Testing a model of drift-feeding using three-dimensional videography of wild brown trout, Salmo trutta, in a New Zealand river

Abstract

We tested the assumptions and predictions of a foraging model for drift-feeding fish. We used three-dimensional videography to describe the foraging behavior of brown trout, Salmo trutta, mapped water depth and velocity in their foraging area, sampled invertebrate drift to determine length class specific drift densities, and captured trout to determine the size composition of their diet. The model overestimated the fish's prey capture rate and gross energy intake rate by a factor of two. Most of this error resulted from the fact that prey detection probabilities within the fish's foraging area averaged only half the expected value. This was the result of a rapid decrease in capture probability with increasing lateral distance from the fish's focal point. Some of the model's assumptions were accurate: equations for predicting reaction distance and minimum prey size supported reliable predictions of the shape and size of the fish's foraging area and the size composition of the diet. Other assumptions were incorrect: fish detected prey within the predicted reaction volume, not on its upstream surface as expected, fish intercepted prey more slowly than the expected maximum sustainable swimming speed, and fish captured about two-thirds of their prey downstream of their focal point, rather than upstream.

The food niche overlap of five fish species in the Úpoř brook (Central Bohemia)

“…In this work, the food of five fish species (brown trout Salmo trutta, chub Squalius cephalus, dace Leuciscus leuciscus, stone loach Barbatula barbatula and common bullhead Cottus gobio) was studied. All these fish species are common in the stream studied, and many authors have studied diet and/or competition in these species (Albertová, 1982;Cavalli et al, 1998;Dyk, 1932Dyk, , 1956Fochetti et al, 2008;Hesthagen et al, 2004;Horton, 1961;Hughes et al, 2003;L'abée-Lund et al, 2002;Legalle et al, 2005;Maitland, 1965;Markovič et al, 2007;Saksgard and Hesthagen, 2004;Yevsin and Ivanov, 1979). The aim of this work was to examine the diet of these five fish species and to evaluate the level of competition as the overlap in their food niches.…”

Movement and Mortality of Adult Brown Trout in the Motupiko River, New Zealand: Effects of Water Temperature, Flow, and Flooding

“…However, the importance of spawning migrations in river trout populations probably depends on the location of good spawning gravels relative to the position of good adult trout habitat (Northcote 1992). Trout may also move to seek better food resources and feeding habitat or thermal conditions so they can maximize their energy intake and growth potential (Gowan and Fausch 2002;Hughes 1998Hughes , 1999Hughes et al 2003). Water temperature is a key variable controlling trout growth and survival.…”

Modelling brown trout spatial requirements through physical habitat simulations

“…Therefore, older trout would move to deeper habitats to minimize energy costs selecting resting positions of low water velocity, while maximizing energy intake feeding in the fast-flowing section of the water column. Hence, they would adjust resting-feeding positions in a three-dimensional territory, the territory volume, which must scale to body mass at a rate consistent with increasing energy requirements, according also to the notion that prey detection locations are distributed throughout the reaction volume, not concentrated on its surface (Hughes et al, 2003). This could explain why in some instances the territory area hypothesis may fail in defining maximum density in pool habitats but not in riffles (see Grant and Kramer, 1990).…”