Four Decades of Changes in Greek Coastal Lagoons (Amvrakikos Gulf, Northwest Greece): A Multi-Indicator Ecological Analysis

Coastal lagoons are highly vulnerable to human and climatic pressures, yet long-term ecological changes remain poorly quantified. We analyzed four decades (1980–2020) of data from fisheries from six lagoons in the Amvrakikos Gulf, Greece, using ecological indicators to assess trophic structure, exploitation status, and ecosystem responses. Cluster analysis of species level fishery production revealed a distinct temporal regime shift in the late 1990s–early 2000s, reflecting a major reorganization of species contributions to total yield. Mean total yield (Y), showed a consistent declining trend across lagoons, ranging from 2.7 ± 2.0 to 7.2 ± 5.0 t km−2. Primary Production Required (PPR) declined (0.8–1.5 × 1010g C km−2 yr−1), while Mean Temperature of the Catch (MTC) increased in five lagoons (19.0–21.4 °C) and remained stable in one (20.0 ± 0.9 °C). Pelagic to demersal (P/D) ratios generally decreased (0.09–1.26), and Q-90 values were variable (0.8–2.2), highlighting site specific ecological dynamics. Short term yield predictions for 2021–2025 ranged from 0.78 to 6.75 t km−2, remaining comparable to recent historical levels, while the estimated carrying capacities varied from 1.79 to 9.11 t km−2, reflecting contrasting exploitation states among lagoons. These results demonstrate that multi-indicator, fishery-based analyses provide a robust framework for quantifying ecological change and guiding adaptive management in lagoon ecosystems.