Microhabitat Models of Large Drift-Feeding Brown Trout in Three New Zealand Rivers

Abstract

We examined summer habitat use by 189 drift‐feeding brown trout Salmo trutta, 45–65 cm long (fork length), by measuring substrate, depth, mean velocity, focal point velocity use, and adjacent velocity into which fish were feeding in three New Zealand rivers. We compared habitat used with habitat available (simulated by hydraulic modeling), and we derived habitat use, habitat preference, and logistic regression models of habitat selection. Focal points usually were associated with large substrate components including bedrock projections, boulders, and large cobbles. Depths between 0.67 and 0.86 m were most commonly used by brown trout but the preferred depth was 1.0 m. Mean velocities between 0.38 and 0.48 m/s were the most commonly used, but preferred mean velocities were 0.05 m/s higher. Optimal focal point velocities, 0.19–0.28 m/s, were lower than mean velocities. Vertical and lateral velocity shears were calculated as measures of the velocity differentials over which fish were feeding. The velocity shears most commonly used by brown trout were between 0.50 and 0.65 m/s per meter for vertical shear and 0.02 and 0.06 m/s per meter for lateral shear. Those most preferred by brown trout were between 0.50 and 1.20 m/s per meter for vertical shear and between 0.06 and 0.26 m/s per meter for lateral shear. Depth, mean velocity, and substrate were selected independently of each other. Significant differences between rivers were found for the use of substrate, depth, focal point velocity, mean velocity, and lateral velocity shear. Depth and mean velocity were consistently significant variables in logistic regression models of habitat selection, accounting for 33–85% of the explained deviances. Large substrate components accounted for 47% of the explained deviance in one river. Lateral and vertical velocity shear together accounted for 15–27% of the explained deviances. Logistic regression and joint habitat preference models were better predictors of suitable habitat in the rivers for which they were developed than were joint habitat use models. However, joint habitat use models may be more general, because, unlike logistic regression and joint habitat preference models, the predictive success of transferred joint habitat use models was similar to that of models tested on the river for which they were developed. Combined‐river habitat use, habitat preference, and logistic regression models are presented for general habitat management applications when habitat criteria are not available for specific rivers.

Macroinvertebrate prey availability and food web dynamics of nonnative trout in a Colorado River tributary, Grand Canyon

“…Each sampling point was classified as a suitable or unsuitable feeding site depending on its depth, velocity, and cover characteristics. We defined optimum feeding sites for brown trout, as depths exceeding 0.3 m with velocities between 0.20 and 0.30 m/s for age 1 and 2 trout and depths exceeding 0.6 m with velocities between 0.15 and 0.29 m/s for age 3 trout (Shirvell and Dungey 1983;Hayes and Jowett 1994;Grant 1999). Cover also had to be present within 1 m of these points.…”

Application of Probabilistic Neural Networks to microhabitat suitability modelling for adult brown trout (Salmo trutta L.) in Iberian rivers

“…These ecological habitat suitability models have become an essential tool in the management and conservation of freshwater fish populations (Frank et al, 2011). The continuous univariate Habitat Suitability Curves (HSCs) are a simple and common modelling approach in studies involving the instream flow assessment (Payne and Allen, 2009), and hence several researchers have developed habitat suitability models in the form of the aforementioned HSCs (Ayllón et al, 2010;Bovee, 1978;Hayes and Jowett, 1994;Raleigh et al, 1986;Vismara et al, 2001). The Weighted Usable Area (WUA) (Bovee, 1998) derived from these models could be used in the assessment of minimum flows.…”

Habitat De La Truite Commune (Salmo Trutta L.) Pendant La Période Juvénile en Ruisseau : Préférences, Mouvements, Variations Journalières Et Saisonnières.

“…En conséquence, un microhabitat trop lent serait limitant en terme d'apport énergétique (nombre de proies insuffisant), alors qu'un habitat trop rapide nécessiterait une grande dépense d'énergie pour maintenir le poste (FACEY et GROSSMAN, 1992) et/ou réduirait la capturabilité des proies (HUGHES et DILL, 1990 ;HILL et GROSSMAN, 1993). (GOSSE et HELM, 1982 ;SHIRVELL et DUNGEY, 1983 ;HAYES et JOWETT, 1994 ;SHULER et NEHRING, 1994). …”