Implications of Fluctuations in Recruitment in Selected Crab Populations

Abstract

Two general categories of crab fisheries exist, shallow-water, nearshore fisheries (e.g. Cancer, Callinectes) and deepwater, offshore fisheries (e.g. Paralithodes, Chionoecetes). Species in the former category are managed typically in a passive manner with no annual restriction of catch on the basis of population abundance, whereas species in the latter category tend to be managed actively through annual catch quotas. Active management of fisheries requires regular resource surveys and provides the most comprehensive data base for recruitment study. Recruitment fluctuations in crab populations are analyzed by considering (1) production of progeny from perceived parent populations, (2) mechanisms which determine magnitude of progeny return to fishery grounds, and (3) factors that determine survival of juveniles. It is concluded that year-class strength at recruitment can be established at any preceding life stage and that while one life stage may appear more critical than others for a given population in a given year, this is unlikely to be the case in future years or apply to different populations. There is little evidence that recruitment magnitude in crab populations has been influenced by past resource management. Management has not stabilized landings in any fishery over the long term, and environmental variables seem to be the major factor influencing recruitment level. The need for prediction of future fishery performance is greatest in actively managed fisheries, with short-term economic benefits and socially acceptable exploitation, not control of recruitment, being the most likely achievement of management.