pH preference and avoidance responses of adult brook trout Salvelinus fontinalis and brown trout Salmo trutta

Abstract

The pH preferred and avoided by wild, adult brook trout Salvelinus fontinalis and brown trout Salmo trutta was examined in a series a laboratory tests using gradual and steep-gradient flow-through aquaria. The results were compared with those published for the observed segregation patterns of juvenile S. fontinalis and S. trutta in Pennsylvania streams. The adult S. trutta tested showed a preference for pH 4·0 while adult S. fontinalis did not prefer any pH within the range tested. Salmo trutta are not found in Pennsylvania streams with a base-flow pH < 5·8 which suggests that S. trutta prefer pH well above 4·0. Adult S. trutta displayed a lack of avoidance at pH below 5·0, as also reported earlier for juveniles. The avoidance pH of wild, adult S. fontinalis (between pH 5·5 and 6·0) and S. trutta (between pH 6·5 and 7·0) did not differ appreciably from earlier study results for the avoidance pH of juvenile S. fontinalis and S. trutta. A comparison of c.i. around these avoidance estimates indicates that avoidance pH is similar among adult S. fontinalis and S. trutta in this study. The limited overlap of c.i. for avoidance pH values for the two species, however, suggests that some S. trutta will display avoidance at a higher pH when S. fontinalis will not. The results of this study indicate that segregation patterns of adult S. fontinalis and S. trutta in Pennsylvania streams could be related to pH and that competition with S. trutta could be mediating the occurrence of S. fontinalis at some pH levels.

Preference and avoidance pH of brook trout Salvelinus fontinalis and brown trout Salmo trutta exposed to different holding pH

“…Preference and avoidance experiments were patterned after those described by Stauffer et al () for temperature studies. Holding tank descriptions, preference–avoidance methodology and statistical analyses were identical to those described by Fost & Ferreri () with the exception that comparisons were made among treatment groups and sample sizes varied. A sample size of 10 fish per species and holding group was targeted for all experiments.…”

Influence of interspecific interactions on avoidance response to contamination

“…Although evidence of avoidance responses to contamination has been widely reported for many fish species (see review by , it is recognized that habitat selection processes may be conditioned by several factors other than contamination, such as temperature (Stehfest et al, 2017), pH (Fost and Ferreri, 2015), presence of predators (Scherer and Smee, 2016) and competitors (Dunlop et al, 2006), among others. In the natural environment, organisms are simultaneously exposed to several factors, so it is necessary to understand the extent to which contamination influences the habitat selection process, and the ways that these factors affect the avoidance response.…”

Effects of aquatic contaminants on the habitat selection and spatial distribution in fish: a complementary approach to traditional ecotoxicological tests

“…Although evidence of avoidance responses to contamination has been widely reported for many fish species (see review by Araújo et al, 2016), it is recognized that habitat selection processes may be conditioned by several factors other than contamination, such as temperature (Stehfest et al, 2017), pH (Fost and Ferreri, 2015), presence of predators (Scherer and Smee, 2016), and competitors (Dunlop et al, 2006), among others. In the natural environment, organisms are simultaneously exposed to several factors, so it is necessary to understand the extent to which contamination determines the habitat selection process and the ways that these factors affect the avoidance response.…”