Statistical Power and the Effects of Old, Wise and Large Fish

ABSTRACT Currently, a major concern for fish populations is their declining resilience to climate events, reduced individual sizes and productivity and increased instability. Population dynamics of fish are often dominated by recruitment, i.e., the number of young fish entering the population. The contribution of old and large female fish (often denoted BOFFs) to recruitment is expected to be disproportionately large; however, the importance is still debated. There is currently a move to expand quantitative knowledge of the effects of BOFFs on recruitment to better cover the thousands of fish species and populations worldwide. Here, we show, using simulations, that time‐series length and uncertainty often reduce the statistical power to levels where the effects are no longer detectable. We suggest system‐specific methods evaluation to reduce the risks of erroneous conclusions.