Evidence for Non-Anadromous Behaviour of Arctic Charr (Salvelinus alpinus) from Lake Hazen, Ellesmere Island, Northwest Territories, Canada, Based on Scanning Proton Microprobe Analysis of Otolith Strontium Distribution

Scanning proton microprobe analysis was used to determine the distribution of strontium (Sr) in otoliths from arctic charr (Salvelinus alpinus) of known non-anadromous, known anadromous, and unknown life histories. Strontium concentration patterns in otoliths of known non-anadromous charr were low and relatively flat (with little variation) from the core area to the outermost edge of the otolith, while patterns for known anadromous charr were characterized by a similar low, flat region for the first several years of life, followed by marked oscillatory increases and decreases in Sr content for the duration of the fish's life. Small and large forms of Lake Hazen charr of unknown life histories exhibited Sr profiles that were similar to those of the known non-anadromous charr, which strongly suggest that Lake Hazen charr are non-anadromous. These results indicate that Lake Hazen is a "closed" system with energy cycling primarily within the system; this conclusion suggests that a conservative approach would be appropriate for the management of the Lake Hazen charr population.À l'aide d'une sonde protonique à balayage, on a procédé à une analyse afin de déterminer la répartition du strontium (Sr) dans des otolithes prélevés sur des ombles chevaliers (Salvelinus alpinus) ayant eu soit un cycle biologique non anadrome connu, soit un cycle anadrome connu ou un cycle inconnu. Les courbes de concentration en strontium dans les otolithes d'ombles reconnus comme non anadromes étaient faibles et relativement uniformes (montrant peu de fluctuations) en allant du centre de l'otolithe vers la périphérie, tandis que les courbes relatives aux ombles reconnus comme anadromes se caractérisaient par une zone de concentrations faibles et uniformes pour plusieurs des premières années de vie, suivie par des oscillations à la hausse et à la baisse très nettes quant au contenu en Sr pour la durée de vie du poisson. De gros et de petits spécimens d'ombles au cycle biologique inconnu, trouvés dans le lac Hazen, affichaient des profils de Sr semblables à ceux des ombles reconnus comme non anadromes, ce qui suggère fortement que l'omble du lac Hazen est non anadrome. Ces résultats révèlent que le lac Hazen est un système où l'énergie circule surtout en circuit «fermé». Cette conclusion suggère qu'il faudrait adopter une approche prudente quant à la gestion de la population d'ombles du lac Hazen

Migration tactics affect spawning frequency in an iteroparous salmonid (Salvelinus malma) from the Arctic.

Otolith strontium and multi-year mark-recapture information were used to characterize associations between migration patterns and spawning frequencies in an anadromous Dolly Varden (Salvelinus malma) population (Rat River, Northwest Territories, Canada) that undertakes a long migration between freshwater spawning/overwintering (Fish Creek; a tributary to Rat River) and marine feeding habitats (Beaufort Sea) (~800 km round trip). Reconstructions of lifetime annual migration histories among otolith annuli was matched to information on reproductive status (current-year 'spawner' or 'non-spawner') that was known in two different, sometimes successive, years for each fish. Two migratory life histories were observed: fish either migrated annually after smoltification or periodically skipped an annual ocean migration to remain in freshwater and spawn. Different spawning frequencies were detected where fish not migrating annually tended to spawn in alternate years (84.6%) more often than those migrating annually (50%). Additionally, annually migrating fish had lower longevity (≤9 years vs. ≤13 years). The evaluation of differences in spawning frequency between sexes, independent of migration tactic, revealed males (84.6%) skipped spawning more often than females (51.2%) suggesting fitness trade-offs between life histories differ between sexes. Further, some fish returned from the sea considerably earlier than the majority of other current-year migrants. Our findings demonstrate intrapopulation diversity in migration behaviour and reproductive frequency

Growth characteristics and age at first migration of anadromous and resident Arctic char (Salvelinus alpinus) and lake trout (Salvelinus namaycush) in the Canadian Arctic (2006-2008)

In the family Salmonidae, lake trout (Salvelinus namaycush) are considered the least tolerant of salt water. There are, however, sporadic reports of lake trout in coastal, brackish habitats in the Canadian Arctic. Otolith microchemistry analyses conducted on lake trout and Arctic char (Salvelinus alpinus) from four Arctic lakes in the West Kitikmeot region of Nunavut, Canada, revealed that 37 of 135 (27%) lake trout made annual marine migrations. Anadromous lake trout were in significantly better condition (K = 1.17) and had significantly higher C:N ratios (3.71) than resident lake trout (K = 1.05 and C:N = 3.34). Anadromous lake trout also had significantly higher d15N (mean = 16.4 per mil), d13C (mean = -22.3 per mil), and d34S (mean = 13.43 per mil) isotope ratios than resident lake trout (means = 12.84 per mil, -26.21 per mil, and 1.93 per mil for d15N, d13C, and d34S, respectively); results were similar for Arctic char and agree with results from previous studies. Mean age of first migration for lake trout was 13 years, which was significantly older than that for Arctic char (5 years). This could be a reflection of size-dependent salinity tolerance in lake trout, but further research is required. These are the first detailed scientific data documenting anadromy in lake trout