1. Humans and the Sea --
Fisheries, management, and
sampling
• Millions of people depend on
fisheries… in what ways?
– Food
• 86 million tons/year
– Jobs
– Products & materials
– Recreation & entertainment
• Sport fishing
• Diving & tourism
• Aquarium trade
2. Fig. 17.2
Lots of people in the world…
and, like other natural
predator/prey relationships,
we take advantage and
harvest many marine
organisms
…thus, competition for
resources
Marine ecosystems provide
over 30% of worldwide
animal protein consumption
How much is this?
3. Are these levels sustainable? How do we prevent
overfishing?
– Depends on what, where, and current practices
4. …stresses on fisheries
– What is the 2010 demand for
fish?
• 10-40 million tons above
production
• Cultural practices,
consumption, etc., varies
worldwide
– E.g. average fish
consumption/person/year
• Japan = 37.7 lbs
• U.S. = 16.6 lbs
5. • Where are the richest fishing grounds?
– Areas of upwelling, bordering continental shelf where primary production is higher
• Most of the largest takes are around industrial nations
– Exploited for the longest time
• Most fishing grounds in Atlantic, Pacific, Mediterranean are in decline or
exhausted
Why and How is this happening?
Fig. 17.4
6. • Gill net: Northeast and worldwide
– panel of webbing of clear monofilament
line; can be set at any depth; fish can’t see
the net, so they swim right into it and are
caught.
– Lots of bycatch (“junk”/non-target) --
animals that are too large to pass through
the webbing (mammals, turtles, etc.)
• Purse seines:
– Vertical, weighted net encircling
aggregates; pulls bottom closed
(drawstring) preventing fish from
swimming down
– Unintended bycatch; i.e. dolphin, sharks,
sea turtles
• Hook and line, and long-line:
– Commercial rigs can setup miles of
unselective longlines (lots of bycatch)
– hard to be selective with this gear…but,
possible. E.g., choosing bait, jigs, lures,
and hook sizes known to catch their target
species.
• Trawls / Bottom trawl: single most
important fishing method in the Northeast
– produces the most noticeable bycatch
problem & demolishes the environment
– bottom trawl is a funnel-shaped net that is
dragged on the bottom of the sea
– Mortality: damaged in the net, brought up
from the depths too quickly, or thrown
back too late.
Fig. 17.6
7. • What are the most
important fish?
– Schooling fish
• Herring, sardines,
anchovies…
• Over continental shelf
& upwelling areas
• Caught by purse seines
– Demersal cold-water fish
• Cod, pollock,
haddock…
• E.g. Alaska pollock is
largest fishery of U.S.
• Caught by trawls
• Over exploited; closed
many fisheries in the
last decade
– Open-ocean fish
• Tuna (skipjack,
yellowfin, albacore,
bigeye, bluefin)
• Caught by seines,
longlines, and gill nets
8. Can we use methods that are
more sustainable and
environmentally responsible?
• Harpooning
– Harpooners catch large, pelagic
predators such as bluefin tuna and
swordfish.
• Hook and Line
– Hook and liners target a variety of
fish, ranging from open ocean
swimmers, like tuna and mahi
mahi, to bottom dwellers, like cod
• Trolling
– Trollers catch fish that will follow
a moving lure or bait, such as
salmon, mahi mahi and albacore
tuna.
9. Fig. 17.10
Policies, regulations, &
enforcement
• Balance between population size,
natural mortality, and fisheries
Sustainable?
# of fish caught ≤ # fish reproduced
• Use sustainable fishing methods
(globally, change our ways) to prevent
population / fisheries collapse
10. Example of sustainable commercial fishery
• http://www.youtube.com/watch?
v=i5mMI8t7vV0&feature=related
13. Fig. 17.12
• Mariculture / Aquaculture
– Farming
• Open vs. closed
• Pros vs. Cons
– High production at expense
to environment; ie, wild
populations, disease,
pollution, etc.
– Use of genetics & biotech
• Faster growth, disease
resistance, etc.
– Salmon, shrimp
• Local sustainable mariculture
– www.carlsbadaquafarm.com
• Local restoration projects
– http://www.pier.org
14. Human Impacts – our role, impacts, and responsibilities
• Habitat destruction
– Fisheries
– Resource management
– Recreation
– Aquaculture
• Pollution
– Coastal runoff
– Sewage
– Oil
• Introduced species
– Invasive / pest species
What can we do instead?
• MPA
– Marine Protected Areas
• Know our impacts and
respect that we are just one
species of nature
• Be an informed consumer
• Reduce, reuse, recycle
