Individual growth profiling improves growth modelling in the geoduck clam Panopea generosa

Abstract

Abstract Contemporary modelling of growth based on shell-length to terminal age (SLTA) in long-lived clams is subject to inaccuracies as a consequence of low representation of early age classes in population samplings. To increase early age representation and improve growth modelling, we implemented an approach that used individual growth profile (IGP) data recorded in shells of the Pacific geoduck (Panopea generosa). We compared IGP against SLTA and a combination of both IGP + SLTA data through a multi-model approach for the southernmost known P. generosa population. The most parsimonious model for both IGP and IGP + SLTA data sets was the Schnute model, with L∞ = 127.9 and 122.5 mm, respectively, with the asymptotic phase attained at ∼15 years. For SLTA data alone, the most parsimonious was the Johnson model, with L∞ = 161.6 mm reaching the asymptotic phase at >25 years. In terms of performance, the IGP and IGP + SLTA data sets informed individual growth models with stronger relationships (r2 > 0.9) and higher modelling efficiency (ME > 0.9) than those fitted to SLTA alone (r2 = 0.51; ME = 0.51). The results demonstrate that IGP yields reliable information from relatively few organisms, improves the biological knowledge of the population, and increases the accuracy of parameter estimates for better fishery management.