Age-based Growth Dynamics Analysis of Recreationally- vs Commercially-Caught Snapper (Chrysophrys auratus) in SNA1 Management Zone

Abstract

This study examines age and growth-based population dynamics of snapper (Chrysophrys auratus) in the SNA1 management area, comparing recreationally- and commercially-caught fish. Fishing gear selectivity influenced age and size distribution, with recreationally-caught snapper (Rod & Reel) displaying a broader range (3–28 years; 260–830 mm SL) than commercially caught snapper (Netting) (2–13 years; 240–439 mm SL). The modal age class was 6–7 years for recreational catches and 5 years for commercial catches, while modal size classes were 300–319 mm and 360–379 mm SL, respectively. Von Bertalanffy Growth Function (VBGF) parameters revealed a slightly higher asymptotic length (L∞) for recreationally-caught snapper (433.48 mm SL) compared to commercially-caught (406.51 mm SL), though both exhibited similar growth coefficients (K = 0.21 and 0.22). Likelihood Ratio Tests and 95% confidence ellipses confirmed significant growth differences between fisheries. However, these differences likely reflect disparities in age and size structures rather than intrinsic biological variation. Our findings emphasise the importance of considering fishery gear selectivity when evaluating growth dynamics and underscore the need for ongoing monitoring to support sustainable snapper management in SNA1.