Assessing opportunity and relocation costs of marine protected areas using a behavioural model of longline fleet dynamics

Increasing use of spatial management tools in fisheries requires an understanding of fleet response, and in particular to where displaced fishing effort is likely to move. We develop a state‐dependent decision‐making model to address the spatial allocation of effort in an Australian tuna longline fishery. We assume that fishers have an economic objective in deciding where to fish, but that decisions in any period are also influenced by the remaining quota held at the time of the decision. Key features of the model include endogenous price dynamics, a moving stock and a competitive pool of different vessel types operating from different port locations. We utilize this model to illustrate fleet responses to marine reserves and limits on fishing effort. The results illustrate that the model framework provides advantages over statistically based models in that decisions made in response to the imposition of a reserve are not consistent with a proportional reallocation of effort. Rather, the stochastic dynamic model yielded an overall profit level of ～4% higher relative to scenarios with no reserve. Incorporating the opportunity cost of a quota into the model resulted in an optimal utilization of effort, in which effort was concentrated in time periods and locations yielding maximized profit. Under a low level of effort relative to the season length, the model indicated an overall profit level 43% greater than the highest obtained when the same level of effort was applied solely within any given quarter of the season.     

中国远洋鱿钓渔业的发展与前景

介绍了中国远洋鱿钓渔业发展的３个阶段。从生产规模、生产效率、作业渔场３个方面介绍了中国远洋鱿钓渔业发展状况,对中国产鱿钓渔业目前的生产和发展提出一些建议,并对中国远洋鱿钓渔业的前景进行了展望。     

中国近海渔船队合理规模的探讨

对中国近海捕捞产量进行了统计与分析，由此得出中国近海渔船队的合理规模：主机功率约为150－360万kW，渔船的数量约为3－13万艘。并就削减后的渔船与渔民出路进行了探讨。     

昆明盆地浅层地下水氮的分布及污染机理

通过对研究区内多年水质监测资料的分析,查明了昆明盆地浅层地下水中三氮的含量及其分布规律,在此基础上,从地下水污染源、区内的地质环境条件以及地下水开采等方面探讨了地下水中三氮的迁移、转化及其污染机理.最后,指出三氮污染已成为昆明盆地浅层地下水污染的普遍问题,地下水三氮入湖通量在一定程度上对滇池的富营养化发展起了作用.     

Theories and behavioural drivers underlying fleet dynamics models

In the domain of decision‐support tools for the management of marine fish resources, considerable attention has been paid to the development of models explaining how fish stocks change over space and time. In most models, fishing effort is assumed to be exogenous and determined by factors such as management. Increasingly, there has been a call for bio‐economic models to also account for the dynamics of fishing fleets, recognizing that fishers respond to changing environmental, institutional and economic conditions. A growing literature has sought to explicitly model the endogenous determinants of the capacity of fishing fleets, the intensity of its use and its temporal and spatial allocation across fishing opportunities. We review this literature, focusing on empirical applications of the behavioural models that have been put forward to explain and predict observed fleet dynamics. We find that although economic factors are usually included as a dominant driver in most studies, this is often based on the use of proxy variables for the key economic drivers, for which adequate data are lacking. Also, while many studies acknowledge that social and social–psychological factors play a significant role in explaining observed fishing behaviour, their inclusion in fishing fleet dynamic models is still very limited. Progress in this domain can only be achieved via the development of multidisciplinary research programmes focusing on applied quantitative analysis of the drivers of fishing fleet dynamics.     

Definition, dynamics and stability of métiers in the Irish otter trawl fleet

The Irish otter trawl fleet operates in a complex multi-species multi-gear fishery, spanning a wide geographic area, and involving around 275 trawlers. Factorial and clustering methods were applied to 2003 fishing trip data to define thirty-three métiers. Definitions were based on six trip characteristics taken from logbooks, namely: fishing gear, mesh size, vessel length, species composition, area, and month. Métiers exploiting demersal species or species groups are characterised by single vessel bottom otter trawls, typically with mesh sizes of 70 mm or more, operating year round. This includes nine Nephrops dominated métiers highlighting the importance of this species to the fleet. Many demersal métiers are characterised by groups of species, such as mixed whitefish or slope species. Métiers exploiting pelagic species are often focussed on single species, and are typically seasonal, mid-water trawling (often paired) with mesh sizes less than 70 mm. Pelagic métiers account for the majority of landings by over an order of magnitude in several cases. Demersal métiers account for the majority of fishing trips and effort, (primarily Nephrops métiers), and vessels (primarily mixed species métiers). The new métier definitions were found to be appropriate remained relevant despite declining fleet landings and effort between 2003 and 2006. Species compositions within these métiers have generally remained similar to the proportions defined in 2003. These robust métier definitions present opportunities to improve fisheries sampling, assessment and management. Although métiers pose complexity challenge for such applications they can be used the building blocks for appropriate management units.     

Risk sensitivity and the behaviour of fishing vessels

Risk sensitivity is an important component of fisher behaviour, yet its impact on fisher decision‐making and utility is poorly understood. Here, we incorporate various forms of risk in a model of location choice by fishing vessels targeting broadbill swordfish, Xiphias gladius, and evaluate the importance of risk sensitivity for predicting location, perceived utility and profit over a fishing season. We consider short‐term, or trip‐level, risk as natural, social or endogenous. Longer‐term, or seasonal, risk includes accumulated profit as a state variable. When considering only short‐term risk, endogenous and social risks are predicted to have the largest impact on profit, while natural risk also is predicted to impact on location choice. When longer‐term (seasonal) risk was considered, the impacts of short‐term (trip‐level) risks on profit were reduced. Model results were somewhat sensitive to assumed input parameters. The model allows users to quantify the extent of risk interaction and the relative sensitivity of perceived utility, location choice and profit. By providing a utility function capturing the fisher decision‐making process, the model provides a platform for the consideration of simultaneous forms of risk under different circumstances.     

禄丰县“4·23”森林火灾航空扑救经验及启示

在2013年春季云南省禄丰县发生的"4·23"森林火灾扑救中,同时投入2架Ka-32直升机和1架As-350直升机,成功开展机群作业,在火灾扑救中发挥了重要作用,是南方森林航空消防机群灭火的一次典型战例。文章对火灾的地理环境及火情特点等进行分析,应用重点设防、合力堵截,敢于取舍,控制全局,协同作战,聚散结合,逐片消灭的战术,并且组织有序,指挥统一,综合协调,保障到位,侦察充分,进行空中指挥,取得了显著效果。     

Towards a sustainable fisheries policy in Europe

The reform of the European Common Fisheries Policy (CFP) in 2013 decides whether the European fisheries can be put on a sustainable course in the next 10 years. The CFP reform must halt overexploitation of fish resources and stop harm to the marine environment by fishing activities. The European Commission published a reform proposal just recently. This proposal is already an important first step in the right direction, but is under threat of being watered down by the Fisheries Council. Necessary improvements of the current CFP include among others a binding definition of a sustainable stock management, a discard ban for all fish species, transferable fishing concessions and a cessation of all aid for building new vessels. These modifications pave the way for placing micromanagement in the hands of regions and fisheries so as to foster self‐responsibility among fishers and give greater consideration to regional circumstances.