Influence of Habitat Manipulations on Interactions Between Cutthroat Trout and Invertebrate Drift

Abstract

The objectives of this study were to examine the interactions of the riparian setting (logged vs. forested) and prey availability on the prey capture efficiency and growth of cutthroat trout, and to determine if the riparian setting influences the impact of trout predation on drift composition. Short-term relative growth rates of cutthroat trout, experimentally confined in stream pools, were greater in a logged than in a forested section of stream. Differences in growth rates were attributed to differences among pools in invertebrate drift density, and to differences in trout foraging efficiency that were related to differences between the sections in the amount of overhead shading and substrate crevices. Mean percentages of introduced prey captured by trout were greater in logged control pools and pools of both sections whose bottoms were covered with fiberglass screening to eliminate substrate crevices than in forested control pools and logged pools that were artificially shaded. A logarithmic relationship was found between trout foraging efficiency and surface light of pools.Drift density significantly increased relative to controls in pools from which trout were removed in the logged reach, but not in the forested section. This may result from habitat features in the logged sec?on that favor greater trout foraging success and the occurrence of behaviorally drifting prey taxa, wh1ch represent a predictable food supply for the trout.

Linking resource availability and habitat structure to stream organisms: an experimental and observational assessment

“…Secondly, the negative growth effect we observed occurred at relatively low fish densities (;0.02-0.9 fish/m 2 ), a pattern observed in other studies (see Jenkins et al 1999). Thirdly, the positive effect of prey availability (in this case, adult Diptera drift) on coho growth confirmed experimental results, and results from similar investigations (Wilzbach et al 1986, Rosenfeld et al 2005, Ward et al 2009). Fourthly, coho in the field showed a strong preference for chironomid pupae and adults relative to their availability, a relationship also observed in the experiment.…”

Nature and Functions of Cover for Riverine Fish.

“…However, in most field studies where confounding factors are numerous, it has been found that the presence of cover has no (SAUNDERS and SMITH, 1962;FAUSCH and NORTHCOTE, 1992;FAUSCH et al, 1995;FLEBBE and DOLLOFF, 1995;GOWAN and FAUSCH, 1996;HARVEY, 1998) or even a negative effect (WILZBACH et al, 1986) on growth although increased growth rates are sometimes attributed to the presence of rootwad cover (NIELSEN, 1992) or riparian cover (VILA-GISPERT et al, 2000). Results obtained in laboratory experiments are also equivocal due to difficulties in defining working hypotheses and to methodological problems (e.g.…”

“…Overall, numerous studies have reported that structural complexity in macrophytes (DIEHL, 1988;SAVINO et al, 1992), woody debris (EVERETT and RUIZ, 1993), and substratum (POWER, 1992;BECHARA et al, 1993) may decrease the effectiveness of fish predation on macroinvertebrates. By impeding their visual field, shade may drastically limit the feeding efficiency of drift-feeders (WILZBACH et al, 1986;O'BRIEN and SHOWALTER, 1993) that may benefit far more from cover structures by taking positions directly downstream from these structures (NIELSEN, 1992). At a higher spatial scale, riparian cover may both greatly reduce autochthonous production of a stream reach thus negatively impacting fish growth, but also provide terrestrial invertebrates which may constitute a large part, at least seasonally, of the diets of some species (MASON and MACDONALD, 1982;COLLARES-PEREIRA et al, 1995;BRIDCUT, 2000;KAWAGUCHI and NAKANO, 2001).…”

“…Food availability seems to greatly control the extent of the association between fish and cover and it allows to understand the equivocal results of the literature. Field observations showed that in the summer growing season salmonids preferred to occupy open areas without cover (WILZBACH et al, 1986;HARVEY, 1998) because, by hindering the ability of these visual predators to detect prey, the drawbacks of cover may have overridden the benefits (WILZBACH, 1985;O'BRIEN and SHOWALTER, 1993). In the same way, experimental studies using behavioural titration techniques reported that in risky sites the antipredator benefits of cover can be compensated by food enrichment (GILLIAM and FRASER, 1987;GRAND and DILL, 1997;GIANNICO, 2000).…”

Interactions between benthic macroinvertebrates and fishes in a low order stream in Campos de Cima da Serra, RS, Brazil

“…As species are not independent entities -taking into account that biotic and abiotic connections are essential for the maintenance of integrity of the lotic systems -the quantification of predator impact on the abundance of prey has been studied by some authors (Thorp and Bergey, 1981;Flecker and Allan, 1984;Wilzbach et al, 1986;Rahel and Stein, 1988;Soluk and Collins, 1988;Lancaster, 1990;Cooper et al, 1990;Hanson et al, 1990;Flecker, 1992;Prejs and Prejs, 1992;Bechara et al, 1993;Lancaster andRobertson, 1995, McIntosh andTownsend, 1996;Dahl, 1998;Billy and Usseglio-Polatera, 2002). Amongst the factors that influence the response of prey to predator are: a) predator feeding characteristics, being that not all the taxa are affected (Billy and Usseglio-Polatera, 2002); b) size of prey and substrate type, presenting a higher or lower degree of shelter sites (Bechara et al, 1993) and c) types of habitats, which may have a differentiated effect, taking into consideration that in habitats made up of riffles and rapids, colonization rates are higher than in pools, causing a lower response to predators (Cooper et al, 1990).…”