Seals and fisheries in the Clyde Sea area (Scotland): traditional knowledge informs science

摘要

Results obtained from circulating a questionnaire on seal/fisheries interaction around two groups of stakeholders (trawlermen and creel fishers) from the Scottish Clyde fishing fleet are presented. An overall return rate of 30% was achieved representing 664 man-years of traditional knowledge. Nowadays, most commercial fishing in the Clyde Sea area targets Norway lobsters (Nephrops norvegicus), using either towed (nephrops trawl) or static (baited creel) gear. Nephrops trawling generates a whitefish by-catch. All those respondents fishing within the confines of the Clyde Sea area reported experiencing seals interfering with their fishing activities. Both grey seals (Halichoerus grypus) and common, or harbour, seals (Phoca vitulina) occur locally but most respondents did not distinguish between them. The majority of trawlermen reported seals taking fishes from nets and damaging fishes. Only 9% of trawlermen, however, noted gear damage in spite of 91% reporting capturing seals (occasionally or rarely) in their gear. Seals caught in trawls were mostly retrieved dead (exact incidence unknown). Sixty-three percent of creelers who responded reported both damage to fishes and interference with creels. Seals may break into, or smash, creels to steal the bait and in so doing liberate catches. Contact with seals was not thought to taint fishing gear. Seals seemed to target cod (Gadus morhua) and hake (Merluccius merluccius) in trawls and seemed to select the larger individuals. Creel fishers highlighted damage to the bellies of fishes whilst trawlermen stressed damage to the tails. As much as 10% of the whitefish caught by trawlermen was unsaleable due to seal damage. Damage caused by seals was readily distinguishable from damage caused by other agents. 'Rogue' individual seals were not solely to blame. Typically, 9-12 seals (even sometimes as many as 25) might be encountered by any one fisher, especially when gear was being hauled. Half the trawlermen who participated regarded seals as being either a 'considerable' or 'moderate' threat to their livelihoods but 45% regarded them as a 'minor' or 'non'-problem. Grey seal populations have undoubtedly increased considerably locally over the last 40 years. Eighty-six percent of trawlermen were in favour of some sort of seal cull (cf. 14% against), with some 45% of trawlermen in favour of halving seal numbers locally. Over 60% of creelers who responded were looking for even more stringent cut-backs in seal numbers, i.e. of more than 70%.