南海北部底拖网渔业资源的数量变动

利用1961～1999年期间南海水产研究所5次渔业资源调查的底拖网渔获率数据,分析了南海北部底拖网渔业资源的数量变动。结果表明,20世纪60年代初至90年代末的30多年间,南海北部大陆架和北部湾底拖网渔获密度的下降非常显著,分别下降72%和81%,其中北部大陆架沿岸、近海和外海分别下降71%、74%和70%。南海北部海域底拖网渔业资源均处于过度开发状态,沿岸和近海过度开发较严重,外海过度开发的强度相对较轻。     

Optimising codend configuration in a multispecies demersal trawl fishery

Abstract The relative efficiencies and selectivities of conventional and modified codends were examined in a demersal trawl fishery targeting several species, including eastern king prawns, Penaeus plebejus (Hess), whiting, Sillago spp. and cephalopods. The modifications to codends included: (i) reducing the circumference; (ii) increasing the mesh size in conventional diamond‐mesh designs; and (iii) orientating meshes on the bar so that they were square shaped. The codends were tested against a fine‐meshed control in paired comparisons onboard three commercial trawlers. The conventional codend comprised 41‐mm diamond‐shaped mesh attached to an anterior extension section at a ratio of 150 to 100 meshes and was demonstrated to be non‐selective for the targeted species. Reducing codend circumference to 100 meshes and increasing the size of mesh to 45 mm both improved selection for eastern king prawns, but the lateral mesh openings were estimated to be insufficient to allow juveniles of the other key species to escape. By contrast, codends made from 35‐ and 41‐mm mesh hung on the bar improved the size selection for eastern king prawns and selected stout whiting, Sillago robusta (Stead) (the smallest commercial‐sized fish) across narrow selection ranges and at 50% sizes of retention (L₅₀s) that were closely correlated to the transverse morphology of fish and the maximum mesh opening. With the exception of a reduction in catches of octopus, Octopus spp., by the 41‐square codend, there were no other impacts on commercial catches by the square‐mesh designs. It was concluded that diamond‐mesh codends are inappropriate for use throughout this multispecies fishery and that a modified design comprising at least 35‐mm mesh hung on the bar is required to minimise the fishing mortality of unwanted sizes of the key target species. The results are discussed in terms of the utility of these types of modifications for closely regulating selection in penaeid‐shrimp trawls.     

Bycatch in a tropical schooling – penaeid fishery and comparisons with a related, specialised trawl regime

Abstract  The bycatch in a tropical Australian banana prawn, Penaeus merguiensis (de Man), fishery is described and contrasted with the closely related tiger prawn, Penaeus semisulcatus De Haan and Penaeus esculentus Haswell, fishery. Most of the similarity between banana prawn fishery catches was accounted for by three teleost species constituting 51.4% of the total bycatch weight. The bycatch assemblage structure of this fishery was significantly different ( P  <   0.05) from the adjoining tiger prawn fishery. The banana prawn fishery had a higher mean bycatch catch rate from shorter duration trawls, but lower estimated total annual bycatch (1502 t yr⁻¹) than the longer duration trawls of the tiger prawn fishery (20 073 t yr⁻¹). This study provides new data for quantifying bycatch and improving the accuracy of quantitative risk assessments currently being used to demonstrate sustainability of bycatch populations. The information will be incorporated into collaborative development of a long-term monitoring programme.     

Analysis of demersal species assemblages from trawl surveys in the South Adriatic sea

Two trawl surveys were carried out in the summer months (June–July) of 1996 and 1997 along the whole South Adriaticarea (Mediterranean sea) for the first time, using the same vessel and the same sampling gear (European Community Research Project `MEDITS'); previous research data referred only to the south-western Adriatic side. A total list of 168 demersal species (fishes, cephalopods and crustaceans) was obtained during the surveys; species abundance data (individuals/trawling hour) were processed accordingto multivariate techniques in order to describe the composition and the distribution of the main species assemblages within the investigated area (10–800-m bathymetric range). Multivariate analysis of MEDITS survey catch data showed a strong relationship betweenfish assemblages and depth, while the influence of depth was lower with respect to cephalopod and especially crustacean assemblage distribution.     

A bio-economic indicators suite for the appraisal of the demersal trawl fishery in the Southern Adriatic Sea (Central Mediterranean)

The state of demersal fishery in the Southern Adriatic Sea (GFCM-GSA 18, Central Mediterranean), years 1996–2003, from a biological, social and economic point of view was analysed using 47 indicators: 22 biological indicators obtained from fishery-independent data through yearly experimental bottom trawl surveys (“Medits” Programme), and 25 socio-economic indicators estimated from fishery-dependent data, available from the monitoring system of the Italian Institute for Economic Research on Fisheries and Aquaculture (IREPA). Biological indicators were applied for “single-species” (Eledone cirrhosa, E. moschata, Illex coindetti, Merluccius merluccius, Mullus barbatus, Nephrops norvegicus, Parapenaeus longirostris, Raja clavata, Zeus faber) and for “multi-species” analysis. Economic indicators describing economic performance, productivity, costs and prices, and the overall economic sustainability of fishery were estimated. Social indicators and a general indicator summarising social sustainability were also considered. Indicators’ values were displayed using the Traffic Light system. Both fishery-independent and fishery-dependent indicators highlighted a progressive decline of the trawl fishery system in the GSA 18. This decline was mainly related to the ongoing depletion of the traditional fishery target species (mostly long-living, late-maturing species) partially replaced by the increase of traditional accessory species (generally short-living species), as well as to the reduction of productivity and increasing costs. The whole procedure was proposed as a contribution to the identification and applicability of bio-economic indicators for fishery management purposes.     

我国当前南海南部拖网渔业的困局和对策

南海南部渔场是广西拖网渔船在南海外海的传统作业区域之一。然而,近年来该海域渔业涉外事故频发,广西渔船损失惨重。为了规避涉外事故,广西拖网渔船不得不频频中断正常生产,转移到南海外海其它涉外风险较低的渔场作业。2013年5月以后,在南海外海生产的广西拖网渔船陆续撤出南海南部,至今未恢复生产。本文采用南海捕捞信息动态采集网络和信息渔船2013年的生产记录,通过统计及对比,分析拖网渔船从南海南部转移后面临的困境和成因。结果表明,渔船转移到6°N以北的南海外海渔场生产,单位捕捞努力量渔获量（CPUE）减少31.25%、优质鱼类所占的比例明显下降、全部航次亏损,生产难以为继。目前南海南部的生产态势明显不利于南海外海渔业的发展。本文提出恢复和坚持南海南部生产是南海外海拖网渔业发展的基础,有关部门应加强渔场巡航护渔、组织综合编队生产及加大对渔船开发南海南部渔业资源的支持力度。为了进一步发展南海外海拖网生产,建议在南海南部探索试验共同渔区模式。     

Adjusting technical efficiency to reflect discarding: The case of the U.S. Georges Bank multi-species otter trawl fishery

Discarding undesirable catch is recognized as a major problem confronting fishery managers. It is widely perceived by managers, however, that reductions in discards can only be accomplished via reductions in good or desirable outputs and technical efficiency. Yet there appear to be few studies which actually examine the relationship between discard reduction and technical efficiency. In this paper, we present an alternative concept of technical efficiency, which explicitly recognizes that measures of technical efficiency should be adjusted for discard levels. This is because traditional measures of efficiency do not consider the resources used in order to discard. We also offer a framework based on data envelopment analysis for assessing efficiency in the presence of undesirable outputs. We examine the relationship between vessel efficiency and regulatory discards in the U.S. Georges Bank multi-species otter trawl fishery on a tow-level basis. We then examine differences between efficient and inefficient tows, and extend our results to the trip level. Further examination of trip-level results then yield insights into the potential impact of trip-limit regulations. Results show that in order to reduce discards, vessels are limited in the amount they can increase their total output, and that trip-limit regulations may have unintended consequences.     

Slack regulation compliance in the Mediterranean fisheries: a paradigm from the Greek Aegean Sea demersal trawl fishery,modelling discard ogives

Annual discard ogives were estimated using generalised additive models (GAMs) for seven demersal fish species (or taxa) and deep‐water rose shrimp, Parapenaeus longirostris (Lucas). Analysis was based on data collected on board commercial bottom trawlers in the central Aegean Sea from 1995 to 2008. Length of specimens and fishing depth (along with year) were the variables that had the most profound effect on the proportion of fish discarded. Compliance with the established minimum catch size of marine organisms (MS) was very low, a fact attributed to the low selectivity of currently used mesh sizes, the market demand for undersized fish, as well as the low control and enforcement effort.     

2008年南海北部拖网渔获组成及其多样性分析

采用分层随机抽样的方法,调查了2008年南海北部海域拖网渔获物组成,利用Shanon-weiner群落多样性指数(H’)、Pileou均匀度(J’)指数、相对多度(RD)等分析其多样性;根据渔获物季度组成,分析了主要种类的季节更替规律。研究表明,拖网渔获组成多样性指数介于3.36~5.36,均匀度指数介于0.54~0.74,优势度指数介于0.08~0.89,季节更替率介于22.83%~32.50%。另外,经济种类的优质鱼类与低质鱼类的产量比例为21∶100,与20世纪80年代相比,优质鱼类与经济鱼类的比率呈下降趋势,优质鱼类个体日趋小型化。     

A review of the offshore trawl fishery for crustaceans on the east coast of South Africa

This paper reviews current knowledge on the trawl fishery for crustaceans on the east coast of South Africa. The shallow water fishery targets penaeid prawns, particularly Penaeus indicus Milne-Edwards, while the deep water fishery targets pink prawns, Haliporoides triarthrus Stebbing, langoustines, Metanephrops mozambicus (Jenkins), and rock lobster, Palinurus delagoae , Barnard. Between 1988 and 1993, annual catches of targeted species averaged about 350 t. There was a total bycatch of about 1700 t per annum, most of which was discarded. Retained bycatch was dominated by the red crab, Chaceon macphersoni , as well as fish and cephalopods. Although trawling effort declined during the period under review, this trend has recently reversed.     

国内外拖网减少副渔获物的研究进展

拖网渔业的兼捕是一个世界性难题,每年因兼捕而产生的渔获物抛弃对渔业资源的持续发展产生较大影响。目前世界各国针对本国拖网渔业的特点、主捕对象开展了卓有成效的选择性研究,并取得了较为理想的效果。但在推广及应用过程中反映出较多的实际问题,有待进一步完善、提高。笔者综合了国内外在开展拖网渔具选择性研究中具有代表性的成功经验,表明单纯的网囊网目很难对副渔获复杂的拖网产生理想的选择效果;选择性装置及其与网片的组合是解决拖网渔具兼捕的有效手段之一。     

Strategies for improving fuel efficiency in the Portuguese trawl fishery

The recent rise in oil prices has brought renewed attention to energy savings in the fishing industry, and particularly in trawling. Coastal trawlers spend most of their time on fishing grounds near the coast. In such cases, the most successful energy-saving modifications ought to result from changes in the fishing gear and towing conditions. The purpose of this study was to identify the energy-economy potential for Portuguese fish trawlers after altering a vessel's operating conditions and improving its trawl gear performance. Two trawlers, named Tricana de Aveiro and João Macedo were selected as subjects in this project. Both vessels work with gear of similar design and size. Experimental sea trials were carried out to elucidate the actual vessel and gear performance. A model trawl was then built and tested in a flume tank, which provided the basis for improving the gear design. Full-scale trials were then carried out with both vessels using the modified trawls in order to assess changes in gear performance. The new trawls maintained their previous ability to catch species of different ecological groups and consumed less fuel at the same commercial trawling speed. An economic study showed potential increases in the net cash flow (NCF) of up to 27% over the range of operational navigation and trawling speeds. Having demonstrated the performance of the new trawls, the skippers of both vessels subsequently adopted the new design for commercial fishing.     

Size selection by diamond- and square-mesh codends in multi-species Mediterranean demersal trawl fisheries

Mediterranean demersal trawl fisheries traditionally operate using small diamond-shape meshes in the codend, which tend to retain almost all animals. We investigated the effect of mesh configuration on the size selectivity of nine species (the scaldfish Arnoglossus laterna, the broad-tail shortfin squid Illex coindettii, the European hake Merluccius merluccius, the red mullet Mullus barbatus, the Norway lobster Nephrops norvegicus, the common pandora Pagellus erythrinus, the deepwater rose shrimp Parapenaeus longirostris, the Mediterranean horse mackerel Trachurus mediterraneus and the poor-cod Trisopterus minutus capelanus) commonly captured in the Mediterranean demersal trawls. Two codends having meshes with the same opening (ca. 38 mm) but different mesh configuration (DM38: diamond-mesh and SM38: square-mesh configuration) were fished daily and alternately on the same trawl. They demonstrated a substantial improvement in selectivity with square-mesh. Selectivity was measured using the covered codend technique, the cover being supported by circular hoops.The results were analysed taking into account the between-haul variation in selectivity. Two other important external variables were identified: the trawling depth and the codend catch, which for some species influenced between-haul variation, but there was no evidence of a coherent effect on selectivity parameters.The selectivity of 40 mm diamond-mesh codend has been reported to be rather poor because a large proportion of the codend catch is immature and smaller than the minimum landing size (MLS) or first maturity size. With the exception of the flatfish (A. laterna), the effect of a change of mesh configuration from diamond- to square-mesh on size selectivity positively affected the retention length at 50% (L₅₀). However, square-meshes were found to be unsuitable for flat and/or deep-bodied fish as these escape more readily from diamond-meshes.The Council Regulation (EC) No. 1967/2006, concerning management measures for the sustainable exploitation of fishery resources in the Mediterranean, establishes the MLS of marine organisms. However, the increase in L₅₀ with square-mesh would not avoid some of the existing contradictions in allowing the use of codend mesh which leads to lower L₅₀ than the MLS.     

2010年莱州湾底层渔业生物群落结构及季节变化

根据2010年春季(5月)、夏季(8月)、秋季(10月)和冬季(12月)在莱州湾进行的19站位弓子网调查数据,对弓子网渔获物组成、底层渔业生物群落结构及季节变化进行了研究。结果表明,全年弓子网调查共捕获渔业生物78种,春季种类最少,而其他季节种类数接近。弓子网渔获物质量组成由高到低依次为甲壳类、鱼类、头足类、贝类;生物量的季节变化趋势由高到低依次为秋季、春季、冬季、夏季。生物量各季节的空间分布差异明显,主要由少数优势种类的季节分布差异引起。优势种季节更替明显,全年优势种为玉蟹科、寄居蟹、斑尾刺虾虎鱼(Acanthogobius ommaturus)和扁玉螺(Neverita didyma)。丰富度指数(D)、多样性指数(H’)和均匀度指数(J’)均以夏季为最高,而其他3个季节则较为接近。分析表明,冬季与其他季节的Jaccard种类相似性较低;春季群落的生物量和丰度组成与其他季节的Bray-Curtis相似性均较低。各季节的迁移指数均大于100,群落稳定性较差。莱州湾底层生物群落主要由小型、低质种类构成,个体平均质量较小,群落优势种类季节更替明显。为保护莱州湾渔业资源,应严格控制弓子网作业渔船数量。     

Selectivity of flexible size-sorting grid in Mediterranean multispecies trawl fishery

ABSTRACT:   The demersal multispecies trawl fishery in the western Mediterranean Sea has a poor selectivity; large numbers of juvenile fish are caught when using the legislated 40-mm diamond mesh cod end. The selectivity of a flexible sorting grid with 20-mm bar spacing (BS20) installed in front the conventional trawl cod end was investigated. The standard covered cod end method was used. Data was adequate for analyzing the selectivity of European hake Merluccius merluccius , poor cod Trisopterus minutus , greater forkbeard Phycis blennoides and Norway lobster Nephrops norvegicus . The selectivity of the 20-mm sorting grid was compared with the performance of 40-mm diamond (DM40) and square mesh (SM40) cod ends. The effect of a guiding funnel on the performance of the grid (BS20-f) was also explored. Finally, the potential changes in yield per recruit (Y/R) and biomass per recruit (B/R) after implementing a sorting grid were explored. An overall improvement in the 50% selection length ( L ₅₀ ) with all four species was substantial when comparing the BS20 to the DM40. Higher improvement in L ₅₀ s was achieved when the grid was equipped with the guiding funnel. When comparing the performance of the BS20-f to the SM40, there was no marked difference in L ₅₀ s. The Y/R and B/R, however, are substantially higher with BS20-f for poor cod and about the same for European hake. BS20 compared to SM40 achieved lower Y/R and B/R for all four species; the smallest difference was observed for Norway lobster. Further development is required if the sorting grid is to be introduced into commercial fisheries.     

南极磷虾四片式小网目中层拖网作业性能分析

为了促进南极磷虾(Euphausia superba Dana)渔业发展,提出2种四片式小网目中层拖网网型设计(型号分别为dh256-1和dh256-2),2种网型网口拉直周长相同,背(腹)网与侧网拉直宽度比(以下简称"WRBS")分别为1和1.11。通过模型实验对2种WRBS小网目南极磷虾拖网的作业性能进行比较,并进行浮沉力(SBSW)、手纲长度和水平扩张系数(以下简称"L/S")的匹配优化实验,结果表明:实验条件下,当L/S介于0.5~0.6时或者L/S为0.45和0.65且拖曳速度≤1.5 m/s时,2种网型网口垂直扩张差异显著(P0.05),dh256-2型拖网网口垂直扩张明显高于dh256-1;为了保持侧网衣受力均匀,dh256-1型拖网浮沉力配备要求显著高于dh256-2型拖网,dh256-1型拖网浮沉力配备应≥4.59 tf,dh256-2型拖网浮沉力配备应≥1.98 tf;2种网型的能耗系数(C_e)差异不明显(P0.05);L/S与能耗系数(C_e)呈反相关;手纲长度≥50 m,手纲长度对2种网型作业性能的影响不明显;综上所述dh256-2型拖网网口垂直扩张性能较好,浮沉力配备要求较低,较适合拖速较低的南极磷虾捕捞,适宜的手纲长度为50 m。以上结论可为小网目南极磷虾拖网网具设计提供参考。     

黄渤海区拖网渔业现状与分析

2010年6—7月和2012年6—8月,利用随机抽样调查方法对黄渤海区的拖网渔业进行了实地调查和现场测量。依据调查资料及有关拖网捕捞分类统计资料,对黄渤海区的拖网渔业进行了研究。结果表明:截止至2012年6月底,三省一市共有拖网渔船12 358艘,其中单拖渔船6 926艘,双拖渔船5 432艘。渔船功率44.1 kW以下的渔船占36.86%,44.1～109.5 kW占30.34%,110.3～219.8 kW占19.41%,220.5～441kW占12.59%,441 kW以上占0.80%。2003—2011年期间,除2007年外,拖网渔船总量呈下降趋势,渔船总功率呈上升趋势。拖网渔业捕捞产量1999年最高,达271.11万t,此后逐年下降,2011年为201.92万t。拖网是黄渤海区的主要作业方式,当前该海区拖网捕捞强度较大,渔船装备落后。因此,应对三省一市拖网渔业的捕捞强度加以控制,在鼓励拖网渔船改造升级的同时,适当压减拖网渔船的总数量,逐步发展外海拖网渔业。     

浙江省单拖渔业现状分析与研究

利用2001~2006年浙江省单拖渔业典型性调查数据和2005~2008年的单拖作业监测资料,从浙江省单拖捕捞力量和产量分布、渔获对象和资源密度变化及经济效益、劳动力组成等几个方面进行了初步分析。结果表明,近几年浙江省单拖作业船数保持在2200艘左右,产量在40×104t左右,单船净利润存在年间波动,以2005年最高;单拖作业渔场分布较广,渔获物以头足类和中下层鱼类为主;近年来经济鱼类比例下降,而其它低值鱼类比例上升。文章最后提出了当前浙江单拖渔业存在的问题,并提出了相应管理建议以供参考。     

闽南-台湾浅滩渔场单船拖网作业调查与分析

根据2009—2010年闽南-台湾浅滩渔场单船拖网作业监测调查资料和生产统计数据,阐明单船拖网作业的渔业地位、渔场分布、网具类型,着重分析该作业渔获种类组成及主要捕捞对象的资源动态。结果表明:单船拖网作业产量位居闽南-台湾浅滩渔场各种海洋捕捞作业的首位,大吨位、大功率渔船数量连续多年不断增长;渔具型式以有翼单囊网具为主;部分渔船使用的拖网网囊尺寸远远低于国家标准;带鱼、二长棘鲷幼鱼损害现象较为严重;秋季8—10月蓝圆鲹和鲐鱼群体绝大多数个体可达到最小可捕规格。调查研究结果还表明,2002年以来单船拖网渔业资源结构已发生较大变化,生命周期短、营养级较低的蟹类、枪乌贼类、乌贼类和虾类资源渔获比重显著增长;原优势种类绿布氏筋鱼资源已出现严重衰竭;二长棘鲷资源量逐年减少,渔获群体明显趋向小型化、低龄化。     

Seabird interactions and by‐catch in the anchovy pelagic trawl fishery operating in northern Argentina

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