Fishers’ knowledge on historical changes and conservation of Allis shad -Alosa alosa (Linnaeus, 1758) in Minho River, Iberian Peninsula

Diadromous allis shad A. alosa is a fish species of high socio-economic and cultural value along the Minho River, and is also susceptible to multiple anthropogenic threats. This study aimed to assess fishers’ knowledge on artisanal fisheries of allis shad, and therefore assist and contribute to its conservation in northern Portugal. Results showed a negative relationship between the number of fish caught on the best day of allis shad fishing and the catch year (R2 = 0.29; p = 0.04) and between the largest individual ever caught and the catch year (R2 = 0.42; p = 0.01). There was a positive relationship between the largest individual ever caught and fishing experience (R2 = 0.13; p = 0.04). Our findings showed a significant differences (F = 5.40; p = 0.01) between fishers’ perceptions (Decrease, Increase, and Unchanged) of allis shad catches regarding fishing experience. Differences in perceptions of allis shad fisheries among fishers of different experience categories suggest the occurrence of the shifting baselines syndrome (SBS). The best fishing years were mainly around between 1950 and 1970, and the worst years of fishing in the most recent decades (1990 and 2010s.) Local management activities had low approval by fishers (I = 0.39). We suggest that fishers and managers must establish common conservation goals through participatory management. Also, a joint and synchronized approach between Portuguese and Spanish local authorities is essential for the management and conservation of A. alosa in the international section of the Minho River. •Diadromous allis shad needs imminent conservation measures in the Iberian Minho River.•Local ecological knowledge indicated the occurrence of the shifting baselines syndrome with the allis shad.•The best fishing years for allis shad were in period 1950–1970.•Fishers showed a tendency to be dissatisfied with the current management.•This study provides crucial information for the conservation of this migratory fish.