Mass mortality and recolonization of Pyura stolonifera (Heller) on the south coast of South Africa

The fauna and flora of two sublittoral communities situated in close proximity on the west coast of South Africa are described and shown to be radically different, despite the fact that both experience similar physical conditions. One of these communities, at Marcus Island, has prolific beds of the black mussel Choromytilus meridionalis (35 954 g wet weight·m^?2) accompanied by a large number of other species, notably sea urchins, holothurians, brittle stars, whelks and barnacles. In contrast, the other site, Malgas Island, is dominated by a large population of rock lobsters Jasus lalandii together with a dense seaweed flora (3 866 and 4 402 g wet weight·m^?2 respectively). The numbers of species are similar at both sites (102 at Malgas Island and 107 at Marcus Island) but only 34 per cent are common to both localities. Although preliminary research indicates that the two sites have fairly similar physical conditions and bottom topography, they maintained their contrasting communities for the whole research period (1983–1986) and have probably done so for at least nine years, suggesting that they represent two stable alternative states of the same ecosystem. In the absence of rock lobsters at Marcus Island, wave action and inter/intraspecific competition are the main forces structuring the benthic community. Stability is maintained here by the resilience and rapid recovery of the mussel population after disturbance by storms. Where rock lobsters are abundant, as at Malgas Island, intense predation pressure is the main force controlling the structure of the benthos, and it is continually maintained because the rock lobsters are resistant to the effect of storms. Therefore, the presence or absence of high densities of rock lobsters is fundamental to the maintenance of these two contrasting communities.     

The end of shark finning? Impacts of declining catches and fin demand on coastal community livelihoods

For several decades, fishing sharks for their fins has provided important livelihoods for eastern Indonesian coastal communities that fish the Halmahera, Arafura and Timor Seas. Fishery and interview data collected in 2012-13 from three case studies on the islands of Seram, Aru and Rote were used to examine changes in shark fishers’ livelihoods over the preceding 20 years. While recent declines in catches and shark fin prices have had a substantial impact on fishers’ livelihoods, the fishery's low visibility in some areas of its geographic range and its political complexity in general have meant that government and international development agencies have largely been unaware of this impact. Many respondents remembered the Asian Financial Crisis in 1997-98 and the turn of the millennium as a time when sharks were still abundant and shark fin prices high, but were concerned about the on-going fall of shark fin prices since March 2012. High-value species, particularly guitarfish, hammerhead and sandbar sharks were most affected, losing up to 40% of their pre-2012 value. These changes, combined with the loss of fishing grounds, few attractive options for alternative income and restrictive debt relationships with shark fin bosses, have led some fishers to resort to high-risk activities such as blast fishing, illegal transboundary fishing, and people smuggling. This paper examines the multi-layered causes and consequences of fishers’ decision-making in response to adverse changes in their fishery, and explores options and obstacles to pursuing livelihoods that carry lower environmental, financial and personal risks.     

渔业生产者参与实施捕捞限额制度意愿的影响因素研究

文章以上海市、浙江省和山东省113户渔业生产者的问卷调研数据为基础,通过运用Logistic回归模型分析渔业生产者参与实施捕捞限额制度意愿的影响因素。研究表明,年龄、受教育水平、渔船总功率、年均捕捞量、捕捞收入与家庭总收入比例、举报奖励额与超额价值比例以及年监管次数均对渔业生产者参与实施捕捞限额制度的意愿产生显著影响。基于实证研究结果,提出应加大渔业培训力度,切实控制渔船功率,暂不设立举报机制以及结合目前的投入控制制度推行循序渐进、逐步严格的监管机制等建议,以提高渔业生产者参与实施捕捞限额制度的意愿,为制定有效的渔业资源管理制度提供参考依据,推进渔业现代化改革。     

我国远洋渔业发展阶段特征、演进动因与趋势预测

随着近海渔业资源的枯竭及近海养护政策的进一步实施,发展远洋渔业成为增加海水产品供给、改善居民膳食结构、实现我国渔业可持续发展的战略选择。文章回顾了新中国成立以来我国远洋渔业的发展历程:按照产量、产值、作业海域、远洋渔业产业结构等指标对其进行阶段划分,依次分为空白期(1949—1971年)、积极筹备期(1972—1984年)、起步期(1985—1990年)、快速发展期(1991—1997年)、调整期(1998—2006年)、优化期(2007年至今)6个阶段,并分析其阶段特征;发现国际渔业合作、远洋技术革新、近海渔业政策和政府补贴引导构成了远洋渔业不同阶段的演进动因。结合当前我国远洋渔业所处阶段的特征和国内外渔业环境,对我国远洋渔业的发展趋势进行预测,即我国远洋渔业发展趋势体现在如下三大转变,(1)由渔业资源依附型转变为科技资源驱动型;(2)资源消耗型转变成资源创造型,推进海外"蓝色粮仓"建设;(3)资源破坏型转变为资源养护型,树立负责任远洋渔业大国的形象。     

Patterns and trends in seabird bycatch in the pelagic longline fishery off South Africa

Both foreign and domestic pelagic longline fishing vessels operate in South Africa’s Exclusive Economic Zone and adjacent international waters where they kill hundreds of seabirds each year as bycatch. To update assessments of the impact of the pelagic longline fishery on seabirds off South Africa, information on necropsied seabirds and national fisheries observer bycatch records were summarised for 2006–2013. Foreign-flagged (Asian) vessels had 100% observer coverage throughout the study period, whereas only 6% of the fishing effort by South African-flagged vessels was observed (with no coverage in 2011–2013). Vessels with observers caught seabirds at a rate of 0.132 birds per 1 000 hooks, resulting in an estimated mortality of 2 851 individuals (356 per year) comprising 14 species. Extrapolation of the observed fishing sets to the unobserved fishing sets by the South African domestic longline fleet suggested that approximately 750 additional birds were likely killed during the study period, therefore a combined 450 birds were killed per year. White-chinned petrel Procellaria aequinoctialis was the most frequently killed species (66%), followed by ‘shy-type’ albatrosses Thalassarche cauta/steadi (21%), black-browed albatross T. melanophris (7%), Indian yellow-nosed albatross T. carteri (3%), and Cape gannet Morus capensis (2%). The seabird bycatch rates were lower than in 1998–2005. Nationality of the vessel, time of line-setting, moon phase, year, season, fishing area, and seabird bycatch mitigation measures all influenced seabird mortality. Concurrent with 100% observer coverage, significant reductions in the seabird bycatch rate occurred in the Asian fleet in the latter years of the study, and these rates now approximate the national target (0.05 birds per 1 000 hooks). However, seabird bycatch rates remained high in the South African fleet, where no observers were deployed during 2011–2013, highlighting the need for independent observer programmes in fisheries—a matter of global interest. Suggestions are made as to how seabird bycatch by pelagic longline fisheries off South Africa may be further reduced.     

Spatial assessment of fishing effort around European marine reserves: implications for successful fisheries management

We examined the spatial dynamic of artisanal fishing fleets around five European marine protected areas (MPAs) to derive general implications for the evaluation of MPAs as fisheries management tools. The coastal MPAs studied were located off France, Malta and Spain and presented a variety of spatial designs and processes of establishment. We developed a standardized methodology to define factors influencing effort allocation and to produce fishing effort maps by merging GIS with geostatistical modelling techniques. Results revealed that in most cases the factors “distance to the no-take”, “water depth”, and “distance to the port” had a significant influence on effort allocation by the fishing fleets. Overall, we found local concentration of fishing effort around the MPA borders. Thus, neglecting the pattern of fishing effort distribution in evaluating MPA benefits, such as spillover of biomass, could hamper sound interpretation of MPAs as fisheries management tools.     

人工培育条件下鲻鱼早期发育的生理生态研究

研究了在人工条件下,鲻鱼MugilcephalusLinnaeus幼体各部分形态、器官的发育时间、行为、营养和变态特点,划分了发育期。仔鱼在生长过程常因畸形、损伤和消化不良而死亡;生长差异则存在于整个发育期,并且差异随时间延长而增大。同时,对鲻鱼早期发育的生物学特点、疾病、变态危险期和生长差异等进行了讨论,指出鲻鱼与环境和饲育条件之间的生态生理关系,以及这种关系对鲻鱼生长和存活的影响。     

Chronic dietary exposure to copper affects growth, tissue lipid peroxidation, and metal composition of the grey mullet, Chelon labrosus

Juvenile grey mullet (Chelon labrosus) were fed either a basal (4.4 mg Cu/kg dry wt) or high-Cu diet (2400 mg Cu metal/kg dry wt) for 10 weeks to assess the relationship between growth and Cu-induced oxidative damage. No mortalities were observed, but growth rate and food intake were reduced by 43 and 29%, respectively, in the high-Cu group. This was not only attributed to peroxidative damage of the food which reduced food intake (palatability), but also to direct effects of hepatic lipid peroxidation. Hepatic α-tocopherol concentrations were 63% lower, while malondialdehyde (MDA) increased by 304% in mullet fed a high-Cu diet for 67d. Cu-exposure reduced apparent α-tocopherol retention by 420%. Hepatic Fe and Zn levels fell, while Cu increased (p < 0.05). The results show that oral Cu exposure induces oxidative stress in grey mullet. Quantification of lipid peroxidation (rancidity) in the food, reflecting palatability, is essential to differentiate the direct toxic effects of Cu on growth from the secondary influences of reduced food intake.     

山东省海洋渔业结构调整研究

在对山东省海洋渔业现状进行了全面调查、研究与分析的基础上,用灰色模型理论,模拟预测山东省渔业发展的特性与趋势;运用平衡产量和经济模型分别评估了山东省海洋捕捞的最高持续渔产量与最大持续经济产量及其相应努力量;运用线性规划的理论与方法,测算了各档次渔船的功率和船只匹配的优化估算值。依据该数值模型所作的评估结果,提出了对山东海洋渔业结构的调整意见。     

龙感湖水生植被

于１９９３年９月对龙感湖水生植被及环境进行了调查研究。龙感湖有水生植物２６科３８属５０种,依据优势种群划分９个群丛,其分布面积２８３．５ｋｍ＾２,占全湖总面积的８９．７％,植被现有年生产力达２１４７７３０ｔ,对渔业生产和生态环境具有十分重要的意义。建议对该湖植被应合理开发利用,如果围网养鱼得到广泛地发展,渔业生产潜力每年可达４１８１．８ｔ。