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LARVAL FISH HABITAT QUALITY : THE EFFECTS OF FRESHWATER FLOW
Citation:
Meng, L AND S. A. Matern. LARVAL FISH HABITAT QUALITY : THE EFFECTS OF FRESHWATER FLOW. Presented at Larval Fish Conference, Gulf Shores, AL, November 10, 2000.
Description:
We sampled larval fish in Suisun Marsh, in the San Francisco Bay estuary from February to June 1994-1999. We used principal components analysis (PCA) and canonical correspondence analysis (CCA) on 13 taxonomic groups making up 99.7% of the catch and several environmental variables. Both analyses identified a distinct group of warm-water fishes dominated by introduced species and a group of native species that generally preferred cooler water and higher outflows. Gobies and sculpins dominated catches, making up 60 and 43% of the total. Catch composition was similar in most sloughs, except Cordelia Slough in the western marsh. Cordelia had higher diversity, more marine species, and most of the longfin smelt (Spirinchus thaleichthys), threespine sticklebacks (Gasterosteus aculeatus) and northern anchovies (Engralis mordax). The CCA showed temperature, salinity and freshwater outflow to be the most important physical factors determining larval catches. Larval fish diversity was highest when freshwater flows into the estuary were intermediate and may be related to positioning the mixing zone in the Suisun Bay area in spring. Species protected by the Endangered Species Act were captured by the survey. Longfin smelt were captured mostly in February and March in the western end of the marsh, whereas delta smelt (Hypomesus transpacificus) catches were later and distributed throughout the marsh. Delta smelt catches overlapped with wakasagi smelt (Hypomesus nipponensis) catches temporally and spatially and suggest potential for hybridization. Larval splittail (Pogonichthys macrolepidotus) catches were confined mostly to 1995 when high flows peaked during their spawning season in March and April. This study suggests that freshwater flow through the marsh is important for determining habitat quality for larval fishes.