Abstract
The purpose of this study is to ascertain whether variations in the limnological parameters of the Corumbataí river resulting from the discharge of a variety of wastes into its waters may be responsible for spatial shifts in the diet and capture of the armored catfish Hypostomus strigaticeps (Regan, 1907). Individuals were collected over a period of two years from two sites with similar physical, albeit distinct limnological characteristics. As a whole, the environmental variables (temperature, pH, dissolved oxygen, electrical conductivity, and total coliforms and fecal coliforms) of the two sites were found to vary significantly. The food items found in the guts of these armored catfish (sediments, diatoms, fungi hyphae, chlorophytes, cyanophytes and non-identified material) ranked differently in samples from the two sites. In the more polluted (site B), diatoms and chlorophytes ranked higher in the diet than in that of individuals caught in the more preserved location (site A). This fact may be related to the greater amount of organic material found at site B, which provides favorable environmental conditions for such algae and, consequently, for algivorous fishes. Even so, fewer fish were captured at site B than at site A, suggesting that although food is more abundant in the more polluted site, its limnological conditions appear, on the whole, to be less beneficial than the conditions at site A.
Highlights
Mankind’s influence on ecosystems is almost always negative (Odum, 1986)
Considering that armored catfish are fairly resistant to altered environments, since they have accessory breathing, and eat algae, whose growth is maximized in waters with a high level of organic material (Harper, 1992; Wetzel, 1993), the purpose of this study is to investigate whether variations in the limnological parameters of the Corumbataí river – as a result of the different wastes it receives – may be responsible for spatial shifts in the diet and abundance of H. strigaticeps
The analysis of the diet of H. strigaticeps clearly showed, in almost all the samples, that the individuals captured at site B consumed diatoms and chlorophytes more often and more intensely that those captured at site A in the Corumbataí river
Summary
For example, anthropic interference seriously impacts aquatic organisms, possibly leading to the disappearance of many fish species and affecting their diversity (Malins & Ostrander, 1994; Magurran & Phillip, 2001). In this context, studies of the possible effects of environmental alterations on fish biology serve to evaluate the extent of damage caused by humans to aquatic systems. Its use has not been carefully planned, for the river is the recipient of domestic, industrial and agricultural wastes and its water quality varies considerably from one section to another
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