Atlantic salmon have had a key role in European and North American oceans and human societies. Salmon are exploited and observed in rivers and along coasts, but there has always been great interest in knowing where salmon are going when they are at sea. Advances in electronic tagging and tracking, isotopic methods, and genetics have helped unravel a new understanding of salmon at sea. Ocean warming and changes to the Atlantic...

Current knowledge on the continental shelf and transatlantic spawning migration of the European eel ( Anguilla anguilla ) is based on silver eels outmigrating from fresh water. However, an unknown proportion of eels grow in marine coastal waters during the continental part of their lifecycle and therefore start their spawning migration while they are already in marine waters. To study the onset of the European eel's spawning m...

Non-native pink salmon ( Oncorhynchus gorbuscha ) have increased rapidly in Norwegian rivers since 2017, yet their marine ecology remains poorly understood. To assess variation in marine growth, we analysed scales from 476 individuals returning to northern (Barents Sea region) and central (Atlantic region) Norway in 2019 and 2021. Clear differences in growth and body size emerged between regions and years, with fish returning...

Introductions of species outside their native range, such as pink salmon ( Oncorhynchus gorbuscha ) in the Laurentian Great Lakes, can serve as unplanned experiments that provide new insights into ecological adaptation. We synthesize available information on the understudied Great Lakes pink salmon invasion and highlight how this case can inform research and management related to expansions and invasions of this species in the...

Upstream fish movement in the Danube River at the Iron Gate is blocked by the massive hydropower dams and ship locks, as shown by tracking six fish species (vimba bream Vimba vimba , common nase Chondrostoma nasus , barbel Barbus barbus , asp Leuciscus aspius , Pontic shad Alosa immaculata and common carp Cyprinus carpio ). In the absence of effective fish passage systems, the current level of river connectivity is insufficien...

Drastic declines in abundance of Atlantic salmon have been attributed to ecosystem change at sea reducing growth in body size, which in turn could impact survival because mortality at sea may be size-selective. A less scrutinized hypothesis proposes that poor growth conditions at sea may also increase mortality if slow growing individuals need more time at sea to become sexually mature with a longer marine residence period als...

Evolution of phenotypic plasticity requires genotype–environment interaction. The discovery of two large‐effect loci in the vgll3 and six6 genomic regions associated with the number of years the Atlantic salmon spend feeding at sea before maturation (sea age), provides a unique opportunity to study evolutionary potential of phenotypic plasticity. Using data on 1246 Atlantic salmon caught in the River Surna in Norway, we show t...

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 bree...

The timing of seaward migration is a key life‐history trait for many anadromous fish species, with growth and survival at sea depending on a match/mismatch scenario between the timing of the sea entry and optimal conditions. Based on a 25‐year study with 15,226 individually tagged brown trout ( Salmo trutta ) in a Norwegian river, we analysed how the within‐season timing of sea migration impacted growth and survival. In both f...

During the last decades, many wild Atlantic salmon populations have declined dramatically. One hypothesis for an observed reduction in salmon marine growth and survival is reduced abundance of prey. However, the effect of spatial and temporal variation in marine prey abundance on post-smolt feeding conditions is poorly understood. Here we use stomach content data from 2572 salmon post-smolts sampled during 25 years in the Nort...

Invasive pink salmon ( Oncorhynchus gorbuscha ) has been present in variable, but low, numbers in Norwegian waters since c . 1960, but beginning in 2017 their numbers have exploded in rivers in northern Norway, with considerable numbers also recorded in rivers in southern Norway and other countries bordering the North Atlantic. Analysis of pink salmon scales from two rivers draining to the western Barents Sea showed declining...

Acoustic telemetry was utilized to track 49 brown trout ( Salmo trutta ) and 37 Arctic charr ( Salvelinus alpinus ) first‐time migrants of wild origin [post‐smolts; mean L F (fork length): 169 and 172 mm] in a large fjord in northern Norway. The S. trutta were registered at sea for more than twice the time of the S. alpinus (medians of 54 and 22 days, respectively). Both species were mostly detected near river mouths (>80% of...

A systematic review and meta-analysis was conducted to evaluate the appropriate tag:fish size ratio when tagging juvenile salmonids (genera Oncorhynchus , Salmo , and Salvelinus ). The review yielded 18 publications with 211 control and treatment groups reporting results from laboratory studies on the effects of passive integrated transponder (PIT) tags, plus a small number of additional studies on acoustic transmitters. A met...

Potamodromous fishes require safe migration routes between spawning, feeding and wintering habitats to complete their life cycle. As knowledge on asp migrations is restricted, this work investigated the movements of adult asp tagged with acoustic transmitters for 3 years in the large Peipsi‐Emajõgi‐Võrtsjärv lake–river system, Estonia, which is free of migration barriers. Asp showed complex migration patterns, moving between a...

“Småblank” is the only population of Atlantic salmon in Europe living its entire life in the river habitat without performing migrations to the sea or lakes. Home range size and habitat use were compared between an unregulated tributary and hydro-power regulated parts of the main river during 2014–2017. In total, 140 småblank were tagged with radio transmitters and tracked for 4–5 months. Tagged fish tended to stay within smal...

The proportion of angled Atlantic salmon Salmo salar L. being caught and released has increased. If individuals are repeatedly captured, this may have fish welfare consequences. Of 995 Atlantic salmon tagged during catch and release in eight Norwegian rivers, 10% were captured twice, while 3% were captured three times within the same fishing season. The probability that released salmon were captured again decreased with decrea...

Salmon smolts were released upstream of a run‐of‐river hydropower site and recaptured downstream for inspection. Descending fish behaviour through three possible migration routes (turbines, fishway, spillway) was analysed using telemetry, fyke nets and diving. Tagged smolts did not follow the main water flow; over 70% used the fishway, which received only about 10% of the flow. The turbines received about 80% of the water, but