Unintentional selection, unanticipated insights: introductions, stocking and the evolutionary ecology of fishes

Abstract

Natural environmental change has produced countless opportunities for species to disperse into and persist in habitats where they previously did not exist. Introduction and stocking programmes have facilitated similar sorts of colonization opportunities across considerably greater geographical scales and often in much shorter periods of time. Even though the mechanism of colonization differs, the result can be the same: evolutionary change in the colonizing population in response to novel selection pressures. As a consequence, some human-mediated fish transfers have unintentionally yielded novel research opportunities to study how phenotypes and genes interact with their environment and affect ecological and evolutionary change. The primary purpose here is to explore how work, directly or indirectly involved with human-mediated transfers, has unintentionally yielded novel research and research opportunities in fish ecology and evolution. Insights have produced new knowledge or altered previously held perceptions on topics such as local adaptation, rate of evolutionary change, phenotypic plasticity, alternative reproductive strategies, population structure and colonization probability. Well-documented stocking programmes, especially in terms of history, numbers and original population sources, can provide highly fertile ground for generating further insights on the ecology and evolution of fishes and of the factors likely to influence the success of conservation-based, restoration programmes.

Genetic changes caused by restocking and hydroelectric dams in demographically bottlenecked brown trout in a transnational subarctic riverine system

“…Similarly, the introduction of non-native species is problematic as local adaptation patterns might be disrupted (Bourret, O'Reilly, Carr, Berg, & Bernatchez, 2011;Hutchings, 2014;Jonsson & Jonsson, 2016). Consequently, supplementary stocking with regional specimens has become a widely applied alternative aiming to both maintain natural genetic diversity and integrity and counteract negative effects stemming from overexploitation, pollution, and artificial migration barriers (Saint-Pé et al, 2018;Vøllestad & Hesthagen, 2001).…”

“…In some cases, stocking has reduced genetic differentiation across wild populations (Eldridge et al, 2009;Eldridge & Naish, 2007;Hansen et al, 2009;Kohout, Jašková, Papoušek, Šedivá, & Šlechta, 2012;Marie, Bernatchez, & Garant, 2010) and altered dispersal behavior of admixed offspring (Saint-Pé et al, 2018). These findings have raised concerns about the loss of local adaptation (Bourret et al, 2011;Hutchings, 2014;Jonsson & Jonsson, 2016) and changes in ecologically important traits through hybridization between wild and captivity-bred fish (Saint-Pé et al, 2018).…”

Interspecific association of brown trout (Salmo trutta) with non‐native brook trout (Salvelinus fontinalis) at the fry stage

“…Species discrimination in fish may be based on visual (Warburton & Lees, 1996), behavioral, and chemical cues (Burnard, Gozlan, & Griffiths, 2008). However, brown trout and brook trout are morphologically similar at the fry stage ( Figure 1) and have a short evolutionary history of coexistence (Hutchings, 2014). This raises the possibility that brown trout do not yet perceive brook trout as a competitor, which could facilitate interspecific association between the species at an early life stage, eventually leading to social learning that changes the feeding preference of brown trout in sympatry with brook trout?…”

The role of ecotype‐environment interactions in intraspecific trophic niche partitioning subsequent to stocking

“…Hatchery and stocking practices may vary among jurisdictions or be species specific, but are generally based on an artificial hatchery production of the target species preceding their release into the wild. While supplementation may represent an efficient method for preservation of wild populations, concerns about its potential negative impacts have long been raised (Allendorf et al 2001, Araki et al 2009, Vandersteen et al 2012, Hutchings 2014.…”