Influence of land-based trout farms on stonefly (Insecta: Plecoptera) larvae assemblage

Abstract

Activities related to agriculture are one of the major problems of freshwater pollution. Even though the influence of such practice is lowest on highland streams and rivers, fish farms localized in the upper course could disturb their homeostasis. Since trout farming has become an important economic activity in Serbia, three trout farms with different annual production were chosen in order to monitor their effect on sensitive stonefly larvae assemblage. The trout farms with low, medium and high annual production are situated along Studenica, Crnica and Mlava rivers, respectively. Research was conducted every two months during the one-year period. Water and biological samples were collected at one control locality and four localities downstream from the trout farms. Water temperature, pH, dissolved oxygen and conductivity were measured in situ, while phosphates and ammonia in the laboratory. Canonical Correspondence Analysis was conducted in order to test how taxa within the Plecoptera assemblage were grouped in relation to measured environmental parameters. Considering CCA analysis, the most important parameters that shaped the Plecoptera assemblage were phosphates and temperature. The greatest diversity of stonefly larvae assemblage was noted in the Studenica river, while the lowest was at the Mlava river, with its absence at the locality immediately downstream from the trout farm.