Pink salmon in Norway: the reluctant invader

Abstract

In 2017, Norway experienced an invasion of the Pacific salmonid pink salmon (Oncorhynchus gorbuscha) in numbers never before seen in rivers all along the coast. Significant numbers were also caught in other parts of northwestern Europe. Pink salmon has been observed in variable numbers in Norwegian waters in the summer and autumn of most years since 1960, after the first successful Russian introduction of pink salmon fry in rivers draining to the White Sea in northwest Russia in 1959. With the exception of 1960, pink salmon have been most abundant in odd years, based on the odd-year broodline of the 2-year life salmonid. Even-year fish has generally been less abundant, but in recent years, significant numbers of this broodline have also been caught. In this paper we review the available information on pink salmon in Norwegian rivers and discuss (1) to what extent the presence of this species in Norway has been driven by Russian introductions and natural reproduction in Russian, and lately in Norwegian, rivers, and (2) the likelihood of reproducing populations of pink salmon being established in more Norwegian rivers. Considering the continued propagule pressure in terms of adult pink salmon entering and spawning in Electronic supplementary material The online version of this article (

Unprecedented widespread occurrence of Pink Salmon Oncorhynchus gorbuscha in Ireland in 2017

“…The risk of O. gorbuscha becoming established in Irish waters will most likely relate to the level of propagule pressure experienced in Ireland over the coming years rather than the periodic presence of small numbers of vagrant fish. Repeated stocking programmes in rivers in north‐western Russia since the 1950s until 2001 are thought to have resulted in the initial expansion and the apparent establishment of self‐sustaining O. gorbuscha populations in northernmost Norway (Niemelä et al ., ; Sandlund et al ., ). Despite their persistent presence there since the 1960s, this is not known to have resulted in such populations establishing further south in Norway to date (Sandlund et al ., ).…”

“…Repeated stocking programmes in rivers in north‐western Russia since the 1950s until 2001 are thought to have resulted in the initial expansion and the apparent establishment of self‐sustaining O. gorbuscha populations in northernmost Norway (Niemelä et al ., ; Sandlund et al ., ). Despite their persistent presence there since the 1960s, this is not known to have resulted in such populations establishing further south in Norway to date (Sandlund et al ., ). Introductions to rivers in the Baltic region were also unsuccessful (Crawford & Muir, ).…”

“…This suggests a low risk of establishment of the species in Ireland at present. Nevertheless, the well‐established range of O. gorbuscha in north‐western Russia and northern Norway is considered to represent a “permanent, but variable propagule pressure on rivers in Norway as well as in the rest of north‐western Europe” (Sandlund et al ., ). An increasing frequency of climatic conditions ( e.g ., more optimum river temperatures for hatching and smolt migration) that favour the development and survival of O. gorbuscha is likely to increase the risk of establishment in Ireland and neighbouring jurisdictions.…”

“…gorbuscha is established in river systems draining into the White Sea and Barents Sea in the Kola Peninsula region of north-west Russia as a consequence of periodic stocking programmes undertaken there since the 1950s (Gordeeva et al, 2015) and self-sustaining populations have established in the Great Lakes region of North America after their unauthorised introduction into the Lake Superior drainage basin in 1956 (Crawford, 2001). Following its introduction to north-west Russia, the species has regularly been recorded in catches in almost all the Atlantic salmon Salmo salar L. 1758 rivers in northern Norway, notably in the Finnmark region, and in some of the same systems further upstream in Finnish territory (Niemelä et al, 2016;Sandlund et al, 2018). Incidences of O. gorbuscha encountered outside its native or established range were sporadic until 2017 when an unprecedented increase in their occurrence was observed across the North Atlantic region including in the waters of eastern Canada, Iceland, Greenland, western and southern Norway, Britain, Ireland and France (Armstrong et al, 2018;ICES, 2018;Mo et al, 2018).…”

Environmental (e)DNA detection of the invasive pink salmon Oncorhynchus gorbuscha during the 2017 Norwegian invasion

“…For this study, water samples were collected from the Lysakerelva river in the south-east 114 region of Norway (Table 1) previously been caught in the Lysakerelva river (>20 fish; Sandlund et al, 2018). 122…”