Can fishermen allocate their fishing effort in space and time on the basis of their catch rates? An example from Spermonde Archipelago,SW Sulawesi,Indonesia

Spatial and temporal patterns in catch rates and in allocation of fishing effort were analysed for the coastal fishery in Spermonde Archipelago, Indonesia, to assess whether fishermen can optimise their strategy from catch information, or whether they fish under great uncertainty and merely minimise risks. On average 517 fishing units operated in the 2800 km² area, catching 21 t fish day⁻¹. Major gear categories were hook and line (59% of total effort and 5% of total catch), and lift nets (16% of total effort and 70% of total catch). The size of individual resource spaces varied with gear type and was smaller in unfavourable weather conditions. Although spatial patterns in catch rates at the scale of the whole archipelago were evident, fishermen could not differentiate between locations, as catch variance within their individual resource spaces was high relative to the contrasts in spatial patterns. The aggregated distribution of fishing effort in Spermonde must be explained by factors such as the small scale of operations, rather than fish abundance.     

Assessment of catch, effort and species changes in the pair-trawl fishery of southern Lake Malawi, Malawi, Africa

Abstract  Catch per unit effort (CPUE) and species composition in the pair-trawl fishery in commercial Area A of southern Lake Malawi were assessed from 1991 to 2001. CPUE declined from 1.7 t day⁻¹ in 1995 to 0.5 t day⁻¹ in 2001 and the fishery is considered depleted. In 2000/2002, catch composition differed significantly from a 1991 survey, and was dominated by haplochromine cichlids (92% by weight). Of 98 haplochromine cichlid taxa identified in the catch, 18 contributed ≥1% by weight. The artisanal fishery targeted similar species of a similar size. It was recommended that: (1) renewed investment and increased effort in the pair-trawl fishery is not advisable; (2) there was a need for effort limitation in Area A and (3) the pair-trawl fishery should not be managed in isolation of the artisanal fishery.     

Quantifying fishing effort: a synthesis of current methods and their applications

The need to accurately quantify fishing effort has increased in recent years as fisheries have expanded around the world and many fish stocks and non‐target species are threatened with collapse. Quantification methods vary greatly among fisheries, and to date there has not been a comprehensive review of these methods. Here we review existing approaches to quantify fishing effort in small‐scale, recreational, industrial, and illegal, unreported and unregulated (IUU) fisheries. We present the strengths and limitations of existing methods, identifying the most robust methods and the critical knowledge gaps that must be addressed to improve our ability to quantify and map fishing effort. Although identifying the ‘best’ method ultimately depends on the intended application of the data, in general, quantification methods that are based on information on gear use and spatial distribution offer the best approaches to representing fishing effort on a broad scale. Integrating fisher’s knowledge and involving fishers in data collection and management decisions may be the most effective way to improve data quality and accessibility.     

Validation of the accuracy of household reporting of subsistence fishing catch and effort: a Fijian case study

Abstract  The accuracy of household reporting of subsistence fishing catch and effort and seafood consumption on the Fijian island of Ono-i-Lau was studied. A creel survey was carried out concurrently to validate the household survey data. Reported estimates of fishing participation, effort, and fish consumption were not significantly different to the creel survey estimates. Householder's appeared to overestimate the number of fish from the most abundant family Lethrinidae, and underestimate rarer fish. However, there was no significant difference between the reported and observed contribution of the majority of finfish families and invertebrate taxa. The reported and observed catch rate estimates were not significantly different, indicating that Ono-i-Lau villagers are relatively accurate in their estimation of the number and size of fish from recalled catches.     

Digital camera monitoring of recreational fishing effort: Applications and challenges

The growing awareness of the impact that recreational fishers can have on fish stocks has highlighted the paucity of information used to inform their management. Most of the available information on the scale and nature of recreational catch and effort has come from intermittent and labour‐intensive surveys that provide fragmented insights into often highly variable fisheries. Digital cameras offer a more cost‐effective means of continuously monitoring trends in recreational fishing effort, and it is surprising that greater use of this approach has not been made to date given its widespread use in other contexts. We share lessons learnt from four early adopter studies in New Zealand, Australia and Germany, where digital cameras have been used to monitor recreational fishing effort. Many of the challenges that we have encountered and overcome were initially unforeseen, and we suggest solutions and strategies to address these issues. We conclude that all aspects of a camera‐based monitoring system should be considered from the outset, to optimize the utility and value of the information they provide over the long term. Aspects to consider include the location and configuration of a camera system, ensuring service continuity, image quality, data storage, image interpretation and ultimately the analysis of any data collected. Robustly designed digital camera monitoring systems can be used to gain greater insight into recreational fishery dynamics, leading to more informed, responsive and effective fisheries management.     

应用分层抽样技术估计北部湾底拖网渔业产量

传统的按行政单元逐级上报的渔业产量调查方法在数据获取过程中受人为因素的干扰,而全面普查的方法受限于时间和经费,相比而言,抽样调查是一种科学合理的方法。本研究于2007年8月对北部湾底拖网产量进行了调查,以全体底拖网渔船为抽样总体,按功率段划分了抽样层次,按比例分配了抽样单元数,分别以生产渔船总数和总功率数推算总产量,并比较了这两种方法的方差。结果表明,用每kW平均产量估计总产量的变异系数为1.13%,用单船平均产量估计总产量的变异系数为14.65%。同时由于渔业抽样调查的难点在于总体船数的掌握,建议统计推断时,采用单位渔捞努力量渔获量（CPUE）推算总体渔获量。     

Effect of fishing effort on catch rate and catchability of largemouth bass in small impoundments

Largemouth bass Micropterus salmoides (Lacepède) catch rates decline with sustained fishing effort, even without harvest. It is unclear why declines in catch rate occur, and little research has been directed at how to improve catch rate. Learning has been proposed as a reason for declining catch rate, but has never been tested on largemouth bass. If catch rate declines because fish learn to avoid lures, periods of no fishing could be a management tool for increasing catch rate. In this study, six small impoundments with established fish populations were fished for two May to October fishing seasons to evaluate the effect of fishing effort on catch rate. Closed seasons were implemented to test whether a 2‐month period of no fishing improved catch rates and to determine whether conditioning from factors other than being captured reduced catch rate. Mixed‐model analysis indicated catch rate and catchability declined throughout the fishing season. Catch rate and catchability increased after a 2‐month closure but soon declined to the lowest levels of the fishing season. These changes in catch rate and catchability support the conclusion of learned angler avoidance, but sustained catchability of fish not previously caught does not support that associative or social learning affected catchability.     

挪威海洋捕捞及渔船管理概述

本文概要介绍了挪威海洋捕捞业和渔船管理状况:2011年,捕捞量230万t,产值159亿挪威克朗(约26.8亿美元);渔民数量12 791人,渔船数量6 252艘;近10年的捕捞量基本稳定,年均捕捞量为250万t,与此同时,渔船和渔民数量则呈持续下降态势,说明挪威渔船的捕捞能力显著增强,捕捞效率明显提升。挪威的渔业管理制度和法规建设比较完善,这为控制捕捞强度、保护海洋渔业资源奠定了法律基础。挪威的经验具有借鉴意义。我国现阶段以实行渔船控制等投入控制制度为主、其他管理方式为辅的渔业资源管理制度,比较符合我国实际。实践证明,减船转产政策是控制捕捞渔船规模和降低海洋捕捞强度行之有效的措施之一。     

Variation in productivity of a key snapper,Chrysophrys auratus,fishery related to recruitment and fleet dynamics

Abstract Temporal variation in production of the Chrysophrys auratus (Forster) fishery of Northern Spencer Gulf, South Australia, between 1984 and 2009 was investigated using commercial fishery statistics and estimates of age and size structures from market sampling. Fishery production was divisible into two periods, i.e. from 1984 to early 2000s and the middle to late 2000s. During the former, cycles in production were relatable to variable fishable biomass. Age structures that displayed considerable differences in age class strength reflected interannual variation in juvenile recruitment, which resulted in high variability in the strength of year classes entering the fishery. Periodic strong year classes were the major influence on fishable biomass as they passed through the population over numerous years. For the latter period, fishery statistics were conflicting as catches and effort were relatively low, whilst the estimates of catch per unit effort (CPUE) were consistently high. These statistics reflect a considerable change to the structure of the fishery that involved a reduction in number of fishers and fishing effort. The fishery statistics may indicate hyperstability, with CPUE estimates remaining high despite declining biomass because of the aggregative behaviour of the fish and the efficiency of remaining fishers.     

Global fishing capacity and fishing effort from 1950 to 2012

Global marine wild‐capture landings have remained relatively stable for >20 years; however, there is a lack of credible fishing capacity and effort information required to assess the sustainability and efficiency of the global fleet. As such, we estimated global fishing capacity and effort from 1950 to 2012 using a relatively comprehensive database developed by the FAO, supplemented by other data sources. Using random sampling techniques, we estimated the uncertainty surrounding many of our estimates enabling the identification of deficiencies and limitations. Global fishing capacity and effort increased rapidly from the late 1970s through to around 2010 before stabilizing. The Asian fleet is more than an order of magnitude larger than any other region in both capacity and effort, and continues to increase. Most other regions have stabilized, and there have been considerable declines in Europe and, to a lesser extent, in North America. Developed nations, as a whole, have decreased in both measures in the recent years and are responsible for the stabilization of the global trend. Developing and undeveloped countries are still increasing with the former having the largest fleet and showing the greatest relative increase with the socioeconomic impacts of reversing these trends likely to be high. The efficiency of the global fleet, in terms of watt days of fishing effort per tonnage of wild marine catch, is now less than in 1950 despite the considerable technological advances, and expansion throughout the world's oceans, that has occurred during this period of time.     

南极磷虾中层拖网捕捞参数对CPUE变动的影响

根据中国在南极海洋生物资源养护委员会(CCAMLR)48.1亚区和48.2亚区内2010—2014年南极磷虾拖网渔船的捕捞数据,采用广义可加模型(generalized additive model, GAM)分析各拖网捕捞参数(因子)对南极磷虾汛期单位捕捞努力量渔获量(catch per unit effort, CPUE )的影响。结果表明:2010—2014年我国南极磷虾作业渔场主要位于南极半岛等岛屿的周边海域,CPUE 值月变化明显,2—5月为捕捞高峰期。 CPUE 最高值为2014年,最低值为2012年,年平均CPUE呈略上升趋势。从月变化来看,除6月外,标准化 CPUE 均大于名义 CPUE;且最大值出现在4月或5月,最小值均出现在10月。GAM分析表明各捕捞参数对 CPUE 的影响由大到小依次为:拖网速度、网口高度、网口水平扩张、拖曳水深、曳纲长度;各因子的偏差解释率分别为22.8%、14.5%、12.7%、6.0%、1.6%,所有因子对 CPUE 的总体偏差解释率为57.6%。研究认为,我国南极磷虾捕捞作业中最适拖网速度范围2.6~3.1 kn;最适网口高度范围22~30 m;最适网口水平扩张范围20~25 m;最适曳纲长度范围100~200 m;最适拖曳水深范围0~40 m。     

Effect of recall period on annual freshwater fishing effort estimates in New York

Abstract Recall bias can influence estimates of fishing effort, with a general trend toward overestimation as the length of the recall period increases. Concern that recall bias may be affecting annual freshwater fishing effort estimates in New York led to the collection of effort data from three angler surveys during 2007 instead of one survey at the end of the year. However, to check for this potential bias and the impact that a change in recall period might have on comparisons with past surveys, a parallel survey with a 12‐month recall period was conducted. For the overall state‐wide estimate of fishing effort, the estimate from the three‐phase survey was slightly greater than from the 12‐month recall survey (the opposite of what was hypothesised). For the major water bodies, the differences were mostly significant but not always in the same direction between the two survey methods. Different results from one study compared with many others do not mean that past recommendations for shorter recall periods should be abandoned. However, the strength of this study – that the implementation methods (i.e. mail surveys) were identical – leads one to be more sceptical of past results.     

闽南渔场蟹笼作业渔获组成和主要种类

2010年1-12月(休渔除外)在闽南海区蟹笼作业渔船上每月采样一次,分析样品10批,累计重量111.37kg。对该渔获进行种类鉴定、组成分析,结果表明:渔获物中共出现72个种,其中鱼类40种、蟹类23种、口足类3种、头足类3种、螺类2种、虾类1种;重量比例为蟹类占45.80%、鱼类占44.46%、口足类占6.47%、头足类占3.11%、螺类占0.12%、虾类0.04%。主要优势种为叫姑鱼(Johnius belengerii)、红星梭子蟹(Portunus sanguinolentus)、口虾蛄(Oratosquilla oratoria)、日本(Charybdis japonica)。     

Commercial fishing in the Brazilian Amazon: regional differentiation in fleet characteristics and efficiency

Regional differentiation in fleet characteristics and economic efficiency, as well as the total elasticity of scale in the commercial fishing fleets of the Brazilian Amazon were analysed. Data were collected in 893 interviews with boat operators in four major ports on the River Amazon. Boats operating from the largest cities (Belém and Manaus) are mostly operated by hired skippers and non‐permanent crews, while boats from smaller cities (Santarém and Tefé) are mostly owner‐operated and use permanent crews. In the lower Amazon, a large proportion of fishermen (89% in Santarém and 53% in Belém) are based in rural areas, while in the upper Amazon commercial fishermen are predominantly urban‐based. A production function analysis identified boat length, gear type used (gill net/purse seine), number of fishermen employed, quantities of fuel and ice used, and education level of the skipper as significant factors determining the catch. The analysis provided no evidence of regional differences in stock levels. The use of purse seines was associated with significantly higher catches (by 32%), all other factors being equal. Purse seines are banned in the lower Amazon (Santarem and Belem), and this results in overall lower levels of technical efficiency in this region. No significant total scale effect on efficiency was detected. These results are discussed with respect to the institutional sustainability of current fisheries co‐management initiatives.     

Spatial distribution of fishing effort in relation to seafloor habitats in the Kattegat,a GIS analysis

• 1. High‐resolution fishing effort data from the Kattegat, an important fishing ground for Swedish and Danish fishermen, was analysed in a Geographical Information System (GIS). Data were based on position data for individual tows reported by Swedish fishermen during 2001–2003.
• 2. Gear dimension and towing speed data were used to calculate an index for area swept per hour for each main gear type in use in the area. These indexes were multiplied by fishing effort and a grid theme of fishing intensity was created after GIS analysis.
• 3. Around 44% of the entire area was affected by Swedish fisheries during the study period, hence 56% was not affected.
• 4. Effort was highly concentrated in certain areas and 10% of the total area was covered more than twice per year.
• 5. Overlaying the effort data set with habitat maps classified according to the European Nature Information System (EUNIS) showed that the fishing pressure differed between habitats. For deep rocky and muddy habitats, almost the entire area was affected by fisheries during the study period, while both intensity and proportion affected were lower in sandy sediments and gravels.
• 6. Around 55% of the deep rocky habitats were trawled more than twice per year. Of the muddy seafloor areas, 41% were covered more than twice per year and 4% more than once a month by trawls.
• 7. The biological effects of the fishing intensities found were analysed using a database (MarLIN) containing assessments of marine habitat recoverability. All habitats except muds are probably in a nearly or fully recovered condition (as defined by MarLIN). A considerable part of the muddy habitats are in a permanently altered condition owing to fishing disturbance taking place more frequently than the indicated recovery time.
• 8. Danish fishermen report more fishing effort in the area than do Swedes. Owing to differences in reporting fishing positions, Danish fisheries could not be included in the present study. Scaling up the results to include Danish fisheries is discussed.
• 9. The results of the present study could be used to target habitat management goals more precisely, while minimizing the negative impact of restrictions on the fishing sector.
• 10. A prerequisite for performing similar studies is the availability of high‐resolution fishing effort data and high‐resolution benthic habitat maps.

Copyright © 2006 John Wiley & Sons, Ltd.     

闽南渔场蟹笼作业渔获组成和主要种类

2010年1-12月(休渔除外)在闽南海区蟹笼作业渔船上每月采样一次,分析样品10批,累计重量111.37 kg.对该渔获进行种类鉴定、组成分析,结果表明:渔获物中共出现72个种,其中鱼类40种、蟹类23种、口足类3种、头足类3种、螺类2种、虾类1种;重量比例为蟹类占45.80％、鱼类占44.46％、口足类占6.47％...     

Global marine yield halved as fishing intensity redoubles

There is widespread concern and debate about the state of global marine resources and the ecosystems supporting them, notably global fisheries, as catches now generally stagnate or decline. Many fisheries are not assessed by standard stock assessment methods including many in the world's most biodiverse areas. Though simpler methods using widely available catch data are available, these are often discounted largely because data on fishing effort that contributed to the changes in catches are mostly not considered. We analyse spatial and temporal patterns of global fishing effort and its relationship with catch to assess the status of the world's fisheries. The study reveals that fleets now fish all of the world's oceans and have increased in power by an average of 10‐fold (25‐fold for Asia) since the 1950s. Significantly, for the equivalent fishing power expended, landings from global fisheries are now half what they were a half‐century ago, indicating profound changes to supporting marine environments. This study provides another dimension to understand the global status of fisheries.     

北斗船位数据提取拖网捕捞努力量算法研究

传统的捕捞努力量统计耗时费力,并且存在延时,不能及时了解宏观的捕捞强度,本研究以象山港拖网渔船为研究对象,选择安装北斗终端的1 508艘渔船,对北斗卫星船位监控系统所获取的渔船船位、航向、航速等信息进行分析挖掘,获得捕捞强度。根据航速统计获得每艘渔船处于捕捞状态的航速阈值,如拖网船300791捕捞状态船位点阈值的航向差最小和最大分别是-50和52°,航速最小和最大分别是0.9和2.0 m/s,两者结合判断捕捞状态点,再采用过滤窗修正,在各渔区格网计算一段时间内渔船捕捞状态点的累计捕捞时间,其值与渔船功率的乘积获得捕捞努力量,物理单位为kW·h,并制作累计捕捞kW·h的格点图和插值图。该方法具有实时、大范围、快速、分辨率高的特点,能够很好地服务于渔业资源保护。