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 (

In birds parental incubation behaviour is an important factor shaping the environmental conditions under which the embryos develop, and sub-optimal incubation temperatures are known to negatively affect early growth and development. It is less well known if variation in incubation temperature can impose life-long differences in individual performance and survival. In the present study we investigated the effects of incubation temperature on long-term survival in a small passerine bird. Using our captive population of the zebra finch Taeniopygia guttata we artificially incubated eggs at three biologically relevant temperatures (35.9, 37.0 and 37.9°C) for two-thirds of the incubation period and then monitored individual lifespan of the hatched chicks for two and a half years. We found that individuals from eggs incubated under the lowest temperature exhibited significantly lower long-term survival compared to those which had been incubated at the highest temperature. Our results show that incubation temperature in birds, and thus parental incubation behaviour, play an important role in shaping the life-history trajectories of offspring.Early developmental conditions are important in determining offspring phenotype (Lindström 1999, Metcalfe and Monaghan 2001) and parental effects play a vital role as a non-genetic source of variation in offspring life-history traits (Badyaev and Uller 2009). The avian embryo is poikilothermic and is dependent on an external heat source in order to grow and develop. Because the maintenance of incubation temperature is energetically costly (Thomson et al. 1998) parents may compromise incubation temperature (by adjusting on-and off-bout dynamics or actively maintaining lower temperatures on average) when faced with demanding incubation conditions (Ardia et al. 2010, Nord et al. 2010. Parental incubation behaviour therefore greatly influence both the mean egg temperature as well as the variability in temperature at which the embryos develop. Although incubation temperatures are know to vary within bird populations (Webb 1987) it is only recently that the consequences of such variation on offspring phenotypes have been thoroughly investigated. In both precocial and altricial species lower than average incubation temperatures have been shown to negatively affect the development of several phenotypic traits that are important for nestling survival such as growth, body size, immunocompetence, locomotor performance and metabolic rate (Hepp et al. 2006, Nord and Nilsson 2011, DuRant et al. 2012. Hence, the incubation environment provided by the parent(s) may play a critical role in shaping the life-history trajectory of the offspring. However, whether sub-optimal incubation temperatures can cause permanent long-lasting differences in physiological performance and survival beyond the nestling stage is not well known. Only one study has previously monitored individual survival into adulthood in relation to incubation temperature, demonstrating a negative effect of lower than average incubation ...

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We report for the first time the geographic distribution, abundance, diet, and body size of invasive pink salmon (Oncorhynchus gorbuscha) in the Norwegian and Barents Seas and Norwegian coast and rivers. We found that pink salmon have spread throughout the Norwegian Sea and along the Norwegian coast, and abundance increased by several orders of magnitude in 2017, with no signs that it has peaked. Marine pink salmon diet comprised mainly fish larvae, amphipods, and krill, but their relative importance varied with geographic distribution. North of 67.5°N, Amphipoda, herring, and saithe were more important, while south of 67.5°N, Euphausiidae and mesopelagic fish abounded. Pink salmon body size was larger in the northern rivers, and to the north of the Norwegian Sea and the Barents Sea, relative to the southern rivers and sea areas. Pink salmon were feeding in the ocean during the winter and spring, and in coastal areas immediately before return to the rivers, but not after they had entered the rivers. There was no geographical pattern in the seasonal timing of river ascent. The geographic pattern in abundance and diet of pink salmon, as reported here, offer a measure of the ecological effect of the invasion.

While populations of other migratory salmonids suffer in the Anthropocene, pink salmon (Oncorhynchus gorbusca Salmonidae) are thriving, and their distribution is expanding both within their natural range and in the Atlantic and Arctic following introduction of the species to the White Sea in the 1950s. Pink salmon are now rapidly spreading in Europe and even across the ocean to North America. Large numbers of pink salmon breed in Norwegian rivers and small numbers of individuals have been captured throughout the North Atlantic since 2017. Although little is known about the biology and ecology of the pink salmon in its novel distribution, the impacts of the species' introduction are potentially highly significant for native species and watershed productivity. Contrasts between pink salmon in the native and extended ranges will be key to navigating management strategies for Atlantic nations where the pink salmon is entrenching itself among the fish fauna, posing potential threats to native fish communities. One key conclusion of this paper is that the species' heritable traits are rapidly selected and drive local adaptation and evolution. Within the Atlantic region, this may facilitate further establishment and spread. The invasion of pink salmon in the Atlantic basin is ultimately a massive ecological experiment and one of the first examples of a major faunal change in the North Atlantic Ocean that is already undergoing rapid changes due to other anthropogenic stressors. New research is urgently needed to understand the role and potential future impacts of pink salmon in Atlantic ecosystems.