Developing co-management in an artisanal gill net fishery of a deep hydro-electric reservoir in Sri Lanka

Abstract Victoria, is a recently (1984) impounded, deep, hydro-electric reservoir in Sri Lanka with an established commercial fishery. Participatory appraisal of the fishing community revealed decreasing reliance on fishing income with many fishermen moving away to supplementary occupations because of declining fish catches. Illegal fishing and theft of fishing gear resulting from open access, difficulties encountered in enforcing fisheries regulations and the need for fishermen to find alternative sources of income during low water levels are the major management problems. The top–down centralized management approach previously practised was ineffective in addressing any of these issues. Therefore, the possibilities and limitations for introducing co-management as an alternative management strategy were discussed. Financial hardship coupled with perceived benefits through state sponsored welfare schemes caused a positive attitude change among fishermen, making them respond favourably to fishery management. Establishing a licensing system for controlled access, ensuring greater user-group participation through equitable distribution of state sponsored benefits among members, attempting to enforce penalties for illegal fishing linked with surprise checks to enforce management regulations, and obtaining stakeholder perceptions regarding management issues are some of the recent steps taken by the Fishermen's Co-operative Society which would positively contribute towards developing effective co-management in this reservoir.     

A new large‐scale and cost‐effective restoration method for cold‐water coral gardens

1. Gorgonians dwelling on the Mediterranean continental shelf are among the most frequent fishing bycatch taxa. These species display several traits, such as long lifespans and slow growth, which make them very vulnerable to the impacts caused by fishing activities with far‐reaching and long‐lasting effects.
2. Hence, restoration and mitigation actions are crucial to enhance and speed up the natural recovery of damaged cold‐water coral gardens. Given the growing concern to develop effective and affordable restoration actions, the present study aims to propose and technically validate a new large‐scale and cost‐effective restoration method.
3. This technique, named ‘badminton method', consists of attaching bycatch Eunicella cavolini colonies to cobble supports and returning them to the continental shelf by gently throwing the gorgonian transplants directly from a boat.
4. Two consecutive field experiments were conducted in order to find the best cobble type support and gorgonian size to be used: first, to evaluate the landing efficiency of gorgonian transplants at different depths (from 5 to 30 m) and second, to evaluate their capability to maintain a correct position over time.
5. Natural cobbles with large gorgonians attached were the best option. Field results and modelling approaches suggest that the transplants would correctly land on the continental shelf seabed in a predicted area of around 60 m². Moreover, they would successfully maintain an upright position ensuring gorgonian survival over time.
6. The success of this method highlights the feasibility of large‐scale and low‐cost restoration actions with promising results for the conservation and recovery of cold‐water coral gardens.

     

Potential distribution and population trends of the smalltail shark Carcharhinus porosus inferred from species distribution models and historical catch data

1. Updated distribution ranges are crucial for conservation status assessments. Comprehensive analyses combining published literature and available data on historical catches and species distribution models (SDMs) are effective tools that could improve the prediction of more realistic scenarios for some species, especially those with limited information available and facing multiple threats.
2. The present study aimed at generating an updated distribution for the smalltail shark Carcharhinus porosus, one of the most threatened and understudied shark species of the western Atlantic Ocean. Estimates of the key areas for this species conservation based on the SDMs, and trends in catch probabilities throughout its distribution range are provided.
3. Four algorithms (BIOCLIM, Domain, Mahalanobis, and Maximum Entropy) were used to model the distribution of C. porosus and calculate its habitat suitability based on marine environmental variables. To assess historical catch probability trends, we built a generalized linear model from published and grey literature data. This analysis was used to estimate catch probability as an indication of population trends.
4. SDMs suggest that the northern coast of South America (NCSA) harbours the most suitable habitats for C. porosus in the world, which was expected given its historically high catch rate in this region. In addition, there was a continuously declining catch probability trend starting in the 1970s. However, the decline was smaller for the NCSA as compared with the Gulf of Mexico and the eastern South America coast.
5. Results indicate that the NCSA should be considered the currently most important area in the world for this species conservation. Furthermore, the lack of data throughout Central and South American marine regions hampers the evaluation of extinction risk throughout its updated distribution. Thus, research in these areas is urgently required for a more comprehensive conservation status assessment.

     

Insights into population genetics,connectivity and demographic history of the longnosed skate Dipturus oxyrinchus (Linnaeus, 1758) in the western Mediterranean Sea

1. Genetic information is crucial for the conservation of Dipturus oxyrinchus (Linnaeus, 1758), a threatened large skate with declining populations over most of its geographical range. The main aim of the present study was to investigate the genetic structure, connectivity and demographic history of the longnosed skate in Sardinia (western Mediterranean Sea).
2. Patterns of population structure were assessed in 175 specimens from six sampling sites. Variation in two mitochondrial genes (cytochrome c oxidase subunit I (COI) and control region) highlighted high genetic diversity and low but significant genetic differentiation among sites, which clustered into three groups corresponding to the north‐west, north‐east and south Sardinian coasts.
3. The observed genetic structuring could presumably depend on a combination of past geological events, contemporary restrictions to dispersal and biological characteristics of the species (e.g. site‐fidelity, no pelagic larval stage, limited dispersal of juveniles and/or adults).
4. Demographic analyses showed signs of past population expansion, but substantial current stability of Sardinian populations. From a conservation perspective, these results are encouraging, and indicate that Sardinian populations are still large and stable, and seem not to have suffered negative side‐effects from the ever‐growing fishing pressure in the region.
5. The occurrence of genetic structuring strongly supported the close monitoring of populations to identify any erosion of their gene pool, and high genetic variability of the Sardinian D. oxyrinchus populations could thus represent priority populations for conservation purposes, providing potential sources for recolonization in cases of local extinctions in other areas of the distribution range of the species.
6. When the sequences from Sardinia were compared with those available from other areas, the data seem to exclude the possibility that the Atlantic and Mediterranean host totally isolated populations or even different species, as recently suggested. However, additional markers and a larger sampling sites are needed to confirm these findings.

     

辽宁近海渔场海蜇增殖放流的回顾与发展

辽宁近海渔场海蜇放流经过1988-1993年、2004年在海洋岛渔场和2002年在辽东湾各渔场的增殖试验与2005-2006年的生产性增殖放流，探索了放流海域选择、放流时间和放流规格，跟踪监测技术，回捕效果检验等相关技术。笔者就海蜇增殖放流情况作系统回顾，并对其大规模发展做以探讨。     

南海灯光罩网沉降性能研究

根据2013年3月至4月南海灯光罩网渔船测定的沉降深度数据及搜集的渔船操作数据和海洋环境数据,对南海灯光罩网沉降深度和沉降速度与时间的关系进行了研究,并构建多元线性回归模型分析了灯光罩网最大沉降深度与放网时间、海流速度等因子的影响关系。结果显示:(1)网口纲一边沉降过程中沉降深度呈现两端深中间浅的趋势,网口纲两端最大沉降深度基本一致;(2)网口纲一边沉降速度呈现两端快中间慢的趋势,网口纲两端沉降速度都在10 m水深达到最大,而网口纲中部在5 m水深达到最大;(3)网具沉降深度与时间的关系式为H=-0.0008t2+0.4766t+1.2063(R2=0.9985),网具沉降速度与时间的关系式为:V=-1E-07t2-0.0018t+0.5269(R2=0.8813);(4)多元线性回归分析显示放网时间、风流向夹角、绞纲时间对网具最大沉降深度影响极为显著(P0.001),而海流速度、风力对网具最大沉降深度影响不太显著(P0.1);且各影响因子之间不存在多重共线性(κ=2.396100)。可为改善南海灯光罩网沉降性能提供参考,并为海上生产提供指导。     

基于渔捞日志的长江靖江段刀鲚渔获量的时空特征分析

江苏靖江段位于近长江口段,是长江刀鲚渔汛最集中的水域。为了弄清靖江段刀鲚的渔汛特征,本文于2008-2009年和2012-2013年对16艘持刀鲚捕捞许可证的渔船作了渔获量监测,分析了渔获量的时空变化及其环境影响。结果表明,靖江段单船日渔获数量NB和重量WB分别为(21±38)ind./d和(2.0±4.1)kg/d,单船全汛总渔获尾数Nt和重量Wt为(890±929)ind.和(92.3±91.1)kg。NB和Nt具有一致性的年变化趋势,以2013年的最大,其他年份比较接近。但WB和Wt的年变化趋势与渔获数量的年变化趋势有所不同,表现为2008-2012年间持续下滑,2013年显著增长。NB和WB在2-3月间均极低,但4月增至(23.0±31.3)ind./d和(2.4±3.5)kg/d,5月达(78.0±81.0)ind./d和(7.7±9.1)kg/d。ANOVA分析显示,西水域的年NB和WB分别为东水域的2.5和2.7倍。研究亦显示,靖江段刀鲚的WB与同日水温和最高潮位均呈极显著的正相关(P﹤0.05)。长江口外的水温提升,可能是刀鲚开始生殖洄游的重要环境诱导因子。而高潮期在靖江段出现最高渔汛,可能是因为所采用的固定刺网过滤了更多的江水所致。     

山东省小型渔船主要参数的确定

以山东省小型渔船为研究对象，用回归分析方法，求出了小型渔船主要参数间关系，并给出了船长、船宽、吃水、船型系数，设计纵倾的估算公式和取值范围。     

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…     

Early Development of the Mandarinfish, Synchiropus splendidus (Callionymidae), with notes on its Fishery and Potential for Culture

The mandarinfish, Synchiropus splendidus, is a small, pelagic-spawning enthic dragonet of the western Pacific. Although popular in the marine aquarium trade, little is known of its fishery or biology. All aquarium-trade animals are currently taken from the wild and the impact of heavy collecting is unknown. The specialized and selective nature of the fishery for mandarinfish is described and its potential to disrupt the mating system identified. As a possible alternative to wild capture and as an aid to sustainable exploitation, egg production and early development relevant to mariculture are described, including egg output, embryo, larva and post-settlement development to 30 days, based on live material. Egg output was determined for 40 females and ranged from 12 to 205 eggs. Embryo and larva development were rapid, with settlement occurring within 14 days at 24–26 °C, and at 3.5 mm TL. The swimbladder is retained in adults. Our limited attempts at raising the mandarinfish to settlement were encouraging and suggest an excellent potential for mariculture with implications for both conservation and improved maintenance of fish in captivity. At present, given that this species is difficult to maintain in captivity, it is only suitable for experienced aquarists. Preliminary diet information is provided. This revised version was published online in August 2006 with corrections to the Cover Date.