Effects of introduced salmonids on macroinvertebrate communities of mountain ponds in the Iberian system of Spain

Abstract

Effects of introduced salmonids on macroinvertebrate communities of mountain ponds in the Iberian system of Spain This study aimed to assess the impact of salmonid stocking on macrobenthic communities in Spanish mountain ponds. Macroinvertebrates were collected with a hand net folIowing a multihabitat, time-limited sampling in eight ponds (four of them stocked with salmonids and four non-stocked) in the lberian system. A number of macroinvertebrate-based metrics, as welI as several physical and chemical variables, were measured and compared between stocked and non-stocked sites. We hypothesised that stocked ponds would have lower abundances and richness of large and mobile taxa and higher amounts of phosphorus in the water column than non-stocked ones. The results proved that macroinvertebrates were adversely affected by salmonid introductions and might be appropriate indicators of this type of impact. Total richness (both measured and estimated) and diversity were significantly lower in disturbed ponds. Coleoptera, Trichoptera and Heteroptera, large and mobile taxa, were particularly sensitive to the impact. No significant differences in nutrients were detected, although total phosphorus concentrations were usually higher in stocked ponds.