Comparison of age-structured and length-converted catch curves of brown trout Salmo trutta in two French rivers

Abstract

Age-structured catch curves (ACC) and two different types of length-converted catch curves (LCC), covering the same size/age range of trout Salmo trutta (Pisces: Salmonidae) in two French rivers, were used to estimate total mortality ( Z). It is shown that standard LCC overestimate Z when ACC are used as controls, while LCC explicitly considering seasonal growth oscillations produce unbiased estimates. The implications of this finding for length-based fish stock assessment are discussed.