5. Overfishing and overdiscarding may thus contribute to a syndrome known as “fishing down of
food webs,” whereby we eliminate apex (top) predators and large species while transforming the
ocean into a simplified system increasingly dominated by microbes, jellyfish, ocean-bottom
invertebrates, plankton, and planktivores. The strongest evidence for the fishing down phenomenon
exists in global catch statistics that show alarming shifts in species composition from high-value,
near-bottom species to lower-value, open-ocean species. In the last three decades of the twentieth
century, the global fishing fleet doubled in size and technology advanced immeasurably. Despite
increased effort and technology, total catch stabilized, but landing rates (rates at which species are
caught) of the most valuable species fell by 25 percent.
6. Conservation organizations have condemned the obvious and extreme waste associated with
bycatch. Public concern over high mortality rates of endangered marine turtles captured in shrimp
trawls led to the development of turtle exclusion devices (TEDs) in the 1980s. TEDs were
incorporated into the shrimp net design with the purpose of directing turtles out of nets without
unacceptably reducing shrimp catches. Marine engineers and fishers also developed shrimp net
designs that incorporate bycatch reduction devices (BRDs), taking advantage of behavioral
differences between shrimp and fish, or between different fishes, in order to separate fishes.
food webs,” whereby we eliminate apex (top) predators and large species while transforming the
ocean into a simplified system increasingly dominated by microbes, jellyfish, ocean-bottom
invertebrates, plankton, and planktivores. The strongest evidence for the fishing down phenomenon
exists in global catch statistics that show alarming shifts in species composition from high-value,
near-bottom species to lower-value, open-ocean species. In the last three decades of the twentieth
century, the global fishing fleet doubled in size and technology advanced immeasurably. Despite
increased effort and technology, total catch stabilized, but landing rates (rates at which species are
caught) of the most valuable species fell by 25 percent.
6. Conservation organizations have condemned the obvious and extreme waste associated with
bycatch. Public concern over high mortality rates of endangered marine turtles captured in shrimp
trawls led to the development of turtle exclusion devices (TEDs) in the 1980s. TEDs were
incorporated into the shrimp net design with the purpose of directing turtles out of nets without
unacceptably reducing shrimp catches. Marine engineers and fishers also developed shrimp net
designs that incorporate bycatch reduction devices (BRDs), taking advantage of behavioral
differences between shrimp and fish, or between different fishes, in order to separate fishes.
