Urban market amplifies strong species selectivity in Amazonian artisanal fisheries

Abstract Despite Amazonia possessing the highest freshwater biodiversity on Earth, urban landing data show how huge fishing pressure is placed on only a dozen species. However, truly characterising the fishery and understanding the drivers of species selectivity is challenging, given the neglect of artisanal fishing activity, who may catch most of the Amazon’s fish. We register the catch of 824 fishing trips by interviewing artisanal fishers in their rural riverside communities. We use these data to characterise the artisanal fishery of the Rio Purus, the main fish source sub-system for the Amazon’s largest city (Manaus), and investigate the factors determining catch composition. Fishers caught 80 fish species, yet just four species made up over half of the harvested biomass. Urban markets appear to drive greater selectivity, with a significantly lower species diversity in commercial compared to subsistence catches. Fish catch composition varied significantly both seasonally and with geographical remoteness from Manaus. The spatial turnover in catch composition appears to be driven by urban access, with more commercially important species dominating where Manaus-based fish-buyers frequent. Our data may partially explain observed overfishing in some commercially important species, particularly as most Amazonians now live in urban areas.

摘要 尽管亚马孙流域拥有全球最高的淡水生物多样性，但城市上岸渔获数据显示，仅十余种鱼类便承受着极高的捕捞压力。然而，由于长期忽视可能捕获亚马孙流域绝大多数鱼类的个体捕捞渔业活动，真正厘清该渔业的特征并理解物种选择性的驱动因素颇具挑战。我们通过在乡村河畔社区访谈个体渔民，记录了824次捕捞作业的渔获数据。本研究利用这些数据，刻画了普鲁斯河（Rio Purus）的个体捕捞渔业特征——该流域是亚马孙流域最大城市马瑙斯的主要鱼类供应子系统，并探究了决定渔获组成的各类因素。此次调研中共记录到80种鱼类，但仅4个物种便占据了总收获生物量的一半以上。城市市场似乎加剧了捕捞选择性：相较于自给性渔获，商品性渔获的物种多样性显著更低。渔获组成不仅存在显著的季节差异，还随与马瑙斯的地理偏远程度变化而显著不同。渔获组成的空间周转似乎由城市可达性驱动：在马瑙斯鱼类收购商频繁到访的区域，商业价值更高的物种占据主导地位。本研究的数据可部分解释部分高商业价值物种所面临的过度捕捞问题，尤其是在如今多数亚马孙居民已居住在城市地区的背景下。