MODELING OF GROWTH DEPENSATION OF GEODUCK CLAM PANOPEA GLOBOSA BASED ON A MULTIMODEL INFERENCE APPROACH

Growth variability has been a common feature within different Panopea species, affecting the accurate estimation of growth parameters and their theoretical trajectories. Recently, the interest in solving this problem has increased; however, the methods used for individual growth modeling of Panopea spp. have not been effective in identifying the variability within the shell length-at-age composition. In the current study, a novel approach is proposed to analyze the effect of shell length-at-age variability on the individual growth and growth parameters of Panopea globosa. The shell length-at-age data were fitted to six candidate growth models: von Bertalanffy, Gompertz, Johnson, Logistic, Generalized von Bertalanffy growth model (GVBGM), and Richards using a negative log-likelihood function. The variance for each age observed (sigma(2)(i)) in the population was estimated for each growth model. The best candidate growth model was selected based on corrected Akaike information criterion (AIC(c)). The results indicated that the candidate growth models analyzed had different patterns of variance. The models that had the widest difference between L-infinity estimates were von Bertalanffy and Johnson growth functions. For individual growth rate parameter, the lower value was estimated for GVBGM, whereas the higher value was computed for Johnson growth model. Estimates for t(0) (age when shell length is theoretically zero) parameter only could be computed for GVBGM and Logistic growth models. The von Bertalanffy growth model showed the higher variance estimated for older individuals (sigma(2)(L infinity)), and this pattern was also observed in the variance for each age observed (sigma(2)(i)), denoting growth depensation in the P. globosa population. The AIC(c) indicated that the best candidate growth model was the Johnson growth model. This approach determined the best model for extracting more accurately the biological information in the shell length-at-age data. The applied methodology should be relevant for further geoduck clam population dynamics studies, providing a tool in aiding in sustainable development of these resource-improving estimates such as yield per recruit, harvest rates, changes in biomass, and expected yield.