Spawning Interactions between Sympatric Brown and Brook Trout May Contribute to Species Replacement

Abstract

The behavior of sexually active brook trout Salvelinus fontinalis and brown trout Salmo trutta was observed on spawning redds in a small Minnesota stream to characterize the nature and frequency of interactions between the two species. Twelve redds were continuously monitored for 24 h with underwater video cameras; a total of 270 h of videotape was analyzed. Fifteen spawning events were observed, four of which involved individuals of different species. Male brown trout and brook trout attended females of both species. Female reproductive behavior was similar whether attended by conspecific or heterospecific males. No diel rhythms that would temporally isolate species during spawning were evident. Our results suggest that brook trout and brown trout spawning behaviors do not contribute to reproductive isolation of the two species and that disruptive interactions between them may be common. These interspecific sexual interactions may play a role in species replacement.

Influences on Brown Trout and Brook Trout Population Dynamics in a Michigan River

“…In addition, increased catch-and-release behavior of anglers appeared to be detrimental to age-1 brook trout survival, possibly because increased release activities limited depletion of populations of large, predatory brown trout (Table 6). Negative effects of brown trout on co-existing brook trout stocks have been shown previously by Waters (1983) and Grant et al (2002). Negative effects of intra-and interspecific competition were quite apparent in growth and survival models with significant negative coefficients occurring for competitors in models developed for both species and all ageclasses, except growth of age-1 brook trout (Table 5).…”

Do native brown trout and non-native brook trout interact reproductively?

“…In particular, we find extensive evidence that brook and brown trout interfere with each other's reproductive success in southem Europe, a phenomenon described previously in North America. Thus, although salmonid species usually spawn in different habitats and seasons, non-native salmonids species can disrupt this process and may lead to replacement of native species (Grant et al 2002). Specifically, we found a high level of reproductive interactions due to a consistent spatial and temporal overlap in redd localizations and spawning periods and interspecific spawning interactions (mixed groups and interspecific subordinate males) resulting in hybridization during the monitored reproductive season in the study area.…”

“…The occurrence of mix.cd groups and rcdds superimposition is a commo:n feature when brook and brown ttout spawning ranges overlap (Witzel and MacCrimmon 1983;Sorensen et al 1995;Grant et al 2002). Although the number of observed mixed groups was relatively low (n=S, representing 7.8% of the total number of active redds), wc round that these groups were principally composed of brook trout dominant males and brown trout females and that they superimposed their redds on existing redds (direct and indirect observations).…”

“…The reciprocal patterns of reproductive inteoections between brook and brown trout in North America and Southern Europe might explain the invasion sucoess of the two species. In North America, brown trout invasion might be facilitated by reproductive inteJ:actions (Grant et al 2002), but in Southem Europe, these interactions might act as a form of biotic resistance 1bat limit or balt brook trout invasion, although its potential threat on native brown trout and invasiveness can occur after a long lag time (Spens et al 2007). Furthermore, there are now examples of non-native fish species, even with small introductions, altering the evolutionary pathway of native species by hybridization and subsequent introgression (Mooney and Cleland 2001;Hanfling 2007).…”

“…In many regions of North America, the adverse impacts of non-native brown trout on native brook trout have been demonstrated (e.g., Nyman 1970;Fausch and White 1981 ;DeWald and Wilzbach 1992). Amongst these effects are numerous reproductive interactions including attempted hybridization that may be partially responsible for the replacement of brook trout by brown trout in sorne locations (Sorensen et al 1995;Essington et al 1998;Grant et al 2002). However, the reciprocal effect of brook trout introduction on native brown trout in Europe has received less attention and is still controversial.…”