The Sequential Influence of a Global Climatic Factor (AMO) and Altered Local Conditions Could Explain the Collapse and Lack of Recovery of an Ancient Eel Fishery in a Western Mediterranean Coastal Lagoon

Abstract

[Abstract] Permanent population collapse has been long known to be caused by the interaction of at least two orthogonal factors. Fisheries collapses adjust to that pattern by the interaction of global and local factors. We focused on the study of this pattern on the collapse of eel fisheries. Specifically, we analysed a long time series of eel landing data (1951–2022) from a coastal wetland in the western Mediterranean (Albufera de Valencia). Landings peaked in 1958 but a strong regime shift was detected in 1968 by means of Rodionov’s sequential t test analysis, with captures dropping by 86% in ten years (1967–1977). Declining landings (1956–1976) showed a strong positive association (r = 0.94; r2 = 0.88) with the 5-year moving average of the Atlantic Multidecadal Oscillation (AMO). However, both time series completely decoupled from 1976 on as AMO moved towards a warm phase favourable to eels but eel landings remained at low levels until present. We explain this decoupling as a result of the anthropogenic alteration of the wetland since the end of the 1960s. The eel fishery collapse occurred almost a decade earlier than in other western Mediterranean wetlands, likely because of the differential timing of eutrophication of these sites. Some urgent management actions are suggested.