Between-watershed movements of two anadromous salmonids in the Arctic

Abstract

A long-term study in the River Halselva in the Arctic region of Norway demonstrated that movements between watersheds were considerably higher in anadromous brown trout (Salmo trutta) than anadromous Arctic char (Salvelinus alpinus).Fourteen smolt year classes of both species were captured in a fish trap, individually tagged, and thereafter registered each time they passed the trap during their migration between the sea and fresh water every summer. Annual mean survival (i.e., recovery rate) after the first entry to sea as smolts was estimated as 31.4% in Arctic char and 26.6% in brown trout. Most surviving Arctic char returned to the River Halselva to overwinter after the same summer that they migrated to sea as smolts. However, several brown trout overwintered one to four times in other watersheds, mainly the considerably larger River Altaelva, before most eventually returned to the River Halselva upon maturation. The substantial difference in movement rate between watersheds between Arctic char (2.2%) and brown trout (39.6%) is expected to be a consequence of local geographic conditions combined with different habitat preferences of the two species.Résumé : Une étude de longue durée de la rivière Halselva dans la région arctique de la Norvège a démontré que les déplace-ments entre bassins versants étaient considérablement plus importants pour la truite brune (Salmo trutta) anadrome que pour l'omble chevalier (Salvelinus alpinus) anadrome. Des saumoneaux de quatorze classes d'année des deux espèces ont été capturés dans un piège à poissons, marqués individuellement, et subséquemment enregistrés chaque fois qu'ils passaient par le piège durant leur migration entre la mer et l'eau douce chaque été. Le taux de survie annuelle moyen (c.-à -d. le taux de récupération) après la première entrée en mer comme saumoneaux a été estimé à 31,4 % pour les ombles chevaliers et 26,6 % pour les truites brune. La plupart des ombles chevaliers survivants retournaient à la rivière Halselva pour passer y l'hiver dès l'été où ils avaient migré vers la mer en tant que saumoneaux. En revanche, plusieurs truites brune ont passé l'hiver d'une à quatre fois dans d'autres bassins versants, principalement celui de la rivière Altaelva, beaucoup plus grande, avant de finalement retourner à la rivière Halselva à la maturité. La différence considérable des taux de déplacement entre bassins versants pour l'omble chevalier (2,2 %) et la truite brune (39,6 %) serait une conséquence des conditions géographiques locales combinées à des préférences différentes des deux espèces en matière d'habitat. [Traduit par la Rédaction]

Disentangling individual movement between populations from effective dispersal in the facultative anadromous Salmo trutta L.

“…Strikingly, while straying movement was detected in high proportions throughout the study area (especially in Nivelle and Nives), no genetic exchange that cannot be attributed to human‐mediated translocation was detected, suggesting that straying sea trout were not sexually mature, did not successfully reproduce, or, if they did so, their fitness was unexpectedly low. The former hypothesis would be in line with recent findings in North Atlantic showing that straying sea trout are more likely young and sexually immature (Jensen et al., ). Sea trout scale reading will possibly contribute to better understand straying behaviour in our river system.…”

“…Sea trout move frequently between river, estuary and sea habitats (Etheridge, Harrod, Bean, & Adams, 2008;Jensen et al, 2012;Pemberton, 1976;Pratten & Shearer, 1983b), and contrary to expectations, upstream movements are not always related to reproduction (King, Hillman, Elsmere, Stockley, & Stevens, 2016;Nall, 1930). Most sea trout individuals stay in seawater nearby their natal river mouth (Berg & Berg, 1987;Skrochowska, 1969b) but may also move to non-natal estuaries (Degerman, Leonardsson, & Lundqvist, 2012) and non-natal streams (Jensen, Diserud, Finstad, Fiske, & Rikardsen, 2015). The propensity to visit non-natal streams during marine migration (straying) appears to be more common among sea trout individuals originating from small streams (Degerman et al, 2012) or among those that have not reached sexual maturity (Jensen et al, 2015).…”

Preference for nearshore and estuarine habitats in anadromous Arctic char (Salvelinus alpinus) from the Canadian high Arctic (Victoria Island, Nunavut) revealed by acoustic telemetry

“…Stock mixing and (or) straying has been documented in Arctic char (e.g., Moore et al 2013Moore et al , 2014Jensen et al 2015), including in the Cambridge Bay region (Dempson and Kristofferson 1987). The telemetry approach used in the present study, however, showed with a greater level of detail that stock mixing is extensive and occurs throughout the summer.…”

“…In some populations, Arctic char forego marine migrations in the year before spawning (Gyselman 1994). Arctic char generally home to their natal system to spawn, but straying and stock mixing can be common (e.g., Dempson and Kristofferson 1987;Jensen et al 2015), especially in years when individuals do not spawn (Moore et al 2013(Moore et al , 2014. In some systems, spawning and overwintering sites are located in different areas, requiring a postspawning migration within fresh water (Johnson 1980;Beddow et al 1998).…”

Water level influences migratory patterns of anadromous brown trout in small streams

“…However, runs of that size appear adequate to maintain viable populations of anadromous brown trout, as reported by Thomson and Lyndon (2018) from the Orkney, UK. Anadromous trout sometimes visit lower parts of rivers other than their home stream (Euzenat, 1999;Jensen et al, 2015;King et al, 2016;Masson et al, 2018;Solomon, 2006). The effective straying rate, however, may be low as immature first-time migrants tend to enter other streams more often than the mature veteran migrants do.…”