Effects of drift- and benthic-foraging fish on the drift dispersal of three species of mayfly nymphs in a Japanese stream

Abstract

Differences in the effects of two common predatory fishes, rainbow trout (Oncorhynchus mykiss) and freshwater sculpin (Cottus nozawae), on drift dispersal of the nymphs of three mayfly species, Baetis thermicus, Cinygmula sp., and Paraleptophlebia chocorata, were examined by manipulative field experiments using stream enclosures in a northern Japanese stream. The diel periodicity of prey consumption rate differed considerably between the two fishes; the prey consumption of the drift-foraging trout was greater at both dawn and dusk, whereas the benthic-foraging sculpin showed a higher consumption rate at night. The drift propensity at night was much greater than during the day for all the mayfly species in each of the trout, sculpin and fishless treatments, as well as under natural conditions with both fishes present. The nighttime drift propensities of the epibenthic grazers, B. thermicus and Cinygmula sp., were greater in the sculpin treatment than in trout and fishless treatments, and they did not differ between the trout and fishless treatments. By contrast, the nighttime drift propensity of P. chocorata, an infaunal collector-gatherer, did not differ among the treatments. The daytime drift propensity did not differ among the treatments for any of the mayfly species. Thus differences in drift response to the predatory fishes could be related to the characteristic microhabitats of the mayfly species. Moreover, the experiments demonstrated that benthic-foraging sculpin had greater overall effects on prey drift than drift-foraging trout.

Selective foraging on terrestrial invertebrates by rainbow trout in a forested headwater stream in northern Japan

“…Rainbow trout, in reality, demonstrated a highly selective utilization of terrestrial invertebrates from stream drift in the Horonai Stream. A clear diel periodicity in foraging activity of rainbow trout was evident, with prey consumption rates being high at dawn and dusk, decreasing around both noon and midnight (see also Miyasaka & Nakano 1999). Most stream salmonids are visual foragers, preying primarily upon drifting invertebrates while maintaining focal points in the water column ( Angradi & Griffith 1990; Nakano 1995).…”

Reciprocal subsidies: Dynamic interdependence between terrestrial and aquatic food webs

“…Mean diameter at the base of the branch was 2.8 Ϯ 0.7 cm (n ϭ 80). The biomass of stream invertebrates was estimated from samples collected from twelve haphazardly chosen locations in the study reach (20). The stream invertebrates were collected by a 225-m mesh Surber net sampler (25 ϫ 25 cm quadrat, 1 m net length).…”

The behavioural, digestive and metabolic characteristics of fishes with different foraging strategies

“…However, little has been done to compare the swimming performance, metabolic characteristics and digestive capacity of fishes with different foraging modes. Previous studies on the foraging mode of fishes have focused on swimming efficiency and prey encounter rate of pelagic fishes (Miyasaka and Nakano, 1999;Asaeda et al, 2001), while the sit-and-wait foraging fishes have received little attention. Thus, the first aim of this study was to determine whether significant differences in routine activity level, swimming performance, metabolic characteristics and digestive capacity exist among fishes with different foraging modes.…”