Sustainable fisheries in shallow lakes:an independent empirical test of the Chinese mitten crab yield model

Next to excessive nutrient loading,intensive aquaculture is one of the major anthropogenic impacts threatening lake ecosystems.In China,particularly in the shallow lakes of mid-lower Changjiang(Yangtze) River,continuous overstocking of the Chinese mitten crab(Eriocheir sinensis) could deteriorate water quality and exhaust natural resources.A series of crab yield models and a general optimum-stocking rate model have been established,which seek to benefit both crab culture and the environment.In this research,independent investigations were carried out to evaluate the crab yield models and modify the optimum-stocking model.Low percentage errors(average 47%,median 36%) between observed and calculated crab yields were obtained.Specific values were defined for adult crab body mass(135 g/ind.) and recapture rate(18%and 30%in lakes with submerged macrophyte biomass above and below 1 000 g/m^2)to modify the optimum-stocking model.Analysis based on the modified optimum-stocking model indicated that the actual stocking rates in most lakes were much higher than the calculated optimum-stocking rates.This implies that,for most lakes,the current stocking rates should be greatly reduced to maintain healthy lake ecosystems.

Recommendations for Development of Stock Enhancement Fishery in China

In 2011,China put the stock enhancement fishery in the same place as aquaculture,fishing,aquatic product processing and circulation industry,and recreational fishery,i. e. one of the five pillar industries of fishery economy. Developing the stock enhancement fishery is a strategic measure for restoring and protecting fishery resources,expanding fishery,replacement environment cost,and promoting sustainable development of fishery. At present,cultivation and development of the new rising industry,the stock enhancement fishery,has certain comparative edge,excellent economic foundation and broad development space in China.

An assessment of “fishing down marine food webs” in coastal states during 1950–2010

Mean trophic level of fishery landings（MTL） is one of the most widely used biodiversity indicators to assess the impacts of fishing. Based on the landing data compiled by Food and Agriculture Organization combined with trophic information of relevant species in Fish Base, we evaluated the status of marine fisheries from 1950 to 2010 for different coastal states in Pacific, Atlantic and Indian Oceans. We found that the phenomenon of ＂fishing down marine food webs＂ occurred in 43 states. Specifically, 27 states belonged to ＂fishing-through＂ pattern, and 16 states resulted from ＂fishing-down＂ scenario. The sign of recovery in MTL was common in the Pacific, Atlantic and Indian Oceans（occurred in 20 states）, but was generally accompanied by significantly decreased catches of traditional low trophic level species. In particular, 11 states showed significant declining catches of lower trophic levels. The MTL-based assessment of ＂fishing down marine food webs＂ needs to be interpreted cautiously.

Responsible fishing operations for clean oceans,healthy ecosystems and sustainable fisheries

This special issue contains selected papers presented at the ICES-FAO Working Group on Fishing Technology and Fish Behavior mini-symposium on“Responsible Fishing Technology for Healthy Ecosystems and Clean Environment”held in Shanghai,China between 8 and 12 April 2019.The symposium was co-sponsored by Food and Agriculture Organization of the United Nations(FAO),International Council for the Exploration of the Seas(ICES)and Shanghai Ocean University,China.The meeting was chaired by Pingguo He(USA),Haraldur Einarsson(Iceland)and Liming Song(China).The special issue was edited by the following guest editors:Pingguo He(managing guest editor),Haraldur Einarsson,Liming Song,and Michael Pol,with the assistance of a number of anonymous reviewers.

Management options for the unfavorable nutrient balance of recreational fishing in Lake Balaton(Hungary)

Various types of ground baits are loaded to lakes by anglers,but the ecological role of these materials is often overlooked.Thus,the aims of this study were to conduct a quantitative and qualitative assessment of the baits used by anglers in the largest lake of Central-Europe(Lake Balaton,Hungary),estimate the annual nutrient balance of recreational fishing,and relate the nutrient loading from this source to the total external load.Our study demonstrated that popular angler baits varied substantially in their nutrient contents and in their molar nitrogen to phosphorus(N:P)ratios.The net nutrient balance of recreational fishing was+19.3 t total N year^(-1)and+5.2 t total P year^(-1),equivalent to 0.7%and 3.2%of the estimated total annual N and P loads,respectively.The rate of nutrient loading may be doubled if the present trends continue:anglers will use 20%more bait with an even higher nutrient content and will also show higher propensity to release the fish after catching.In turn,sustainable nutrient balance of fisheries management could be achieved by limiting the anglers’bait use to 1.5 kg day^(-1)and restricting baits to those which have relatively low P(<0.3%)and N(<1.5%)contents.