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Effects of Trawling and Dredging on Seafloor Habitat
Effort reduction is the cornerstone of managing the effects of fishing, including, but not limited to, the effects on habitat. However, effort reduction alone is insufficient to address all circumstances in which fishing gear disturbs bottom habitat. The success of fishing effort reduction depends on the resilience and recovery potential of the habitat. Each of the other management tools generally requires effort reduction to achieve maximum benefit.
Gear modifications will be most useful for finfish species that can be caught with gear that does not rely on disturbing the bottom to catch the fish. This could include shifts to a different gear type, such as long lines or fish traps, but the social and economic consequences of such reallocation must be recognized and addressed. Also, the overall ecological benefits of using another, and often less efficient, type of gear, can be reduced if there is a subsequent increase in fishing effort or if there is significantly higher bycatch with the alternative gear.
Closed areas are necessary to protect a range of representative habitats. Closures are particularly useful for protecting areas with emergent epifauna (e.g., corals, bryozoans, hydroids, sponges) that are vulnerable to even low levels of fishing effort. As evidenced by the case of Georges Bank (Box 6.2), damage to emergent epifauna is recoverable after areas are closed. In general, area closures will need to be paired with effort reductions to offset the effects of displaced effort in the open fishing grounds.
It is unlikely that any one measure can resolve all seafloor habitat issues. Rather, some combination of options will often be most effective. The choice, utility, and limitations of a particular combination of the three measures to control fishing effects on seafloor habitats in a specific situation depends on the current regulatory setting, social and economic characteristics of the fishery and its participants, available habitat types, and the specific fishery management goals and objectives. Ideally, the choice of the particular mix of the three tools for any one case should be informed by analyses of the full suite of benefits and costs over a reasonable period. As demonstrated by the case studies, creative solutions can be found to lessen the effects of fishing on seafloor habitats while maintaining viable, long-term commercial fisheries. In fact, the two are inextricably connected.