scholarly journals Frequency of vateritic otoliths and potential consequences for marine survival in hatchery‐reared Atlantic salmon

2021 ◽  
Author(s):  
Benedikte Austad ◽  
L. Asbjørn Vøllestad ◽  
Anders Foldvik



Author(s):  
Eva B. Thorstad ◽  
Doug Bliss ◽  
Cindy Breau ◽  
Kim Damon‐Randall ◽  
Line E. Sundt‐Hansen ◽  
...  


Aquaculture ◽  
1997 ◽  
Vol 156 (3-4) ◽  
pp. 349-358 ◽  
Author(s):  
R Rahkonen ◽  
M Salminen ◽  
E Erkamo


2015 ◽  
Vol 17 (3) ◽  
pp. 714-730 ◽  
Author(s):  
Knut Wiik Vollset ◽  
Randi Ingebjørg Krontveit ◽  
Peder A Jansen ◽  
Bengt Finstad ◽  
Bjørn Torgeir Barlaup ◽  
...  


Author(s):  
Samuel Shephard ◽  
Patrick Gargan

Abstract Impacts on marine survival of Atlantic salmon Salmo salar include sea lice Lepeophtheirus salmonis infestation from coastal aquaculture, and ocean climate forcing. These effects may interact because infestation compromises smolt growth and body condition, and thus response to environmental conditions. We hypothesized that migrating smolts exposed to lice from salmon farms would show (i) reduced one sea-winter (1SW) returns to natal rivers and (ii) a shift in relationships between ocean climate and returns. Annual counts of 1SW fish were studied from ten rivers in Ireland, including five “control” systems without salmon aquaculture. Most counts showed a downward trend, consistent with declines in Atlantic salmon populations. Rivers with aquaculture showed lesser returns (mean 33%, range 19–46%) in years following high lice levels on nearby salmon farms. The level of likely lice pressure also modified how annual 1SW returns varied with ocean conditions. Returns to control rivers showed a weak negative relationship with the Atlantic Multi-decadal Oscillation (AMO) in the late summer (September) of the out-migrating year. This negative AMO effect became much stronger for fish migrating in low lice years but was not evident for high lice years. Smolts experiencing mild-to-moderate lice infestation may show greater sensitivity to ocean warming.



2014 ◽  
Vol 71 (7) ◽  
pp. 1653-1670 ◽  
Author(s):  
Félix Massiot-Granier ◽  
Etienne Prévost ◽  
Gérald Chaput ◽  
Ted Potter ◽  
Gordon Smith ◽  
...  

Abstract We developed a hierarchical Bayesian integrated life cycle model for Atlantic salmon that improves on the stock assessment approach currently used by ICES and provides some interesting insights about the population dynamics of a stock assemblage. The model is applied to the salmon stocks in eastern Scotland. It assimilates a 40-year (1971–2010) time-series of data compiled by ICES, including the catches in the distant water fisheries at Faroes and West Greenland and estimates of returning fish abundance. Our model offers major improvements in terms of statistical methodology for A. salmon stock assessment. Uncertainty about inferences is readily quantified in the form of Bayesian posterior distributions for parameters and abundance at all life stages, and the model could be adapted to provide projections based on the uncertainty derived from the estimation phase. The approach offers flexibility to improve the ecological realism of the model. It allows the introduction of density dependence in the egg-to-smolt transition, which is not considered in the current ICES assessment method. The results show that this modifies the inferences on the temporal dynamics of the post-smolt marine survival. In particular, the overall decrease in the marine survival between 1971 and 2010 and the sharp decline around 1988–1990 are dampened when density dependence is considered. The return rates of smolts as two-sea-winter (2SW) fish has declined in a higher proportion than return rates as one-sea-winter (1SW) fish. Our results indicate that this can be explained either by an increase in the proportion maturing as 1SW fish or by an increase in the mortality rate at sea of 2SW fish, but the data used in our analyses do not allow the likelihood of these two hypotheses to be gauged.



1998 ◽  
Vol 55 (12) ◽  
pp. 2533-2538 ◽  
Author(s):  
Carl Walters ◽  
Bruce Ward

There have been profound declines in marine survival rates of steelhead trout (Oncorhynchus mykiss), coho salmon (O. kisutch), chinook salmon (O. tschawytscha), and Atlantic salmon (Salmo salar) since the mid-1980s, and these declines have been particularly acute in sunny regions. We suggest that the problem may originate in freshwater with radiation (e.g., UV-B) damage to metabolic machinery that is expressed during stressful periods of smolting and ocean entry and that progressively worse damage may soon appear as reduction in freshwater survivals as well. This hypothesis can be tested quickly by management agencies by comparing survival rates of hatchery-reared fish with and without radiation protection during rearing.



Author(s):  
Miguel Fillion Barajas ◽  
Timothy F Sheehan ◽  
Ruth Haas-Castro ◽  
Brandon Ellingson ◽  
Katherine Mills

Beginning in the 1980s, return rates of Atlantic salmon to the Penobscot River, Maine U.S.A. declined and have persisted at low levels. This downturn coincided with similar declines in North American and European Atlantic salmon stocks and with changes in the Northwest Atlantic ecosystem. Previous studies investigated whether early marine growth explained the declines, but results varied, with decreased growth associated with declines in European stocks but not North American stocks. In this study, we evaluate whether growth over the entire marine stage is related to Atlantic salmon marine survival. We constructed a growth time series from scales of returned Penobscot River Atlantic salmon spanning periods of varying marine survival. We used ANOVA and post-hoc tests to quantify seasonal growth increment differences and principal component analysis to characterize variability among the suite of growth increments. We observed reduced growth during the second winter and second marine year starting in the 1990s, with compensatory seasonal growth relationships. These results indicate that diminished growth during late marine stages is associated with low return rates in this population.



2009 ◽  
Vol 96 (2-3) ◽  
pp. 289-295 ◽  
Author(s):  
Irma Kallio-Nyberg ◽  
Matti Salminen ◽  
Irma Saloniemi ◽  
Laura Kannala-Fisk


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