The presence of rainbow trout reduces drift of aquatic insects in Yungas streams (Tucumán, Argentina)

SERRA GREPPI, IRIS C.; MOLINERI, CARLOS

Revista de la Sociedad Entomológica Argentina

RSEA

Año: 2021 vol. 80 p. 74 - 80

The drift or transport of individuals downstream is an important phenomenonof rivers and streams, since most aquatic organisms participate in it at some period of theirlife cycle. This work describes the assemblage of macroinvertebrate drift from ten sites ineight mountain streams of Tucumán, and evaluates the effect of the presence of rainbow trout(Oncorhynchus mykiss Walbaum), an exotic fish and visual predator, on this fraction of thecommunity. Thirty-one (31) families of drifting aquatic invertebrates were identified, mainlyimmature insects and to a lesser extent water mites (Acari: Hydrachnidia), oligochaetes(Annelida: Oligochaeta) and nematodes (Nematoda). The richness and diversity of the siteswith trout did not differ from the others, except when comparing lower and upper reaches ofa same stream. Samples from rivers without trout or with low density of trout did not showsignificant changes in drift density of macroinvertebrates. In contrast, in rivers with high troutdensities, a notable decrease in insect taxa was observed (those with large sized individuals):Baetidae (Ephemeroptera), Gripopterygidae (Plecoptera) and Leptoceridae (Trichoptera). Onthe contrary, the density of small Diptera, water mites, oligochets and nematodes increasedin trout-streams.