Bayesian estimates of turban snail (Lunella torquata) growth off south-eastern Australia

In response to a lack of data describing the population parameters of Turbinidae off south-eastern Australia, but a requirement for such information to support emerging harvest strategies, the growth of Lunella torquata was assessed from mark-recapture data using maximum likelihood and Bayesian approaches. Data for 564 tagged and recaptured L. torquata (29–90 mm shell lengths; SL) from 7658 tagged specimens were assessed in various competing models, but the final iteration (our ‘best’ model) comprised eight parameters for six characteristics, including growth at 40 and 80 mm SL, growth variability, measurement errors, outliers and seasonal variation—with the two seasonal growth parameters of most interest. This model was subsequently applied separately to data available for females and males. Growth rates at the selected indicator SLs of 40 and 80 mm were 17.4 and 4.0 mm year–1 for females and 19.1 and 4.9 mm year–1 for males. Regardless of sex, peak growth occurred in March, coinciding with the warmest water temperature. The results imply the smaller individuals would require 2+ years to reach a current minimum legal size of 75 mm SL. This growth rate, combined with the accessibility of the species to commercial and recreational fishers, might support a precautionary approach to management.