Interannual and long-term variation in the nearshore fish community of the mesohaline Hudson River estuary |
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| Authors: | Email author" target="_blank">Thomas?P?HurstEmail author Kim?A?McKown David?O?Conover |
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| Institution: | (1) Department of Zoology, College of Agriculture and Life Sciences, North Carolina State, Box 7617, USA;(2) Hokkaido National Fisheries Research Institute, Kushiro, Hokkaido;(3) Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato, Hakodate, Hokkaido, 041-8611, Japan;(4) Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, 32610, U.S.A |
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| Abstract: | The detection of long-term shifts in species composition and spatial structuring of aquatic communities may be obscured by
high levels of interannual variation. Estuarine fish communities are likely to exhibit high levels of variation owing to the
influence of riverine forcing and the importance of anadromous and transient species, whose abundances may not be locally
controlled. We describe patterns of interannual variation and long-term shifts in the nearshore fish community of the mesohaline
Hudson River estuary based on 21 yr of beach seine sampling conducted annually between late August and mid November. Of the
60 species encountered, the most abundant were Atlantic silversides (Menidia menidia), striped bass (Morone saxatilis), white perch (Morone americana), American shad (Alosa sapidissima), and blueback herring (Alosa aestivalis). Relationships between annual community composition and seasonal flow and temperature regimes were examined with canonical
correspondence analysis. Annual variation was most closely correlated with river flows in the 3-mo period preceding fish sampling,
indicating a persistent effect of environmental conditions on community structure. Despite significant interannual variation
in composition, longer-term trends in community structure were observed. These included declines in catch rates of freshwater
and estuarine species and a dramatic increase in the catch of Atlantic silversides, an annual marine species. Associated with
these changes were declines in community diversity and increased compositional variation. These results indicate that analyses
of temporal changes in community structure need to account for the multiple time scales under which forcing factors and community
composition vary. |
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