This interesting paper was published online some weeks ago:
Nussle S, Bornand CH, Wedekind C (2009) Fisheries-induced selection on an Alpine whitefish: quantifying genetic and environmental effects on individual growth rates. Evolutionary Applications (in press)
There was a closed, steadily and intensively fished population, and growth of nearly all individuals in the population could be analysed based on scale samples collected over 25 years. The authors estimated selection differentials, and found consistent changes in growth but no changes in maturation schedule or energy allocation to reproduction. The conclusion was that 1/3 of the change seen in growth could be an evolutionary response to fishing, the rest environmental.
After reading the paper, I started to wonder this: if 33% of the change in growth was an evolutionary response to fishing, but no shifts were seen in maturation, how common this kind of response might actually be in exploited fish populations? Perhaps studies investigating phenotypic impacts of fishing should start to pay much more attention on shifts in growth, rather than only those in maturation.