Factors affecting growth rates of young tropical floodplain fishes: seasonality and density-dependence |
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Authors: | Peter B Bayley |
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Institution: | (1) Illinois Natural History Survey, 607 East Peabody Drive, Champaign, IL 61820, USA |
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Abstract: | Synopsis Deviations of growth increments from a model describing average growth of 12 common fish species, mostly juveniles, were compared
with hydrological variables and biomass density (ranging from 1 gm-2 to 83 gm-2 of potentially competing species of similar size ranges (guilds). Seasonal effects on growth were highly significant for
omnivores but not for detritivores. Omnivores exhibited faster growth during the rising water season, and higher growth rates
were associated with periods of increased rates of flooding during this season, which could be associated with increased availability
of food. No species exhibited density-dependent growth when all seasons were considered together. During the rising-water-level
season, no inverse relationship between growth and biomass density was found in any of the 11 species tested at p = 0.05.
During the short falling-water season, 2 of 8 species tested did exhibit density-dependent growth but a sign test of correlation
coefficients from all species was not significant. These two significant results were from four omnivores tested. However,
density-dependent growth was not indicated when the data were pooled within either detritivore or omnivore guilds by hydrological
season. It was concluded that with the possible exception of juvenile omnivores during the limited falling-water season, density-dependent
growth, and by implication interspecific competition, had no effect in regulating the species' populations investigated in
the floodplain environment. Conversely, the importance of a seasonal hydrological regime in maintaining growth rates, at least
for omnivores, was evident. |
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Keywords: | Amazon floodplain Competition Hydrology |
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