implication is that the addition of a higher predator, i.e., the fishery, may not be possible."
The above conclusion does not imply that no sustainable deep-sea fisheries are possible. A few localized fisheries have been conducted for many decades, apparently sustainably, such as the Madeira fishery for black scabbardfish (Aphanopus carbo) (Merrett and Haedrich 1997). But technological improvements and economic considerations such as the need to recoup capital investments have generally led recent large-scale deep-sea fisheries to deplete their target species. Management of such fisheries is made especially difficult by the lack of information, the lack of institutional authority when the fish are outside all countries' jurisdictions, and the very long generation times of most deep-sea fishes. Those factors make it even harder than usual to evaluate the effects and effectiveness of management.
In addition to catching fish and other target species, fishing can affect ecosystems in other ways, most significantly through mechanical changes to the bottom caused by dragging fishing gear across it. Auster et al. (1996) described the effects of mobile bottom-fishing gear on the seafloor communities of the Gulf of Maine. At Swans Island, a conservation area that had been closed since 1983 was compared in 1993 with adjacent sites outside the area. At Jeffreys Bank, surveys made in 1987 were compared with surveys in 1993, after a new type of mobile bottom-fishing gear had allowed fishing on the rock-strewn bottom. Stellwagen Bank, a heavily fished area, was observed in 1993 and 1994. At all sites fished, significant and large reductions in various components of the benthic community had occurred. In some cases the changes (and losses of animals) were observed in the paths of scallop dredges and trawls; at Jeffreys Bank, the previously protected areas (because of the large rocks) showed large losses of benthic communities after the new gear allowed fishing there.
Auster et al. (1996) and Dayton et al. (1995) reviewed literature showing significant effects of bottom-fishing gear, including reduction of habitat complexity and destruction of physical refuges for animals (including biotic structures such as the tubes of tube-worms). They concluded that those processes directly reduced the diversity and productivity of many benthic communities and indirectly could affect such processes as recruitment, growth, and reproduction of many species, including commercially important ones. It seems likely that large areas of continental-shelf waters worldwide have been affected by bottom fishing, and some deepwater areas (up to 1,000m) could have been affected as well, depending on the gear rigging and type and the substrate. Lenihan and Peterson (1998) described the degradation of oyster reefs caused by oyster-dredging in Chesapeake Bay and North Carolina's Neuse River, and showed that the physical degradation interacts with water quality to cause the observed pattern of oyster