Temporal changes in maturation, mean length-at-age, and condition of spring-spawning Atlantic herring (Clupea harengus) in Newfoundland waters
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AbstractWheeler, J. P., Purchase, C. F., Macdonald, P. D. M., Fill, R., Jacks, L., Wang, H., and Ye, C. 2009. Temporal changes in maturation, mean length-at-age, and condition of spring-spawning Atlantic herring (Clupea harengus) in Newfoundland waters. – ICES Journal of Marine Science, 66: 1800–1807. We investigated temporal trends in some life-history traits of Atlantic herring. Population size of Newfoundland herring stock complexes declined precipitously through the 1970s. Maturation age and size also decreased substantially, but not until the late 1980s. Although significant effects were found for region and gear type, these were only minor compared with the general trend. No effects were found for sex. Changes in maturation age and size can represent an evolutionary response to fishery-induced selection, or phenotypic plasticity as a result of a compensatory response to stock declines, or a response to other changes in the environment. Length-at-age and body condition decreased concurrently with changes in maturation, suggesting that declines in maturation age and size were not a compensatory response to reduced stock sizes. This supports the hypothesis of evolutionary changes in maturation. However, increases observed in the most recent year classes, and concurrent changes in other species, suggest that changes in the environment may have also affected age- and size-at-maturation.
