解决鱼虾混获问题的刍想

在世界虾渔业中,捕捞效率最高的是虾拖网。因此国外不断改进虾拖网渔具渔法或设计新型虾拖网。在我国南海,现有的虾渔具为拖网、流刺网、张网、敷网等,也以拖网渔获量占居优势。长期以来,鱼虾混获成为世界虾拖网渔业者迫切希望解决的一个重大问题。在我国南海虾拖网渔业中,鱼虾混获问题也十分突出。 (1)南海现用的虾拖网主要是扒罟网,这些网的网目尺寸比鱼拖网小得多,尤其是     

渔业活动对东海海域海底光缆安全的影响

通过对东海海域海底光缆路由区作业渔场的捕捞方式、作业范围等的分析,结合已建海底光缆故障的调查结果,探讨了渔业活动对东海海域海底光缆路由调查和已建海底光缆安全的影响。结果表明,东海海域海底光缆主要穿越了长江口、江外、舟山、舟外、鱼外等5大主要作业渔场,各渔场的渔业活动频繁,拖网、张网和流刺网等不同捕捞作业方式集中,对海底光缆的安全带来严重威胁。同时,捕捞渔船船只的数量逐年增多、触底深度的不断增加、作业时间的不断延长,使海底光缆路由调查时所获得调查资料的质量受到严重影响,船只、渔具的日益大型化以及拖网、张网、围网等捕捞活动范围的持续扩大,更使得海底光缆的故障频繁发生。为保护海缆的安全,在目前的经济技术条件下,建议选择休渔期时进行路由调查,在捕捞活动的频繁区,选择双层铠装型(DA)的海底光缆,并适当加大埋设深度,以降低渔业活动对海底光缆工程的影响。实践表明,将海底光缆埋设深度增加至3.0 m以上,可有效地保护海底光缆的安全。     

海洋油气田水下设施的防渔业损坏

为保障海洋油气开采的安全和顺利,文章以我国南海东部海域为例,在概述渔场和渔船基本情况的基础上,分析拖网对海洋油气田水下设施可能造成的损坏,并提出相关建议。研究结果表明:对海洋油气田水下设施影响最大的捕捞作业方式是拖网;双拖网渔船产生的最大拖曳力远大于脐带缆所能承受的最大拉力,很有可能损坏脐带缆等水下设施;应对渔船作业水域的海洋油气田水下设施采取保护措施,限制可能损坏水下设施的渔船作业,加强管理和培训以及通过技术手段对相关情况进行监测和处理。     

闽南-台湾浅滩二长棘鲷食性研究

二长棘鲷(Parargyrops edita)是暖水性底层鱼类,分布于日本南部、东海、台湾海峡、台湾浅滩、南海北部以及印度尼西亚沿岸,为我国东南沿海底拖网渔业的主要捕捞对象,近几年来,由于捕捞过度,北部湾和南海北部沿岸二长棘鲷资源严重衰退,唯独台湾浅滩地形复杂,底拖网不易作业,二长棘鲷资源却受到自然保护.在闽南-台湾浅滩底拖网渔获中,二长棘鲷仍然是主要优势种.     

寿光市400kW渔船大网目拖网革新试验

山东省寿光市的拖网作业至今已有近百年历史,长期的生产实践曾经形成了扒贝和拖网两大生产优势,并成为寿光市海洋捕捞的支柱之一。然而,自2000年以来,近海渔场各种捕捞作业发展迅速,捕捞强度增大,作业之间竞争激烈。另外,中日、中韩渔业协定的大力实施,又限制了寿光市渔船的作业范围。目前因海水污染贝类资源大量     

捕捞和气候变化在南海北部湾口鱼类长期种类演替和种群动态的作用

捕捞压力在改变南海鱼类种类演替和生物量波动方面所起的作用大于气候和环境因素是一个普遍的、有争议的假设。根据1959~2010年南海北部北部湾口底拖网的调查数据,报告了该海域鱼类种类组成、优势类群的丰度比例、生物量的季节和年际变化。建立了鱼类生物量与捕捞压力和气候变化外部因素之间的广义加性模型。结果表明,捕捞压力驱动底层渔业资源急剧下降的主要因素,并随着时间的推移,高值鱼类被低值鱼类所取代。1993年和1998年期间鱼类生物量的突然减少与同期厄尔尼诺事件相对应,气候变化可能是渔业拖网捕捞中中上层鱼类比例变化的主要驱动因素。为了更好地了解鱼类群落动态,需要区分捕捞压力和环境驱动因素对不同生活史策略鱼类物种的影响。     

基于船位监控系统的拖网捕捞努力量提取方法研究

为了基于船位监控系统提取拖网捕捞努力量,通过统计航速获得3个峰值,拖网作业在第2个峰值,即1~2.1 m/s,拖网作业航向差一般在–50°~50°。利用航速、航向差阈值设定,把拖网船状态划分为慢速、作业、航行,然后提取出捕捞作业状态点,1 423艘拖网船共提取到处于捕捞状态的点318 433个,合计拖网捕捞时间15 921 h,利用反距离加权插值法生成捕捞强度分布变化趋势图。捕捞努力量在渔业资源研究中是重要的参考值之一,与传统的捕捞努力量计算方法相比,该方法具有实时、大范围、快速、分辨率高的特点,能够用于辅助渔业资源保护。     

拖网渔船成本收益分析 ——基于荣成、象山、北海的调查数据

近年来,拖网渔船捕捞成本不断上升,经济效益受到影响,捕捞成本和收益成为渔民最为关心的问题。文章依据2018年荣成、象山和北海的调研数据,对3个海区拖网渔船的成本收益进行分析。结果显示：在成本结构方面,油、冰、水支出占比最大,其次是雇工支出;在收益结构方面,捕捞生产收入占了绝大部分比重;在经济效益方面,利润由高到低依次为象山、荣成和北海,但总体来看利润都较低;在盈亏平衡和敏感性分析中,荣成拖网渔船捕捞风险最高,而北海拖网渔船更容易受到市场波动的影响,规避市场风险的能力最弱。基于此,拖网渔业渔船通过渔业合作社集中购买柴油的方式,以及使用现代捕捞设备等途径来降低成本,提高捕捞效益。渔业相关部门应完善相应的补贴政策,同时也要重视对渔民捕捞技术的培训,提高产品附加值以及加强对渔业资源养护与管理。     

黄海北部日本枪乌贼的分布和渔获量

日本枪乌贼Loligo jaaonica Steenstrup在我国,仅分布于黄、渤海;在日本则分布于南、北部暖水海域,分布中心为北部海域。黄、渤海区有较高渔获量,是拖网渔业及某些定置渔业的主要捕捞对象之一。本种与火枪乌间、     

东、黄海底拖网渔业渔捞努力量修正方法的探讨

渔捞努力量在渔业资源研究中是一个重要参数。在以往的东、黄海底拖网渔业资源研究中,投网次数常作为渔捞努力量的度量单位。在底拖网渔业中有很多影响渔捞努力量的因素,其中船型大小、实际捕捞时间的长短以及网具改进是主要因素。本文针对这三个因素应用上海市海洋渔业公司的资料,提出了一种修正方法,并对修正后标准渔捞努力量的效果进行了分析探讨。     

Assessing the impacts of trawling breeding lobsters (Panulirus ornatus) on the catch of the Torres Strait lobster fishery shared between Australia and Papua New Guinea

The shared Torres Strait rock lobster (Panulirus ornatus) fishery provides important income for commercial and traditional fishers in Australia and Papua New Guinea. The lobster stock is first fished in Torres Strait by divers from both countries and then becomes vulnerable to Australian prawn trawlers, followed by Papua New Guinea trawlers during its annual breeding migration. Lobster catch sharing arrangements are governed by the Torres Strait Treaty ratified in 1985, but the sequential trawling of breeding lobsters has been controlled by bilateral agreements. A trawl ban was implemented in 1984 in both countries to conserve the breeding stock, but some trawling has been conducted in the Gulf of Papua since then and there is renewed interest in Papua New Guinea to resume trawling. To evaluate the impact of trawling migratory breeding lobsters on the lobster fishery, a model that combines a cohort depletion model with a stock recruitment relationship was developed in this study. The model showed that when the fishery is fully or over‐exploited by the dive fishery, trawling breeding lobsters would reduce both the spawning stock and the total catch of the fishery. The reduction in catch would increase with increasing fishing mortality. If trawling occurred on the Papua New Guinea side only, a redistribution of catch between Australia and Papua New Guinea would result in a small gain in catch for Papua New Guinea at the expense of the Australian dive fishery. But when fishing mortality reaches a certain level, any trawling in any country will incur catch loss to both countries. For the long‐term sustainability and maximum production of the fishery, regulations should be implemented in both countries under a co‐management scheme of a shared fish stock.     

Export market influence on the development of the Pacific shrimp fishery of Sonora,Mexico

The Pacific shrimp fishery is the most economically important and ecologically impactful fishery in Mexico. Strong export markets have had a tremendous influence on the technological development and structure of this fishery. This article describes the historical development, current status, ecological impacts and management of the open ocean trawling component of the shrimp fishery in the Sonoran waters of the Gulf of California. We trace the economic factors influencing the development of the Mexican Pacific trawler-based shrimp fishery, with a focus on the port of Guaymas, Sonora, and summarize the events leading to the current overcapitalized and inefficient state of that fishery. The Sonoran shrimp fishery is characterized by high rates of by-catch and a decline in catch per boat trends. A review of economic factors indicates that the decision-making process in this fishery is driven by export markets and does not adequately consider the local ecosystems and fishing communities impacted by shrimp trawling. Management priorities for the fishery include fleet size reduction, habitat protection and alternative technology development. Successful management depends on the participation of powerful export–import companies, along side producers, government resource management agencies, NGOs and scientists. This paper describes recent efforts in collaborative management and calls for the expansion of these efforts.     

Effect of deepwater trawling on the macro-invertebrate assemblages of seamounts on the Chatham Rise,New Zealand

Seamounts, knolls, pinnacles and other “seamount-like” features are prominent and widely distributed features of the New Zealand marine environment, and also the focus of important commercial fisheries and some exploratory mineral mining. There is considerable debate about the effects of such activities on the benthic habitat of deep-water seamounts. In 2001 a study was undertaken of eight seamount-features on the Chatham Rise, an area that has been heavily trawled for orange roughy since the early 1990s. Half of the study seamounts were considered unfished and the other half fished. Benthic macro-invertebrate assemblages of each seamount were sampled using epibenthic sleds, whilst the presence of habitat-forming fauna (e.g., live corals), substrate type and indications of trawling (e.g., trawl door marks) were determined using a towed underwater camera. Fisheries catch-effort data were examined to determine the amount and distribution of bottom trawling effort on the seamounts. Analyses of camera data revealed that unfished seamounts possessed a relatively large amount of stony coral habitat comprising live Solenosmilia variabilis and Madrepora oculata (predominantly on the seamount peaks) whereas fished seamounts had relatively little coral habitat. Indications of trawling were observed over six times more frequently on seabed images from fished as opposed to unfished seamounts, and appeared related to the amount of fishing effort on individual seamounts. Multivariate analyses of sled data revealed a significant difference in macro-invertebrate assemblage composition between fished and unfished seamounts. The variability observed in assemblage composition between seamounts can in part be explained by the relative fishing pressure measured by a fishing effects index. The results of the study are discussed with respect to management of seamount habitat, and the need for ongoing monitoring and research to derive conservation practices that allow for sustainable seamount fisheries.     

Trawl fisheries,catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for seafloor stewardship?

Proponents of catch share-based fisheries have claimed ecological stewardship can result from the assignment of individual catch quotas. This claim is examined by analyzing the distribution of benthic habitat protection measures adopted by quota-owning industry sectors within the exclusive economic zones (EEZs) of the U.S. (Alaska), New Zealand, and high seas seamounts within the Southern Indian Ocean Deepsea Fishers Association (SIODFA) competence area. Results suggest the protection of both benthic ecosystems and essential fish habitat (EFH) are marginal at best when quota owners have primacy in determining the boundaries of bottom trawl closures. The majority of the areas in these three regions that are closed to trawling are too deep to fish, may not contain vulnerable marine ecosystems, and do not have high abundances of commercially important species. “Freezing the footprint” of bottom trawling is not the best method for benthic habitat protection in areas where the fishing industry is actively fishing vulnerable habitats. Analytical methods should be applied to help determine boundaries of future bottom trawl closures rather than allowing the fishing industry to place benthic protection areas (BPAs) in areas where they are not interested in fishing.     

Impacts of trawling on benthic macro-fauna and -flora of the Spencer Gulf prawn fishing grounds

The overall effects of trawling on benthic habitats and their assemblages are dependent on the distribution and intensity of trawl effort. The benthic habitats of the Spencer Gulf prawn trawling grounds are subjected to known variable levels of trawling disturbance recorded from fisher's logbooks. These habitats have not been quantitatively investigated. The aim of the study was firstly to characterise the macro-faunal and -floral assemblages and secondly, to comparatively assess trawl impact by testing the null hypothesis of no differences between five sites exposed to different intensity of trawl effort. The distribution and abundance of benthic macro-fauna and -flora were studied at two sampling resolutions by using beam trawl sampling (10,000 m²) and underwater stereophotography (4.5 m²) at five sites with different levels of trawl disturbance (effort). The results showed that the Spencer Gulf prawn trawling grounds are characterised by sandy sediments with a low content of silt and clay, with the exception of one site with very fine gravel. Biomass, abundance and cover of macro-fauna and -flora were generally low throughout, but with large differences among sites. Biomass, abundance and cover were found to be negatively correlated to both trawl hours from 1994–1998 and during the period of study. ANOSIM and SIMPER analyses using biomass, abundance and percentage cover as variables showed significant differences between sites with eight species or taxonomic groups contributing more than 10% to the observed similarity within sites. The two northern sites were dominated by sponges and the bearded mussel, Trichomya hirsutus, and the southern hammer oyster, Malleus meridianus. Other species that contributed to the similarity within sites were the ascidian, Polycarpa viridis, mobile epifauna (the blue swimmer crab, Portunus pelagicus, and the western king prawn, Penaeus (Melicertus) latisulcatus) and demersal fish species (Degens leatherjacket, Thamnaconus degeni, and the Melbourne silver belly, Parequula melbournensis). Simpson's Index of Diversity (1 − λ) and species richness in the beam trawl samples were fairly even across all sites, but a significant effect of site was found in the stereophotographic transect samples. It was concluded that prawn trawling has a strong influence on the structure of the benthic habitats of the Spencer Gulf prawn fishing grounds highlighted by the magnitude of change and the strength of the gradient of effects. Confounding factors linked to the biophysical attributes of the sites are believed to be minor.     

Investigation into the declining trend in chokka squid Loligo vulgaris reynaudii Catches made by South African trawlers

The trawl fishery, which targets Cape hake Merluccius spp. and Agulhas sole Austroglossus pectoralis, takes chokka squid Loligo vulgaris reynaudii as by-catch. Catch and effort data from the trawl fishery for the period 1978–1996 are used to obtain annual estimates of catch rate (catch per unit effort cpue) for that period. Examination of the cpue trend shows a sharp decline in the early 1980s and, in order to identify factors that could have influenced that decline, the distribution of fishing effort is investigated both temporally and spatially. There is a possible change in the incidence of squid-directed catches over time, but their overall scarcity could have had only a small impact on the annual cpue trend. Further, using distribution of fishing effort to evaluate the effects of possible changes in fishing patterns, rather than changes in resource abundance, on the trend in trawl cpue, it became clear that there had been a contraction of the trawling grounds and changes in fishing patterns in relation to depth over time. Finally, a general linear model (GLM) is developed to quantify the effect on cpue of factors such as vessel characteristic, depth and position of the drag, season and target species, so obtaining a standardized trawl cpue index of chokka abundance. Analysis of that trend reveals a mean 7.7% annual decline for the period investigated, which should be interpreted as a strong sign of resource decline.     

The economic sustainability of artisanal fisheries: the case of the trawl ban in the Gulf of Castellammare, NW Sicily

Small-scale fisheries and the communities they support are often given the protection of designated fishing zones from which non-artisanal vessels are excluded. This paper looks at one example of this approach, the trawl ban introduced in the Gulf of Castellammare (NW Sicily), focussing on the economic sustainability of the artisanal fishery currently operating within the protected area. The consequences of lifting the trawl ban and how far this would jeopardise the sustainability of the artisanal fishery are explored via an analysis of the financial viability of trammel net vessels under alternative assumptions concerning catch rates. The paper also investigates fishermen's attitudes towards the trawl ban and their predisposition either to remain in the fishery or to quit in the event of the ban being removed.     

Considering community allocations: Power and the politics of enclosure in the Gulf of Alaska

In 2012, the North Pacific Fishery Management Council initiated the process of designing a new management structure for the Gulf of Alaska trawl groundfish fleet. The new program is currently structured as a catch share program and driven by the need to end the ‘race for fish’ and provide the trawl fleet with the tools to reduce bycatch. To date much of the discussion among policy makers and stakeholders has centered on community protection measures and how best to avoid the negative social and economic impacts of catch share programs including impacts to crew, consolidation and the flight of quota and resource wealth from Gulf of Alaska fishery dependent communities. This paper examines how community protection measures related to the distribution of benefits and access to fishery resources are considered and challenged in the North Pacific today. Special attention is given to the ongoing debate surrounding the potential inclusion of an initial allocation to place-based Gulf of Alaska communities via a Community Fishing Association. As part of this effort, this paper examines the political space and underlying power dynamics in which consideration of alternatives to the commodification of fishing rights occurs.     

Fuel use and greenhouse gas emission implications of fisheries management: the case of the new england atlantic herring fishery

Commercial fisheries are heavily dependent upon the combustion of fossil fuels and as such contribute to increased atmospheric concentrations of greenhouse gases and the concomitant impact on the world's climate. The fuel use and greenhouse gas intensity of a fishery is a function of several variables. One that has not been previously investigated is the role of fisheries management. Using historical gear-specific fuel use and landings data, we employ scenarios to examine the potential impact that recent changes in the management of the New England fishery for Atlantic herring (Clupea harengus) may have on fishery-related fuel use and greenhouse gas emissions. Specifically, we consider the direct effect of the seasonal ban of midwater trawling in favor of purse seine and fixed gears within Atlantic herring fishing Area 1A. We also evaluate the indirect effect of reductions to the Area 1A total allowable catch of Atlantic herring on the regional supply of bait and the resulting potential need to import bait herring from Canada. Our results indicate that because of the five-fold lower fuel intensity of purse seining, relative to midwater trawling (21 L/ton versus 108-118 L/ton), the seasonal ban on midwater trawling has the potential to markedly reduce overall fuel use and greenhouse gas emissions associated with the herring fishery. These results indicate that management decisions can strongly influence energy demands and resulting greenhouse gas emissions of fisheries. We urge those involved with fisheries management to take this into account when developing policy and management measures.