The history of the minnow Phoxinus phoxinus (L.) in Norway: from harmless species to pest

Abstract

The causes, effects and extent of minnow Phoxinus phoxinus introductions in Norway are reviewed to assess why the introductions have had severe effects, especially where brown trout Salmo trutta is the only fish species present. 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. 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 richness.

Distribution of Eurasian minnows (Phoxinus: Cypriniformes) in the Western Balkans

“…The sympatry of minnows and salmonids (Museth et al, 2007;Kottelat, 2007;Kottelat and Freyhof, 2007) supports the hypothesis of introductions of Phoxinus species throughout the Europe through fish trade and recreational fishing practice. Caution is needed in biogeographic interpretation because human-mediated translocations of Phoxinus species could mask their natural distribution ranges (Kottelat, 2007).…”

“…The distribution range of Phoxinus species in Europe considerably expanded throughout the 20th century, especially in the mountain areas of Norway and Pyrenees, due to the usage of minnows as live bait for angling (Museth et al, 2007;Miró and Ventura, 2015). Translocation of minnows without previous species determinations could have led to the introduction of non-native Phoxinus species in drainages occupied by autochthonous species of Phoxinus (Kottelat, 2007).…”

“…Translocation of minnows without previous species determinations could have led to the introduction of non-native Phoxinus species in drainages occupied by autochthonous species of Phoxinus (Kottelat, 2007). Moreover, introductions of minnows can represent a serious threat to trout fisheries (Museth et al, 2007).…”

“…Since the beginning of the 20th century, minnows have expanded outside their native distribution range, especially in the mountain areas of Scandinavia where they were used as live bait (Museth et al, 2007) and Pyrenees as a by-product of trout stocking (Miró and Ventura, 2015). Presently, the Eurasian minnows of the genus Phoxinus include at least 15 species (Eschmeyer et al, 2017) adapted to cold and well-oxygenated waters of fast-flowing mountain streams, large lowland rivers and lakes (Kottelat and Freyhof, 2007).…”

Why Should We Preserve Fishless High Mountain Lakes?

“…The distribution of minnow expanded considerably throughout the twentieth century in the north European lakes of Scotland and Norway, especially in mountain areas, due mainly to the use of minnows as live bait for angling (Maitland and Campbell 1992;Museth et al 2007). When minnow is introduced in lakes with autochthonous trout, it reduces recruitment and annual growth rates of trout, causing a decrease of the trout abundance by 35% on average; however, the effect on other native fauna takes place primarily in the shallow littoral areas (Museth et al 2007). …”