Resource Assessment & Conservation Engineering  (cont.)

Fisheries Oceanography Coordinated Investigations  ( FOCI )

Ichthyoplankton surveys have been conducted by the AFSC in the northeast Gulf of Alaska from 1977 to the present, primarily during spring.  FOCI scientists conducted a retrospective analysis of historical (1977-79) larval capelin abundance in the Gulf of Alaska over a 17 month period in four Kodiak Island bays and the adjacent continental shelf and slope.  The sampling provided an opportunity to examine seasonal and spatial patterns in abundance of capelin larvae during a period when adult abundance was high, prior to a decline documented during the early 1980s.  Analyses indicate that in 1978, capelin populations in this area spawned during the summer and autumn in inshore waters, with a peak in spawning activity during June-July.  Distribution patterns of capelin larvae suggest that subsequent to hatching and emergence into the plankton, larvae are transported from the bays and coastal zone around Kodiak Island into adjacent shelf waters, probably by tidal flushing and wind-induced surface currents.  Mixing processes on the shelf seaward of Kodiak Island, reflecting variable current patterns in this area, are likely to enhance the dispersal of larvae as indicated by the uniformity observed among distribution patterns of several length categories of larvae.  A comparison of larval abundance and length between bongo and neuston samples suggests that capelin larvae greater than 30 mm in length actively migrate to the surface layer.  Our observations represent a picture of capelin early life history during a period of high adult abundance that has been linked to a cold phase in the oceanographic environment of the Gulf of Alaska.  This work was presented by Miriam Doyle as a paper “Capelin, What Are They Good For?” at the ICES symposium held in Reykjavík, Iceland in July 2001 and will appear as a paper in the ICES J. Mar. Sci. by Doyle, Busby, Duffy-Anderson, Picquelle, and Matarese.

AFSC Quarterly
Research Reports
Oct-Dec 2001