Indicators to support an ecosystem approach to fisheries

Indicators are needed to support the implementation of an ecosystem approach to fisheries (EAF), by providing information on the state of the ecosystem, the extent and intensity of effort or mortality and the progress of management in relation to objectives. Here, I review recent work on the development, selection and application of indicators and consider how indicators might support an EAF. Indicators should guide the management of fishing activities that have led to, or are most likely to lead to, unsustainable impacts on ecosystem components or attributes. The numbers and types of indicators used to support an EAF will vary among management regions, depending on resources available for monitoring and enforcement, and actual and potential fishing impacts. State indicators provide feedback on the state of ecosystem components or attributes and the extent to which management objectives, which usually relate to state, are met. State can only be managed if the relationships with fishing (pressure) and management (response) are known. Predicting such relationships is fundamental to developing a management system that supports the achievement of objectives. In a management framework supported by pressure, state and response indicators, the relationship between the value of an indicator and a target or limit reference point, reference trajectory or direction provides guidance on the management action to take. Values of pressure, state and response indicators may be affected by measurement, process, model and estimation error and thus different indicators, and the same indicators measured at different scales and in different ways, will detect true trends on different timescales. Managers can use several methods to estimate the effects of error on the probability of detecting true trends and/or to account for error when setting reference points, trajectories and directions. Given the high noise to signal ratio in many state indicators, pressure and response indicators would often guide short‐term management decision making more effectively, with state indicators providing longer‐term policy‐focused feedback on the effects of management action.     

渔业生态系统方法简述

考虑到生态系统状态对渔业的重要影响,渔业生态系统方法(Ecosystem Approach to Fisheries,EAF)把对生态的关注加入渔业管理框架中,并以生态系统管理和渔业管理2个理论为基础,扩展了传统渔业管理的框架:以生态系统健康与人类福利的依存关系为基础,关注多物种管理,均衡生态、人文和制度3个维度的目标,实现渔业的可持续发展。本研究介绍了EAF的由来、定义、基本原则以及功能要素,概述了EAF的实践基础和模型构建的技术路径,对比了EAF与EBFM的异同。虽然EAF的理论和实践仍处于完善和发展阶段,但确为渔业管理的发展方向,介绍EAF对促进我国渔业可持续发展具有重要意义。     

关于促进渔民增收的几点思考

渔民收入倍增既然是一项工程,必然要历经复杂、漫长的过程,并不是一朝一夕就能实现的;但实现这一目标也并非遥遥无期,这个期限是按照“两个率先”的时序要求,实现全面小康目标确定的。要实现这一目标关键是渔业经济要得到快速发展,渔民劳动力转移要有新的突破。     

Constraints to polyculture

Patterns of rearing several compatible aquatic food species together (polyculture) in fresh, brackish and salt water are discussed. Emphasis is on technologies that seize on compatibilities of the organisms for spatial and/or temporal cohabitation and on adaptation to different markets. In fresh water, use of avian or mammalian stock is included. Constraints discussed comprise water quality and quantity as well as some aspects of technical infrastructure. Also, present land and water management conditions in tropical Asia whence most examples are taken, except for Japan, suggest that best gains can be made not by creating new installations but by upgrading existing ones through large scale establishment of hatcheries and through the improvement of management skills.     

关于去西亚地区开发对虾养殖的建议

西亚地区可分南、北两个部分。南部包括也门、沙特阿拉伯、卡塔尔、巴林、阿曼和阿拉伯联合酋长国等。北部包括土耳其、塞浦路斯、叙利亚、黎巴嫩、约旦、伊拉克、科威特、巴勒斯坦等地区和国家。这里讨论仅限于西亚南部地区诸国和伊朗。一、西亚地区南部诸国具有哪些共同特征     

Proximity of Pacific cod to the sea floor: Using archival tags to estimate fish availability to research bottom trawls

The percentage of Pacific cod available to Alaskan bottom trawl surveys was estimated from the proximity of tagged cod to the seafloor. Archival tags recorded time and depth data at 15- or 30-min intervals. The distance of a cod above the bottom was computed by subtracting tag depth from bottom depth, estimated as the maximum depth recorded during each 24-h day. These estimates of bottom depth are based on the assumption that cod approach the seafloor at least once a day, and do not undergo migrations up or down bottom gradients. To ensure that migrations over variable bottom gradients did not confound our estimates of bottom depth, we narrowed our analysis to 11 tagged cod that were recaptured in areas of flat bathymetry, and only analyzed data recorded within one month prior to recapture (N = 29,462 depth recordings). Pacific cod maintained short distances above the seafloor that often differed between day and night. Over 95% of the daytime tag recordings occurred within 10 m of the seafloor. Average effective headrope heights for survey bottom trawls currently used in the eastern Bering Sea and Alaska Gulf/Aleutian Islands groundfish surveys are approximately 2.5 and 7 m, respectively. In the absence of any behavior responses to an approaching trawl, we would expect 47.3% of the cod within the water column are available to the trawl used on the eastern Bering Sea survey and 91.6% are available to the trawl used on the Gulf/Aleutian Islands surveys. This study demonstrated that Pacific cod are highly demersal, and current values of trawl survey catchability (Q) used in current stock assessments are consistent with estimates of cod availability to the trawl gear.     

A method to assess the sensitivity of sedimentary communities to fishing activities

• 1. Methods of sensitivity assessment to identify species and habitats in need of management or protection have been available since the 1970s.
• 2. The approach to sensitivity assessment adopted by the Marine Life Information Network (MarLIN) assumes that the sensitivity of a community or biotope is dependent on the species within it. However, the application of this approach to sedimentary communities, especially offshore, is complex because of a lack of knowledge of the structural or functional role of many sedimentary species.
• 3. This paper describes a method to assess the overall sensitivity of sedimentary communities, based on the intolerance and recoverability of component species to physical disturbance. A range of methods were applied to identify the best combinations of abundant, dominant or high biomass species for the assessment of sensitivity in the sedimentary communities examined.
• 4. Results showed that reporting the most frequent species' sensitivity assessment, irrespective of the four methods used to select species, consistently underestimated the total sensitivity of the community. In contrast, reporting the most sensitive assessment from those species selected resulted in a range of biotope sensitivities from very low to very high, that was better able to discriminate between the sensitivities of the communities examined.
• 5. The assumptions behind the methodology, its limitations and potential application are discussed.

© Crown copyright 2008. Reproduced with permission of Her majesty's stationery office. Published by John Wiley & Sons, Ltd.     

From one to ten: Canada's approach to achieving marine conservation targets

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