Fish Conservation damage all reef corals to some degree Widespread death of corals, of course, has potentially severe implications for coraldependent fish and human communities Coral reefs are the oldest and largest structures built by living things When scientists first surveyed them in the 1950s and 1960s, most coral reefs were poised on the edge of profound change in the composition and abundance of species and the functioning of coral reef communities For example, Caribbean overfishing had already depleted herbivorous fishes to very low levels when algae-eating sea urchins crashed from a disease (Roberts, 1995) Without herbivores, algae overgrew corals, killing them over large areas, and altering the community Conversely, heavy fishing off East Africa depleted fish that prey on coral-eating sea urchins With their predators largely fished-out, the urchin populations exploded to densities that were 100 times the normal, and proceeded to inflict significant damage to reefs The depletion of predator fishes has also been implicated in destructive outbreaks of the coraleating sea star known as the crown-of-thorns Such ecological changes affect large communities of organisms Fishing often kills corals directly when people use explosives to kill fish, or pound the coral with rocks tied to lines to scare fish toward nets, or use cyanide to stun fishes All of these methods cause extensive destruction of coral reefs, through either breakage or, in the case of cyanide, death to corals by poisoning Coral reef systems are perhaps more sensitive to environmental change than most other marine ecosystems For various reasons, species of algae may overtake a damaged reef preventing corals from recovering or recolonizing Many coral reefs are now degraded by human activities, their fish communities modified, and the living corals replaced by algae growing on dead corals The Caribbean region has lost 80% of its live coral since the 1970s because of overfishing, diseases, algal overgrowth, sewage overfertilization, and smothering silt running off deforested land areas Some scientists believe these changes may be very long-lasting Aside from coral reef areas, continental shelves nearly everywhere are affected by bottom trawling – the towing of large bag-shaped nets or shellfish dredges over the seafloor Trawling is the fishing method that takes half of the world catch The vast majority of the world’s seabed is encrusted or honeycombed by living things, and trawling causes enough incidental damage of nontarget invertebrates, plants, shellfishes, and fishes to cause major community changes over large areas Trawling crushes, kills, exposes, and removes these living sources of nourishment and hiding places, making life dangerous for young fishes and almost certainly lowering the habitat’s capacity to produce abundant fish populations In one study of a scallop fishery, only 12% of the scallops in an area were actually caught, but many of those not caught were crushed by scallop dredges Until recently, trawlers were unable to work on high-relief, bouldery, or rubble-strewn bottom habitats without risking hanging up and losing their nets and gear But nowadays, new kinds of trawls make every kind of seabed – whether silt, sand, clay, gravel, cobble, boulder, rock reef, worm reef, mussel bed, seagrass flat, sponge bottom, or coral reef – vulnerable to trawling Furthermore, trawls hit many areas repeatedly each year The seafloor structures that juvenile fishes rely on are 453 often easily destroyed by bottom trawls, which kill or disperse the organisms that create those structures Our focus on extracting edible fishes at all costs has effectively blinded fishery managers to the essential food and shelter that these fish themselves require Trawling is not uniformly bad for all species or all bottom habitats, and in fact some species better in trawled than in undisturbed habitats (just as a few species better in logging clear-cut areas) But most species are not helped by trawling, and some communities are seriously damaged Recovery of certain bottom communities could require up to a century even if trawling was stopped today Writing in the journal Nature, Daniel Pauly and Villy Christensen observed that, ‘‘Contrary to some terrestrial systems such as rainforests, of which large undisturbed tracts still exist,y the overwhelming bulk of the world’s trawlable shelves are impacted by fishing, leaving few sanctuaries where biomasses and biodiversity remain high.’’ The Course Ahead Marine Protected Areas In times past, fisheries benefited from de facto refuges: undiscovered locations or places too deep or remote to probe But now, because of new technologies, when fish run they cannot hide Facing this reality, some scientists have proposed that simply closing some areas to fishing and resource extraction, to allow them to function naturally, while leaving adjacent areas open, is the best way to manage fishing These closed areas have been suggested especially where precise estimates on population sizes and sustainable catch levels are lacking and where gathering lots of data or intensive management and monitoring are impractical Such marine reserves allow fish to go through their normal patterns of growth, abundance, reproduction, genetic diversity, and community structure Marine reserves can (1) protect critical spawning adults, (2) maintain natural size and age structure, (3) maintain genetic diversity, (4) prevent serial overfishing, where one species and then the next and the next are depleted, (5) maintain natural communities, while allowing fishing to continue nearby, and (6) provide scientific areas for the study of more naturally functioning systems (Norse, 1993) A global review (Halpern, 2003) of marine protected areas (MPA) determined that within reserves, fish sizes are 30% larger, densities are double, and biomass levels are triple compared with unprotected areas Over 5000 MPAs exist, but they cover less than 1% of the world’s ocean And even in many reserves, fishing is allowed Fishing, for example, is allowed in all US National Marine Sanctuaries Marine reserves have been established in several parts of the world, and as populations recover, fish reach their normally evolved maximum size, and their offspring begin wandering outside the reserve, they can increase fish yields in adjacent areas In the Philippines, catches adjacent to one reserve tripled within two years of the reserve’s designation In a small Caribbean reserve, overall biomass of commercially important species increased 60% and snappers increased 220% in two years; but groupers did not increase, probably because severe depletion eliminated any source of larvae