Behavioural traits of rainbow trout and brown trout may help explain their differing invasion success and impacts

Abstract

Animal behaviour is increasingly recognised as critical to the prediction of non-native species success and impacts. Rainbow trout and brown trout have been introduced globally, but there appear to be differences in their patterns of invasiveness and ecological impact. Here, we investigated whether diploid rainbow trout and diploid and triploid brown trout differ among several key behavioural measures linked to invasiveness and impact. We assessed activity, boldness, aggression, and feeding, using open field, novel object, shelter, mirror, feeding, and functional response experiments. We also tested within each fish type for behavioural syndromes comprising correlations among activity, boldness and aggression. Rainbow trout were more active and aggressive but less bold than diploid and triploid brown trout. In small groups, however, rainbow trout were bolder than both types of brown trout. Diploid brown trout were more active and bolder than triploids when tested individually, and had a higher functional response than both rainbow trout and triploid brown trout. In terms of behavioural syndromes, there was no association between activity and boldness in rainbow trout, however, there was in both brown trout types. The increased activity and aggression of rainbow trout may reflect an increased stress response to novel situations, with this response reduced in a group. These results suggest that rainbow trout do not manage their energy budgets effectively, and may explain why they have limited survival as invaders. In addition, the lower functional response of rainbow trout may explain why they are implicated in fewer ecological impacts, and the triploidy treatment also appears to lower the potential impact of brown trout. Comparative analyses of multiple behaviours of invasive species and genetic variants may thus be key to understanding and predicting invader success and ecological impacts.

Age-Related Changes in Survival Behaviour in Parasite-Free Hatchery-Reared Rainbow Trout (Oncorhynchus mykiss)

“…The findings of Johnsson et al [36] determined that due to the altered behavioural patterns observed in captive-bred brown trout, they may pose a threat to wild populations. Brown trout are a more successful invasive species compared to Rainbow trout, though Rainbow trout have higher levels of aggression in novel situations [37]. When considering the impact of released trout on ecosystems, the above findings suggest that breeding from wild-caught adults may be beneficial as these fish may be shyer and have less impact on the ecosystem.…”

Resilient Amphipods: Gammarid Predatory Behaviour is Unaffected by Microplastic Exposure and Deoxygenation

“…Functional response trials were conducted with individual Gammarus from each species in the experimental arenas. The arenas were placed on a black surface to imitate a more natural environment, with the outsides covered in a layer of masking tape to prevent external visual stimulation, as used in similar experiments (Dickey et al, 2021;McGlade et al, 2022). Arenas were arranged in a random formation among treatments to prevent blocking effects.…”

The Physiological Effects of Some Stress Indicators in Rainbow Trout Raised in Different Systems

“…Worldwide, the highest colonization rate for commercial exploitation is observed in rainbow and brown trout. However, the two species have different responses in terms of adaptation capacity and ecological impact [1].…”