Minnow introductions in mountain lakes result in lower salmonid densities

Abstract

Small fish species such as minnows (Phoxinus sp.) are introduced into mountain lakes by anglers that use them as live bait for fishing salmonids that were previously introduced in these naturally fishless habitats. Introduced fish severely impact native biota but minnows are nevertheless released believing to provide forage for game fish, i.e., salmonids. However, our results indicate that minnows negatively interact with game fish, reducing their relative densities. On some occasions, minnows can remain the only present fish following trout extinction. We believe that this information should be urgently disseminated among anglers as a pragmatic argument to also convince anglers less sensitive to conservation issues that carrying minnows to the mountains is not a good idea whatever the main interest is, e.g., nature conservation or outdoor recreation.

Evaluation of visual encounter surveys as a method for the rapid assessment of fish presence and relative density in high mountain lakes

“…All study lakes are typical mountain lakes (Figure 2) with surface areas between 0.2 and 30.2 ha, cold and ice covered for 4–9 months per year, located close to or above the local treeline, with altitudes ranging between 1,618 and 2,747 m. Introduced fish include both Salmonidae (brown trout Salmo trutta L. 1758, brook trout Salvelinus fontinalis Mitchil 1751, Arctic charr Salvelinus alpinus L. 1758, and rainbow trout Oncorhynchus mykiss Walbaum 1792) and small Cyprinidae used as live bait to fish for trout (European minnows belonging to the Phoxinus species complex and vairone Telestes muticellus Bonaparte 1837) (Figure 3). Because of such collateral introductions, 19 lakes have both salmonids and cyprinids, and 11 lakes are occupied by cyprinids only (Figure 1), after salmonid populations underwent extinction maybe as a result of interactions with minnows (Borgstrøm, Museth & Brittain, 2010; Tiberti et al, 2022). The remaining 22 lakes only had salmonids (Figure 1).…”

“…To be considered reliable, VES results should provide (i) the same or similar detection probabilities as gill-and fyke-netting methods, not adversely influenced by lake size, and (ii) density indices significantly correlated with those achieved by gill-and fyke-netting methods. 1), after salmonid populations underwent extinction maybe as a result of interactions with minnows (Borgstrøm, Museth & Brittain, 2010;Tiberti et al, 2022). The remaining 22 lakes only had salmonids (Figure 1).…”

Invaders they are a‐changing†: A recent, unexpected surge of invasive loaches in Catalonia

“…Once established, non‐native fish species tend to spread across naturally isolated basins (Clavero & Garcia‐Berthou, 2006) and drive the decline of the highly endemic and threatened native fish fauna (Hermoso et al, 2011). Fish introductions in the Iberian Peninsula have been primarily related to sport fishing, either involving species targeted by fishermen (large‐bodied fish, often predators) or species perceived to favour game fish by providing food (the so‐called forage fish , most often small‐bodied cyprinids; Carpio et al, 2019; Tiberti et al, 2022).…”

Unravelling the molecular mechanisms of fish salinity adaptation in the face of multiple stressors: A comparative multi-tissue transcriptomic study in the Llobregat River, Barcelona, Spain

“…The Phoxinus spp. invasions into several new catchments have led to ecological consequences, such as competition for food and predation on eggs, adversely affecting native species (Borgstrøm et al, 2010;Garcia-Raventós et al, 2020;Tiberti et al, 2019Tiberti et al, , 2022. Notably, their adaptability to high salinity in brackish waters, observed in certain coastal regions, may bolster their potential to invade upstream and colonize systems facing altered ecological conditions due to freshwater salinization.…”