Walleye pollock recruitment in Shelikof Strait: applied fisheries oceanography

Abstract

ABSTRACTFisheries‐Oceanography Coordinated Investigations (FOCI) is a National Oceanic and Atmospheric Administration (NOAA) research programme seeking to understand recruitment processes of commercially exploited Alaskan fishes. The FOCI is mainly comprised of scientists at the Pacific Marine Environmental Laboratory and the Alaska Fisheries Science Center who study both the biotic and abiotic environment, including processes within larval patches through integrated field, laboratory, and modelling studies. The initial focus of studies was walleye pollock (Theragra chakogramma) spawning in Shelikof Strait, Gulf of Alaska. The choice of this population for our research was based on development of a large fishery and the substantial variation in recruitment that was observed in the late 1970s and early 1980s. Also, the early life history of this population is quite predictable and restricted both temporally and spatially. Walleye pollock spawn consistently in a small part of Shelikof Strait in early spring from which a large patch of eggs and later larvae is produced. In most years this concentration of larvae drifts to the south‐west through the strait during April and May. Large numbers of larvae are often found in eddies which frequent the area and we have observed improved feeding conditions for larvae, in as opposed to out of eddies. We have found that first‐feeding larvae have higher survival rates during calm periods, rather than in storms, and that in many years recruitment is largely set by the end of the larval period, although in some years age‐0 juvenile mortality is also important. FOCI now generates information that is being used for management of this resource.