Fishing destabilizes the biomass flow in the marine size spectrum

Fishing impacts on marine food webs are predicted by simulations of a size spectrum community model. In this model, predation is determined by predator and prey size and abundance, and drives predator growth and prey mortality. Fishing amplifies temporal oscillations in the biomass flow. Oscillations appear at lower fishing intensity and have wider amplitude when fishing is selective (removes a narrow size range) and/or when large fish are targeted, than when fishing is more balanced (catching a larger size range) or when small fish are targeted. A novel index of size diversity is developed, and is shown to be sensitive to both fishing intensity and selectivity. To avoid unstable food web dynamics with potential harmful consequences for fisheries, limiting both fishing intensity and selectivity might be an appropriate exploitation strategy.     

Rights Based Fishing: Use Rights versus Property Rights to Fish

The basic economic problem of commercial fisheries can be seen as the absence of property rights to the fish stocks. There are, however, both practical and principal obstacles to applying that solution. Instead, the preferable arrangement appears to be stock control by public agencies, combined with exclusive use rights granted, leased or sold to the fishing industry in order to achieve economic efficiency. Incentives to establish such rights can be found both in government circles and in the industry. Both have a vital role to play; plans to establish use rights such as ITQs have run aground on more than one occasion because of opposition from the industry. Use rights can be seen as a tool for government agencies to achieve economic efficiency in the industry. If desired, these gains can be distributed over a wider public through user fees of some kind. There are few examples, however, of substantial user fees, and the industry has been successful in getting such schemes abolished when they have been put into effect. The experience of Russia and, in particular, Estonia is discussed. The absence of user fees can be explained by the need to obtain support for use right schemes from the industry, and the windfall gains from gratis use rights are vehicles for this. Norway and Iceland are two countries which have put in place use rights, but they have done so in different ways. Iceland has an ITQ system while Norway has fishing concessions combined with individual vessel quotas. Some success appears to have been achieved in both countries with these systems.     

The last jewel in a disintegrating crown— The case of japanese distant water Tuna Fisheries

Japan retains its position as one of the world's major distant water fishing nations. This article analyzes Japan's distant water Tuna Fisheries, which are currently facing significant external and internal constraints on operation of their vessels. It examines multipronged strategies that the industry and the government have adopted to ensure survival of Japan's tuna operations—the last important distant water fishery that remains for Japan's fishing industry.     

中国淡水渔业碳汇强度估算

【背景】碳汇是指从大气中消除二氧化碳的过程、活动或机制,我国最先提出碳汇渔业概念。【方法】捕捞鱼类的碳均来自天然饵料,故以其平均碳含量估算碳移出量。而养殖鱼类中,一般假定不考虑施肥养鱼的碳输入;鲢和鳙是滤食性鱼类,主要摄食浮游生物,鳜属鱼类以其他种鱼类为食物,而这些鱼类主要摄食天然饵料,故可以认为其碳均来自天然饵料。此外,假设草鱼、鲫和鲤等产量的20%来自天然饵料,而河蟹产量的50%来自天然饵料。基于渔业统计年鉴(2011—2015年),估算了我国近5年来淡水渔业碳汇强度。【结果】2010—2014年,全国淡水养殖碳移出量逐年稳步增长,分别为136.2万、140.5万、146.0万、153.0万和164.5万t,平均每年的碳移出量为148.0万t。2010—2014年全国淡水捕捞碳移出量分别为29.3万、28.7万、29.6万、29.7万和29.6万t,平均每年的碳移出量为29.4万t。【结论与意义】在自然资源日益减少的情况下,淡水养殖渔业碳汇的发展必然会成为淡水渔业经济发展的主体。     

Changes in tropical fish assemblages associated with small-scale fisheries: a case study in the Pacific off central Mexico

Information from artisanal marine fisheries inColima, Mexico is analyzed to find evidence ofchange in the composition of fish assemblagesresulting from fishing pressure. Catchcomposition from up to 20 boats per day, during2 to 6 days a month, were recorded from 1983 to1998. Stability of the species composition wasanalyzed using rank correlation methods, andmeasures of diversity (specific richness,Shannon-Wiener index, evenness) were estimatedfrom data. The resulting time-series wereanalyzed to detect trends. No significantdifferences were found in the number of speciescaught by month nor were significant trends indiversity detected. The composition of the fishassemblages is dynamic. The presence ofpersistent and resilient species that definedthe values obtained of diversity and evennesswas detected, but did not determine thestructure of the community, which is apparentlydefined by other factors. The changes incomposition of the catch probably are aconsequence of environmental fluctuations andrandom events, and not a direct consequence offishing pressures on the fish community.     

传统渔业活动对广西英罗港红树林区渔业资源的影响与管理对策

广西英罗港红树林区滩涂和光滩潮水中大型底栖动物和游泳动物曾很丰富。近4年来由于海鲜价格不断提高,林区的人为滥捕已使大型底栖动物和游泳动物的数量分别下降了约60%和80%。捕获方式有挖掘滩涂底栖动物,在红树林光滩潮水和林内潮沟进行网捕、炸鱼和毒鱼,网眼小至0.25 cm。传统的捕获萎缩了生态食物网的通量,破碎了生境,威胁着种群的繁衍。由于红树林区的渔业多少是当地群众的生计,完全封闭滩涂进行保育目前不可能。为此建议对英罗港红树林区滩涂施行封滩轮育,同时加强公众教育。