Composition of the Eurasian perch (Perca fluviatilis) catches in ice fishing: Does capture order predict body size?

Many ecological and evolutionary effects of recreational fishing depend on the selectivity of fishing with regard to body size, sex, behaviour and maturity. Here, we recorded the body size and condition of the Eurasian perch, Perca fluviatilis, in relation to the order of capture in standardized ice fishing, in ten different populations, to study if larger perch would become captured before smaller individuals. In addition, we studied the composition of the catch with regard to sex, size and maturity within and among different waterbodies. Both the total length and body mass but not the condition factor of the captured fish decreased with the order of capture (on average 1 mm and 1 g per fish) suggesting potential size based dominance in feeding hierarchy. According to additional one-sample t-tests on the population-specific slopes between the total body length and capture order, the effect was statistically significant in two independent populations. However, no relationship was found between the order of capture and the deviation of individual's length-at-age from the population mean length-at-age in these two populations. In addition, fish caught in one location were more homogenous in size than fish within the population in general, suggesting that perch form size assortative shoals in wintertime. Our study shows that the ecological implications of capture order effects depend on the mobility of anglers, but are in general population dependent and likely of minor importance compared to the potential overall size-selectivity of recreational angling. However, more studies are needed to examine if angling is selective for behavioural, growth-related traits in general. (c) 2011 Elsevier B.V. All rights reserved.