Comparison of population dynamics parameters estimated for 34 bony fishes in oligotrophic Mediterranean shelf/break...

Understanding the life-history patterns of fish species is crucial for effective fisheries management across temporal and spatial scales. This study investigates the population dynamics of fish inhabiting the shelf and break zone of the Gulf of Antalya, a highly oligotrophic region of the Mediterranean Sea that serves as a major spawning ground for various species, including fast-growing deep-sea fishes that reach maturity within 1-2 years. Population parameters, such as asymptotic length and growth rate, were estimated from length-frequency distributions using ELEFAN I in the FISAT programme. Multi-species analyses, particularly of dominant taxa, were performed to evaluate their interactions within the study area, while seasonality and environmental variability were also considered. A total of 165 demersal and some pelagic fish species were recorded throughout the year, of which 34 bony fish species were examined in detail. The results showed that population parameters varied significantly with both fish size and bottom depth. Along the shelf (10-75 m), asymptotic length (L_∞) and growth rate (K) decreased with depth. At the shelf edge (200 m), L_∞ remained high and K declined, whereas at the shelf break (300 m), L_∞ decreased and K increased. Mortality rates [total mortality (Z) and natural mortality (M)] declined with increasing fish size, with medium-sized fishes exhibiting the highest Z values. The relationship between maximum age (tmax) and natural mortality (M) showed a significant correlation, particularly across size classes rather than depth strata. A comparative analysis with data from 524 publications indicated that population parameters are strongly influenced by geographical location within the Mediterranean, temporal variation (e.g., pre-2000s, 1990s-2000s, post-2000s) and west-east spatial gradients. This study also provides the first comprehensive population characteristics for four species - Epinephelus aeneus, Glossanodon leioglossus, Macroramphosus scolopax and Pagrus caeruleostictus - with important ecological and management implications.