Habitat overlap between southern bluefin tuna and yellowfin tuna in the east coast longline fishery - implications for present and future spatial management

Southern bluefin tuna (SBT) are presently a quota-managed species in the multi-species eastern Australian tuna and billfish longline fishery (ETBF). Capture of SBT is regulated by quota, as is access to regions likely to contain SBT. A habitat prediction model combining data from an ocean model and pop-up satellite archival tags is used to define habitat zones based on the probability of SBT occurrence. These habitat zones are used by fishery managers to restrict access by ETBF fishers to SBT habitat during a May-November management season. The zones display a distinct seasonal cycle driven by the seasonal southward expansion and northward contraction of the East Australia Current (EAC) and as a result access by fishers to particular ocean regions changes seasonally. This species also overlaps with the commercially valuable yellowfin tuna (YFT), thus, we modified the SBT model to generate YFT habitat predictions in order to investigate habitat overlap between SBT and YFT. There is seasonal variation in the overlap of the core habitat between these two species, with overlap early (May-Jul) in the management season and habitat separation occurring towards the end (Aug-Nov). The EAC is one of the fastest warming ocean regions in the southern hemisphere. To consider the future change in distribution of these two species compared to the present and to explore the potential impact on fishers and managers of the future, we use future ocean predictions from the CSIRO Bluelink ocean model for the year 2064 to generate habitat predictions. As the ocean warms on the east coast of Australia and the EAC extends southward, our model predicts the suitable habitat for SBT and YFT will move further south. There was an increase in the overlap of SBT and YFT habitat throughout the management season, due to regional variation of each species’ habitat. These results illustrate that a management tradeoff exists between restricting fisher access to SBT habitat and allowing access to YFT habitat. We suggest that some options to address this tradeoff are possible by identifying the seasonal variability of the overlap.     

Shark fishing effort and catch of the ragged-tooth shark Carcharias taurus in the South African competitive shore-angling fishery

An integrated telephone and on-site questionnaire survey was used to estimate total shark fishing effort and specific catch of the ragged-tooth shark Carcharias taurus by coastal club-affiliated shore-anglers, primarily along the east coast of South Africa. Mean total shark fishing effort was estimated to be 37 820 fisher-days year^?1 (95% CI = 28 281–47 359 fisher-days year^?1) with a mean cpue of 0.073 C. taurus fisher^?1 day^?1 (95% CI = 0.068–0.078 fisher^?1 day^?1). Cpue for C. taurus varied significantly along the coast and ranged from a high of 0.260 fisher^?1 day^?1 in the Eastern Cape to zero fisher^?1 day^?1 on the West Coast. The total number of C. taurus caught annually by coastal club anglers was estimated at 1 764 fish year^?1 (95% CI = 321–3 207 fish year^?1). The majority (92.1%) of young-of-the-year sharks (<1.2m total length, TL) were recorded between East London and Jeffreys Bay, suggesting that this may be the primary nursery area for C. taurus. Post-release mortality ranged from 3.8% for young-of-the-year sharks to 18.5% for adult sharks (>2.4m TL). The majority (76.2%) of anglers interviewed stated that they now fished less for sharks since the banning of vehicles on beaches in December 2001. As a result of this ban, almost half (49.2%) of interviewed anglers stated that they now fished more for non-cartilaginous species.     

基于GAM模型研究水温垂直结构对热带中西太平洋黄鳍金枪鱼渔获率的影响

黄鳍金枪鱼索饵水层影响延绳钓捕捞效率,而黄鳍金枪鱼索饵水层分布受水温垂直结构的影响,因此本文采用GAM模型分析次表层环境变量对延绳钓黄鳍金枪鱼渔获率的影响,评估黄鳍金枪鱼垂直水层分布对中西太平洋黄鳍金枪鱼延绳钓单位捕捞努力量渔获量(Catch Per Unite Effort, CPUE)的作用。模型结果表明,环境因子对热带中西太平洋延绳钓黄鳍金枪鱼渔获率空间分布影响明显。黄鳍金枪鱼延绳钓CPUE在2012年之后快速增多,高渔获率月份出现在北半球夏季,空间上在10°S,140°E附近区域。温跃层上界温度和深度、温跃层下界深度、18℃等温线深度、△8℃等温线深度及其和温跃层下界深度的深度差对延绳钓渔获率影响较大,是影响热带中西太平洋黄鳍金枪鱼延绳钓渔获率的关键环境因子。随着温跃层上界温度和深度值变大,延绳钓CPUE逐渐递增,对延绳钓CPUE影响密切的温度和深度分别为27～28℃和70～90 m。温跃层下界深度对延绳钓CPUE影响在250～280 m时最大;之后随着下界深度的变大,CPUE快速下降。18℃等温线深度对延绳钓CPUE影响呈现先震荡后递增的趋势,影响密切的区域在230 m深度上下。△8℃等温线深度与温跃层下界深度的差值对热带中西太平洋黄鳍金枪鱼延绳钓CPUE影响呈现先快速递减后缓慢增加的趋势,在深度差为70 m上下时影响最密切。研究结果揭示,在黄鳍金枪鱼活动水层受限或栖息水层和延绳钓作业深度相吻合时,延绳钓渔获率最高。依据黄鳍金枪鱼垂直活动水层调整延绳钓投钩,可以提高渔获率。因此,采用延绳钓CPUE进行渔场和资源评估时要考虑金枪鱼适宜垂直活动空间。     

The management of the distant water tuna fishery in Taiwan

Since the 1960s Taiwan has been a significant player in the global distant water tuna fisheries (DWTF). However, Taiwan's lack of political recognition has led some fisheries businesses to employ less conventional methods including Flags of Convenience (FOCs) in harvesting tuna resources. Meanwhile, Taiwan has been experiencing the painful cost of readjusted DWTF policies. This paper compares the readjusted policies in accordance with international management instruments and tuna compliance requirements (Compliance Agreement and UNFSA) and domestic laws are already undergoing adjustments to take these into account. This again demonstrates Taiwan's unique position in the international community: despite it not being a member of the United Nations, Taiwan spares no effort to ensure the sustainability of marine resources, and does its utmost to fulfill the responsibilities and duties of a Flag State.     

Comparison of nominal and standardized catch per unit effort data in quantifying habitat suitability of skipjack tuna in the equatorial Pacific Ocean

In the western and central Pacific Ocean, upper strata waters exhibit highly dynamic oceanographic features under ENSO variability. This has been proved to be responsible for the dynamic change of both abundance and zonal distribution of skipjack tuna(Katsuwonus pelamis). Although causality has been suggested by researchers using physical–biological interaction models, cumulative evidence needs to be obtained and the tenability of assertion needs to be tested from an ecological habitat perspecti...     

Slow steps towards management of the world's largest tuna fishery

Today, the tuna fishery of the western and central Pacific is one of the world's largest fisheries. Annual catches exceed 2 million mt—approximately 50% of the global tuna catch—with an estimated landed value of USD 3 billion (in 2005). The fishery expanded rapidly from the mid 1980s, following the development of the purse-seine fishery. From the mid 1990s, it was recognised that a Regional Fisheries Management Organisation was required to facilitate cooperation in the management of the resource. Following almost a decade of negotiations and planning, the Western and Central Pacific Fishery Commission (WCPFC) was established in 2004. During the interim period, stock assessments for the key tuna species were developed and revealed that for two species (yellowfin and bigeye tuna) there was concern regarding the increased levels of fishing mortality. However, declarations and resolutions calling for restraint in the expansion of fishing effort were largely unheeded over the last decade and, to date, the WCPFC has been unable to introduce any measures to effectively reduce (or limit) the level of fishing mortality on yellowfin and bigeye tuna. This paper proposes a number of mechanisms for improving the performance of the WCPFC with respect to meeting the conservation and management objectives of the commission and argues that Pacific Island nations need to collectively take the lead to ensure the effective management of the resource.     

Ecological risk assessment of the Marshall Islands longline tuna fishery

To support implementing an ecosystem approach to fisheries management, ecological risk assessment (ERA) methods have recently been developed for the continuum of data-deficient to data-rich fisheries. A semi-quantitative ERA was conducted for the Marshall Islands longline bigeye tuna (Thunnus obesus) fishery. The study used information from analyses of observer data, surveys of captains and crew and inventories of gear and equipment. Relative risks were evaluated through a consideration of phylogenetic uniqueness, risk of population extirpation, risk of species extinction and importance in ecosystem regulation. The fishery presents a highest relative risk to leatherback (Dermochelys coriacea), hawksbill (Eretmochelys imbricata), green (Chelonia mydas) and olive Ridley (Lepidochelys olivacea) sea turtle Regional Management Units that overlap with the fishery, in that order. The next highest relative risk is to affected stocks of oceanic whitetip (Carcharhinus longimanus), blue (Prionace glauca), and silky (Carcharhinus falciformis) sharks, in that sequence. Seabird bycatch is likely not problematic. There was inadequate information to assess risks to cetacean populations. Risks to stocks of market and non-market species of marine fishes with r-selected life history characteristics were not assessed. This is because estimates of critical threshold levels of local and absolute abundance and current biomass are not known for many of these stocks. Several best practice gear technology methods to mitigate problematic catch of vulnerable species groups are currently employed: monofilament leaders, whole fish for bait, single-hooking fish bait, no lightsticks, and no fishing at shallow submerged features. Setting terminal tackle below 100 m and carrying and using best practice handling and release equipment were methods identified to reduce fishing mortality and injury of vulnerable species. More information is needed to determine if weaker hooks should be prescribed to mitigate cetacean bycatch. The large benefit to sea turtles of replacing remaining J-shaped hooks with circle hooks might outweigh a possible small increase in elasmobranch catch rates. The consumption of 2024 l of fuel per tonne of landed catch, which is within the range of available estimated rates from similar fisheries, could be reduced, reducing greenhouse gas emissions, through more frequent maintenance and upgrading vessel equipment and materials. Observer data quality may be adequate to support a quantitative Level 3 ERA to determine the significance of the effect of various factors on standardized catch rates and to estimate population-level effects from fishing mortality.     

中西太平洋金枪鱼围网渔场聚类及其原因分析

本文根据1995-2010年我国中西太平洋金枪鱼围网生产统计数据,按年和月不同时间空间分辨率对金枪鱼围网渔场进行聚类分析,划定不同渔场类型;同时结合海表温度（SST）及Niño3.4区指数,探讨其渔场类型形成的原因。研究表明,在月为时间尺度下气候异常事件（El Niño和La Niña事件）发生频次与渔场聚类结果类别相关联,在1-12月发生气候异常事件频数分布可划分为以下几个阶段:1-3月、4-6、7-9月、10-12月,与月时间尺度下金枪鱼围网中心渔场4种聚类结果的时间范围具有一致性。通过渔场重心聚类结果和El Niño和La Niña事件分类统计对比发现,在年时间尺度下,气候异常事件的类型与聚类结果相关联,聚类结果同一类别包含的年份发生的气候异常事件具有一致性,即在同一类别下1995年、1997年为强El Niño年;1998年、2007、年、2009年为正常年份;2010年为强La Niña年;1999年、2000年、2001年为La Niña年;1996年、2008年为La Niña年;2002年、2004年为El Niño年。研究认为,中心渔场的年际聚类变化与El Niño、La Niña事件的发生分布具有很强的相关性,因此可以利用El Niño、La Niña指标来预测渔场的年间和月份间的变化。     

海洋渔业对海洋生态系统的影响

海洋捕捞渔业生产为人类的生存和发展作出了重要贡献,但同时对海洋生态系统及其持续发展也造成了许多不利的生态影响,且随着渔捞技术的进步和渔捞努力量的加大,这种影响将继续加大。海洋渔业活动可以引起海洋物种品质的下降,明显影响自然海域海洋生物的生物量,破坏海洋生物栖息地,使海洋生物群落结构发生改变,影响到食物链的传递,导致某些海洋生物种类的消失和灭绝,从而在各个水平上使海洋生物多样性降低,使生态系统的结构和功能遭到一定程度的破坏。强烈的海洋渔业活动可能造成海洋生物种类的系列性枯竭。     

The FAO global capture production database: A six-decade effort to catch the trend

With data series extending for 60 years, including catch data for almost 1850 species items, and reflecting geo-political, historical and natural events, the FAO capture database provides a service to the community interested in fishery information. Over 600 articles from refereed journals cited the database in the last 15 years. Species included grew significantly in the last decade and an analysis of annual reporting showed more timely data submissions, although the number of non-reporting countries remained stable throughout the years. An evaluation of data quality found over half developing countries reporting inadequately but also one-fourth of reports by developed countries were not satisfactory. This article also provides meta information on historical developments, data sources and coverage, and advice on what should be kept in mind when using the database for trend studies.     

我国金枪鱼围网渔业的初步研究

报道2002年6月至2003年5月两艘围网渔船在中西太平洋围捕金枪鱼及每月作业状况。结果显示,70%的网次围捕浮水鱼群,其空网率达52.5%,30%的网次围捕流木鱼群,其空网率为9.5%;渔获物中鲣鱼(Katsuwonuspelamis)占90%,优势体长为40～60cm,黄鳍金枪鱼(Thunnasalbacares)占10%左右,优势体长为100～150cm;作业渔场位于5°N～5°S,137°E～178°E;两艘船每月的空网率为9%～64%,每月渔获量在185～940t之间波动,平均有效网次产量不低于20t,最大网次产量为260t。     

Seasonally and spatially referenced estimates of recreational shore-angling effort,catch composition,catch rates and total catch in the Goukamma Marine Protected Area,South Africa

A roving creel survey of the recreational shore fishery along the 16.4-km coastline in the Goukamma Marine Protected Area on the south coast of South Africa was conducted from 2009 to 2011. Some 838 patrols were stratified equally among months, areas and years, but intentionally biased towards weekends. Angler densities at Buffalo Bay and Groenvlei were 0.59 and 0.28 anglers km?1, respectively. Weekend densities were double to quadruple weekday densities and fishing during winter was more popular than during summer. Area, habitat and distance to access points explained variation in angler densities. Shannon–Wiener diversity in catches declined from 2.18 in an earlier (1993–2002) survey to 1.79. Although the order of species abundance in the catches remained largely unchanged, blacktail Diplodus capensis dominance increased to 57.3% by number, at the expense of galjoen Dichistius capensis. Habitat explained 27% of the variance in catch composition. The catch per unit effort (CPUE) for the top nine species ranged from 0.19 to 6.35 fish 100-h?1. The CPUE of all species, except spotted grunter Pomadasys commersonnii, declined. Blacktail and galjoen CPUE declined by 17% and 77%, respectively. The total catch estimate was 2 986 fish y?1. Transgressions of size limits were common. The results suggest that the fishery is overexploited and that catch rates are declining.     

Bluefin tuna fishery policy in Malta: The plight of artisanal fishermen caught in the capitalist net

The bluefin tuna fishery has undergone a major shift in Malta, moving from an open access artisanal nature to a privatized and industrialized activity dominated by the purse seining fleet and the BFT ranching industry. The shift has been exacerbated by the national implementation of an individual transferable quota system, which has enabled the concertation of quotas into fewer hands. The main objective of this article is to understand how privatization has evolved within the sector and the way the Maltese artisanal fishermen are experiencing the shift. This study takes an exploratory mixed-method approach to quantitatively and qualitatively understand how policy underpinnings interplay with the sustainability dimension of the small-scale fishing sector. Results show that the transition of the bluefin tuna fishery from artisanal to industrial has generated a legitimacy crisis over fishing rights, decreased profitability amongst most of the artisanal fleet, and led to a series of socio-ecological impacts on the artisanal fisheries system at large. It is concluded that the neo-liberal trajectories of industrialization have directly undermined the continued sustainability of artisanal fishing communities.     

Quota concentration in the New Zealand fishery: Annual catch entitlement and the small fisher

New Zealand's quota management system (QMS) was introduced in 1986 to enhance the sustainability of New Zealand's fishery. This paper examines trends in quota and catch share concentration across a range of important fish stocks. It demonstrates that continuing concentration is occurring in the ownership of quota for deepwater species. At the same time there has been an increase in participation by small scale fishers in the inshore fishery. This appears to be driven by the introduction of the Annual Catch Entitlement (ACE) regime, allowing annual catch shares to be accessed at reduced transaction cost.