Feeding variability among individual aquatic predators in experimental channels

Abstract

Experiments were conducted in experimental channels to study feeding variability through time and between conspecific individuals of four species of lotic predators. Large and small Rhyacophila dorsalis (Trichoptera: Rhyacophilidae) were given black fly larvae, mainly Simulium ornatum (Diptera: Simuliidae) of two size classes during laboratory feeding trials lasting up to 5 days. Acroneuria lycorias (Plecoptera: Perlidae) were also given black fly larvae (Prosimulium fuscum, S. venustum) during 11-day laboratory feeding trials. Paragnetina media (Perlidae) and Isoperla signata (Plecoptera: Perlodidae), were supplied with a mixed prey assemblage of black fly larvae and mayfly nymphs, Baetis flavistriga (Ephemeroptera: Baetidae), and Epeorus vitrea (Heptageniidae), for 9 days in field experiments. There was significant variability in the consumption of prey among individuals of R. dorsalis, this being true for both large and small predators. Significant among-predator and day-to-day feeding variability also occured with A. lycorias, P. media, and I. signata. Our experiments showed that there are significant differences in prey consumption among individual predators within a given species, and these differences need to be considered when planning, and interpreting, future studies on predator – prey interactions, particularly those conducted in experimental streams.