Sediment preferences and size-specific distribution of young-of-the-year Pacific halibut in an Alaska nursery

A.W. Stoner, A.A. Abookire-2002

Journal of Fish Biology, 61(3): 540-559

Abstract:

A combination of laboratory experiments and field surveys was used to test the hypotheses that responses to sediments change with fish size and that sediment grain-size is the predominant environmental factor affecting small-scale distribution in young-of-the-year (yoy) Pacific halibut Hippoglossus stenolepis. Laboratory tests showed that the smallest fish (31-40mm L_T) chose fine sediments (muddy and fine sands), fish 51-70mm had high selectivity (primarily medium sand), and the largest fish (80-150mm) were not selective although they avoided the largest grain-sizes (pebbles and granules). Sediment preferences were correlated with size-dependent burial capabilities. Beam trawl collections were made over a 6 year period in Kachemak Bay, Alaska, to examine the distribution of yoy Pacific halibut (14-120mm L_T) using small size classes (e.g. 10mm intervals). Canonical correlation analysis showed that the per cent of sand in the sediment was a highly significant variable for all but one size and date combination. Catch per unit of effort (CPUE) for newly settled fish (<30mm L_T) was highest on very fine sand, fish 41-80mm were most abundant on fine sand, and the largest yoy fish (81-120mm) were abundant over a range of sediments from fine sand to mud. Except for the smallest fish, Pacific halibut in the field were associated with sediments somewhat finer than predicted from the laboratory experiments; however, virtually all were captured where they could bury easily. The ability of flatfish to bury and shelter in sediment is related to fish size; consequently, habitat associations shift rapidly during the first year of life. Habitat models for yoy flatfishes should consider size-dependent shifts in capabilities and preferences.

(Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, 2030 S. Marine Science Dr., Newport, Oregon, 97365, U.S.A., Tel.: +1 541 867 0165; fax: +1 541 867 0136; email: al.stoner@noaa.gov)

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