Bayesian State‐Space Assessment ( BSM ) and Ensemble Forecast for Indian White Prawn ( Penaeus indicus

ABSTRACT

The Indian white prawn ( Penaeus indicus ) is the dominant shrimp species in the northern Oman Sea and plays an important role in the economy of coastal communities in the region. In this study, a Bayesian state‐space surplus production model (BSM) was applied to assess stock status and estimate key population parameters of P. indicus in the northern waters of the Oman Sea (Iran), using a 22‐year time series of catch and catch per unit effort (CPUE) data from 2003 to 2024. The model estimated an intrinsic growth rate ( r ) of 0.81 (95% CI: 0.74–0.91), a carrying capacity ( K ) of 1928 t (95% CI: 1790–1966 t), a current biomass of 959 t (95% CI: 895–997 t), and a maximum sustainable yield (MSY) of 389 t (95% CI: 371–439 t), with BMSY estimated at 964 t (95% CI: 893–998 t). While the current biomass is close to the target level (B/BMSY ≈ 0.99), the fishing mortality rate currently exceeds the sustainable level (F/FMSY = 1.26), indicating that overfishing is ongoing, although the stock is not yet classified as overfished in terms of biomass. To forecast future shrimp catches, a set of models including GLM, GAM, Random Forest, Neural Network, and ARIMA was evaluated using LOOCV. The results showed that Random Forest achieved the best predictive performance, with the lowest RMSE (153.07), followed by the Ensemble model (155.62). GLM and GAM performed similarly, with RMSE values of 167.04 and 167.42, respectively, whereas Neural Network (186.77) and ARIMA (185.08) showed comparatively higher prediction errors. Despite these differences in model accuracy, the ensemble forecasting results indicated a gradual upward trend in shrimp catch from 2025 to 2029. However, these ensemble projections should be viewed as indicative scenarios rather than deterministic forecasts; the widening uncertainty bounds highlight the need for precautionary management and do not support an increase in future catch limits. Overall, the findings indicate that although the stock biomass remains close to the target reference point, current exploitation is above sustainable limits, highlighting the urgent need for effective management measures such as science‐based catch quotas and seasonal closures to ensure the long‐term sustainability of P. indicus in the northern Oman Sea.