Common, rare or extirpated? Shifting baselines for common angelshark, Squatina squatina (Elasmobranchii: Squatinidae), in the Northern Adriatic Sea (Mediterranean Sea)
Historical baselines are needed to reconstruct long-term changes in marine animal populations and enhance our ability to articulate management recommendations. We reconstructed common angelshark (Squatina squatina) abundance in the Northern Adriatic Sea over the last two centuries by integrating different sources of formal and informal information. The wide amount of information collected helped assessing if the species is actually extirpated from the area, as stated in previous studies. According to naturalists’ accounts and historical documents, in the nineteenth and early twenty-first centuries the species was so abundant to sustain targeted fisheries, and large quantities of S. squatina were sold in the main fish markets. In the 1960s, the species collapsed and got economically extinct. Even if it was never caught in the area through scientific surveys during the period 1948–2014, from fishermen interviews emerged that the species is not extirpated. However, only 50% of interviewees caught S. squatina at least once and they were significantly older than the fishermen that never caught it (shifting baseline syndrome). Moreover, the size of the fish caught significantly decreased through time, indicating the depletion of larger individuals. Our integrated approach can be applied to any poorly assessed species so that appropriate international conservation measures can be prioritized.
KeywordsEndangered species Naturalists’ accounts Landings Scientific survey Historical ecology Fishers’ ecological knowledge
We would like to thank all fishers that participated in the interviews and self-sampling activities, and all our colleagues that helped us collect the data, especially Monica Mion, Camilla Piras and Valentina Bernarello. This work also benefited from a range of data collected by ISPRA (formerly ICRAM), OGS, CNR-ISMAR, IOF, FRIS and LMBF under several national and international programs. All researchers, technicians and fishers that participated in such activities are gratefully acknowledged. We also thank two anonymous reviewers for their thoughtful comments. This study was benefited from discussions with colleagues of the ICES Working Group on the History of Fish and Fisheries. This article is based upon work from COST Action on Oceans Past Platform, supported by COST (European Cooperation in Science and Technology), and from GAP2 project (www.gap2.eu), supported by the European Union under the FP7 Science in Society (SiS) Framework, SiS-2010-1.0-1, Mobilization and Mutual Learning Actions, Coordinating and support actions, Grant Agreement No. 266544.
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