Eurasian Minnow (Phoxinus phoxinus) is a 14cm long “Demersal; potamodromous fish that can live up to 11 years. “Originally, minnows were spread because fishermen used them as live bait for catching species like brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), perch (Perca fluviatilis) and pike (Exos lucius) (Huitfeldt-Kaas 1918). This practice is considered to be the main reason for most introductions throughout the 1900s. However, minnows have also been accidentally introduced in a large number of lakes together with stocked hatchery-reared brown trout (Borgstrøm 1973; Lura and Kålås 1994). Brown trout stocking has been routinely done especially in lakes modified as hydropower reservoirs, in order to compensate for reduced natural
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The natural distribution of minnow in Norway was mainly restricted to low altitude localities in the south-eastern part of the country and in some northern areas. According to Museth et al. 2007, the distribution area expanded considerably throughout the 1900s, especially in mountain areas, due in part to the use of minnows as live bait for angling. Although minnow densities do not seem unusually high in the relatively complex fish communities of its native range, the species can achieve very high population densities when introduced to communities with few fish species, such as in the numerous recently invaded lakes where brown trout was the only fish species present. The dense minnow populations in these lakes appear to have led to reduced recruitment and growth rates in the brown trout, with abundances on average 35% lower in lakes where minnow has been introduced. The success of minnow in harsh habitats demonstrates their phenotypic and ecological plasticity, but also implies that their original distribution in Norway was restricted by early immigration history and not by environmental limitations. This suggests that human-assisted spread of the species could have strong adverse effects in Scandinavia lakes of low fish species …show more content…
phoxinus. In Lake Øvre Heimdalsvatn, the introduction of P. phoxinus caused major changes in the benthic community (Brittain et al. 1988, 1995 ; Næstad and Brittain 2010). Benthic diversity declined, with a marked increase in numbers of oligochaetes and small forms, especially chironomids. There was also a marked decline in numbers of Gammarus lacustris, especially the proportion of larger individuals. However, total benthic densities remained similar to pre-introduction. G. lacustris formed a major component of the P. phoxinus’ diet, while its occurrence in brown trout stomachs declined greatly. Lepidurus arcticus also virtually disappeared from the trout diet, probably due to minnow predation. In a Norwegian reservoir, introduced P. phoxinus fed on the planktonic stages of L. arcticus, and after a few years adult specimens became an insignificant part of the diet of brown trout (Borgstrøm et al. 1985). The degree of diet overlap and declining growth rates of both brown trout and P. phoxinus in Lake Øvre Heimdalsvatn indicate substantial competitive interactions between the two fish species (Museth et al.
The natural distribution of minnow in Norway was mainly restricted to low altitude localities in the south-eastern part of the country and in some northern areas. According to Museth et al. 2007, the distribution area expanded considerably throughout the 1900s, especially in mountain areas, due in part to the use of minnows as live bait for angling. Although minnow densities do not seem unusually high in the relatively complex fish communities of its native range, the species can achieve very high population densities when introduced to communities with few fish species, such as in the numerous recently invaded lakes where brown trout was the only fish species present. The dense minnow populations in these lakes appear to have led to reduced recruitment and growth rates in the brown trout, with abundances on average 35% lower in lakes where minnow has been introduced. The success of minnow in harsh habitats demonstrates their phenotypic and ecological plasticity, but also implies that their original distribution in Norway was restricted by early immigration history and not by environmental limitations. This suggests that human-assisted spread of the species could have strong adverse effects in Scandinavia lakes of low fish species …show more content…
phoxinus. In Lake Øvre Heimdalsvatn, the introduction of P. phoxinus caused major changes in the benthic community (Brittain et al. 1988, 1995 ; Næstad and Brittain 2010). Benthic diversity declined, with a marked increase in numbers of oligochaetes and small forms, especially chironomids. There was also a marked decline in numbers of Gammarus lacustris, especially the proportion of larger individuals. However, total benthic densities remained similar to pre-introduction. G. lacustris formed a major component of the P. phoxinus’ diet, while its occurrence in brown trout stomachs declined greatly. Lepidurus arcticus also virtually disappeared from the trout diet, probably due to minnow predation. In a Norwegian reservoir, introduced P. phoxinus fed on the planktonic stages of L. arcticus, and after a few years adult specimens became an insignificant part of the diet of brown trout (Borgstrøm et al. 1985). The degree of diet overlap and declining growth rates of both brown trout and P. phoxinus in Lake Øvre Heimdalsvatn indicate substantial competitive interactions between the two fish species (Museth et al.