Gérald Chaput

The emerging role of climate in post-smolt growth of Atlantic salmon

Friedland, K. D., Chaput, G., and MacLean, J. C. 2005. The emerging role of climate in post-smolt growth of Atlantic salmon. e ICES Journal of Marine Science, 62: 1338e1349. Though it is well established that mortality during the post-smolt year is critical in shaping recruitment patterns in Atlantic salmon (Salmo salar L.), the controlling mechanism for North Atlantic stocks remains elusive. The emerging paradigm is based on relationships between survival and ocean thermal conditions during the early marine phase. The survival of post-smolts from both Europe and North America has been correlated to sea surface temperature conditions during their first month at sea. In addition, data for European fish support the hypothesis that growth mediates survival during that time. Thus, the working model for a salmon recruitment mechanism is analogous to those proposed for other fish species. We present growth data for two stocks, the Girnock Burn, which is a tributary to the River Dee, Scotland, and the Margaree River, Canada. Circuli spacing data for Girnock Burn fish suggest post-smolt growth is negatively correlated with temperature in the migration corridors during the first months at sea, while post-smolt growth of Margaree fish appears to be positively correlated with temperature. Growth is either patterned by a physiological response to an optimal temperature, or is co-varying with some ecosystem effect on growth, and the growth response might affect mortality and maturation of the stocks. Published by Elsevier Ltd on behalf of International Council for the Exploration of the Sea.

Conservation genomics of anadromous Atlantic salmon across its North American range: outlier loci identify the same patterns of population structure as neutral loci

Anadromous Atlantic salmon (Salmo salar) is a species of major conservation and management concern in North America, where population abundance has been declining over the past 30 years. Effective conservation actions require the delineation of conservation units to appropriately reflect the spatial scale of intraspecific variation and local adaptation. Towards this goal, we used the most comprehensive genetic and genomic database for Atlantic salmon to date, covering the entire North American range of the species. The database included microsatellite data from 9142 individuals from 149 sampling locations and data from a medium‐density SNP array providing genotypes for >3000 SNPs for 50 sampling locations. We used neutral and putatively selected loci to integrate adaptive information in the definition of conservation units. Bayesian clustering with the microsatellite data set and with neutral SNPs identified regional groupings largely consistent with previously published regional assessments. The use of outlier SNPs did not result in major differences in the regional groupings, suggesting that neutral markers can reflect the geographic scale of local adaptation despite not being under selection. We also performed assignment tests to compare power obtained from microsatellites, neutral SNPs and outlier SNPs. Using SNP data substantially improved power compared to microsatellites, and an assignment success of 97% to the population of origin and of 100% to the region of origin was achieved when all SNP loci were used. Using outlier SNPs only resulted in minor improvements to assignment success to the population of origin but improved regional assignment. We discuss the implications of these new genetic resources for the conservation and management of Atlantic salmon in North America.

Prespawning, Spawning, and Postspawning Behavior of Striped Bass in the Miramichi River

Abstract Acoustic telemetry was used to describe the behavior of individual striped bass Morone saxatilis and their use of the Miramichi River estuary during two consecutive spawning seasons in 2004 and 2005. In both years, prespawning striped bass staged in the lower and middle sections of the Miramichi River estuary downstream from the spawning area. Males and females moved in synchrony from the staging area to the spawning grounds in the Northwest Miramichi River. The dates of arrival at the spawning grounds were similar between sexes in both years, but significantly later (by about a week) in 2005. There were no significant differences in average daily water temperature on the dates of arrival at the spawning grounds for male and female striped bass, but water temperatures on the arrival dates were significantly cooler in 2005. Increases in temperature rather than the absolute temperature was the apparent cue initiating the movements of striped bass onto the spawning grounds. Females occupied the spaw...

Hydrometeorological Trends in the Miramichi River, Canada: Implications for Atlantic Salmon Growth

Abstract Hydrometeorological conditions are important determinants of the distribution and productivity of Atlantic salmon Salmo salar in freshwater habitats. Environmental conditions, such as temperature, precipitation, and streamflow, affect an aquatic organisms growth rate, developmental rate, behavior, and ultimate survival. In the Miramichi River, New Brunswick, Canada, climatic and hydrological conditions have been monitored for over 30 years, providing a unique opportunity to examine long-term changes in temperature, precipitation, and streamflow and their effects on juvenile Atlantic salmon. Average air temperature in the Miramichi region increased over time, particularly in spring and summer months. Coincident changes in water temperature were not observed, with only summer water temperature increasing in the Southwest Miramichi River. Extreme summer water temperatures in the Southwest Miramichi River regularly exceeded the upper temperature threshold for growth of Atlantic salmon (22.5°C). Few ...

Spawning-strategy-dependent diets in two North American populations of Atlantic salmon Salmo salar

The diet of repeat-spawner Atlantic salmon Salmo salar was investigated using carbon and nitrogen stable-isotope values from the outer growth band of scales, which reflect the fishs consumption and growth during their most recent marine phase. Isotope values for S. salar displaying different spawning strategies were compared between and within the Miramichi and Nashwaak Rivers, New Brunswick, Canada and a Bayesian mixing model was used to infer dietary contributions from potential prey items. Significant differences in the stable-isotope values were found among spawning strategies and between rivers, indicating differences in diet and feeding area, consistent with hypotheses. Bayesian mixing model results inferred the main prey items consumed during marine feeding by S. salar to consist of hyperiid amphipods and capelin Mallotus villosus for repeat alternate spawners from both rivers, sandlance Ammodytes sp. for repeat consecutive spawners from the Miramichi River and amphipods for repeat consecutive spawners from the Nashwaak River. These results demonstrate the diversity of feeding tactics among S. salar spawning strategies from the same river and between populations from different rivers. Accounting for differences in prey availability and the subsequent impact on S. salar diet and spawner return rates (i.e., marine survival) will facilitate the application of ecosystem-based management practices, such as ensuring that fisheries for forage species do not indirectly adversely affect S. salar return rates.