Individual Growth in the Patagonian Gastropod Buccinanops cochlidium (Nassariidae): A Field Tagging-Recapture Experiment

Abstract

This study describes the growth of individuals in a population of Buccinanops cochlidium (Nassariidae) through the identification of the best-fitting growth model based on field tag-recaptured experimental data. A total of 48 individuals (8.6% of total tagged snails) were recaptured after 2 to 25 months, representing a remarkable proportion for a field experiment with infaunal organisms. The sex ratio was not different from 1:1. Males measured between 63.4 and 89.0 mm (n = 25), while females measured between 50.9 and 103.2 mm (n = 23) in shell length. The maximum annual length increment obtained was 35.74 mm, mean annual length increment was 4.51 and 8.43 mm for females and males, respectively. Because no statistically significant differences were found between male and female growth increments, a single growth model was fitted to the entire data set. Regarding individual growth modeling, the inverse Logistic (iLog) model adequately described the pattern in the data, but showed heteroscedasticity. A refitting of iLog using weighted least squares, weighted inverse Logistic (iLog*), better fit the data (and agrees with biological knowledge of B. cochlidium) than the inverse Logistic (iLog), exponential (Exp), von Bertalanffy (vB) and Gompertz (Gz) models. Estimated parameters for the iLog* model were MaxΔL: 27.83, L50: 69.89, L95: 93.36. The results of this study are valuable for assessment of snail fisheries in Patagonia and suggest fisheries management policies for a sustainable future of this potential stock prior to extensive exploitation.