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

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

Fig. 17.2

How much is this?

Are these levels sustainable? How do we prevent overfishing?– Depends on what, where, and current practices

…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

• 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

• 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

• 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

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.

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

Fig. 17.10

Example of sustainable commercial fishery

• http://www.youtube.com/watch?v=i5mMI8t7vV0&feature=related

Research and Restoration provides evidence/data to inform regulations

• “spaghetti” tags

• Archival tags

• Satellite tags

• Acoustic telemetry

• 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

Fig. 17.12

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