View all publications

Assessing aquatic invertebrate prey indices for fish: trout

Publication date:  May 2019
Publication reference number:  CR 348

Invertebrates living in streams and rivers (referred to as macroinvertebrates) are an important food source for many species of fish including trout. This report examines whether measures of the macroinvertebrate community can provide information on the health of the trout populations that feed on them, based on existing data.

Several commonly used macroinvertebrate metrics were tested, and a new Trout Prey Index was developed and tested, to determine whether there were relationships with trout diet or biomass (the total weight of trout in a location).

The study results do not support using the Trout Prey Index, Macroinvertebrate Community Index (MCI), Quantitative MCI, or Ephemeroptera, Plecoptera, Trichoptera (EPT) indices as indicators of trout diet or biomass. However, the study showed other ways of measuring macroinvertebrates were relevant indicators for trout, particularly total benthic invertebrate community density and biomass.

This study provides a foundation for further research on this topic.