Gear-based management of a tropical artisanal fishery based on species selectivity and capture size

The population density, species composition and lengths of fish landed by artisanal fishermen using six types of gear: large and small traps, gill nets, hand lines, spears and beach seines were studied in the multi‐species fishery of southern Kenya. Selectivity and catch composition among gears were determined by studying the species richness, diversity, size and mean trophic level of the catches for each gear type, to develop gear‐based management recommendations for this artisanal reef lagoon fishery. One hundred and sixty‐three reef and reef‐associated species from 37 families were recorded in the catch. Beach seines and small traps accounted for the highest number of fish landed (34–35 individuals per fisherman per day). These gears also caught smaller fish than big traps, spears and gill nets. Beach seines caught the highest number of species (14 ± 7 species per day) while most other gears caught four to five species per day with no differences between gears. Predatory species with a mean trophic level of 3.6 dominated catches from hand lines, while the mean trophic level of the other gears was low and ranged from 2.6 to 2.9 with no differences between the gears. The high diversity and small size of fish caught in beach seines indicates that its selectivity overlapped most with large traps and gill nets. Spears and small traps also showed high similarity in species selectivity and small traps captured the smaller mean size of fish, indicating that they are likely to pre‐empt the resource of spears. Large traps, hand lines and spears catch the largest individuals and the species composition of the catch differed sufficiently such that their selectivity should overlap the least and may, therefore, be the preferred mix of gears. The elimination or reduction of beach seines and small traps should reduce the catch of small fish and overlap in selectivity among the existing gears.     

日本资源管理型渔业体系下的典型作业方式管制实践

通过文献研究,对日本资源管理型渔业体系下的典型作业方式管理措施进行梳理,以期对我国典型作业方式准入制度的构建和完善提供参考。对围网、底拖网、刺网和流网、定置网及鱿钓等5种日本渔业主要作业方式的管理措施体系进行了分类和介绍,认为日本的渔业管理通过不同层级的权限许可,根据海洋渔业资源的自然属性差异采取区域化的管理模式,并以恢复渔业资源为目标,逐步推进从总可捕量管理制度向捕捞努力量控制制度的转变。     

A framework for adaptive gear and ecosystem‐based management in the artisanal coral reef fishery of Papua New Guinea

• 1. Artisanal fishing on coral reefs in Papua New Guinea is an important livelihood activity that is managed primarily at the level of local communities. Pockets of overexploitation exist and are expected to increase with plans for increased commercialization.
• 2. This paper provides a current assessment of the artisanal multi‐species coral reef fishery by examining selectivity of the dominant gear, namely line fishing, spearguns, and gill nets. Each gear has its own strengths and weaknesses in terms of use and conservation of resources, with no clear problem gear.
• 3. The three gears utilize different resources but there was moderate overlap in the species caught, particularly between gill nets and line fishing and marginally between lines and spearguns. Gill nets have the disadvantage of being destructive to coral and the advantage of catching commercial species. Line fishing catches an intermediate number of species but mostly large‐bodied and predatory species that could potentially reduce predation and the mean trophic level of the fishery. Spearguns catch the highest numbers of species, including many non‐commercial and herbivorous fish and could reduce the diversity of fish and encourage algal growth.
• 4. This information could be used in combination with scientific monitoring and traditional ecological knowledge to develop an adaptive management framework that uses local restrictions on the various gears to restore or balance the fishery and ecosystem. Restrictions could be selectively imposed: on gill nets when coral cover is low, line fishing when large‐bodied predators are depleted, and spearguns when biodiversity is reduced and algal abundance high.

Copyright © 2008 John Wiley & Sons, Ltd.     

Changes in a coral reef fishery along a gradient of fishing pressure in an Indonesian marine protected area

相似文献   

A socio-economic perspective on gear-based management in an artisanal fishery in south-west Madagascar

Abstract  Artisanal fisheries are important socially, nutritionally and economically. Poverty is common in communities dependent on such fisheries, making sustainable management difficult. Poverty based on material style of life (MSL) was assessed, livelihoods surveyed and the relationship between these factors and fishery data collected using a fish landing study were examined. Species richness, diversity, size and mean trophic level of catches were determined for six fishing gears in an artisanal fishery in south-west Madagascar. There was little livelihood diversification and respondents were highly dependent on the fishery. No relationship was found between poverty and gear use. This suggests that poverty does not have a major impact on the nature of the fishery; however, this study was dominated by poor households, so it remains possible that communities with more variation in wealth might show differences in fishing methods according to this parameter. The fishery was heavily exploited with a predominance of small fish in the catches. Beach seines caught some of the smallest fish, overlapped in selectivity with gill nets and also had the highest catch per fishers. Thus, a reduction in the number of beach seines could help reduce the catch of small fish and the overlap in selectivity among gears.     

Recreational charter fishery attributes and variation in key species catches and discards: Resource management considerations

Strategic long‐term sampling programmes that deliver recreational catch, effort and species demographic data are required for the effective assessment and management of recreational fisheries and harvested organisms. This study used a spatially and temporally stratified observer programme to examine variation in the rates, quantities and lengths of retained and discarded catches of key species in a recreational charter fishery. Geographic region, but not season, significantly influenced catch rates of key demersal species, being driven by temporally persistent latitudinal clines in environmental conditions influencing species distributions. There was considerable trip‐to‐trip variation in catch rates that were attributed to localised differences in fishing operations, locations, environmental conditions and client preferences. Broad trends in retained and discarded catch rates were nevertheless, similar across different fishing effort standardisations (per‐trip, per‐hour, per‐client, per‐client/fished hour), demonstrating that the coarsest unit of effort could be used in fishery assessments. Discard rates of organisms were variable and driven by a combination of mandated legal lengths, individual client and operator preferences for particular species and sizes of organisms, and not due to attainment of catch quotas or high‐grading. This study has identified important fishery attributes that require consideration in assessing charter fisheries and stocks of recreational fish species.     

The hidden value of artisanal fisheries in Honduras

Declining fisheries catches are a global trend, with management failing to keep pace with growth in fishing effort and technological advances. The economic value of Honduras’ catches was estimated within the industrial and artisanal sectors. Catches were found to be 2.9 times greater than the official statistics between 1950 and 2015. The merging of industrial and artisanal catch data masked the decline in industrial catches and hid the strong growth of artisanal fisheries. In 1996, annual artisanal fisheries landed catches surpassed the industrial fishery sector, and in 2000, the annual net value of artisanal fisheries eclipsed the value of the industrial fisheries. These data highlight the importance of artisanal fisheries in Honduras and challenge the long‐held belief that the industrial sector contributes more to the national economy. The global paucity of fisheries data highlights the need for comprehensive strategies to collect more detailed and accurate fisheries data.     

Unveiling unselective fishing in China: A nationwide meta-analysis of multispecies fisheries

Understanding and managing fishery selectivity to target species and desirable size are instrumental to fisheries management. China, as the world's largest producer of marine capture fisheries, has been widely perceived to possess unselective domestic fisheries. To date, this perception remains largely anecdotal and conjectural, hindering the development of evidence-based and effective management solutions. Here, we conducted a literature review to examine the magnitude and scale of unselective fisheries in China. By collating and analysing 140 fishery-level and 807 species-level records from 66 peer-reviewed publications from 2010 to 2021, we found that primary target species were absent in 59% of fisheries, while unidentifiable low-value and juvenile mixed catch were universal. Key commercial taxa were subject to nationwide multi-gear and multispecies fisheries, each involving an average of 3.33 types of gear and accounting for less than 25% of catch individually. The ‘permissible gears’ defined by the national gear regulatory catalogue were selective over target species and caught negligible by-products, though they were used less frequently, representing only 24% of catch records. While unselective fishing can provide seafood supplies for China's large population and potentially facilitate balanced harvest, management actions are needed to control the fishing pressure on primary target species and by-product species. Amid the ongoing fisheries management reform in China, we proposed management recommendations tailored to China's needs and social contexts, including accounting for the trade-off between socio-economic and ecological goals, contemplating impacts of unselective fishing when implementing TAC programmes, and strengthening fisheries monitoring to inform management at multiple scales.     

Effectiveness of fishing gears to assess fish assemblage size structure in small lake ecosystems

Measurement of fish body‐size distributions is increasingly used as a management tool to assess fishery status. However, the effects of gear selection on observed fish size structure has not received sufficient attention. Four different gear types (experimental gill nets, fine mesh bag seine, and two different sized mesh trap nets), which are commonly employed in the study area for fisheries surveys, were used to fish in five small (< 200 ha) lakes to evaluate differential catch in terms of species composition and assemblage size distributions. Kolmogorov–Smirnov tests revealed that, out of the five lakes and six comparisons, the four gear types captured fish of statistically similar size distributions in only one instance. Non‐metric multi‐dimensional scaling followed by a multi‐response permutation procedure revealed that the species composition of fish captured by these gears also differs. These results support the notion that multiple gear types should be used to assess body‐size distributions as well as fish assemblage composition.     

Gear restrictions create conservation and fisheries trade-offs for management

Gear-based management for coral reef fisheries is often overlooked in the scientific literature. Empirical studies have demonstrated the conservation benefits of gear-restricted areas (i.e. prohibiting fishing gears), which can support greater biomass than unrestricted areas and protect species that play key functional roles. However, population dynamics of functional feeding groups of reef fishes under specific gear-restriction regimes remains uncertain. Here, we constructed a multi-species, length-based fisheries model to observe relative biomass and catch of reef fishes under various gear-restriction management scenarios. We used fishery-dependent and fishery-independent data to determine the catchability of functional groups and selectivity of size classes for hook-and-line, net and spear fishing, which are widely used gear types on coral reefs globally. Our model revealed trade-offs involved with gear-restriction management such that no single management strategy was able to maximize biomass or catch of all functional groups simultaneously. Also, we found that spear fishing (i.e. prohibiting hook-and-line and net fishing) maintained the highest total biomass summed across functional groups, whilst hook-and-line fishing (i.e. prohibiting net and spear fishing) and a ban on spears maintained the lowest biomass. However, hook-and-line fishing generated the highest catch-per-unit-effort. Our model results were primarily driven by differential growth rates, maximum per capita production of recruits, and catchability of functional groups targeted by each fishing gear. We demonstrate that gear restrictions can be a critical management tool for maintaining biomass and catch of certain functional groups but will likely require additional management to protect all key functional feeding groups of coral reef fishes.     

Feasibility of a single-species quota system for management of the Malaysian multispecies purse-seine fishery

Malaysian fisheries employ multiple measures to improve management; however, not all are well-suited to the multispecies fisheries. As part of a pilot project, an individual quota system was introduced for the purse-seine fishery off the East Coast of Peninsular Malaysia (ECPM), but no assessment of this particular measure nor the feasibly of its implementation has been confirmed. Therefore, this study analysed spatial and temporal patterns of purse-seine fishing, by collecting catch composition data per landing and its fishing ground within three period fishery surveys between August 2017 and September 2018 at six different landing sites. Similarity and cluster analysis examined species composition and diversity to determine the feasibility of implementing a single-species quota system in this multispecies fishery. Some overlapped of indices results and minor difference in catch composition were found due to changes in spatial and temporal fishing activities. However, no specific spatial or temporal patterns were discernible as structuring the fishing grounds used by purse-seiners. The absence of patterns, using the available data, might be attributable to huge species aggregations and widely distributed and homogenously mixed fish stocks. Thus, it is likely impractical to manage species individually in such a multispecies fishery.     

Wasted fishery resources: discarded by-catch in the USA

Fishery by‐catch, especially discarded by‐catch, is a serious problem in the world's oceans. Not only are the stocks of discarded species affected, but entire trophic webs and habitats may be disrupted at the ecosystem level. This paper reviews discarding in the marine fisheries of the USA; however, the type, diversity and regulatory mechanisms of the fisheries are similar to developed fisheries and management programmes throughout the world. We have compiled current estimates of discarded by‐catch for each major marine fishery in the USA using estimates from existing literature, both published and unpublished. We did not re‐estimate discards or discard rates from raw data, nor did we include data on protected species (turtles, mammals and birds) and so this study covers discarded by‐catch of finfish and fishable invertebrates. For some fisheries, additional calculations were required to transform number data into weight data, and typically length and weight composition data were used. Specific data for each fishery are referenced in Harrington et al. (Wasted Resources: Bycatch and discards in US Fisheries, Oceana, Washington, DC, 2005). Overall, our compiled estimates are that 1.06 million tonnes of fish were discarded and 3.7 million tonnes of fish were landed in USA marine fisheries in 2002. This amounts to a nationwide discard to landings ratio of 0.28, amongst the highest in the world. Regionally, the southeast had the largest discard to landings ratio (0.59), followed closely by the highly migratory species fisheries (0.52) and the northeast fisheries (0.49). The Alaskan and west coast fisheries had the lowest ratios (0.12 and 0.15 respectively). Shrimp fisheries in the southeast were the major contributors to the high discard rate in that region, with discard ratios of 4.56 (Gulf of Mexico) and 2.95 (South Atlantic). By‐catch and discarding is a major component of the impact of fisheries on marine ecosystems. There have been substantial efforts to reduce by‐catch in some fisheries, but broadly based programmes covering all fisheries are needed within the USA and around the world. In response to international agreements to improve fishery management, by‐catch and discard reduction must become a regular part of fishery management planning.     

Reducing seabird bycatch in longline, trawl and gillnet fisheries

With an increasing number of seabird species, particularly albatross and petrels, becoming threatened, a reduction of fishery impacts on these species is essential for their future survival. Here, mitigation methods to reduce and avoid seabird bycatch are assessed in terms of their ability to reduce bycatch rates and their economic viability for longline, trawl and gillnet fisheries worldwide. Factors influencing the appropriateness and effectiveness of a mitigation device include the fishery, vessel, location, seabird assemblage present and season of year. As yet, there is no single magic solution to reduce or eliminate seabird bycatch across all fisheries: a combination of measures is required, and even within a fishery there is likely to be refinement of techniques by individual vessels in order to maximize their effectiveness at reducing seabird bycatch. In longline demersal and pelagic fisheries, a minimum requirement of line weighting that achieves hook sink rates minimizing seabird bycatch rates should be tailored with a combination of strategic offal and discard management, bird‐scaring lines (BSLs) and night‐setting, particulary in Southern Hemisphere fisheries. Urgent investigation is needed into more effective measures at reducing seabird interactions with trawl nets and gill nets. In trawl fisheries, a combination of offal and discard management, the banning of net monitoring cables, paired BSLs, and a reduction in the time the net is on or near the surface are likely to be the most effective in reducing seabird interactions with the warp cables and net. Few seabird bycatch reduction methods have been developed for gillnet fisheries, although increasing the visibility of the net has been shown to reduce seabird bycatch. Further studies are required to determine the efficacy of this technique and its influence on target species catch rates.     

Artisanal fisheries in urban reservoirs: a case study from Brazil (Billings Reservoir, São Paulo Metropolitan Region)

Billings Reservoir is an urban reservoir located in the São Paulo Metropolitan Region. It supports 101 active artisanal fishermen. To describe this fishery, landings were recorded daily between February 1996 and January 1997 at Colônia (23° 50' 57' S; 46° 40' 02' W). In every landing, a data collector recorded catch, effort, fishing gears and fishing grounds. A total of 147 593 kg of fish were recorded in 3515 fishing trips. The exotic Nile tilapia, Oreochromis niloticus (L.), was the main species exploited (81.4% of the annual catches). Five other species were also targeted: the characid Astyanax eigenmaniorum (Cope) (13.0% of the annual catches); the erythrinid Hoplias aff . malabaricus (Block) (2.1%); the exotic cyprinid Cyprinus carpio L. (Campos & Fernández-Yépez) (2.4%); the curimatid Cyphocharax modestus L. (1.1%); and the pimelodid Rhamdia sp. (0.1%). Two main groups of fishermen were discriminated using Principal Components Analysis; these were associated with the type of fishing gear and fishing strategies, i.e. those who exploited Nile tilapia with cast nets and beating gill nets, and those who exploited other species with set gill nets. Management and maintenance of this fishery should consider the positive top-down effects that Nile tilapia could have in controlling eutrophication and also the social benefits.     

Assessing and managing data‐limited ornamental fisheries in coral reefs

Coral reefs support numerous ornamental fisheries, but there are concerns about stock sustainability due to the volume of animals caught. Such impacts are difficult to quantify and manage because fishery data are often lacking. Here, we suggest a framework that integrates several data‐poor assessment and management methods in order to provide management guidance for fisheries that differ widely in the kinds and amounts of data available. First, a resource manager could assess the status of the ecosystem (using quantitative metrics where data are available and semi‐quantitative risk assessment where they are not) and determine whether overall fishing mortality should be reduced. Next, productivity susceptibility analysis can be used to estimate vulnerability to fishing using basic information on life history and the nature of the fishery. Information on the relative degree of exploitation (e.g. export data or ratios of fish density inside and outside no‐take marine reserves) is then combined with the vulnerability ranks to prioritize species for precautionary management and further analysis. For example, species that are both highly exploited and vulnerable are good candidates for precautionary reductions in allowable capture. Species that appear to be less vulnerable could be managed on a stock‐specific basis to prevent over‐exploitation of some species resulting from the use of aggregate catch limits. The framework could be applied to coral reef ornamental fisheries which typically lack landings, catch‐per‐unit‐effort and age‐size data to generate management guidance to reduce overfishing risk. We illustrate the application of this framework to an ornamental fishery in Indonesia.     

Is it good or bad to fish with FADs? What are the real impacts of the use of drifting FADs on pelagic marine ecosystems?

The use of fish aggregating devices (FADs) by purse seine fisheries has come under increasing criticism for its potential deleterious impacts on tuna stocks, for high levels of by‐catch and threats to the biodiversity of tropical pelagic ecosystems. Here, we review the current state of scientific knowledge of this fishing technique and current management strategies. Our intent is to encourage objective discussion of the topic and highlight areas worthy of future research. We show that catching juvenile tuna around FADs does not necessarily result in overfishing of stocks, although more selective fishing techniques would likely help obtain higher yield. Levels of non‐tuna by‐catch are comparable to or less than in other commercial tuna fisheries and are primarily comprised of species that are not considered threatened. Accordingly, to minimize impacts on ecosystem balance, there is merit in considering that all species captured in purse seine fisheries (excluding vulnerable species such as turtles and sharks) should be retained, but the consequences of such a measure should be carefully examined before implementation. The take of vulnerable species could be further reduced by introduction of additional mitigation measures, but their potential benefits would be limited without parallel efforts with other gears. Finally, there is no unequivocal empirical evidence that FADs represent an ‘ecological trap’ that inherently disrupts tuna biology although further research should focus on this issue. We encourage RFMOs to expand and improve their FAD management plans. Under appropriate management regimes, FAD fishing could be an ecologically and economically sensible fishing method.     

闽东渔场底层三重流刺网作业调查分析

底层三重流刺网作业是福建省闽东地区近几年发展起来具有一定代表性的作业。笔者通过调查霞浦县三沙镇189艘流刺网作业船,占全镇总数的89%,分析其经济效益及对渔业资源的利用情况。结果表明,目前闽东的底层三重流刺网已经完全替代了传统的流刺网。该网具的渔获物选择性较强,渔场适应性广,生产水平高,效益好,但由于网目规格偏小,对经济鱼类的幼鱼损害较大,要适度发展该作业则应限制网目使用最小规格,以减少渔业资源损害,保障渔业资源的可持续利用。     

Dynamics of fishing gear allocation by fishers in small-scale coastal fisheries of Pelabuhanratu Bay, Indonesia

Abstract  Fishing gear usage in small-scale coastal fisheries of Pelabuhanratu Bay, Indonesia was explained by two approaches: temporal fishing gear allocation analysis and adaptive responses of fishers to external factors, especially climate and abundance of target species. Gear usage, with the exception of hand lines and seine nets, was more intensive during the dry season than the rainy season. The decision to use seine nets was governed by seasonal variability in the abundance of Auxis thazard , Lacepède, and Trichiurus spp. to the catch. Sustainable management of fishing activities in Pelabuhanratu Bay requires proportional reductions in the use of lift nets and fixed gillnets across the seasons rather than gear specific effort reductions.     

海南岛上岸渔获调查与分析

上岸渔获调查是调查渔业资源的主要方法之一。通过2010年9月至2011年8月监测海南岛主要渔港渔情,统计分析渔获上岸量、渔获组成和作业类型,评估南海渔业资源开发现状并提出建议。结果表明,1）低值幼鱼渔获比例超过40％,经济渔获蓝圆鲹（Decapterusmaruadsi）、带鱼（Trichiurushaumela）、马鲛（Scomber-morus）、眼镜鱼（Menemaculata）、金线鱼（Nemipterus）和头足类（Cephalopoda）的总和不足25％;2）蓝圆骖和带鱼是海南岛上岸渔获的优势种;3）拖网是海南岛近海渔获量最高的作业类型;4）海南岛近海底层渔业资源已严重衰退,远海中上层渔业资源具有巨大开发潜力。建议禁止海南岛近海拖网生产,允许南海休渔期间灯光围网和灯光罩网生产,通过增加远海作业船只的柴油补贴等途径扶持灯光围网和灯光罩网生产,构建“养护近海渔业、开发远海渔业”的新捕捞格局。