© 2011 Pearson Education, Inc. Emptying the Oceans : The state of ocean fisheries Marine protected areas and reserves

© 2011 Pearson Education, Inc. Emptying the oceans Overharvesting is the worst marine problem We are putting unprecedented pressure on marine resources -Half the world’s marine fish populations are fully exploited and can’t be fished more intensively -28% of fish population are overexploited and heading to extinction Total fisheries catch leveled off after Despite increased fishing effort The maximum wild fisheries potential has been reached

© 2011 Pearson Education, Inc. The global fisheries catch has increased It is predicted that populations of all ocean species we fish for today will collapse by 2048

© 2011 Pearson Education, Inc. We have long overfished People began depleting sea life centuries ago Species have been hunted to extinction: Caribbean monk seal, Steller’s sea cow, Atlantic gray whale Overharvesting Chesapeake Bay oyster beds led to its collapse, eutrophication, and hypoxia Decreased sea turtle populations cause overgrowth of sea grass and can cause sea grass wasting disease Overharvesting nearly exterminated many whale species People never thought groundfish could be depleted -New approaches or technologies increased catch rates

© 2011 Pearson Education, Inc. Fishing has industrialized Factory fishing = huge vessels use powerful technologies to capture fish in huge volumes -Even processing and freezing their catches at sea Driftnets for schools of herring, sardines, mackerel, sharks, shrimp Longline fishing for tuna and swordfish Trawling for pelagic fish and groundfish

© 2011 Pearson Education, Inc. Fishing practices kill nontarget animals Bycatch = the accidental capture of animals Drift netting drowns dolphins, turtles, and seals -Fish die on deck -Banned in international waters -But it is still used in national waters Longline fishing kills turtles, sharks, and over 300,000 seabirds/year -Methods (e.g., flags) are being developed to limit bycatch

© 2011 Pearson Education, Inc. Dolphins and tuna Dolphins are trapped in purse seine nets used to catch tuna -Hundreds of thousands of dolphins were killed The 1972 Marine Mammal Protection Act forced fleets to try to free dolphins -Bycatch dropped dramatically Other nations fished for tuna, and bycatch increased The U.S. government required that nations exporting tuna to the U.S. minimize dolphin bycatch -Dolphin-safe tuna uses methods to avoid bycatch

© 2011 Pearson Education, Inc. Dolphin deaths have declined, but … Other animals (e.g., sharks) are still caught Dolphins have not recovered -Too few fish to eat Rules and technology have decreased dolphin deaths

© 2011 Pearson Education, Inc. Bottom-trawling destroys ecosystems Heavy nets crush organisms and damage sea bottoms -It is especially destructive to complex areas (e.g., reefs) It equals clear-cutting and strip mining -Georges Bank has been trawled three times -Destroying young cod as bycatch -The reason the cod stock is not recovering

© 2011 Pearson Education, Inc. Modern fleets deplete marine life rapidly Grand Banks cod have been fished for centuries -Catches more than doubled with industrial trawlers -Record-high catches lasted only 10 years George Bank cod fishery also collapsed

© 2011 Pearson Education, Inc. Industrialized fishing is destroying fisheries Worldwide, industrialized fishing is depleting marine populations with astonishing speed -90% of large-bodied fish and sharks are eliminated within 10 years after fishing begins -Populations stabilize at 10% of their former levels Communities were very different before modern fishing -Removing animals at higher trophic levels allows prey to proliferate and change communities Oceans today contain only one-tenth of the large-bodied animals they once did

© 2011 Pearson Education, Inc. Several factors mask declines Industrialized fishing has depleted stocks -But global catch has remained stable for the past 20 years How can stability mask population declines? -Fishing fleets travel farther to reach less-fished areas -Fleets fish in deeper waters (now at 250 m) -Fleets spend more time fishing and set more nets -Improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting Fleets expend more effort to catch the same number of fish

© 2011 Pearson Education, Inc. We are “fishing down the food chain” Figures on total global catch do tell the whole story 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 more abundant species -Shifting from large, desirable species to smaller, less desirable ones -This entails catching species at lower trophic levels

© 2011 Pearson Education, Inc. Purchasing 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 -Avoid: Atlantic cod, wild- caught caviar, sharks, farmed salmon Best choices: farmed catfish, mussels, oysters, tilapia

© 2011 Pearson Education, Inc. Diversity loss erodes ecosystem services Factors that deplete biodiversity threaten ecosystem services of the oceans Systems with reduced species or genetic diversity show less primary and secondary production -They are less able to withstand disturbance Biodiversity loss reduces habitat for nurseries for fish and shellfish Less diversity leads to reduced filtering and detoxification -Resulting in algal blooms, dead zones, fish kills, beach closures

© 2011 Pearson Education, Inc. Fisheries management Based on maximum sustained yield to maximize harvest -While keeping fish available for the future -Managers may limit the harvest or restrict gear used Despite management, stocks have plummeted -It is time to rethink fisheries management Ecosystem-based management shifts away from species and toward the larger ecosystem -Considers the impacts of fishing on habitat quality, species interactions, and long-term effects -Sets aside areas of oceans free from human interference

© 2011 Pearson Education, Inc. IV Emptying the Oceans 1.Describe the trends in global fish capture over the past 55 years and over the past 20 years, and 2.Describe an example of how overfishing can lead to ecological damage and fishery collapse 3.Name three industrial fishing practices, and explain how they create by catch and harm marine life.