FY 1995

Neustonic ichthyoplankton in the western Gulf of Alaska during spring

Doyle, M.J., W.C. Rugen, and R.D. Brodeur

Fish. Bull., 93, 231–253 (1995)

Species diversity and abundance of fish eggs in shelf waters of the western Gulf of Alaska were similar in both surface neuston net tows and subsurface bongo net tows, but a unique group of fish larvae appear to be associated with the neuston in this region. The dominance of larvae of an osmerid, several hexagrammids, cottids, bathymasterids, Anoplopoma fimbria, Cryptacanthodes aleutensis, and Ammodytes hexapterus in this group resembles the neustonic assemblage of fish larvae found in the California Current region along the U.S. west coast and most of these taxa are considered obligate members of the neuston. Several taxa, however, appear to be abundant in the neuston only at night suggesting a facultative association with the neuston through a diel pattern of vertical migration. The facultative association of certain species of larvae with the neuston varies with larval size. The distribution patterns observed for most taxa of fish larvae in the neuston during this study suggest that during spring, spawning and emergence of larvae into the plankton and subsequently into the neuston take place mainly around Kodiak Island (except along the seaward side) and along the Alaska Peninsula to the southwest. Analysis of multispecies spatial patterns using recurrent group analysis and numerical classification did not reveal the existence of more than one neustonic assemblage of fish larvae in the study area. Apart from perhaps Pleurogrammus monopterygius larvae, which are known to occur throughout the Gulf of Alaska, and to a lesser extent A. fimbria and Hemilepidotus hemilepidotus, members of this neustonic assemblage of larvae are not commonly found in the oceanic zone. The ecological significance of a neustonic existence for larvae of fish that are primarily demersal spawners in the Gulf of Alaska is considered to be trophic in nature. Neustonic fish larvae seem to be able to exploit to their advantage the unique feeding conditions which exist at the sea surface.