Reprint Series No. 36

DISTRIBUTION AND ABUNDANCE OF FISHES OCCURRING IN THE NEARSHORE SURFACE WATERS OF NORTHERN PUGET SOUND

Kurt Leigh Fresh

1979

Bibliographic Citation
Fresh, Kurt Leigh. 1979. Distribution and abundance of fishes occurring in the nearshore surface waters of northern Puget Sound, Washington. Master of Science Thesis, University of Washington, Seattle, Washington. 120 pp. Washington State Department of Ecology (Publication No. 01-06-030), Padilla Bay National Estuarine Research Reserve Reprint Series No. 36.

Abstract
Fishes occurring in the nearshore surface waters of northern Puget Sound, Washington, were studied during 1974-1976 using a two-boat surface trawl (townet). Five sites, each representing a different habitat type (as defined by degree of exposure and substrate type), were sampled in each of three geographic areas. Principal objectives of the study were to document the abundance, spatial and temporal distribution of fishes occurring in nearshore surface waters of northern Puget Sound.

Nearshore surface waters were utilized as nursery and rearing areas by numerous fish species. While the townet was not designed to sample larvae, larval fish were caught abundantly, primarily in spring. Mainly juvenile fish were found throughout the entire year in nearshore habitats studied. Few large fish were caught, perhaps because of avoidance.

Of the 71 fish species captured, the 6 most abundant species comprised 98 percent of the total numerical catch. Twenty species were schooling whereas 51 were demersal; schooling species generally were more frequently occurring and more abundant than non-schooling species. Catches of most species were highly seasonal and indicated a lack of permanent resident species. Young-of-the-year Pacific herring was the dominant fish species occurring in nearshore surface waters. Herring catches were especially large at sites associated with protected eelgrass bays and in areas near known spawning grounds. Maximum catches of herring occurred during the spring and summer whereas minimum catches occurred in the fall and winter. Other abundant species included young-of-the-year Pacific sand lance, juvenile and adult threespine stickleback, larval to adult surf smelt, and larval to adult longfin smelt. While numerically not abundant, juvenile salmonids (mostly chinook salmon) occurred consistently in spring and summer primarily in the Cherry Point and Anacortes areas.

Seasonal trends were consistent between the two years sampled, although magnitudes of CPUE and numbers of species varied. Catches of all species were lowest during the winter and resulted in similar CPUE levels at all sites. CPUE and numbers of species increased at all sites during the spring, principally because of the occurrence of large numbers of larvae. Maximum CPUE occurred at most sites during the spring and summer due to large catches of herring, sand lance, and stickleback. A substantial fall decrease in CPUE suggested an offshore movement of fishes out of the nearshore surface zone, possibly in response to increased exposure levels, reduced food supplies, and/or reduced temperatures.

The dominant nearshore pelagic species were present throughout the various nearshore habitats of northern Puget Sound with little evidence of distinct assemblages in different habitats. However, even though the dominant species exploit the entire nearshore spectrum of habitats, there were preferred habitats and areas.