摘要:

Red king crab (Paralithodes camtschaticus) formerly represented one of the most lucrative fisheries in the Bering Sea and Gulf of Alaska. Following rapid capitalization, the fishery exploded in the late 1970s with peak catches nearing 70,000 tons in the eastern Bering Sea alone, but in the early 1980s the productivity of this fishery collapsed by over an order of magnitude. Despite extensive management effort, harvest levels have remained fairly low and stable for the last 15 years.Factors in the life history of Alaskan red king crab and the Bering Sea ecosystem are discussed, especially as they pertain to continued low crab biomass. Reduction in crab abundance due to natural predators, habitat and resource limitations, and human impacts may present “bottlenecks” to future recruitment at a number of different life history stages. These stages include egg and larval supply, the early benthic phase, pre-fishery juveniles, and breeding adults. There is evidence that an environmental “regime shift” may have occurred in the late 1970s characterized by warming sea surface temperatures, altered circulation patterns, and changes in the productivity patterns of the Bering Sea and Gulf of Alaska. Since this period, a number of potential predators and resource competitors of the red king crab have increased in abundance, including pelagic planktivores and a number of invertebrate and benthic fish species. The suite of changes in the ecosystem since the 1970s may have altered the relative importance of survival at different ages as the ultimate regulator of population abundance and fishery recruitment in red king crab.We suggest that the successful management of this species, and sensitive species in general, relies on attention to the species' particular life history patterns and population bottlenecks. Specifically, management must focus on identifying and reducing anthropogenic impacts on valuable species. These impacts may be direct, such as capture in fisheries, or may be indirect, impacting the target species via effects on other species with which it interacts. We use this ecosystem management approach (the “Critical Intersections Approach”) as a model to suggest a shift in red king crab management. Present scenarios for red king crab concentrate on maximizing female biomass, but this approach may not be sufficient to increase population levels. Evidence exists that total egg supply may not be the primary limiting factor presently controlling crab abundance in the Bering Sea. Rather, survival during early post-settlement stages may regulate overall recruitment to the fishery.Given this possibility, we present a hypothetical biological and economic management plan that encompasses, (1) near-shore trawl management areas to protect crab nursery habitat, (2) deeper-water trawl management areas to protect breeding stock, (3) encouragement and incentives to fisheries that reduce crab-predator biomass, (4) establishment of ITQs for the fishery, (5) introduction of mandatory increased utilization of harvested crab, and (6) integrating a research program into the management plan.

ISSN:1064-1262    

DOI:10.1080/10641269891314285

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Comparisons of catch and effort data from 5 seasons by dhow and industrial fleets showed annual landings to vary around the long-term average of 2100 tons. No direct long-term effects of the Gulf War were identified, but indirect effects have caused substantial changes in Kuwait's shrimp fishery. The effort expenditure in 1993/94 reached an all-time high of 17,615 industrial boat-days, more than the sum total of the last three seasons' effort (16,400 industrial boat-days) prior to the War. With a fixed number of industrial vessels, dhow boats have been responsible for the increased effort. Low total landings and catch rates since the Gulf War reflect low stock abundance and high effort.Penaeus semisulcatus, Kuwait's most important shrimp species, dominated shrimp landings for all 5 seasons, but its importance to the total landings declined to a historical low during the 1995/96 season accounting for only 50% of the dhow landings and presumably the industrial boat landings. The primary factors for this decrease appear to be increasing fishing pressure during the shrimp season as well as illegal trawling during closed season and altered discharge rates of the Shatt Al-Arab. Growth performance indices forP. semisulcatus,Metapenaeus affinis, andParapenaeopsis styliferaduring the 1995/96 season compared closely with those of the 1988/89, 1989/90, 1991/92, and 1992/93 seasons when shrimp populations experienced high densities, decreased water temperatures resulting from the oil-fire smoke, or overfishing and other environmental conditions. Fishing mortality of all species for 1995/96 exceeded the natural mortality, a clear indication of overexploitation. Results of bio-economic analysis show that 4000 industrial boat-days would maximize economic returns, while 8000 industrial boat-days would maximize the sustainable yield. Both the values are higher than estimates prior to the War. With both reversible (overfishing) and irreversible (altered Shatt Al-Arab discharge influences operating), prudent management of trawling effort will become increasingly important if Kuwait is to maintain its position as a shrimp exporter.

ISSN:1064-1262    

DOI:10.1080/10641269891314276

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor