Taking Refuge from Bycatch Issues: Red King Crab (Paralithodes camtschaticus) and Trawl Fisheries in the Eastern Bering Sea

Abstract

Concerns about possibly heavy impacts of bottom trawl fisheries on red king crab (Paralithodes camtschaticus) pot fisheries in the eastern Bering Sea led in 1987 to an emergency closure of trawling in an area of adult and juvenile crab habitat. We examine the effectiveness of this bycatch refuge in protecting and possibly enhancing the crab resource using three approaches. First, bycatch of crab in trawl fisheries is a small proportion of total estimated abundance throughout the southeastern Bering Sea but may be high relative to stock abundance within the closed area and relative to annual crab landings; recent regulations have diminished this apparent effect. Effects of direct bycatch on the stock are obscured by lack of evidence on indirect effects of trawling, including crushing of crab and degredation of juvenile habitat. Second, surveys inside and outside the refuge before and after closure show no significant changes in abundance of female and prerecruit male crab. Third, important breeding and hatching grounds and juvenile habitat are not protected by the refuge, leaving long-term stock renewal subject to trawl impacts. We suggest that full consideration of the needs of all life history stages could lead to a more effective refuge design.

Management of Bristol Bay Red King Crab: A Critical Intersections Approach to Fisheries Management

“…1.5). Armstrong et al (1993) further demonstrate that the availability of these sites varies from year to year. Since larvae are carried on currents throughout the pelagic phase and the location of spawn ing areas is not static, the precise location of larvae at the time of settlement is not consistent.…”

“…Additional accounts of huge gear losses compound the amount of waste generated during those years (lost gear continues to fish, commonly called ghost fishing). Lost gear has been estimated to be 10% of the annually deployed pots (Armstrong et al 1993). Overcapitalization was prevalent because everyone wanted to participate in the second most valuable Alaskan fishery (after salmon) (Matulich et al 1988).…”

“…1.3). The precise location of larval concentrations varies among years, reflecting variations in the precise location of breeding assemblages (Armstrong et al 1993).…”

“…These features provide physical refuge from predation, as well as a source of food. Cobble habitat, which may serve as important settlement substrate, appears to be limited and patchy, and is con fined to three general regions in water <50 rn in depth: (1) on the north shelf near the mouth of Togiak Bay, (2) to the east in Kvichak Bay, and (3) along the southern shelf in the area of Port Moller (Armstrong et al 1993). Figure 1.4 shows the location of such substrates and the location of early post-settlernentju venues in a typical year.…”

“…In 1987, the first no-trawl zone in Bristol Bay was established for the domestic fleet; this zone comprises the waters south of 58°N and between 160°and 162°W, excluding nearshore waters <25 fm deep (Armstrong et al 1993). The rationale behind prohibiting bottom trawling is twofold: (1) red king crab are a component of trawl bycatch, and (2) bottom trawling crushes crab and has a disastrous impact on the benthic habitat that supports the red king crab (Armstrong et al 1993).…”