Changes in life history and ecological characteristics of coral reef fish catch composition with increasing fishery management

Abstract Length, life history and ecological characteristics of landed fish communities were studied over a 10‐year period to test theories of fishing disturbance during a time of increased gear and closure management in heavily utilised fisheries. It was predicted that with greater management restrictions: (1) the earliest and fastest responses in the fishery will be seen in those species with faster turnovers, or relatively lower vulnerabilities to fishing; (2) the fishery would transition to a landed catch with higher mean trophic levels, and greater mean body lengths. In addition, the removal of a non‐selective, small‐mesh seine nets should benefit the catch of gears that previously had the greatest species selectivity overlap with the seine net. Many predictions were supported, although maximum lengths and lengths at maturity responded more rapidly than anticipated. The response to eliminating the non‐selective seine net was a more rapid increase in sizes caught by gears with a larger overlap in size (hook and lines) than species selectivity (gill nets). The simultaneous comparison of management systems over time indicates that open‐access fishing grounds can benefit from restrictions imposed in adjacent fishing grounds. The study indicated that multi‐species coral reef fisheries management objectives of maximising yields, as well as maintaining the fish community’s life‐history diversity, require management trade‐offs that balance local socio‐economic and biodiversity needs.     

Decreasing but still high: bycatch of seabirds in gillnet fisheries along the German Baltic coast

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Cumulative impacts of fisheries in the California Current

Ecosystem‐based fisheries management calls for the consideration of the indirect and cumulative effects of fishing, in addition to estimating direct fishing mortality. Here, we quantify such effects of fishing fleets, and their interactions, using a spatially explicit Atlantis simulation model of the food web and fisheries in the California Current. Simulations testing the effects of single fleets suggested that bottom trawl, fixed gear, and hake (Merluccius productus) trawl primarily have direct impacts on their target and bycatch species. Few indirect effects from these three fleets extended through predator–prey links to other parts of the food web. In contrast, effects of the purse seine fleet extended beyond the three groups it harvested, strongly altering the abundance of predators, planktonic prey, and benthos. In terms of nine ecosystem attributes, our experiments involving single fleets identified six fleets that caused the bulk of negative impacts. Specific fleets impacted different aspects of the ecosystem, for instance with groundfish gears causing reductions in piscivore abundance, and hake trawl and purse seine increasing krill through reducing abundance of planktivores. In terms of interactions among fleets' effects, the vast majority of effects were simply additive – the combined effect of two fleets was simply the sum of the individual fleets' effects. The analyses offer one way to sharpen the focus of ecosystem‐based fisheries management in the California Current, emphasizing impacts and interactions of particular stressors.     

A framework for adaptive gear and ecosystem‐based management in the artisanal coral reef fishery of Papua New Guinea

• 1. Artisanal fishing on coral reefs in Papua New Guinea is an important livelihood activity that is managed primarily at the level of local communities. Pockets of overexploitation exist and are expected to increase with plans for increased commercialization.
• 2. This paper provides a current assessment of the artisanal multi‐species coral reef fishery by examining selectivity of the dominant gear, namely line fishing, spearguns, and gill nets. Each gear has its own strengths and weaknesses in terms of use and conservation of resources, with no clear problem gear.
• 3. The three gears utilize different resources but there was moderate overlap in the species caught, particularly between gill nets and line fishing and marginally between lines and spearguns. Gill nets have the disadvantage of being destructive to coral and the advantage of catching commercial species. Line fishing catches an intermediate number of species but mostly large‐bodied and predatory species that could potentially reduce predation and the mean trophic level of the fishery. Spearguns catch the highest numbers of species, including many non‐commercial and herbivorous fish and could reduce the diversity of fish and encourage algal growth.
• 4. This information could be used in combination with scientific monitoring and traditional ecological knowledge to develop an adaptive management framework that uses local restrictions on the various gears to restore or balance the fishery and ecosystem. Restrictions could be selectively imposed: on gill nets when coral cover is low, line fishing when large‐bodied predators are depleted, and spearguns when biodiversity is reduced and algal abundance high.

Copyright © 2008 John Wiley & Sons, Ltd.     

Incidental capture of Caretta caretta in trammel nets off the western coast of Sardinia (Italy): statistical models of capture abundance and immediate survival

• 1. Trammel nets are one important cause of sea turtle mortality resulting from incidental capture. This study presents findings over a 10‐year period during which loggerhead turtle by‐catch in trammel nets, set off the central west coast of Sardinia (Italy) in the summer months, was recorded by 17 fishing vessels.
• 2. Since the by‐catch registered represented counts of a rare event, data from the 17 vessels were used in the zero‐inflated Poisson (ZIP) model to determine the abundance of turtle by‐catch in trammel nets of the entire fleet, while a binomial generalized linear model was used to assess the probability of immediate survival for sea turtles incidentally caught in this gear.
• 3. The ZIP model quantified in about 45% the probability that 0.6 turtles have been caught by each vessel using trammel nets during summer over the 10‐year period. In addition, the model estimated a total of 916 by‐catch if the entire small‐scale fleet was to use trammel nets in the study area in the summers between 1992 and 2001, with a direct mortality rate of 69%.
• 4. The probability of immediate survival for sea turtles caught in trammel nets seems to be directly related to the size of the specimens caught; however, this relationship is plausible only when incidental capture in the net occurs shortly before gear retrieval.
• 5. The study area represents a region where the abundance of sea turtle by‐catch per vessel in trammel nets was much higher in July and August than in June and could represent a potential hot spot for the presence of juvenile loggerhead turtles, with high levels of interactions between the species and this fishing gear. Further research should better characterize the incidents of by‐catch and assess potential innovative solutions that allow small‐scale fisheries to coexist alongside sea turtles. Copyright © 2010 John Wiley & Sons, Ltd.

     

黄渤海区张网渔业

2010年6～7月,利用抽样调查方法对黄渤海区32个主要渔港、渔村的张网渔业进行了实地调查和现场测量。依据调查资料并结合2009年度河北、辽宁、山东以及天津三省一市的渔具渔法调查报告、1983～2009年中国渔业年鉴中记载的张网捕捞产量分类统计资料,对黄渤海区的张网渔业进行了研究。结果表明,1998年张网产量最高,达90.43万t,贡献率为17.18%,此后逐年波动下降。当前,张网是黄渤海区捕捞作业的重要渔具渔法之一,处在第3位,年产量为38.15万t,贡献率为10.49%。目前在黄渤海区进行捕捞作业的张网共有4个型、7个式、19种张网网型、总量69万顶。辽宁省的张网数量占三省一市张网数量的53.54%,主要分布在辽东湾作业;河北省的张网数量占24.69%,主要分布在渤海湾作业;山东省的张网数量占23.08%,主要分布在日照至烟台近海作业。其中以捕捞海蜇、虾类和小杂鱼为主的并列单片张网占54.51%;以捕捞毛虾为主的双锚竖杆张网占16.12%。大多数张网的最小网目尺寸均在4～30mm之间。综合分析表明,张网在黄渤海区渔业中所占比重较大、选择性较差、最小网目尺寸偏小,不利于黄渤海区渔业资源可持续利用。     

A review of ghost fishing: scientific approaches to evaluation and solutions

ABSTRACT:   Research on ghost fishing became active in the late 1980s. Ghost fishing has been confirmed for traps, gillnets, trammel-nets and small seine nets. Some lost traps are functional for a long period of time, even in shallow waters. Consequences for gillnets after loss depend on seabed conditions. The ghost fishing function of gillnets remaining on flat seabeds declines rapidly with decreasing heights and increasing visibility. Gillnets left tangled around an artificial reef, for example, three-dimensionally maintain the initial magnitude of ghost fishing for a long period of time, even after badly fouled. There are increasing numbers of researches working on the total number of mortality per gear after gear loss for gillnets and trammel-nets. It has become also possible to estimate the total number of mortality for a unit period of time in a certain fishing sector. This paper reviews research which has provided evidence and quantitative data on ghost fishing, and proposes five items important for future studies on ghost fishing.     

Changes of eel exploitation in Polish lakes

The paper discusses briefly eel exploitation and traditional methods of catching eel. Attention is drawn to changes taking place in eel exploitation in Polish lakes, and to their causes. Most effective methods of eel catching are reviewed. It is pointed out that utilization of active fishing gear, mainly seine nets and electric aggregates, creates significant possibilities of increasing eel catches. Eel yields up to 40 kg/ha are not unusual with this type of gear. Furthermore, active fishing gear is more effective and can be used also in lakes in which it is difficult to apply traditional eel traps. The latter fact is of special significance in view of the increasing number of lakes stocked with eel, and improvement of eel stocking effectiveness.     

The sinking performance of the tuna purse seine gear with large-meshed panels using numerical method

This paper reports an improved version of the numerical method used in a previous study on the dynamic simulation of purse seine gear in three dimensions. The improvement is achieved by refining the mass–spring model to take into account both the drag coefficient as a function of the attack angle and Reynolds number as applied to the setting operation of the purse seine gear. The validity of the numerical simulation is assessed by comparing the measured and calculated values for the sinking depth of the net. The numerical simulation is used to examine the sinking performance of the different designs in which large meshed-panels and netting materials are used together in the main body section of the netting. The results indicate that, compared to the prototype net, nets bearing larger mesh panels require more sinking depth with much more pronounced operational depth at corresponding times of the fishing operation when heavier netting material is used. Moreover, in the new net designs, lower tensile forces are exerted on both ends of the pure wire during pursing. The new net constructions with regard to the operational depth represent alternatives that may reduce the potential problem of frequent failed setting of the tuna purse seine gear.     

Illegal ingegno fishery and conservation of deep red coral banks in the Sicily Channel (Mediterranean Sea)

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辽东湾不同型刺网捕捞性能的比较

为了提高近海渔业资源养护型捕捞与管理技术,促进《全国海洋捕捞渔具目录》的实施,2014年10-11月在辽东湾进行了网目尺寸为40 mm、50 mm、60 mm的单片刺网、双重刺网和三重刺网以及生产对照网的选择性对比实验.结果显示,各种实验网的渔获种类数均在6-9种之间,优势种口虾蛄(Oratosquilla oratoria)的优势度随网目尺寸的增大而减小,但花鲈(Lateolabrax japonicas)的优势度随网目尺寸的增大而增大.同型试验网在不同网目尺寸条件下的渔获量有显著性差异,其中,60 mm试验网与40 mm同型试验网的单位捕捞努力量渔获量(CPUE)比较,单片刺网为800％,双重刺网为650％,三重刺网为500％;而异型试验网在网目尺寸相同条件下对渔获量的影响相对较小.试验网的组内渔获组成平均相似度分别为单片刺网59.24％,双重刺网62.63％,三重刺网66.51％;组间分别为71.44％、67.50％和70.58％;对组内和组间平均相似度贡献最高的种类均为口虾蛄和花鲈.随着网目尺寸的增大,各型试验网的渔获物幼鱼比例呈下降趋势.     

Damage by monk seals to gear of the artisanal fishery in the Foça Monk Seal Pilot Conservation Area, Turkey

The present study examines the operational interaction between critically endangered monk seals Monachus monachus and artisanal fisheries in the Foça Pilot Monk Seal Conservation Area, Turkey between 1994 and 2002. One to four permanent researchers collected the data on this interaction during the seal sighting data inquiries. Interviews with the fishermen provided 142 direct interactions with monk seals around the fishing gear. Among these encounters damage to fishing gear, including gill nets (53%), trammel nets (37%), longlines (9%) and a lure (1%) was recorded 90 times. However, no difference was found in damage between gill and trammel nets. Although, the damage inflicted by seals per occasion was found to be substantial (maximum 462.5 USD per occasion), the overall annual economic impact on the artisanal fishery was found to be modest. Limitation in soaking time of nets; long-line use instead of nets in MPAs where monk seals survive; and low interest credits to be given to those fishermen who suffer monk seal damage, are proposed as appropriate management practices.     

福建海洋捕捞"技术效率"的时间序列分析

根据1981-2003年福建省渔业统计及相关调查资料，应用DEA法，分析了全省海洋捕捞作业及五种主要作业捕捞“技术效率”的年间变化，结果表明：1981～2003年全省海洋捕捞作业综合“技术效率”的变化范围为61．8％～100%，平均为76．4％，综合“技术效率”的年间变化呈现先降后升的态势；1990年以来，全省灯光围网和张网作业捕捞能力的发挥比较好，其次为刺网和底拖网作业，钓具作业捕捞能力的发挥较差；渔获选择性低的底拖网和张网作业的捕捞“技术趋势”年间变化保持平稳上升，渔获选择性高或较高的刺网、钓具和灯光围网作业的捕捞“技术趋势”年间变化则呈波动式上升或处于波动状态；各种投入因子对不同作业类型的捕捞”技术效率”的约束力各不相同，主动性较大的底拖网和灯光围网作业对渔船功率的依赖程度相当大，而主动性较小的刺网、钓具作业和被动性的张网作业，对网(钓)具使用数量的依赖度较大；作业天数对五种作业类型的“技术效率”发挥都有不同程度的影响。     

Optimal economic fishing efforts in Korean common octopus Octopus minor trap fishery

The Korean Government is in the process of establishing a plan for managing fishing effort by setting up the maximum fishing gear usage per fishery type for the recovery of fishery resources. This will aid settlement of disputes between fishery sectors over fishing gears, and the stability of fishing business conditions. Especially in the setting up of the maximum fishing gear usage, economic standards as well as biological standards are being considered as significant factors to promote the sustainable and economically viable development of fisheries. This study is, thus, to analyze the optimal economic fishing gear usage (E_MEY) as the most economically efficient usage for the common octopus trap fishery, one of the most controversial sectors in establishing maximum fishing gear usage. Data from logbooks per trip were used for estimation of E_MEY per trip because it was considered there were limitations of data available for analyses. As a finding drawn from the analyses, the E_MEY of common octopus trap vessels per trip has to be decreased by approximately 13%. That is, reducing the trip trap usage up to the level of E_MEY can lead to the reduction of trip fishing costs, thereby resulting in increased trip profits.     

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.     

尼罗罗非鱼行为习性及其捕捞渔具的设计

尼罗罗非鱼(OreochromisniloticaL.)属热带性鱼类,为我国1978年从国外引进的优良海淡水养殖对象,具有食性杂、生长速度快、肉质鲜美、经济价值高等优点[1]。目前已在我国数个省、市开展养殖。尼罗罗非鱼性喜群游,其最适生长水温为24～32℃,水温降至14℃时,活动迟缓,停止摄食,水温降至12℃以下时便逐渐死亡[2]。因此,在我国北方地区养殖的尼罗罗非鱼,一般在严冬前开始进行捕捞。水温达到20℃以上时,雄鱼会在池边或者池底挖洞,当遇到外界刺激或拉网捕捞受惊后,便潜入洞中或软泥中。尼罗罗非鱼的这一行为习性给捕捞造成很大困难,因此各地一般…     

几何相似原理在过滤性渔具网目选择性研究中的应用

利用几何相似原理将传统的过滤性渔具选择性曲线转化为选择性曲面。运用选择性方程，并假设不同网目大小的渔具对相同尺寸渔获个体的渔获服从多项分布后，对过滤性渔具的网目选择性建立模型。使用极大似然估计法对模型进行拟合，同时，通过假设检验对模型进行简化。使用平行作业法试验条件下的张网渔具的黄鲫(Setipinrm taty)渔获数据进行模型拟合。结果显示，所建模型可以在没有对照网的情况下估算出各不同网目大小网囊的选择率，并同样适用于套网法试验条件下的选择性分析。模型的建立为今后进行过滤性渔具网目选择性试验方法改革提供了理论参考。通过与SELECT模型比较，认为模型使用选择性方程并区分渔获能力和捕捞努力量使得模型更具普遍性。     

辽宁省海洋渔具渔法结构调整的研究

根据辽宁省海洋捕捞产量的统计资料,运用灰色关联法分析了拖网、围网、流刺网、钓具、定置网5种主要渔具渔法的产量与海洋捕捞总产量的关联度,运用改进的层次分析法确定了5种主要渔具渔法产量的权重。结果表明,海洋捕捞产量与定置网、拖网的产量的关联度高,与围网、钓具和流刺网的产量关联度低;拖网、围网、流刺网、钓具、定置网产量的计算权重分别约为23．3％、16．1％、31．1％、20．4％、9．1％。对辽宁省渔具渔法产量结构调整进行了讨论。     

抑制差减杂交法克隆牙鲆变态早期差异表达的基因

单根方是吕泗渔场一种主要的定置作业渔具，其产量占江苏海洋捕捞产量一定的比重。根据监测，自4月份开始，主要经济鱼类幼鱼开始在渔获物中出现，随着时间推移，幼鱼比例逐渐增加。6月份单根方渔获样品中经济鱼类幼鱼尾数比例1990—2004年期间年平均为48．63％，重量比例为35．86％，其中小黄鱼（Larimichthys polyactis）、银鲳（Pampas argenteus）、带鱼（Trichiurus japonicus）尾数合计比例年平均为45．21％，重量合计比例年平均为33．29％。7、8月份样品中主要是小黄鱼、银鲳幼鱼，9月份鱼类幼鱼比例降至20％左右。本文着重对6月份单根方作业经济幼鱼进行了分析，建议对定置作业休渔时间进行调整，以利于保护经济鱼类幼鱼资源。