Fishers “local ecological knowledge” (LEK) can be used to reconstruct long-term trends of species that are at very low biomass due to overfishing. In this study, we used historical memories of Sicilian fishers to understand their perception of change in abundance of cartilaginous fish in the Strait of Sicily over the last decades. We conducted interviews with 27 retired fishers from Mazara del Vallo harbor (SW Sicily) working in demersal fisheries, using a pre-defined questionnaire with a series of open and fixed questions related to the abundance of sharks and rays. The questionnaire included specific questions about the trends they perceived in catch or by-catch of cartilaginous fish abundance between the 1940s and 2000s compared to the present. Information was gathered for 18 species, including Carcharhinidae, mesopredatory demersal sharks (Squalidae, Hexanchidae, Centrophoridae, Oxynotidae, Triakidae, Scyliorhinidae, and Squatinidae) and batoids. Overall shark catches were perceived to have diminished since the early 1940s: about 95% of fishers reported the decline of commercially important species (e.g., Mustelus spp.) and indicated species that could have been depleted or locally extinct (e.g., Squatina spp., Sphyrna lewini, Mustelus asterias, etc.). Our study shows that LEK of fishers can be beneficial for reconstructing long-term population trends of exploited species when traditional standard data on fisheries catch or species relative abundance from surveys is limited or only available for recent periods. The results obtained clearly indicate the rapid and alarming decline of elasmobranchs in the Strait of Sicily highlighting the need for urgent conservation measures to be adopted.

中文翻译：

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利用当地渔民生态知识重建西西里海峡鲽种群丰度趋势

渔民的“当地生态知识”（LEK）可用于重建由于过度捕捞而生物量非常低的物种的长期趋势。在这项研究中，我们利用西西里渔民的历史记忆来了解他们对过去几十年西西里海峡软骨鱼类丰度变化的看法。我们对 27 位来自马扎拉德尔瓦洛港（西西里岛西南部）从事底层渔业工作的退休渔民进行了采访，使用预定义的调查问卷，其中包含一系列与鲨鱼和鳐鱼数量相关的开放和固定问题。调查问卷包括关于他们认为 1940 年代至 2000 年代与现在相比，软骨鱼类丰度的渔获量或副渔获量趋势的具体问题。收集了 18 个物种的信息，包括 Carcharhinidae、中掠食性底层鲨鱼（Squalidae、Hexanchidae、Centrophoridae、Oxynotidae、Triakidae、Scyliorhinidae 和 Squatinidae）和蝙蝠鲨。自 1940 年代初以来，人们认为鲨鱼的总捕获量有所减少：大约 95% 的渔民报告说，具有重要商业价值的物种（例如，Mustelus spp.）减少了，并表明可能已经枯竭或在当地灭绝的物种（例如，Squatina spp.、 Sphyrna lewini、Mustelus asterias 等）。我们的研究表明，当渔业捕捞量或来自调查的物种相对丰度的传统标准数据有限或仅适用于最近时期时，渔民的 LEK 有助于重建开发物种的长期种群趋势。