Abstract

Adult returns to many Atlantic salmon wild and hatchery stocks of the North Atlantic have declined or collapsed since 1985. Enhancement, commercial fishery closures, and angling restrictions have failed to halt the decline. Human impacts such as dams, pollution or marine overexploitation were responsible for some stock declines in the past, but adult returns to river and hatchery stocks with no obvious local impacts have also declined or collapsed since 1985. Multiple studies have postulated that the recent widespread occurrence of low adult returns may be caused by climate change, salmon farming, food availability at sea, or marine predators but these possibilities are unsupported by stocks that persist near historic levels, loss of stocks remote from farm sites, a diverse marine prey field, and scarcity of large offshore predators. The decline and collapse of stocks has common characteristics: 1) cyclic annual adult returns cease, 2) annual adult returns flatline, 3) adult mean size declines, and 4) stock collapses occurred earliest among watersheds distant from the North Atlantic Sub-polar Gyre (NASpG). Cyclic annual adult returns were common to all stocks in the past that were not impacted by anthropogenic changes to their natal streams. A flatline of adult abundance and reduction in adult mean size are common characteristics of many overexploited fish stocks and suggest illegal, unreported, and unregulated (IUU) fisheries exploitation at sea. Distance from the NASpG causing higher mortality of migrating post-smolts would increase the potential for collapse of these stocks from IUU exploitation. By-catch of post-smolts and adults in paired-trawl fisheries off Europe and intercept adult fisheries off Greenland, in the Gulf of St. Lawrence, and off Europe have been sources of marine mortality but seem unlikely to be the primary cause of the decline. Distribution in time and space of former, legal high-sea fisheries indicated fishers were well acquainted with the ocean migratory pattern of salmon and combined with lack of surveillance since 1985 outside Exclusive Economic Zones or in remote northern regions may mean high at-sea mortality occurs because of IUU fisheries. The problem of IUU ocean fisheries is acute, has collapsed numerous stocks of desired species worldwide, and is probably linked to the decline and impending collapse of the North Atlantic salmon population.

摘要

自 1985 年以来，北大西洋的许多大西洋野生鲑鱼和孵化场的成鱼数量下降或崩溃。加强、商业渔业关闭和钓鱼限制未能阻止下降。过去，水坝、污染或海洋过度开发等人类影响是造成一些种群下降的原因，但自 1985 年以来，没有明显局部影响的成鱼对河流和孵化场种群的回归也下降或崩溃。多项研究假设最近普遍发生的成鱼低回报率可能是由气候变化、鲑鱼养殖、海上食物供应或海洋捕食者造成的，但这些可能性并没有受到持续接近历史水平的种群、远离农场的种群损失、多样化的海洋猎物场的支持，以及大型近海捕食者稀缺。股票的下跌和崩盘具有共同的特征：1）周期性的年度成人回报停止，2）年度成人回报持平，3）成人平均规模下降，4）股票崩盘最早发生在远离北大西洋次极环流的流域(NASpG)。过去，所有未受其出生流的人为变化影响的股票都具有周期性的年度成年回报率。许多过度捕捞的鱼类种群的共同特征是成鱼丰度和成鱼平均体型的减少，这表明在海上进行非法、未报告和无管制 (IUU) 渔业开发。与 NASpG 的距离会导致迁移后小鱼的死亡率更高，这将增加这些种群因 IUU 开采而崩溃的可能性。欧洲外海成对拖网渔业中的小鱼和成鱼副渔获物，以及格陵兰、圣劳伦斯湾和欧洲外海的成鱼捕捞活动，一直是海洋死亡的来源，但似乎不太可能是造成海洋死亡的主要原因。衰退。前合法公海渔业的时间和空间分布表明渔民非常熟悉鲑鱼的海洋洄游模式，再加上自 1985 年以来在专属经济区以外或偏远北部地区缺乏监测可能意味着海上死亡率很高因为IUU渔业。IUU 海洋渔业的问题非常严重，已经导致全世界大量所需物种的种群数量减少，并且可能与北大西洋鲑鱼种群的减少和即将崩溃有关。欧洲和欧洲以外地区一直是海洋死亡率的来源，但似乎不太可能是下降的主要原因。前合法公海渔业的时间和空间分布表明渔民非常熟悉鲑鱼的海洋洄游模式，再加上自 1985 年以来在专属经济区以外或偏远北部地区缺乏监测可能意味着海上死亡率很高因为IUU渔业。IUU 海洋渔业的问题非常严重，已经导致全世界大量所需物种的种群数量减少，并且可能与北大西洋鲑鱼种群的减少和即将崩溃有关。欧洲和欧洲以外地区一直是海洋死亡率的来源，但似乎不太可能是下降的主要原因。前合法公海渔业的时间和空间分布表明渔民非常熟悉鲑鱼的海洋洄游模式，再加上自 1985 年以来在专属经济区以外或偏远北部地区缺乏监测可能意味着海上死亡率很高因为IUU渔业。IUU 海洋渔业的问题非常严重，已经导致全世界大量所需物种的种群数量减少，并且可能与北大西洋鲑鱼种群的减少和即将崩溃有关。合法的公海渔业表明渔民非常熟悉鲑鱼的海洋洄游模式，再加上自 1985 年以来在专属经济区以外或偏远北部地区缺乏监测，可能意味着 IUU 渔业导致海上死亡率高。IUU 海洋渔业的问题非常严重，已经导致全世界大量所需物种的种群数量减少，并且可能与北大西洋鲑鱼种群的减少和即将崩溃有关。合法的公海渔业表明渔民非常熟悉鲑鱼的海洋洄游模式，再加上自 1985 年以来在专属经济区以外或偏远北部地区缺乏监测，可能意味着 IUU 渔业导致海上死亡率高。IUU 海洋渔业的问题非常严重，已经导致全世界大量所需物种的种群数量减少，并且可能与北大西洋鲑鱼种群的减少和即将崩溃有关。