Abstract:
The allowable catch of Nemipteridae family in the northern South China Sea has been assessed, but management parameters for specific species are lacking. It is necessary to conduct a quota evaluation of
Nemipterus virgatus to obtain more practical reference points for output control. Applying the CMSY++ approach, we analyzed the catch time series of
N. virgatus reconstructed from stratified sampling survey data together with sixteen catch-per-unit-effort time series (CPUE). CMSY and BSM models were run to estimate biological reference points such as carrying capacity k, resilience r, catchability coefficient q, and maximum sustainable yield (MSY). Residual analysis was conducted to verify the applicability of CPUE datasets. Representative CPUE datasets were selected, the exploitation status of
N. virgatus across different fishing methods was compared based on the trends of
B/BMSY and
F/FMSY, and the overall exploitation status of
N. virgatus in 2023 was evaluated using the Kobe plot. The resilience r of
N. virgatus in the northern South China Sea was estimated at 0.79~0.89, carrying capacity
k at 704.47-817.20 thousand tons, the catchability coefficient at 0.03×10
-3-2.63×10
-3, and MSY at 151.66-164.71 thousand tons. Three CPUE datasets were identified as unsuitable for CMSY++ analysis through runs test of residuals and outlier diagnosis of residuals. For Three
B/BMSY and
F/FMSY trajectories were similar from 2008 to 2018 that represented trawl, gillnet, and longline fisheries respectively. The
B/BMSY curve for gillnets began to recover in 2019 and rose above the safe level of 1.0 by 2022, whereas the corresponding curves for the other two gear types remained below 1.0. The
F/FMSY for gillnets dropped markedly after 2019 and fell below 1.0, while the
F/FMSY ratios for the other two gear types stayed above 1.0. Based on the risk probability indicated by the Kobe plot, the
N. virgatus stock was considered to be overfished in 2023. A total allowable catch (TAC) of 132 thousand tons is recommended for the current stage. Statistical analysis based on catch surveys enables the understanding of stock exploitation status from multiple perspectives, and the design and long-term implementation of a sound catch survey program, along with the acquisition of accurate fishery production data derived therefrom, will contribute to the stock assessment and management of mixed fisheries.