A1 Refereed original research article in a scientific journal
Effects of marine conditions, fishing, and smolt traits on the survival of tagged, hatchery-reared sea trout (Salmo trutta trutta) in the Baltic Sea
Authors: Kallio-Nyberg I, Saloniemi I, Jutila E, Saura A
Publisher: NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS
Publication year: 2007
Journal: Canadian Journal of Fisheries and Aquatic Sciences
Journal name in source: CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES
Journal acronym: CAN J FISH AQUAT SCI
Volume: 64
Issue: 9
First page : 1183
Last page: 1198
Number of pages: 16
ISSN: 0706-652X
DOI: https://doi.org/10.1139/F07-084
Abstract
The marine survival of tagged sea trout (Salmo trutta trutta) smolt groups (n = 236) stocked from 1970 to 2001 in the Baltic Sea was analysed using a linear mixed model. The response variable, survival rate, was associated with smolt size, release date, sea surface temperature in May, and prey fish abundance, and interactions among these factors. The effect of smolt size was in interaction with Baltic herring (Clupea harengus membras) abundance; smolt size had an optimum of about 22 cm in years when herring were abundant, but when herring were less abundant, the survival of larger smolts was higher. Early stocking in warm springs or late stocking in cold springs gave the best survival rates for trout. Changes in return activity or fishing methods have made tag returns a less reliable way of estimating survival during the last 30 years. The actual return rate of undersized fish (< 40 cm) compared with their estimated proportion among captured fish decreased over time, which suggests that the survival rate for the later years was probably underestimated. It is likely that we were unable to include all the relevant explanatory variables in the model, as year effects remained significant, suggesting unknown annual variation affecting survival.
The marine survival of tagged sea trout (Salmo trutta trutta) smolt groups (n = 236) stocked from 1970 to 2001 in the Baltic Sea was analysed using a linear mixed model. The response variable, survival rate, was associated with smolt size, release date, sea surface temperature in May, and prey fish abundance, and interactions among these factors. The effect of smolt size was in interaction with Baltic herring (Clupea harengus membras) abundance; smolt size had an optimum of about 22 cm in years when herring were abundant, but when herring were less abundant, the survival of larger smolts was higher. Early stocking in warm springs or late stocking in cold springs gave the best survival rates for trout. Changes in return activity or fishing methods have made tag returns a less reliable way of estimating survival during the last 30 years. The actual return rate of undersized fish (< 40 cm) compared with their estimated proportion among captured fish decreased over time, which suggests that the survival rate for the later years was probably underestimated. It is likely that we were unable to include all the relevant explanatory variables in the model, as year effects remained significant, suggesting unknown annual variation affecting survival.
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