Evaluating the role of condition indices in predicting maturity in Black Sea whiting

Understanding the factors influencing fish maturation is crucial for predicting reproductive potential and ensuring sustainable management of aquatic resources. In this study, we evaluated the role of individual condition in explaining maturation probability in female Black Sea whiting (Merlangius merlangus), an overexploited demersal species. Using Fulton's K, the relative condition factor (K_r), and the liver condition index (LKr), we assessed their contribution to maturity probability alongside conventional predictors such as age and size. While condition indices positively influenced maturation likelihood, their overall contribution to explained variance was limited compared to age and length. However, among individuals of similar age and size, those in better condition had substantially higher odds of being mature, underscoring the value of condition metrics for refining maturity estimates. The pre-spawning fitness threshold (Kspawn50) was estimated at 0.82, within an observed K range of 0.4 to 3.4, representing the critical condition level associated with spawning readiness. These findings highlight that, although condition indices may be limited as standalone maturity benchmarks, they substantially enhance the precision of maturity predictions when integrated with age and length, emphasizing the value of multi-variable assessment approaches. Furthermore, by linking physiological condition to reproductive dynamics, our study provides insights into the resilience of demersal fish populations under fishing pressure, contributing to a broader understanding of ecosystem health in semi-enclosed seas like the Black Sea.