Continental slope and deep-sea fisheries: implications for a fragile ecosystem

Koslow, J. A., Boehlert, G. W., Gordon, J. D. M., Haedrich, R. L., Lorance, P., andParin, N. 2000. Continental slope and deep-sea sheries: implications for a fragileecosystem. – ICES Journal of Marine Science, 57: 548–557.Exploited deepwater (>500 m) species generally exhibit clear ‘‘K-selected’’ life-history characteristics markedly dierent from most shelf species: extreme longevity,late age of maturity, slow growth, and low fecundity. Many also aggregate onrestricted topographic features such as seamounts, and as a consequence are notablyunproductive, highly vulnerable to overshing, and have potentially little resilienceto overexploitation. Since 1964, deepwater sheries have contributed 800 000–1 000 000 t annually to global marine sh landings. Underlying this apparent overallstability is the ‘‘boom and bust’’ cycle that has characterized many individualsheries. The accumulated biomass of previously unshed stocks is typically sheddown, often within 5–10 years, to the point of commercial extinction or very lowlevels. Most deepwater stocks are today overshed or even depleted. Depletion ofspecies from deep-sea environments that dominate mid to upper trophic levels mayhave long-term ecological implications, but the risks of reduced stock size and agestructure to population viability, the potential for species replacement, and theimpacts on prey and predator populations are not generally known. However, trawlsheries have been shown to have potentially severe impacts on the benthic fauna ofseamounts, where these sh aggregate. This fauna, dominated by suspension feeders,such as corals, is typically restricted to the seamount environment and is character-ized by high levels of endemism, which suggests limited reproductive dispersal. Theability of the benthic community to recover, following its removal by trawling, is notknown.