Abstract
Fisheries‐induced evolution (FIE) can result when harvest imposes artificial selection on variation in heritable phenotypic traits. While there is evidence for FIE, it remains difficult to disentangle the contributions of within‐generation demographic adjustment, phenotypic plasticity, and genetic adaption to observed changes in life history traits. We present evidence for FIE using dozens of Coho salmon (Oncorhynchus kisutch) populations in which males adopt one of two age‐invariant, heritable life history tactics: most mature as large three‐year‐old “hooknose” and typically fight for spawning opportunities, while some mature as small two‐year‐old “jacks” and fertilize eggs through sneaking. The closure of a fishery targeting three‐year‐old fish provided an experimental test of the prediction that fishery‐imposed selection against hooknose males drives an evolutionary increase in the proportion of males adopting the jack tactic. The data support the prediction: 43 of 46 populations had higher jack proportions during than after the fishery. The data further suggest that changes in jack proportion were not solely the result of demographic adjustments to harvest. We suggest that systems where fisheries differentially exploit phenotypically discrete, age‐invariant life histories provide excellent opportunities for detecting FIE.
Highlights
Fisheries impose artificial selection on exploited populations when harvest targets a nonrandom subset of phenotypes (Arnold & Wade, 1984; Heino, Pauli, & Dieckmann, 2015)
While it is reasonable to assume that Fisheries-induced evolution (FIE) can occur, for a number of reasons it is difficult to unequivocally conclude that observed changes in life history traits are the result of FIE
For Coho salmon populations in the wild, a fishery that harvests hooknose males will impose artificial viability selection against fish with high SC and/or slow juvenile growth (Figure 2c). Such fisheries can drive FIE increases in jack proportion by increasing a population's mean condition at age SA and/or decreasing the population's mean SC at age SA (Figure 2d). This evolutionary response will be modified by the genetic architecture of and correlations between relevant traits (Merilä & Sheldon, 1999; Schluter, 1996), any environmentally induced changes in juvenile growth rates that affect the distribution of condition at age SA, and the effects on lifetime fitness of changes in density- and frequency-dependent sexual selection acting on the mature male phenotypes (Berejikian et al, 2010; Fleming & Gross, 1994; Roff, 1996)
Summary
Fisheries impose artificial selection on exploited populations when harvest targets a nonrandom subset of phenotypes (Arnold & Wade, 1984; Heino, Pauli, & Dieckmann, 2015). There is a compelling collection of case studies suggesting that FIE can occur in exploited wild fish populations (reviewed by Heino et al, 2015) These observational studies are supported by experimental work showing that fish life history traits such as growth rate and maturation age evolve rapidly under selection regimes relevant to those imposed by commercial fisheries (Biro & Post, 2008; Conover & Munch, 2002; Reznick & Ghalambor, 2005). We use male Coho life history variation, the “pulse experiment” of a fishery and its closure, and demographic data from dozens of populations to test the prediction that fishery-imposed selection against three-year-old males increased the proportion of two-year-old males in breeding populations (Gross, 1991; Myers, 1986) The data support this prediction and offer additional evidence that FIE contributed to the observed changes in male life history
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
