That brings us to Shelley's second cause of overfishing capital investments. Technology, the third prong of the problem, has not only caused a dip in desirable species, it has killed fish that weren't even meant to be caught. When the fine-meshed trawl nets needed to trap shrimp in the Gulf of Mexico are hauled up, for instance, they hold an average of 50 to 90 percent bycatch of fish. Among them are lots of young red snapper, which die in the nets and are too small to sell. The National Academy of Sciences estimates bycatch at about one-quarter of the annual catch worldwide.
Technology can also destroy fish habitats.
Many commercially desirable species, including scallops, shrimp, flounder, cod, and rockfish, live on or near the ocean bottom. Even if overfishing doesn't harm habitat, it can alter predator-prey relationships. In the Gulf of Mexico, overfishing of menhaden has contributed to an explosion in the population of jellyfish, which compete with menhaden for food. In the Gulf of Maine, the decline of cod opened the neighborhood to dogfish, small sharks that compete with and sometimes eat cod but aren't as commercially valuable. The federal government delegates most regulatory decisions to eight regional fishery-management councils, made up mainly of representatives from the fishing industry and government, with others from environmental and consumer groups.