A quantitative evaluation of the pollock Gadus chalcogrammus restocking programme in South Korea

The collapse of the Korean pollock (Gadus chalcogrammus) stock in the late 1990s is hypothesised to be due to environmental changes, overexploitation, or a combination of both factors. However, due to limited data availability, no conclusive scientific analysis is available to support any of these hypotheses. In response to the stock collapse, the South Korean government initiated a restocking programme in 2015. As of early 2024, approximately 1.9 million young-of-the-year pollock have been released into the ocean. Despite nearly a decade of implementing this programme, there has been no indication of stock recovery. This study quantitatively evaluated the potential for stock rebuilding under varying restocking rates to assess the efficacy of the restocking programme. Given the scarcity of historical data on the stock, we applied a stochastic stock reduction analysis using a length-based, age-structured model developed specifically for this analysis. A wide range of alternative models was considered to account for structural and parameter uncertainties. The results suggest that, even under the most optimistic assumptions, the restocking practice is unlikely to facilitate stock rebuilding.