual dimorphism if any are to be noted. In addition to this, the local names should be
written on the label. The specimens thus collected from the landing centre has to be
preserved as mentioned above. The label also should include scientifc name, popular
name, sex and name of the collector. Specimens less than 10 cm (TL) can be
preserved directly in 8% formalin solution. Ten percent concentration will suit for most
of the fishes. For specimens measuring 10-30 cm TL, a slit should be made along the
belly, preferably to the right side of the midline of the body without injuring the
alimentary canal. The preservative i.e., formalin should be allowed to enter through this

slit. Before preservation, entire fish and all the fins of the fish have to be stretched in a
measuring board and should be preserved.
2.4.2 Cataloguing
Murugan Sir Notes Added
Research collections should be housed at research libraries, in fire proof buildings that
are reasonably dust proof. All the specimens of a particular species collected at a given
locality or by one expedition are entered in the catalogue. This greatly facilitates the
subsequent retrieval or distributional data and the preparation of faunistic
analyses. Cataloguing should be done after identifying the species. Catalogue entries
of fishes must contain the following items:
1. Consecutive museum number
2. Original field number
3. Scientific name
4. Sex
5. Exact locality
6. Date of collection
7. Name of collector
8. Method of capture
9. Depth of capture
10. Remarks
Chapter 5:Commerically Important Saw-Fishes, Skates and Rays
2.5.1 Diagnostic Characters of Commercially Important
Body more or less disc-shaped, rounded or sub-angular, flattened, with the pectorals
fused along the sides of the head. Eyes superior. Mouth inferior, more or less
protractile. Gill slits 5, inferrior. Spiracles present. Dorsal fins, when present, placed
on tail. No anal fin. Tail always redued, sometimes merely a filament. In many cases,
the early embryos show shark-like affinities in not having the pectorals joined to the
head, a fusion that occurs with development, occasional failures producing
monstrosities. In this order are well-known flattened bottom-dwelling fishes, abundant
and wide-spread, rather degenerate. The spiracles are of more importance to these
than to any other cartilaginous fishes, being used in breathing. Water is drawn in at the
gills and out via the spiracles, where the strong current may easily be felt by the
hand. Many of these fishes are of importance as food.

The group termed “batoid fishes” comprise a variety of forms commonly known as rays,
skates, saw-fishes and guitar-fishes.
1. Pristidae (Saw-fishes)
• Body rather elongate, snout usually pointed.
• Snout produced and saw-like toothed, bony.
• Posterior most rostral teeth ending well anterior two pairs of rostrum.
2. Rhinobatidae (Guitarfishes)
• Body rather elongate, snout usually pointed.
• Snout broad, soft and rounded. First dorsal fin triangular. It is orgin
anterior to base of pelvic fins.
• Eyes slightly smaller and entirely separated from spiracles.
3. Torpedinidae (Electric rays)
• Body either rounded or angular, laterally widened.

• Two Large electric organs in the front part of the disc on either side of
head, the eyes are quite small.
• Dorsal surface spotted against a brown background pale bellow.
Eg. Narcine timlei
4. Rajiidae (Skates)
• Body and head greatly depressed; united with pectorals forming a
rhomboidal disc.
• Tail ending up in blunt tip without caudal fin.
• Two dorsal fins posteriorly.
• Caudal fairly thick, dorsal fins distinct, small, near and end of caudal.
Eg. Raja mamillidens

5. Mobulidae (Devil rays and Manta rays)
• Winlike, enlarged pectoral fin.
• Caudal thin, dorsal fin feeble or absent.
• Snout produced as fleshy flap each side.
• Distinct modified cephalic organs in pair at head.
Eg. Mobula diabolus, Manta birostris
6. Myliobatidae (Eagle rays, Cownose rays)

• Head elevated above pectorals.
• Tail whip-like, longer than body length.
Eg. Aetobatus narinari
7. Dasyatidae
• Disc at most 1.3 times as broad aslong, tail much longer than disc width,
floor of mooth with several fleshy papillau.
• Snout normal.
• Head not elevated.
• One or two serrated spines in the tail.
Eg. Dasyatis zugei

3
Unit 3: Major Taxa of Marine Fishes- Major Classes
Chapter 1: General Introduction
3.1.1 Introduction
The study of organic diversity has changed its objectives and enlarged its scope in the
course of history as it happens in any branch of science. Our knowledge of biodiversity
is incomplete. Only 1.70 million of the earth’s estimated 10 - 100 million species have
been scientifically erected, named and classified. In the marine biota, 340000 species
are known including many unnamed species. It would be impossible to deal with the
enormous diversity if it were not ordered and classified. Systematic zoology solves this
problem and develop many methods and principles to make this task possible.
The systematic zoology is the science that discovers names, determines relationships,
classifies and studies evolution of living organisms. It is an important branch in biology
and is considered to be one of the major subdivisions of biology having a broader base
than genetics, biochemistry and physiology. Systematics includes taxonomy and the
term taxonomy is derived from the Greek word ‘taxis’ - arrangement and ‘nomos’ -
law. The name taxonomy was first proposed by Candolle (1813). Taxonomy is defined
as the theory and practice of classifying organisms. On the whole systematics is a
synthesis of many kinds of knowledge, theory and method applied to all kinds of
classification of organisms.
In taxonomy, the terminology classification overlaps with identification. The term
identification and classification are often confused among taxonomists. The
phraseology classification refers ordering of animals into groups on the basis of their
relationship. The population or groups of population are classified at all levels of

taxon. In the identification of a species, the individuals are placed by deductive
procedure to each taxon.
Taxonomy is classified into three stages. They are ‘alpha taxonomy’ which emphasis
only description of new species and its arrangement in comprehensive genera. In ‘beta
taxonomy’ the relationships are worked out on the species level and on higher
categories. In ‘gamma taxonomy’ emphasis is given to intra specific variations and its
evolutionary relationship and casual interpretation of organic diversity.
3.1.2 Marine Finfish taxonomy
Finfish taxonomy is the only subject in ichthyology which deals with populations,
species and higher taxa. No other branch in fisheries science occupies itself in a similar
manner with this level of integration in the organic world. The contribution of finfish
taxonomy to fisheries science has been both direct and indirect. For conservation and
management of our fishery resources the identification of finfishes is vital.
Ichthyotaxonomical study reveals numerous interesting evolutionary phenomena in
piscine phylogeny and the study is most indispensable for culturing fish fauna. The
correct identification of a particular candidate finfish for aquaculture is very important for
successful culture practices. On the whole taxonomic study on finfishes furnishes the
urgently needed information about species and it cultivates a way of thinking and
approaching of all biological problems which are much needed for the balance and well
being of fish biology as a whole.
Pisces are the most numerous, highly diversified groups exhibiting enormous diversity
in their morphology, in the habitats they occupy and in their biology. Fishes constitute
almost half the total number of vertebrates (Nelson, 1976). According to Cochen (1970),
the estimated number of fishes is about 20,000 - 22,000 and Nelson’s (1976) estimate
is 18,818 living fishes. Fishes can be simply defined as aquatic poikilothermic
vertebrates and have gills throughout their life span and limbs if any in the shape of fins.
Most fishes fall into one of six broad categories. They are rover-predator, lie-in-wait
predator, surface-oriented fish, bottom fish, deep bodied fish and eel like fish. Thus their
ecological diversity is reflected in variety of body shapes and means of locomotion they
possess. The modern living fishes could be broadly classified into two categories
namely, elasmobranchs and teleosts.
Chapter 2: Major taxa of marine fishes upto family level
3.2.1 Elasmobranch fishes
The shark, ray and skate are cartilaginous fishes and they all come under the class
Chondrichthyes. In global waters, about 600 - 700 species are represented in this
group. The cartilaginous group are considered as primitive compared to their counter
part, the bony fishes. Some of the members of cartilaginous fishes are specialized in

their own way as are the teleosts among bony fishes. This group could be distinguished
by the following characters:
1. Notochord constricted by vertebrae
2. Cartilaginous skeleton - The cartilage are calcified giving the appearance
of bone.
3. Swim bladder absent.
4. Skull lacks sutures in living forms.
5. Teeth usually not fused to jaws and replaced serially.
6. Nasal openings on each side usually single and more or less ventral in
position.
7. Intestinal spiral valve present.
8. Fertilization external or internal.
9. Males with pelvic claspers.
10. Embryo encapsulated in a leather like case.
The cartilaginous fishes come under the class Chondrichthyes. This class includes two
subclasses - viz. (i) Elasmobranchii and (ii) Holocephali.
The subclass, Elasmobranchii (sharks, rays and skates) includes 128 genera and 608
living species. The characteristics that are diagnostic to elasmobranchs are:
1. Five to seven gill openings with spiracle (secondarily lost in some
species).
2. Body covered with placoid scales.
3. Upper jaw not fused to cranium but attached with either amphistylic or
holostylic suspension.
4. Numerous teeth.
5. Cloaca present.
6. Males usually have intromittant organs.
The fossil forms of this group are recorded from Devonian time onwards.
The members, of the subclass Holocephali are called as ratfishes because of their long
slender tail. The chimaeras come under this subclass and about twenty five species are

represented in this group and most of the species come under the family,
Chimaeridae. The following are the diagnostic characters of this group:
1. Four gill openings and spiracle absent.
2. Upper jaw fused to skull.
3. Teeth few in number, large, flat plates.
4. Scales absent.
5. In males, claspers are seen on head region (in addition to the pelvic
claspers).
3.2.1.1 Elasmobranchii
Subclass Elasmobranchii
The subclass, Elasmobranchii includes the following superorders (Compagno, 1973):
1. Galeomorphii
2. Squatinomorphii
3. Squalomorphii
4. Batoidea
Superorder Galeomorphii
Galeomorph sharks have varied shapes. Some of the species differ markedly from the
typical body shape of a shark. This superoorder includes the following orders (living
groups):
1. Heterodontiformes
2. Lamniformes
Order Heterodontiformes
Popularly called as horn sharks and are considered to be ancestral group of living
elasmobranchs (Moyle et al., 1982). The members of this group are sluggish and are
shallow water bottom dwellers. This group contains a single family, Heterodontidae
having 6 species.
Order Lamniformes

This order includes seven families. They are i) Orectolobidae (nurse sharks), ii)
Odontaspididae (sand sharks), iii) Lamnidae (thresher sharks or mackerel sharks), iv)
Scyliorhinidae (cat sharks), v) Carcharhinidae (smooth sharks), vi) Sphyrnidae
(hammerhead sharks) and vii) Rhiniodontidae (whale sharks). This order has 56
genera and 200 species.
The typical sharks come under the family, Lamnidae and Carcharhinidae. The sharks
of this order are mostly pelagic forms, large with blade like teeth. Most of the members
of this group are highly predacious feeding on large fishes, squids, cuttlefishes and
marine mammals. Some of the sharks, Carcharodon carcharias, Isurus oxyrinchus and
Galeocerdo cuvieri are the man eating sharks.
The whale sharks (Rhiniodon typus) and the basking sharks (Cetorhinus maximus) are
not capable of biting attacks on humans and have developed mechanisms for straining
plankton. The whale shark attaining a maximum length of 18 m is considered as world’s
largest fish.
Superoorder Squatinomorphii
The angel sharks are represented in this superorder. This superorder includes a family
Squatinidae. The family includes one genus, Squatina having 11 species. The
members of this group appear to be intermediate between sharks and rays and shares
many characters of sharks and rays, at the same time possess its own
specifications. Because of these features, Compagno (1973) placed the angel sharks in
the superorder, Squatinomorphii. However, Nelson (1978) placed this group under the
superorder, Squalomorphii.
Superorder Squlomorphii
Though morphologically these sharks look like a ray with flattened body, yet the large
pectrol fins are not attached to head. Large spiracles are located on top of head, the
five gill openings are more laterally located with terminal mouth. Two dorsal fins are
located on the caudal region of the body and anal fins are wanting.
This superorder includes three orders namely, Hexanchiformes, Squaliformes and
Pristophoriformes. Six species are represented under the order, Hexanchiformes and
are deep water forms (Moyle and Ceech, 1982). Six or seven gill openings are

seen. This order includes two families namely, Chlamydoselachidae and
Hexanchidae.
Cow sharks coming under the order are rather flabby, bottom oriented sharks with weak
jaws and have small teeth. This group comes under the family, Hexanchidae. The
order, Squaliformes contains two families viz. Squalidae (dog fish sharks) and
Echinorhinidae (bramble sharks).
The order, Pristiophoriformes, the saw sharks, have teeth attached to their snout and is
extended as a long flat blade. The pristiophorids have many ray like characters and are
closely related to Batoidimorpha. Two genera and four species are included in this
family.
Superorder Batoidea
This superorder includes rays and skates having the following characters:
1. Gill openings ventral in position.
2. The pectoral fins enlarged, attached to side of head anterior to the five gill
openings.
3. No anal fins.
4. Eyes and spiracle located on the top of the head and pavement like teeth
present.
5. Nictitating membrane absent.
The members of this group are primarily adapted for bottom living and are benthic in
habitat. This superorder includes the following orders:
1. Rajiformes
2. Pristiformes
3. Torpediniformes
4. Myliobatiformes
3.2.2 Bony fishes
Subclass Elasmobranchii
The subclass, Elasmobranchii includes the following superorders (Compagno, 1973):

1. Galeomorphii
2. Squatinomorphii
3. Squalomorphii
4. Batoidea
Superorder Galeomorphii
Galeomorph sharks have varied shapes. Some of the species differ markedly from the
typical body shape of a shark. This superoorder includes the following orders (living
groups):
1. Heterodontiformes
2. Lamniformes
Order Heterodontiformes
Popularly called as horn sharks and are considered to be ancestral group of living
elasmobranchs (Moyle et al., 1982). The members of this group are sluggish and are
shallow water bottom dwellers. This group contains a single family, Heterodontidae
having 6 species.
Order Lamniformes
This order includes seven families. They are i) Orectolobidae (nurse sharks), ii)
Odontaspididae (sand sharks), iii) Lamnidae (thresher sharks or mackerel sharks), iv)
Scyliorhinidae (cat sharks), v) Carcharhinidae (smooth sharks), vi) Sphyrnidae
(hammerhead sharks) and vii) Rhiniodontidae (whale sharks). This order has 56
genera and 200 species.
The typical sharks come under the family, Lamnidae and Carcharhinidae. The sharks
of this order are mostly pelagic forms, large with blade like teeth. Most of the members
of this group are highly predacious feeding on large fishes, squids, cuttlefishes and
marine mammals. Some of the sharks, Carcharodon carcharias, Isurus oxyrinchus and
Galeocerdo cuvieri are the man eating sharks.
The whale sharks (Rhiniodon typus) and the basking sharks (Cetorhinus maximus) are
not capable of biting attacks on humans and have developed mechanisms for straining
plankton. The whale shark attaining a maximum length of 18 m is considered as world’s
largest fish.

Superoorder Squatinomorphii
The angel sharks are represented in this superorder. This superorder includes a family
Squatinidae. The family includes one genus, Squatina having 11 species. The
members of this group appear to be intermediate between sharks and rays and shares
many characters of sharks and rays, at the same time possess its own
specifications. Because of these features, Compagno (1973) placed the angel sharks in
the superorder, Squatinomorphii. However, Nelson (1978) placed this group under the
superorder, Squalomorphii.
Though morphologically these sharks look like a ray with flattened body, yet the large
pectrol fins are not attached to head. Large spiracles are located on top of head, the
five gill openings are more laterally located with terminal mouth. Two dorsal fins are
located on the caudal region of the body and anal fins are wanting.
Superorder Squlomorphii
This superorder includes three orders namely, Hexanchiformes, Squaliformes and
Pristophoriformes. Six species are represented under the order, Hexanchiformes and
are deep water forms (Moyle and Ceech, 1982). Six or seven gill openings are
seen. This order includes two families namely, Chlamydoselachidae and
Hexanchidae.
Cow sharks coming under the order are rather flabby, bottom oriented sharks with weak
jaws and have small teeth. This group comes under the family, Hexanchidae.
The order, Squaliformes contains two families viz. Squalidae (dog fish sharks) and
Echinorhinidae (bramble sharks). The order, Pristiophoriformes, the saw sharks, have
teeth attached to their snout and is extended as a long flat blade. The pristiophorids
have many ray like characters and are closely related to Batoidimorpha. Two genera
and four species are included in this family.
Superorder Batoidea
This superorder includes rays and skates having the following characters:
1. Gill openings ventral in position.
2. The pectoral fins enlarged, attached to side of head anterior to the five gill
openings.
3. No anal fins.

4. Eyes and spiracle located on the top of the head and pavement like teeth
present.
5. Nictitating membrane absent.
6. Rajiformes
The members of this group are primarily adapted for bottom living and are benthic in
habitat. This superorder includes the following orders:
3.2.2.1 Subclass Dipneusti
Lungfishes are placed in this group. They are all freshwater fishes with a long
independent evolutionary history. The living lungfish genera are Neoceratodus
(Australian lungfish - N. forsteri), Lepidosiren (South American lungfish - L. paradoxa)
and Protopterus (African lungfish).
3.2.2.2 Subclass Crossopterygii
The fringe finned fishes are represented in this group. Latimeria chalumnae, a living
species comes under this subclass. This species was discovered by J.L.B. Smith,
having distribution in South Africa and Comores Archipelago.
3.2.2.3Subclass Brachiopterygii
This subclass is represented by a single family, Polypteridae, which includes 10
species. The members of this group have ganoid scales and spiracle is present. The
fishes of this group respire with gills, supplementing them with lungs (e.g.,
Calamoichthys calabaricus).
3.2.2.4 Subclass Actinopterygii
The subclass, Actinopterygii, ray finned fishes contain most of the bony fishes. This is
divided into three infraclasses namely, Chondrostei, Holostei and Teleostei.
Chondrostei
Ganoid scales and a spiracle are present; heterocercal tail and interoperculum are
absent, 25 species are represented in this group.
Holostei
Two families namely, Lepisosteidae (gars) and Amiidae (bow fishes) are included in this
group. This infraclass includes two genera and 9 species.
Teleostei

Teleostei are the most diversified group of all vertebrates. This group includes about
18000 species placed in 31 orders, 455 families and 3869 genera (Nelson, 1976).
Chapter 3: Commercially important marine fishes of India
3.3.1 Order: Auguilliformes
· Pelvic fins and supporting bones absent
· Pectoral fins absent in some fishes
· Skeleton lack bony connection to skull
· Anal fin and dorsal fin join with caudal fin
· Scales are usually absent
· Gill rakers absent
· Large swimbladder present
· Body slender and elongate
· Leafy, transparent like leptocephali larvae
· Myomeres are more than 100 in larva
3.3.1.1 Anguillidae (Freshwater eels)
Small oval scales present, embedded in skin and arranged in a basket-weave pattern.
• Body elongate; snake like
• Dorsal fin origin aboe anus or very nearly so.
• Dorsal fin begins variously between pectoral fin and anus or over anus.
• No pelvic fin
• Lower jaw longer than upper, projecting; angle of mouth a little behind near margin of
eye
• Pectoral fins well developed
· Anus in the anterior half of the body
· Vertical slit like gill opening
· Lateral line complete on body and head

· Vertebrae 100 – 119
· Catadromy, migrate from freshwater to marine during spawning
· Leptocephali metamorphosis into elvers
Eg. 1. Anguilla bicolar bicolar
2. Anguilla bengalensis bengalensis
Similar Families
Congridae - No scales; lower jaw equal to, or shorter than upper; dorsal fin being above
or before pectoral lips.
Muraenesocidae - No scales; mouth very large extending to beyond eye; large gill
opening.
Ophichthidae - No scales; in most genera no caudal fin but tail tip a hard, burrowing
point; a median supraorbital pore present.
Muraenidae - No scales, no pectoral fin; gill opening a small hole.
Xenocongridae - Gill opening a small hole; reduced lateral line system/pectoral fins
present or absent.

3.3.1.2. Muraenidae (Morays)
• Commonly called as moray eel
• The dorsal profile above and behind the eye is steep
• Each gill opening restricted to a small, roundish, lateral hole or slit
• Dorsal fin and anal fin continuous around tail
• Pectoral and pelvic fins absent
• No lateral line pores on body, but a reduced complement of lateral line pores on
head, including typically 1 or 2 above and before gill opening (branchio lateral
line pores)
• No scales
• Gill opening is small round like
• Gill arches reduced
• Posterior nostril high in head
• Most of the fishes bear fang like teeth
• Number of vertebrate usually 110 -200
• Over 200 species are reported under 15 genera
Ex: Echidna, Gymnothorax, Muraena
Eg. Lucodontis meleagris

3.3.1.3 Family: Ophichthidae: worm eels and snake eels
· Elongate slender and cylindrical body
· Gill opening small
· No pectoral
. Dorsal fin originating about a pectoralfin length behind tips of pectoral fins.
· Vertebrae 171- 173
· Eg. Muraenichthys and Callechelys.
3.3.1.4 Muraenesocidae (pike congers)
• Body long to very long, more or less cylindrical in front, compressed along tail
• Mouth well developed and extends beyound eye
• Dorsal fin begins more or less above gill opening, snout very pointed. Mouth
terminal, extending well beyond eye
• No pelvic fiin
• No scales
• Teeth well developed and fang like
• Pectorals present
• Eyes large and covered with skin
• Body very long with only tail compressed

• Snout elongate
• Vertebrae 120-216
Eg. Muraenesox cinerons
3.3.1.5 Family : Nemichthyidae : Stipe eels
• Extremely long jaws, needle like
• body long and slender
• Pectoral fin present
• Eyes relatively large
• Anus far forward
• Ex. Nemichthys.
3.3.1.6 Congridae (Conger eels)
• Dorsal fin and anal fin continuous around tail
• Dorsal fin begins more or less above gill opening and originates before pectoral
fin tip
• No pelvic fins
• No scales
• Supratemporal pore in front of dorsal fin
• Robust body without scales.
• Lateral line complete
• Mouth not extending beyond eye
• Teeth well developed but no canines in jaw
• Lower jaw equal to or shorter than the upper jaw.
• Vertebrae 205 to 225.
Eg. Uroconger lepturus

3.3.2 Clupeiformes
3.3.2.1 Clupeidae (Herrings, Shads, Sardinellas, Sprats, Sardines)
• Scutes present along belly (absent in Dussumieria, Spratelloides)
• Fins lacking spiny rays
• Single dorsal fin
• No lateral line
• Caudal fin deeply forked
Eg. Amblygaster sirm, Dussumieria acuta, Herklotsichthys quadrimaculatus, Hilsa kelee
, Nematalosa nasus, Ilisha megaloptera, Sardinella albella, Spratelloides gracilis .
3.3.2.2 Engraulidae (Anchovies)
• Scutes present along belly
• Snout pig-like and projecting, lower jaw characteristically ‘underslung’

• Hind tip of upper jaw (Maxilla) extending far backward, sometimes projecting
beyond gill cover
• Single dorsal fin. No spiny rays in fins, no lateral line.
• Snout usually pig-like and projecting, lower jaw characteristically under slung.
Eg. Coilia dussumieri, Stolephorus indicus, Thryssa vitirostris

Similar Families
Clupeidae - Short maxilla; lower jaw deep; mostly mouth terminal.
Atherinidae - Terminal mouth; short upper jaw; 2 dorsal fins; no scutes along belly.
3.3.2.3 Chirocentridae (Wolf-herrings)
• Very elongate, highly compressed fishes resembling the clupeidae but without
scutes along belly
• Large canine teeth in both jaws
• A single dorsal fin set well behind midpoint of body; pectoral fins set low on body
• Pelvic fins about equidistant between pectoral base and anal origin
• Caudal fin deeply forked
Eg. Chirocentrus dorab
Similar Families
• Lack canine teeth.
• May have scutes along belly (Clupeidae).
• Dorsal fin more advanced (Engraulidae) or two dorsal fins and body rounded
(Sphyraenidae).

3.3.3 Siluriformes
Order: Siluriformes
Mesopterygoid very reduced
Pre opercle and inter opercle relatively small
Adipose fin usually present
Spine like (=spinous) rays present at the front of the dorsal and pectoral fins
Dorsal fin of most cat fishes has two spines; The first being very short and forming a
locking mechanism for the second spine.
Body either naked or covered with bony plates.
Usually up to barbells present on head
The nasal and chin barbels may be variously absent.
Maxilla toothless and rudimentary (except in Diplomystidae and the extinct
Hypsidoridae)
Caudal fin rays 18 or fewer (most with 17)
Caudal skeleton varying between having six separate hypural plates to complete fusion
of caudal elements.
Eye usually small
Air breathing organs present in Claridae and Heteropreustidae
Many cat fishes have a maximum length of below 12 cm. The largest cat fish is Silurus
glanis (commonly reaches 3m in length)
Pangasiid and Pimelodid are also known to reach exceptionally large sizes.
Siluriformes consists of
Families : 34
Genera : 412
Species : 2,405
Of which, about 1,440 species are presently available.

Ariidae and Plotosidae consist largely of marine species but also representatives that
are frequently found in brackish, coastal waters and sometimes only in fresh water.
Other families are freshwater, although some have species that can invade brackish
water.
3.3.3.1 Ariidae (Marine catfishes)
• Snout and head rounded to depressed
• 1-3 pairs of barbels present
• Head covered with a bony shield
• A short adipose dorsal fin present
• First dorsal fin short with a short spine or buckler.
• Two pairs of adjacent nostrils on each side of snout.
Eg. Osteogeneiosus militaris, Batrachocephalus mino, Arius dussumieri
Similar Families
All other catfish - Either have widely separated nostrils, a barbel on posterior nostril or
dorsal fin and anal fin continuous with caudal fin.
Plotosidae - Pelvic fin with 12 to 14 rays; A dendric apparatus present.
3.3.3.2 Plotosidae (Stinging catfishes/coral reef catfishes/eel catfishes/barbel

eels)
• Elongate body, compressed, tapering to a point posteriorly
• 4 pairs of barbels present with 1 pair nasal, 1 pair maxillary and 2 pairs mental;
• First dorsal fin short-based with a serrated spine and 4-6 soft rays; second dorsal
fin (or dorsal procurrent caudal fin), caudal fin and anal fin confluent
• Absence of adipose fin
• Pectoral fins with 1 serrated spine and 9 to 16 soft rays
• A dendritic organ consisting of many vascularised epithelial folds present directly
posterior to anus
• Caudal fin rounded or pointed
Eg. Plotosus lineatus
Similar Families
All other catfish families- Dendritic organ absent.
Ariidae / marine catfishes- Forked caudal fin; adipose fin present; anal and caudal fins
not confluent; 3 pairs of barbels present.
Clariidae and Heteropneustidae- Spines in dorsal fin absent.
Bagridae - Adipose fin present; caudal fin forked; anal and caudal fin not confluent.
Charcidae - Anal and caudal fins not confluent; origin of 2 nd dorsal fin not opposite to
pelvic fin origin.
3.3.4 BELONIFORMES
Either snout beak like with upper jaw or lower jaw greatly prolonged or enlarged Wing
like pectoral fin, sometime pectoral or pelvic fin present Lateral line near ventral profile
of the body.

A single dorsal fin consists of soft rays located in the posterior part of body Pelvic fin is
in abdomen
3.3.4.1 Belonidae (Needle fishes)
• Elongate fishes with both upper and lower jaws extended into long beak
• Dorsal and anal fins posterior in position
• Pelvic fins located in abdominal position
Eg. Strongylura leiura, Tylosurus crocodilus crocodilus
Similar Families
Hemiramphidae - Only lower jaw prolonged or none of the jaw prolonged.
- Lacking needle-sharp teeth.
Sphyraenidae - Jaws pointed but not prolonged into a beak; 2 dorsal fins; the first spiny;
pelvic fins thoracic in position.
Exocoetidae (Flyingfishes)
3.3.4.2 Exocoetidae (Flyingfishes)
• Pectoral fins high on sides, strikingly long, always extending beyond dorsal fin
origin.
• Pelvic fins abdominal in position and greatly enlarged in many.
• Caudal fin deeply forked with lower lobe longer than the upper.
Eg. Cheilopogon furcatus

Similar Families
Hemiramphidae - Pectoral fins short to medium never reaching dorsal fin origin; lower
jaw much longer than upper jaw.
3.3.4.3 Hemiramphidae (Halfbeaks)
• Elongate fishes with a prolonged lower jaw (except Oxyporhampus) and a short
triangular upper jaw.
• Dorsal and anal fins posterior in position; pelvic fins in abdominal position.
• Lateral line running down from pectoral fin origin and then backward along
ventral margin of body.
Eg. Hemiramphus fur
Similar Families
Belonidae (needle fishes) - Both upper and lower jaws elongated and armed with
needle sharp teeth.
Exocoetidae (flying fishes) - Lack the prolonged lower jaw characteristic of most half
beaks; pectoral fins or both pectoral and pelvic fins enlarged and used for aerial gliding.

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