Microhabitat Use by Stream-Resident Brown Trout: Bioenergetic Consequences

Abstract

Seasonal shifts in the microhabitats used by feeding brown trout Salmo trutta in a northern Spanish river were related to changes in habitat availability. At higher flows, mean water column velocities, focal velocities, and depths occupied by brown trout were greater and focal elevations above the substratum were less, but no changes in substratum use were detected. Cover use differed between dates, apparently according to the presence of suitable materials. In May, a lower proportion of the observed fish were holding feeding positions than in July, October, or January. Total metabolic costs associated with holding feeding stations were primarily determined by swimming costs, and both costs varied substantially between dates, mainly as a consequence of the different swimming speeds of brown trout on the different dates. Standard metabolism was less important than swimming cost in total energy expenditure and showed no obvious relationship with total metabolic rate. Brown trout exhibited considerable individual variation in swimming costs, which seemed not to be related to fish size.

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

“…Unfortunately, our results do not provide information about its discernment. From a univariate perspective, the mean velocity showed a wider suitable range in comparison with the optima in most of the studies in the Iberian Peninsula (0.0-0.4 m/s) (Ayllón et al, 2010;Rincon and Lobon-Cervia, 1993). However, our results were comparable with other authors (Hayes and Jowett, 1994) who did not attribute the highest suitability to very slow microhabitats, in contrast with other studies (Heggenes, 1996;Vismara et al, 2001) where habitat availability was more limited than in the present study.…”

“…Some studies on brown trout indicated such stable suitability for deep habitats (Bovee, 1978;Vismara et al, 2001). However, other studies indicated a decrease (Hayes and Jowett, 1994;Heggenes, 1996;Lambert and Hanson, 1989;Rincon and Lobon-Cervia, 1993) with optima approximately ranging from 0.5 to 1 m. This phenomenon could be a result of the modelling approach (Category II HSCs, after Bovee et al, 1998) or the absence of incoming drift (Hauer et al, 2012) rather than a negative direct effect of depth on the habitat suitability. Unfortunately, our results do not provide information about its discernment.…”

“…Therefore, we finally considered other studies from Europe and other continents that used multivariate approaches or due to their proven relevance (Bovee, 1978;Heggenes, 1996;Jorde et al, 2001;Jowett and Davey, 2007;Rincon and Lobon-Cervia, 1993).…”

“…These rivers showed the maximum suitability within the velocity (Ayllón et al, 2010). In this regard, we considered our target rivers of intermediate size in comparison with previous studies (Ayllón et al, 2010;Heggenes, 1996;Jowett and Davey, 2007;Lambert and Hanson, 1989;Rincon and Lobon-Cervia, 1993) especially concerning the available depth. Thus, the observed pattern in the multivariate habitat suitability plot (Error!…”

Daytime habitat selection for juvenile parr brown trout (Salmo trutta) in small lowland streams

“…Substrate is generally considered very important for parr brown trout as a cover source (Heggenes, 1988b), with preference for coarser over finer substrates (Bachman, 1984;Huusko et al, 1997;Maki-Petays et al, 1997), and with fish size being positively correlated to grain size (Heggenes et al, 1999). Coarse substrate also reduces energy expenditure if fish are using surface tension velocity refuges (Heggenes and Saltveit, 1990;Rincon and Loboncervia, 1993) to act as direct cover from predators. It is known that the parr use the interstitial spaces between the substrate as refuge (Bachman, 1984;Bardonnet and Heland, 1994), and it can provide visual isolation from other juvenile trout (Shuler et al, 1994).…”