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Evolution of age and length at maturation of Alaskan salmon under size-selective harvest.

Kendall NW, Dieckmann U, Heino M, Punt AE, Quinn TP - Evol Appl (2013)

Bottom Line: PMRN midpoints decreased in six of nine populations for both sexes, consistent with the harvest.These results support the hypothesis that environmental changes in the ocean (likely from competition) combined with adaptive microevolution (decreased PMRNs) have produced the observed life-history patterns.PMRNs did not decrease in all populations, and we documented differences in magnitude and consistency of size selection and exploitation rates among populations.

View Article: PubMed Central - PubMed

Affiliation: School of Aquatic and Fishery Sciences, University of Washington Seattle, WA, USA ; Washington Department of Fish and Wildlife Olympia, WA, USA.

ABSTRACT
Spatial and temporal trends and variation in life-history traits, including age and length at maturation, can be influenced by environmental and anthropogenic processes, including size-selective exploitation. Spawning adults in many wild Alaskan sockeye salmon populations have become shorter at a given age over the past half-century, but their age composition has not changed. These fish have been exploited by a gillnet fishery since the late 1800s that has tended to remove the larger fish. Using a rare, long-term dataset, we estimated probabilistic maturation reaction norms (PMRNs) for males and females in nine populations in two basins and correlated these changes with fishery size selection and intensity to determine whether such selection contributed to microevolutionary changes in maturation length. PMRN midpoints decreased in six of nine populations for both sexes, consistent with the harvest. These results support the hypothesis that environmental changes in the ocean (likely from competition) combined with adaptive microevolution (decreased PMRNs) have produced the observed life-history patterns. PMRNs did not decrease in all populations, and we documented differences in magnitude and consistency of size selection and exploitation rates among populations. Incorporating evolutionary considerations and tracking further changes in life-history traits can support continued sustainable exploitation and productivity in these and other exploited natural resources.

No MeSH data available.


Ocean age 2 sockeye salmon LP50 values for females and males of Iliamna Lake and Wood River lakes populations. Error bars are 95% CIs estimated from bootstrap analysis. Best-fit lines are for the populations where LP50 values decreased significantly over time (males and females from Copper River and Gibraltar Creek in Iliamna Lake and males and females from all populations in the Wood River lakes).
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fig01: Ocean age 2 sockeye salmon LP50 values for females and males of Iliamna Lake and Wood River lakes populations. Error bars are 95% CIs estimated from bootstrap analysis. Best-fit lines are for the populations where LP50 values decreased significantly over time (males and females from Copper River and Gibraltar Creek in Iliamna Lake and males and females from all populations in the Wood River lakes).

Mentions: The GLMs indicated that length, population, cohort, and sex all affected maturation (Table 1). The GLM P-values associated with many cohorts were <0.05 for the best-fit model and the AICc value of a model not including the cohort term was much larger than the model including it (Table 1), emphasizing variation in PMRNs over time. Linear regression models showed that LP50 values for ocean age 2 fish decreased over time for males and females in all populations. These decreases were statistically significant for both males and females in two of five Iliamna Lake populations (linear models, slope P < 0.01, F = 9.0–11.6 for significant populations) and for males and females in all four Wood River lakes populations (linear models, slope P < 0.01, F = 31.5–188.7). Most populations in the best-fit GLM also had corresponding P-values <0.05, suggesting significant differences in LP50 values among them, and that of sex was <0.001 for both Iliamna and Wood River lakes, signifying that this term was very important to understand LP50 differences and thus that males and females had different LP50 values. AICc values of GLM models not including the population or sex term were much larger than models with them (Table 1), emphasizing variation among populations and that female PMRNs were significantly different than those of males. Iliamna Lake LP50 values (determined by linear regression; details above) decreased by 0.1–0.4 mm per cohort for females (Fig. 1A) and 0.2–0.7 mm per cohort for males (Fig. 1B) between the 1960 and 2004 cohorts. Wood River lakes LP50 values declined even more, by 0.8–1.3 mm per cohort for females (Fig. 1C) and 1.1–1.7 mm per cohort for males (Fig. 1D) between the 1958 and 2004 cohorts.


Evolution of age and length at maturation of Alaskan salmon under size-selective harvest.

Kendall NW, Dieckmann U, Heino M, Punt AE, Quinn TP - Evol Appl (2013)

Ocean age 2 sockeye salmon LP50 values for females and males of Iliamna Lake and Wood River lakes populations. Error bars are 95% CIs estimated from bootstrap analysis. Best-fit lines are for the populations where LP50 values decreased significantly over time (males and females from Copper River and Gibraltar Creek in Iliamna Lake and males and females from all populations in the Wood River lakes).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927891&req=5

fig01: Ocean age 2 sockeye salmon LP50 values for females and males of Iliamna Lake and Wood River lakes populations. Error bars are 95% CIs estimated from bootstrap analysis. Best-fit lines are for the populations where LP50 values decreased significantly over time (males and females from Copper River and Gibraltar Creek in Iliamna Lake and males and females from all populations in the Wood River lakes).
Mentions: The GLMs indicated that length, population, cohort, and sex all affected maturation (Table 1). The GLM P-values associated with many cohorts were <0.05 for the best-fit model and the AICc value of a model not including the cohort term was much larger than the model including it (Table 1), emphasizing variation in PMRNs over time. Linear regression models showed that LP50 values for ocean age 2 fish decreased over time for males and females in all populations. These decreases were statistically significant for both males and females in two of five Iliamna Lake populations (linear models, slope P < 0.01, F = 9.0–11.6 for significant populations) and for males and females in all four Wood River lakes populations (linear models, slope P < 0.01, F = 31.5–188.7). Most populations in the best-fit GLM also had corresponding P-values <0.05, suggesting significant differences in LP50 values among them, and that of sex was <0.001 for both Iliamna and Wood River lakes, signifying that this term was very important to understand LP50 differences and thus that males and females had different LP50 values. AICc values of GLM models not including the population or sex term were much larger than models with them (Table 1), emphasizing variation among populations and that female PMRNs were significantly different than those of males. Iliamna Lake LP50 values (determined by linear regression; details above) decreased by 0.1–0.4 mm per cohort for females (Fig. 1A) and 0.2–0.7 mm per cohort for males (Fig. 1B) between the 1960 and 2004 cohorts. Wood River lakes LP50 values declined even more, by 0.8–1.3 mm per cohort for females (Fig. 1C) and 1.1–1.7 mm per cohort for males (Fig. 1D) between the 1958 and 2004 cohorts.

Bottom Line: PMRN midpoints decreased in six of nine populations for both sexes, consistent with the harvest.These results support the hypothesis that environmental changes in the ocean (likely from competition) combined with adaptive microevolution (decreased PMRNs) have produced the observed life-history patterns.PMRNs did not decrease in all populations, and we documented differences in magnitude and consistency of size selection and exploitation rates among populations.

View Article: PubMed Central - PubMed

Affiliation: School of Aquatic and Fishery Sciences, University of Washington Seattle, WA, USA ; Washington Department of Fish and Wildlife Olympia, WA, USA.

ABSTRACT
Spatial and temporal trends and variation in life-history traits, including age and length at maturation, can be influenced by environmental and anthropogenic processes, including size-selective exploitation. Spawning adults in many wild Alaskan sockeye salmon populations have become shorter at a given age over the past half-century, but their age composition has not changed. These fish have been exploited by a gillnet fishery since the late 1800s that has tended to remove the larger fish. Using a rare, long-term dataset, we estimated probabilistic maturation reaction norms (PMRNs) for males and females in nine populations in two basins and correlated these changes with fishery size selection and intensity to determine whether such selection contributed to microevolutionary changes in maturation length. PMRN midpoints decreased in six of nine populations for both sexes, consistent with the harvest. These results support the hypothesis that environmental changes in the ocean (likely from competition) combined with adaptive microevolution (decreased PMRNs) have produced the observed life-history patterns. PMRNs did not decrease in all populations, and we documented differences in magnitude and consistency of size selection and exploitation rates among populations. Incorporating evolutionary considerations and tracking further changes in life-history traits can support continued sustainable exploitation and productivity in these and other exploited natural resources.

No MeSH data available.