闽南、台湾浅滩渔场单拖作业渔获物组成分析

根据2000~2001年单拖作业渔获物调查资料,着重对渔获物种类组成、个体大小进行分析。结果表明:闽南、台湾浅滩渔场单拖网作业渔获物品种繁多、个体小,优势种数量多、比重小,占周年总渔获量1%以上的品种有19种,鱼类、甲壳类、头足类渔获个体平均体重仅为11.4g/ind,周年中,5~6月个体最小,建议将该渔场单拖作业伏季休渔时间调整为5月1日至7月15日。     

巴塔哥尼亚大陆架海域阿根廷滑柔鱼渔场分布及与表温的关系分析

根据 2 0 0 2年 1～ 6月中国大陆地区鱿钓渔船在西南大西洋的生产统计及其海表水温数据 ,按 1°× 1°的格式进行统计分析 ,并用MarineExplore 4 .0软件进行作图 ,对阿根廷滑柔鱼渔场、CPUE分布及其与表温的关系进行了分析。结果表明 ,1～ 3月份中心渔场集中在 4 5°S、6 0°W一带 ,4～ 6月份作业渔场集中在 4 2°S、5 7°W附近。各月产量和CPUE有很大变动 ,其中 1月份产量最高 ,3月份开始下降 ,6月份达到渔汛的末期。全年产量较高海区的表温为 12～ 15℃ ,各月份的最适渔获表温不同 ,1月为 14～ 15℃ ,2月为 13～ 15℃ ,3月为 12～ 14℃ ,4月为 9～ 13℃ ,5月为 8～ 10℃ ,6月为 7～ 9℃ ,并且每月的作业水温逐渐降低 ,平均每月下降约 1℃。经K S检验 ,结果表明 ,各月表温和CPUE的差异均不显著。     

Does unreported catch lead to overfishing?

Catches are commonly misreported in many fisheries worldwide, resulting in inaccurate data that hinder our ability to assess population status and manage fisheries sustainably. Under‐reported catch is generally perceived to lead to overfishing, and hence, catch reconstructions are increasingly used to account for sectors that may be unreliably reported, including illegal harvest, recreational and subsistence fisheries, and discards. However, improved monitoring and/or catch reconstructions only aid in the first step of a fisheries management plan: collecting data to make inferences on stock status. Misreported catch impacts estimates of population parameters, which in turn influences management decisions, but the pattern and degree of these impacts are not necessarily intuitive. We conducted a simulation study to test the effect of different patterns of catch misreporting on estimated fishery status and recommended catches. If, for example, 50% of all fishery catches are consistently unreported, estimates of population size and sustainable yield will be 50% lower, but estimates of current exploitation rate and fishery status will be unbiased. As a result, constant under‐ or over‐reporting of catches results in recommended catches that are sustainable. However, when there are trends in catch reporting over time, the estimates of important parameters are inaccurate, generally leading to underutilization when reporting rates improve, and overfishing when reporting rates degrade. Thus, while quantifying total catch is necessary for understanding the impact of fisheries on businesses, communities and ecosystems, detecting trends in reporting rates is more important for estimating fishery status and setting sustainable catches into the future.     

Economic impacts of TAC regulation: A supply-driven SAM approach

The Galician fishing fleet is one of the most important of all the European fleets that fish in European Union waters and hake is its vital species. The aim of this article is to estimate some of the economic impacts that a reduction in the TAC of hake during the period 1999–2003 have on the entire Galician economy. We use a “supply-driven” Social Accounting Matrix (SDSAM) model for the Galician fishing sector that takes hake production as exogenously given. In this respect, the present work constitutes a first attempt at applying a SDSAM model to fisheries. It also presents both the traditional backward linkage effects as well as the lesser known forward linkage effects. The SDSAM model allows us not only to compute impacts on production but also to estimate the impact distribution on household incomes and production factors. Impacts on employment have also been calculated. These results may be useful to policy makers as they provide some perceptions into the consequences of one of the measures of the Common Fisheries Policy (CFP) and may help to design policy initiatives.     

印度洋温带海域长鳍金枪鱼延绳钓渔获组成分析

根据2008年3～5月"中荣6号"在印度洋温带公海(19°35'S～32°01'S,58°25'E～75°52'E)金枪鱼延绳钓渔业的调查,期间共投钩45航次,钓获27种鱼类,包括金枪鱼类(1 730尾,占总渔获尾数的58.5%),剑旗鱼类(175尾,5.92%),软骨鱼类(187,6.32%)和其他鱼类(865尾,29.25%)。分析了延绳钓渔获物的长度和重量组成和渔获组成的影响因素,并提出减少兼捕渔获的对策。     

不同降水条件下北方日光温室填闲季糯玉米对土壤残留氮风险阻控研究

我国北方设施蔬菜生产中存在着不合理灌溉施肥的现象,严重影响着设施农业的可持续发展。本试验在种植季节外填闲期间,以休闲田地为对照,采用填闲作物种植和溴深层示踪技术研究了夏季填闲作物对土壤提氮作用。试验结果表明:夏季种植填闲作物可显著降低根区土壤中无机氮素的含量,尤其是土壤表层的无机氮含量。休闲处理,土壤(0～180 cm)各层的无机氮含量均有增加。但在干旱条件处理下种植填闲作物后,土壤(0～120 cm)各层的无机氮含量均出现下降。夏季降雨量是造成土壤氮素淋洗的主要因素,且土壤中无机氮含量越高,氮素淋洗量越大。种植填闲作物可以有效地吸收土壤中氮养分,在模拟干旱年份和正常年份降雨量的处理中,种植糯玉米从土壤中吸收氮量分别为172.6,146.6 kg/hm2。溴标记试验进一步证明了填闲作物的提氮能力,下层土壤中溴均出现向上运移的现象。本研究证实了种植填闲作物糯玉米具有有效利用菜田土壤残留氮与阻控氮淋洗风险的作用,为北方日光温室典型种植模式氮素优化管理提供了科学参考。     

Use of individual types of fishing effort in analyzing catch and effort data by use of a generalized linear model

Fishing effort is a function of many (continuous) variables which fishers can manipulate. However, when catch and fishing effort data are analysed using a generalized linear model, individual types of fishing effort usually enter as a composite quantity. But not all quantities can be combined into a composite quantity. Use of such data this way generally leads to a loss of information and incurs a model bias. In this paper, I analyse catch and effort data for the blue swimmer crab off South Australia by a direct use of individual types of fishing effort to extract a relative index of biomass, and use the concept of homogeneous functions to present some of the results. I also give formulae for choosing a combination of different types of fishing effort to effect a specified level of catch in both absolute and relative terms. Assuming that catch follows an independent gamma, normal, negative binomial, or Poisson distribution, fitting of a generalized linear model with a log-link function to the commercial catch and effort data suggests that: (1) the exploitable biomass remained relatively constant from 1 July 1983 to 30 June 1996; (2) the relative instantaneous rate of fishing mortality of a particular sex and age (if gear selectivity was constant over time) slightly increased over time; (3) a 1% increase in the number of days fished gave about 0.85% increase in catch whereas a 1% increase in the number of people on a boat led to only about a 0.45% increase in catch. This implies that use of a composite measure of fishing effort such as boat days and man days when analysing catch and effort data is inappropriate for this fishery. Although a generalized linear model may be a reasonable first-order approximation, catch and effort data are best interpreted through a process model.     

Approaches to fully documented fisheries: practical issues and stakeholder perceptions

The Common Fisheries Policy (CFP) reform sets out a move to a land‐all catch policy in European Union waters with a requirement for full reporting of fishing and on‐board processing activity. We explore the merits, stakeholder perceptions and applicability of different technology and approaches to the full documentation of fisheries that might be considered in the context of implementing the CFP reform. While recent efforts have focused on demonstrating how remote electronic monitoring (REM) systems can be utilized in fully documented fisheries (FDF), other technologies and approaches such as reference fleet and self‐sampling exist that could contribute to delivering FDF. Perceptions of fishers show that they would prefer using a reference fleet or self‐sampling to REM systems as a future method of implementing FDF. In general, there is support from the fishing industry for data collection and enhancement, but there remains some mistrust concerning the use of the data. Findings show that the most appropriate means and methods of FDF will depend on the circumstances and objectives for full documentation whether in enforcing a discard ban, documentation of total catch or data enhancement. We conclude that any technology or approach that will be used to deliver the monitoring requirements for FDF needs to make practical and commercial sense at the fishing vessel level.     

中东太平洋金枪鱼延绳钓渔获量及其分布

根据2000年9月至2002年8月两年的中东太平洋金枪鱼延绳钓探捕调查结果,对延绳钓渔获量及其分布特征进行了初步分析。结果显示,延绳钓渔获物以金枪鱼为主,大眼金枪鱼(Thun-nusobesus)等3种金枪鱼的渔获量占总渔获量75·9%。“海欣”船延绳钓作业的平均日产量为(994·8±19·9)kg/d,上钩率为(12·5±0·3)ind/103钩。主要目标鱼种大眼金枪鱼和黄鳍金枪鱼(Thunnusalbacares)的平均日产量分别为(466·9±13·9)kg/d和(190·6±7·2)kg/d。探捕期间日产量的月间差异显著(P<0·001),6~8月为渔发汛期,日产量较高;2~5月为相对淡季,日产量较低。探捕区南部的平均日产量最高,与中、北部比较差异显著(P<0·001);东部平均日产量与西部比较差异不显著(P>0·05)。