Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fish Harvesting Marine Ecosystems

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Central Case: Collapse of the Cod Fisheries No fish has more impact on human civilization than the Atlantic cod Eastern Canadians and U.S. fishermen have fished for cod for centuries Large ships and technology have destroyed the cod fishery Even protected stocks are not recovering -Prey may now be competing with, and eating, young cod

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Cod are groundfish They live or feed along the bottom -Halibut, pollock, flounder Cod eat small fish and invertebrates They grow to cm long and can live 20 years Inhabit cool waters on both sides of the Atlantic There are 24 stocks (populations) of cod

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Emptying the oceans We are placing unprecedented pressure on marine resources -Half the world’s marine fish populations are fully exploited -25% of fish population are overexploited and heading to extinction Total fisheries catch leveled off after 1998, despite increased fishing effort -It is predicted that populations of all ocean species we fish for today will collapse by the year 2048

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The total global fisheries catch has increased

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings We have long overfished People began depleting sea life centuries ago Some species hunted to extinction: Steller’s sea cow, Atlantic gray whale, Caribbean monk seal Overharvesting of Chesapeake Bay oyster beds led to the collapse of its fishery, eutrophication, and hypoxia Decreased sea turtle populations causes overgrowth of sea grass and can cause sea grass wasting disease People never imagined that groundfish could be depleted -New approaches or technologies increased catch rates

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fishing has industrialized Factory fishing = highly industrialized, huge vessels use powerful technologies to capture fish in huge volumes -Even process and freeze their catches while at sea Driftnets for schools of herring, sardines, mackerel, sharks Longline fishing for tuna and swordfish Trawling for pelagic fish and groundfish

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Beam Trawl Opening of net kept open by a beam

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Demersal Otter Trawl Large cone shaped net towed across the seabed; Forward part of net kept open by otter boards; Fish herded between boards into mouth of trawl swimming until exhausted, then drift back through net funnel into codend

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Drift Net Mobile – drift with prevailing currents; used on high seas; tuna, squid, shark, salmon, swordfish, albacore; Threat to dolphins, etc.

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gill or Fixed Nets Fish try to swim through, get caught, attempts to back out and caught by gills;

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Trammel nets Wall of net divided into 3 layers; anchored at base, floated by headline; inner net looser than outer 2, ensuring fish become entangled in it;

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Jigging Mostly for squid; jerk in water to snag fish in its body

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Long Lining Long line with baited hooks; threat to seabirds and dolphins and turtles

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings `Pelagic trawl Between seabed and surface; target fish swimming; seabass, mackerel, herring; also catches marine mammals that eventually drown

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Purse seining Encircling school of fish with a large wall of net; captures large, dense shoals of mobile fish such as tuna, mackerel, herring

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fishing practices kill nontarget animals By-catch = the accidental capture of animals Driftnetting drowns dolphins, turtles, and seals -Fish die from air exposure on deck -Banned or restricted by many nations Longline fishing kills turtles, sharks, and albatrosses -300,000 seabirds die each year Bottom-trawling destroys communities -Likened to clear-cutting and strip mining

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Modern fishing fleets deplete marine life rapidly Grand Banks cod have been fished for centuries Catches more than doubled with immense industrial trawlers -Record-high catches lasted only 10 years

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Industrialized fishing depletes populations Catch rates drop precipitously with industrialized fishing -90% of large-bodied fish and sharks are eliminated within 10 years -Populations stabilize at 10% of their former levels Marine communities may have been very different before industrial fishing -Removing animals at higher trophic levels allows prey to proliferate and change communities

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Oceans today contain only one-tenth of the large-bodied animals they once did

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Several factors mask declines Industrialized fishing has depleted stocks, global catch has remained stable for the past 20 years -Fishing fleets travel longer distances to reach less- fished portions of the ocean -Fleets spend more time fishing and have been setting out more nets and lines, increasing effort to catch the same number of fish -Improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting -Data supplied to international monitoring agencies may be false

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings We are “fishing down the food chain” Figures on total global catch do not relate the species, age, and size of fish harvested As fishing increases, the size and age of fish caught decline -10-year-old cod, once common, are now rare As species become too rare to fish, fleets target other species -Shifting from large, desirable species to smaller, less desirable ones -Entails catching species at lower trophic levels

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Consumer choices influence fishing practices Buy ecolabeled seafood -Dolphin-safe tuna Consumers don’t know how their seafood was caught -Nonprofit organizations have devised guides for consumers -Best choices: farmed catfish and caviar, sardines, Canadian snow crab -Avoid: Atlantic cod, wild-caught caviar, sharks, farmed salmon

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fisheries management Based on maximum sustained yield -Maximum harvest while keeping fish available for the future -Managers may limit the harvested or restrict gear used Despite management, stocks have plummeted -It is time to rethink fisheries management Ecosystem-based management -Shift away from species and toward the larger ecosystem -Consider the impacts of fishing on habitat and species interactions -Set aside areas of oceans free from human interference

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings We can protect areas in the ocean Marine protected areas (MPAs) = established along the coastlines of developed countries -Still allow fishing or other extractive activities Marine reserves = areas where fishing is prohibited -Leave ecosystems intact, without human interference -Improve fisheries, because young fish will disperse into surrounding areas Many commercial, recreation fishers, and businesses do not support reserves

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Reserves work for both fish and fisheries Found that reserves do work as win-win solutions Overall benefits included… -Boosting fish biomass -Boosting total catch -Increasing fish size Benefits inside reserve boundaries included… -Rapid and long-term increases in marine organisms -Decrease mortality and habitat destruction -Lessen the likelihood of extirpation of species

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Areas outside reserves also benefit Benefits included… -A “spillover effect” when individuals of protected species spread outside reserves -Larvae of species protected within reserves “seed the seas” outside reserves -Improved fishing and ecotourism

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Conclusion Oceans cover most of our planet and contain diverse topography and ecosystems We are learning about the oceans and coastal environments, intensifying our use their resources and causing severe impacts Setting aside protected areas of the ocean can serve to maintain natural systems and enhance fisheries We may once again attain the ecological systems that once flourished in our waters