Stock Status of Ompok bimaculatus in Kaptai Lake: A Length‐Based Approach for Sustainable Fisheries Management

ABSTRACT

Ompok bimaculatus , a silurid catfish, is a commercially valuable and endangered species in Bangladesh. Kaptai Lake is a critical habitat for this species, yet growing market demand and ecological pressures jeopardize stock sustainability. Therefore, this study employed a length‐based approach integrating LB‐SPR and aLBI to conduct the baseline stock assessment of the species in the lake. The LB‐SPR suggests that the stock may be experiencing overfishing with a reduced spawning potential ratio ( SPR = 0.30) and unsustainable fishing pressure ( F / M  = 1.32). Furthermore, the length at 50% selectivity ( SL ₅₀  = 19.67 cm) fell below the length at 50% maturity ( L ₅₀  = 21.02 cm), indicating potential growth overfishing. The aLBI model estimated the key length parameters: asymptotic length ( L _∞  = 36.32 cm), length at maturity ( L _mat  = 21.04 cm) and optimum length ( L _opt  = 21.72 cm). The percentage of mature fish ( P _mat  = 65.03%) and the percentage of optimally sized fish ( P _opt  = 42.49%) fell short of the target of 100%. The percentage of mega‐spawners ( P _mega  = 31.78%) exceeding 20% suggests potential recruitment overfishing. In addition, the probability of stock biomass being below the target (TSB40) and limit reference points (LSB25) was 100%, remaining completely stable across ±5% and ±10% parameter variations ( L _∞ and L _mat ) before exhibiting dynamic shifts at ±15%. Based on these findings, this study recommends implementing a length range between L _opt and L _opt  + 10% of L _opt  to protect juveniles and mega‐spawners. Finally, addressing the underlying drivers of overfishing to reduce F / M is essential.