Causes of interestuarine variability in bay anchovy (<Emphasis Type="Italic">Anchoa mitchilli</Emphasis>) salinity at capture |
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Authors: | Ernst B Peebles Scott E Burghart David J Hollander |
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Institution: | 1.College of Marine Science,University of South Florida,St. Petersburg |
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Abstract: | Salinities occupied by different life stages of bay anchovy (Anchoa mitchilli) were compared over annual cycles at 128 stations in 12 Florida estuaries. The comparison included eight stations in an oligotrophic,
groundwater-based estuary in which all life stages were rare or absent. At other stations, adults, eggs, and early larvae
occurred in intermediate to high salinities (10-30 psu) with no apparent central salinity tendency. The larva-juvenile transition
was marked by an upstream shift to lower salinities (0-15 psu), also with no central salinity tendency. Mean salinities of
the juvenile catch were strongly dependent on the salinities of the sampling effort. This dependence was strongest in estuaries
that had weak horizontal salinity gradients. Weak salinity gradients were either natural or resulted from estuarine dams.
After using nonlinear regression to account for the interaction between effort salinity and catch salinity, catch salinities
were found to be similar from year to year within estuaries, but widely different among estuaries, with interestuarine differences
ranging as high as 10–13 psu. Lower salinities were occupied by juveniles in estuaries that had long freshwater turnover times.
Inherent geomorphic and inflow-related effects on the distribution of prey resources, coupled with an ontogenetic diet shift,
are proposed as the explanation for both the habitat shift and the strong interestuarine variability in salinity at capture. |
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