Factors determining the structure of fish communities in Pantanal lagoons (MS, Brazil)

The fish communities of lagoons in the Nhecolândia Pantanal were studied to determine the factors which are responsible for the composition and abundance of species. Fishes were collected in 19 lagoons during August 1997, after their isolation from the River Negro, using beach seines (15 × 1.5 m; 2 mm mesh). A total of 51 species were collected. In the lagoons, or in parts with dense macrophytes, a screened box trap was used. Fishing was also accomplished with hooks of several sizes. Species richness was estimated by the jack-knife procedure, after adjustment to the log-normal distribution and with von Bertalanffy's equation (asymptotic). The most important factors in the community organization were macrophyte cover, piscivore abundance and depth of the lagoons. The role of these habitats in the Pantanal ecosystem was discussed.     

Factors regulating diversity and abundance of fish communities in Pantanal lagoons, Brazil

The factors effecting fish species richness, evenness and relative abundance in 19 floodplain lagoons in the Pantanal (Brazil) were examined. Richness and evenness were strongly correlated with the lagoon's: (i) isolation time from the main river; (ii) depth; and (iii) distance from the main river. Abundance of the five dominant fish species was correlated mainly with: (a) macrophyte cover; (b) the distance from the main river; and (c) piscivore abundance. These results suggest that the species select lagoons to avoid or minimize their confinement in inappropriate floodplain habitats. A combination of strategies, together with variations in the lagoon's connection period, determines the diversity and abundance of the fish species in the Nhecolândia Pantanal.     

Effects of fisheries management on fish communities in the floodplain lakes of a Brazilian Amazonian Reserve

Abstract –  We compared fish abundance, diversity and species composition between lakes open (fished) and closed (no-take) to fishing activities in Mamirauá Sustainable Development Reserve in the Central Brazilian Amazon, in order to investigate potential influences of the common-based management. We sampled 1483 fishes from 70 species through gillnet fishing during the low-water season, in seven fished and seven no-take lakes. Contrary to expected, the mean values for abundance, size, diversity and species-richness of fish did not differ between fished and no-take lakes. There was no difference between fished and no-take lakes considering only the abundance of the 14 fish species more intensely targeted by fishermen. However, the abundance of an important commercial fish, the tambaqui ( Colossoma macropomum ) was higher in no-take lakes. Such data from a rapid assessment may be useful to monitor this and other fishery co-management schemes.     

Fish resources of Dhofar khawrs (coastal lagoons) in the Sultanate of Oman

Abstract A fish resource monitoring programme was undertaken during 1992–1993 in nine Dhofar khawrs (coastal lagoons) of Oman. The khawrs contained a large number of fish comprising mostly milkfish, Chanos chanos (Forsskal), and mullet, Mugil cephalus L. A wide range of species were recorded (47) with Khawr Sawli supporting the highest number (26). Most fish use khawrs as nursery grounds and migrate to the sea for breeding. Mullets matured in winter, milkfish in early spring and the other species in spring-summer except the sleeper, Ophiocara porocephala (Valenciennes), which breeds all year round. Three species of invertebrates with commercial value were collected: Indian white shrimp, Penaeus indicus H. Milne Edwards, Mud crab, Scylla serrata (Forskal), and swimming crab, Portunus pelagicus (L.). Khawr water temperature followed a seasonal cycle and surface temperatures were higher than the deeper waters. Heavy rains in early spring caused extensive flooding and opening of khawrs to the sea. This had little effect on water salinity in some khawrs (Rawri and Mughsayl), while others displayed marked elevation in salinity (Taqah, Sawli and Jnawf) or reduced salinity by 50% (Qurm al-Kabir). Sedimentation and organic decomposition added during flooding produced drastic reduction in dissolved oxygen. Khawrs were again connected to the sea during monsoon (June–September) as water levels increased. Intrusion of sea water increased salinity and continued for several months in shallow khawrs (Jnawf); however, freshwater seepage reduced salinity in most khawrs. Massive fish mortality following heavy rains was the most significant seasonal occurrence. Extensive fish losses also occurred when water levels dropped after opening khawrs to the sea, and left many fish stranded in shallow areas. Other environmental perturbations existed in most khawrs (e.g. pollution and overgrazing). However, these khawrs have potential for small-scale fisheries and different types of aquaculture. Management problems are identified and options for solutions suggested.     

滤食性鱼类在淡水渔业中的碳汇作用初探

气候变暖威胁人类的生存与发展,减少CO2等温室气体的排放,发展低碳经济,缓解全球气候变暖的低碳经济是人类的共识。滤食性鱼类通过滤食浮游生物,间接降低大气中的CO2浓度而发挥碳汇作用。本文描述了一个不投饵的淡水生态系统的碳循环,探讨了滤食性鱼类在淡水生态系统中的碳汇作用,依据2009年全国水产养殖相关统计数据,估算了全国滤食性鱼类养殖的年碳汇量,为淡水渔业的低碳发展提供新思路,以推进现代化渔业的科学健康发展。     

An evaluation of tropical brush and vegetation park fisheries

Brush and vegetation parks are common features of many tropical river fisheries. Areas of branches of certain tree and bush species combined with floating vegetation are placed in shallow, sheltered water so as to attract fish. They provide cover and spawning areas for many fish species. They are particularly rich trophically because of the abundance of epiphytic organisms, boring insects and molluscs on the submerged surfaces of the wood and the root systems, and because of the enriched bottom mud caused by decay of the woody material. Yields depend on the amount of woody material used and the age of the park. The economics of their operation can be complex and larger structures rely on a high degree of social organization for their installation and fishing. Fish parks are controversial in many areas, being viewed as an extractive method of fishing, a source of siltation and creator of social inequalities. However, when properly managed very high yields per unit area can be obtained and the structures can change from simple fish attracting devices to a form of aquaculture whereby net production from a river or lake can be increased.     

滤食性鱼类在淡水渔业中的碳汇作用初探

气候变暖威胁人类的生存与发展,减少CO2等温室气体的排放,发展低碳经济,缓解全球气候变暖的低碳经济是人类的共识。滤食性鱼类通过滤食浮游生物,间接降低大气中的CO2浓度而发挥碳汇作用。本文描述了一个不投饵的淡水生态系统的碳循环,探讨了滤食性鱼类在淡水生态系统中的碳汇作用,依据2009年全国水产养殖相关统计数据,估算了全国滤食性鱼类养殖的年碳汇量,为淡水渔业的低碳发展提供新思路,以推进现代化渔业的科学健康发展。     

Fish aggregating devices in the eastern tropical Pacific marine corridor,according to the Colombian Fisheries Observer Program

1. Fish aggregating devices (FADs) are floating objects that facilitate the aggregation of fish; those that aggregate pelagic species such as tunas are of particular interest for artisanal and industrial fisheries.
2. Due to the increasing use of these devices worldwide, bodies responsible for the administration and management of fishery resources have proposed control and surveillance activities focused on the use of such devices. To achieve this, it is essential to have access to quality information, which is usually obtained through on-board observer programmes such as the Colombian Fisheries Observer Program.
3. Based on the historical records of this programme, and for the first time, the spatial–temporal distribution of the FADs in the eastern tropical sector of the Eastern Pacific Ocean is presented, analysing 166 records of tuna fishing operations carried out between 2009 and 2015. Of the 2,328 sets identified in the records, 957 corresponded to sets on FADs, of which 80.56% were effective and caught 12,246 tons of tuna.
4. The number of sets of FADs increased over time, representing approximately 86.9% of the sets recorded in 2015, compared to 4.8% of this type of set recorded in 2009, with the Eastern Tropical Pacific Marine Corridor being the area of greatest concentration of sets.
5. Considering that the Eastern Tropical Pacific Marine Corridor was designed to promote the conservation and sustainable use of biological diversity in the Eastern Tropical Pacific, this study highlights the need to include as a research priority, the potential effect that aggregation devices may have on the biological connectivity processes present in the corridor, as well as on the dynamics of large pelagic fish populations of commercial interest.
6. In terms of management of FADs, it is recommended that a precautionary approach be adopted and that regulations related to the maximum number of FADs per vessel be adjusted according to their Inter-American Tropical Tuna Commission class, in addition to assigning a maximum number of sets per vessel.

     

渔业协会、渔村社区组织及其渔业资源管理功能

改革开放以来,随着渔业经济的快速发展,我国的渔业发展面一临着渔业资源严重枯竭、渔业监管困难、渔民收入增长幅度放缓等诸多问题。为此学术界在渔业资源管理方法上提出了许多意见,同时也存在着一些分歧。文章通过理论推演,结合文献数据,探讨了渔村社区组织与我国渔业协会的关系,分析了包括渔业协会在内的渔村社区组织对渔业资源管理的作用,通过对代表性渔业资源管理理论的利弊分析,剖析了渔民协会等渔村社区组织的渔业资源管理职能。同时指出由于渔业协会在资源管理中具有重要作用,但因其自身也存在着一定局限性,因此,培育渔业协会、完善其资源管理职能,实行基于渔业协会等渔村社区组织的合作管理也就成为我国加强渔业资源管理的一种制度选择。     

Fisheries and cage culture of three reservoirs in west Java, Indonesia; a case study of ambitious development and resulting interactions

Abstract The interactions between cage culture and wild fishery activities in three Indonesian reservoirs, Saguling, Cirata and Jatiluhur, of the greater Ciratum watershed, West Java, were evaluated using historical data and interviews with cage culture operators. In all three reservoirs, cage culture of common carp, Cyprinus carpio L., and later of common carp and Nile tilapia, Oreochromis niloticus (L.), were encouraged as an alternative livelihood for persons displaced by the impoundment. Currently, a two‐net culture system, locally known as ‘lapis dua’, in which in the inner cage (7 × 7 × 3 m) is used for common carp culture and the outer cage (7 × 7 × 5/7 m) is stocked with Nile tilapia, is practised. On average each cage is stocked with approximately 100 kg fingerlings each of common carp and Nile tilapia. The numbers of cages and production of cultured fish has increased in the reservoirs, but total and per cage production began to decline from about 1995 in Saguling from 2200 kg cage^?1 in 1989 to <500 kg cage^?1 in 2002, and in Cirata from a peak of approximately 2300 kg cage^?1 in 1995 to approximately 400 kg cage^?1 in 2002. In Jatiluhur, which has a considerably lower cage density, total fish production and production per cage has increased since 2000, and currently is approximately 4000 kg cage^?1, close to production in the early years of cage culture activities. The cage culture operations also resulted in substantial nutrient loading, estimated at 3.2, 15.2 and 3.1 t of nitrogen and 134, 636 and 128 kg of phosphorous per year in the maximum years of production for Saguling, Cirata and Jatiluhur reservoirs, respectively. In later years, when cage culture production was high, fish kills occurred in the cages, and in Jatiluhur reservoir coincided with a dramatic decline in wild fishery catches. An attempt is made to determine the maximum number of cages for each of the reservoirs that will bring long‐term sustainability of cage culture operations and the wild fisheries in the three reservoirs.     

我国渔业合作经济组织发展特征分析

渔业经济是农业经济的重要组成部分,但渔业生产经营模式不同于以种植业为主体的农业经济。在分析渔业合作经济组织与农业合作经济组织异同及相关特征的基础上,提出了促进渔业合作经济组织健康发展的相关对策。     

我国绿色水产品发展思考

在对绿色水产品与无公害水产品进行辨析的基础上，从我国水产业发展过程中面临的问题出发，论述了发展绿色水产品的目的和意义，并对阻碍我国绿色水产品发展的问题进行了初探，进而提出了一些建议和对策。     

Fish populations in tropical floodplain pools: a re-evalution of Holden's data on the River Sokoto

Abstract– In this study we asked whether the fish populations of residual pools in a seasonally fluctuating African river varied between years. We used a series of data on the fish of the permanent floodplain pools of the River Sokoto, Nigeria compiled by M. J. Holden (1963) to address this objective. Holden provided estimates for the size and biomass of fish populations in 12 permanent dry season pools over a period of 2 to 3 years. On average, only 22% of the species present in a pool were absent from that pool in the following sampling period. Despite low interannual variability in the species composition of the pools, rank correlation analysis indlcated significant variation in the relative numbers and biomass of the 10 most numerically abundant species in most pools. Altering the spatial scale of analysis to include all possible combinations of 2 and 6 pools did not affect the results. Indices of similarity also indicated relatively high annual variability in the relative abundance of species in the pool communities. We suggest that habitat selection may contribute to the continued occurrence of fish species in pools from year to year, and such factors as changes in the overall abundance of fish species in the system and haphazard trapping during flood decline may contribute to annual variation in their relative abundance.     

关于发展象山现代渔业的思考

发展现代渔业是当前海洋与渔业经济面临的新任务新挑战,本文作者结合当地渔业的发展实际,分析了渔业发展当前存在的问题,并就＂十二五＂期间如何发展现代渔业进行探讨。     

Community-based management of subsistence fisheries in Samoa

Much subsistence fishing in tropical regions is based in discrete communities which have a high level of marine awareness and some degree of control of adjacent waters. These factors provide an ideal basis on which to motivate communities to manage their own marine resources. A fisheries extension programme in Samoa encouraged each village community to define its key problems, discuss causes, propose solutions and take appropriate actions. Various village groups, including women's and untitled men's groups, provided information which was recorded (as problem/solution trees) on portable white-boards. The extension process culminated in a community-owned Fisheries Management Plan which listed the resource management and conservation undertakings of the community. Undertakings ranged from enforcing laws banning destructive fishing methods to protecting critical marine habitats. Within the first 2 years, the extension process commenced in 65 villages, of which 44 have produced Village Fisheries Management Plans to date. A large number (38) of these villages chose to establish community-owned Marine Protected Areas.     

我国渔业经济基本管理制度演变的研究

制度建设是构成一个国家、一个行业、一个企业综合竞争力的重要因素。建国以来,我国渔业制度发生了巨大的变化,特别是党的十一届三中全会以来我国渔业体制的重大改革和法制建设的推进,为我国渔业经济的发展起了重要的促进和保障作用。当前,我国渔业正处于由渔业大国向渔业强国的转变过程中, 加强渔业制度建设的理论研究具有现实意义。     

Influence of gear switching on recapture of Atlantic salmon (Salmo salar) in catch‐and‐release fisheries

Anglers that release Atlantic salmon (Salmo salar) in recreational fisheries do so with the intention that the fish will survive and contribute to succeeding generations. In some instances, salmon that are released may be recaptured, but mechanisms associated with recapture are unclear. To test whether gear avoidance influences recapture rates, we analysed data from tagging programmes in major Norwegian Atlantic salmon fishing rivers to determine how frequently salmon were recaptured by different gear than that by which they were initially captured (i.e. gear switch). Among 339 salmon captured, externally tagged and released in 2012 and 2013, 46 (14%) were recaptured; 70% of these recaptured salmon exhibited gear switch. To test whether this gear switch percentage could be expected in the absence of gear avoidance, a simulation was conducted, which accounted for variation in catch probability among rivers and across time with different gear types based on comprehensive catch data. Each simulation step provided a simulated rate of gear switch under the null hypothesis of no gear avoidance. A distribution was generated, which described the probability that we would observe 70% gear switch. The simulated results indicated that this rate of gear switch was highly unlikely (P = 0.003) if recapture gear is assumed to be independent of initial capture gear, suggesting that salmon avoided familiar gear types. Changes to behaviour after release, including learned hook avoidance, may explain our observation of gear avoidance by recaptured salmon.     

The challenge of sustainable use of the Danube Delta Fisheries, Romania

The Danube Delta was designated a Biosphere Reserve in 1990. Subsequently the sustainable use of the fish stocks within the reserve became a challenge for management. The fisheries exploit a variety of habitats distributed over about 580 000 ha of wetland. They yield between 5000 and 10 000 t year^–1, equivalent in value to 6.3 million US$, making this one of the most important inland fisheries in Europe. Approximately 15 000 inhabitants within the Delta and a further 160 000 from adjacent regions depend fully or partly on the fishery resource. The fisheries are diverse, consisting of lake, river, marine coastal and anadromous fisheries. Fisheries in the Delta operated under an open access system during the transition from a fully controlled state economy to a market economy. New fishing regulations have been established to minimise the risk of the fisheries collapsing as a result of the open access regime. Core regulations including close seasons and closed areas, minimum mesh sizes and fish lengths, output controls (catch quota), and input regulations (limited access to fishery) were introduced.     

福建省海洋渔业经济科学发展的思路

本文分析了近年来福建省海洋渔业经济持续发展及海洋渔业产业结构变化的发展现状，指出在海洋渔业经济发展中，存在海洋渔业资源的衰退局面还未得到有效遏止和海水养殖业发展中存在制约因素等问题，提出大力发展高科技集约化海水鱼类养殖、实施海洋捕捞业从“量增长”转为“质增长”战略、实施“走出去”稳步扩大远洋渔业规模战略、发展休闲渔业开创渔区经济新的增长点等解决问题的对策及科学发展的思路。     

福建海洋渔业产业结构调整对策的探讨

一种产业的高速发展能否得以持续,关键在于是否对该产业结构进行不断调整,使之趋于最合理状态。为再度振兴福建海洋渔业,不失时机地进行渔业结构战略性调整是唯一选择。