Estimation of individual growth of the violet oyster Chama coralloides Reeve, 1846 (Bivalvia: Venerida) using Schnute model cases

Chama coralloides Reeve, 1846 is a commercially important mollusk in Acapulco, Mexico. There is currently no fisheries regulation or protection. Therefore, the objective of the present work was to estimate the growth parameters of C. coralloides using the Schnute model cases. Shell length data collected from March 2019 to December 2021 were used. A multinomial analysis was performed to determine the modal groups monthly. Using the mean lengths of each modal group, a modal progression was performed to define the time increments increment t, which were taken as equivalent representations of the data from direct age estimation methods (mark-recapture). These data were used to estimate the individual growth parameters using the five cases of the Schnute model and to define the case that best describes the growth. 2804 organisms were analyzed, with lengths ranging from 7.61 to 116.30 mm SL. Multinomial analysis showed one to four modal groups per month and 14 cohorts were identified. The best-fit case was case 5 (wi = 0.72) with an L infinity = 114.2 mm, followed by case 1 (wi = 0.28) with an L infinity= 109.8 mm. Both cases (5 and 1) were modeled and because the best model did not reach 90%, a mean model was estimated. C. coralloides presented a type of asymptotic growth, with an estimated L infinity that can be reached nearly 22 years.