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.     

Decreasing but still high: bycatch of seabirds in gillnet fisheries along the German Baltic coast

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Understanding fishing‐induced extinctions in the Amazon

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A breath of fresh air: avoiding anoxia and mortality of freshwater turtles in fyke nets by the use of floats

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Are circle hooks effective management measures in the pelagic longline fishery for sharks in the Gulf of Gabès?

1. This study evaluated the circle hook use as a tool for shark management in the pelagic longline fishery in the Gulf of Gabès.
2. The usual J‐hook No. 2 with 10° offset, which has been traditionally used by the fishery, was compared to the 18/0 non‐offset circle hook in an alternating fashion along the main line. In total, 22 experimental longline sets were deployed through the shark fishing seasons of 2016 and 2017 to examine the effects of hook types on the catch composition, the catch rates, the hooking location, and the status at haulback.
3. The catch composition differed significantly among hook types. Moreover, an overall increase in catch rates for the main species, the sandbar shark Carcharhinus plumbeus, and the shortfin mako shark Isurus oxyrinchus, was observed when using circle hooks.
4. There was no size‐selective effect of circle hooks for the common species. The circle hooks were not effective at reducing at‐haulback mortality of sandbar shark. Conversely, shortfin mako and smooth‐hound shark Mustelus mustelus showed significantly lower relative mortality at haulback with circle hooks than with J‐hooks. Furthermore, circle hooks were more frequently hooked externally than the J‐hooks for the three shark species.
5. Results demonstrated that the use of 18/0 non‐offset circle hooks in the pelagic shark longline fishery can reduce mortality at haulback for some species without any benefit for the dominant species, the sandbar shark.
6. Overall, it is difficult to promote the adoption of the use of circle hooks as a management measure in this specialized fishery. Management measures focusing on fishing effort controls, fishing closures in critical habitats, and size limits could have significant benefits for the conservation of shark species and may help to improve the sustainability of the shark fishery in the Gulf of Gabès.

     

Standardized catch and survival rates,and effect of a ban on shark retention,Palau pelagic longline fishery

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Changes in life history and ecological characteristics of coral reef fish catch composition with increasing fishery management

Abstract Length, life history and ecological characteristics of landed fish communities were studied over a 10‐year period to test theories of fishing disturbance during a time of increased gear and closure management in heavily utilised fisheries. It was predicted that with greater management restrictions: (1) the earliest and fastest responses in the fishery will be seen in those species with faster turnovers, or relatively lower vulnerabilities to fishing; (2) the fishery would transition to a landed catch with higher mean trophic levels, and greater mean body lengths. In addition, the removal of a non‐selective, small‐mesh seine nets should benefit the catch of gears that previously had the greatest species selectivity overlap with the seine net. Many predictions were supported, although maximum lengths and lengths at maturity responded more rapidly than anticipated. The response to eliminating the non‐selective seine net was a more rapid increase in sizes caught by gears with a larger overlap in size (hook and lines) than species selectivity (gill nets). The simultaneous comparison of management systems over time indicates that open‐access fishing grounds can benefit from restrictions imposed in adjacent fishing grounds. The study indicated that multi‐species coral reef fisheries management objectives of maximising yields, as well as maintaining the fish community’s life‐history diversity, require management trade‐offs that balance local socio‐economic and biodiversity needs.     

Eff icacy of angler catch data as a population and conservation monitoring tool for the f lagship Mahseer f ishes (Tor spp.) of Southern India

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Incidental catch of marine turtles by Italian trawlers and longliners in the central Mediterranean

• 1. The fishing effort and turtle catch of vessels harbouring at Lampedusa island and fishing in the wider central Mediterranean area was monitored using a voluntary logbook programme. Two large trawlers were monitored between 2003 and 2005 and six small vessels using trawl nets, pelagic longline or bottom longline were monitored in the summer 2005.
• 2. The observed turtle catch rates of pelagic longline and bottom trawl were among the highest recorded in the basin, and high catch rates by bottom longline were observed too. This suggests that the area contains major oceanic and neritic habitats for the loggerhead turtle Caretta caretta in the Mediterranean Sea.
• 3. When fishing effort is considered, these results suggest a very high number of captures by Italian trawlers and longliners in the area, as well as by fleets from other countries. This is reason of concern for the conservation of the loggerhead turtle within the Mediterranean Sea.
• 4. Different fishing gear have different technical/operational characteristics affecting turtle catch and mortality and the present knowledge about associated parameters of these gear varies too.
• 5. All this considered, specific actions are recommended: (i) an awareness campaign to fishermen to reduce post‐release mortality, (ii) technical modifications to pelagic longline gear to reduce turtle catch, (iii) further investigation into turtle bycatch in all fishing gear, with priority given to bottom longline fishing and quantification of mortality caused by trawlers, (iv) assessment of the turtle populations affected by fishing activity in the area, and (v) international cooperation in undertaking threat assessments, and implementing regulations, management measures and monitoring.

Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

Fishing and trade of devil rays (Mobula spp.) in the Bay of Bengal,Bangladesh: Insights from fishers’ knowledge

1. Devil rays (Mobula spp.) are globally threatened cartilaginous fishes that have attracted global conservation concern owing to their high extinction risk and lack of protection in many countries. Limited resources and data on threatened marine species, including devil rays, impede conservation actions, particularly in developing countries, many of which have high biodiversity.
2. Devil ray catch is a component of artisanal fisheries in Bangladesh, but data on their fisheries and trade are limited. To characterize devil ray fishing practices, fishers’ perception and trade, 230 fishers and traders were interviewed between 4 June 2018 and 22 June 2019, in four areas of south-east Bangladesh. Catch data were also opportunistically collected at landing sites.
3. Six devil ray species were documented, caught in an array of gill nets, set-bag nets and longlines. All interviewed fishers reported life-long devil ray bycatch in some numbers, and also noted a decline in catch over the last decade. Bottom trawling, increased bycatch levels, increased demand for devil ray products and, in some cases, ecosystem changes were identified by fishers as threats to devil ray populations.
4. Unregulated and undocumented trade and retained bycatch, especially by gill nets and set-bag nets, are fuelled by local consumption of devil ray meat and international trade in meat and gill rakers. Compliance with international trade control treaties for all Mobula spp. or the Bangladeshi law protecting Mobula mobular was low, with the majority of fishers (87%, n = 174) unaware of their existence.
5. To manage devil ray fisheries, and prevent possible population declines, we propose a combination of legally enforced gear modifications, and catch and trade control through community-owned implementation strategies. Additionally, we propose the simultaneous implementation of inclusive, community-based awareness and stewardship projects in conjunction with a coast-wide ray monitoring programme. Finally, we emphasize that more research and action rooted in a sustainable fishery model is urgently needed to protect Bangladeshi devil ray populations.

     

Are the exploitation pressures on the Nile perch fisheries resources of Lake Victoria a cause for concern?

Abstract Lake Victoria is one of the African Great Lakes, and an important source of affordable protein food in the form of fish. It provides employment, income, and export earnings to the riparian communities. Despite this importance there are major concerns about the status and exploitation of the fisheries. This study assesses if current extraction rates/yield of Nile perch, Lates niloticus (L.), from Lake Victoria are sustainable for the foreseeable future. The paper reviews trends in catch and effort in the Nile perch fishery and models the expected scenarios using ECOPATH. The fishery exhibits, classic indicators of intensive fishing, erring towards overexploitation, including: (i) decline in total estimated catch of Nile perch in recent years from the peaks in the 1990s. This is coupled with a shift in contribution of catches from higher trophic level species (Nile perch) to lower trophic level (dagaa) species. (ii) Three major trends in the fishing effort are evident: (a) almost doubling of the number of fishers and fishing boats between 1990 and 2000, and the even greater expansion between 2000 and 2002; (b) a large scale increase in the number of gears operational in the lake; and (c) the propensity for use of ‘illegal’ gears. (iii) Catch‐per‐unit‐effort has declined from about 80 to 45 kg per boat day. (iv) Predictive modelling (ECOSIM) of the future of the Nile perch fisheries under a scenario of increased fishing effort suggests that the fisheries are unsustainable and will decline in the long term. It appears that the Nile perch stocks in the three riparian countries are under intense fishing pressure, and unless concerted action is taken, the potential for degradation of the resources is prevalent. In view of the importance of these fisheries, it is recommended that a precautionary approach to further intens‐ification of the fisheries is adopted until such time empirical evidence shows that the fisheries are capable of further expansion and intensification. The main options for management are devolvement of responsibilities for the fisheries to the communities, enforcement of existing regulations, improved monitoring and data collection processes, reducing post‐harvest losses and increasing the value of the products to the export market.     

Incidental capture of Caretta caretta in trammel nets off the western coast of Sardinia (Italy): statistical models of capture abundance and immediate survival

• 1. Trammel nets are one important cause of sea turtle mortality resulting from incidental capture. This study presents findings over a 10‐year period during which loggerhead turtle by‐catch in trammel nets, set off the central west coast of Sardinia (Italy) in the summer months, was recorded by 17 fishing vessels.
• 2. Since the by‐catch registered represented counts of a rare event, data from the 17 vessels were used in the zero‐inflated Poisson (ZIP) model to determine the abundance of turtle by‐catch in trammel nets of the entire fleet, while a binomial generalized linear model was used to assess the probability of immediate survival for sea turtles incidentally caught in this gear.
• 3. The ZIP model quantified in about 45% the probability that 0.6 turtles have been caught by each vessel using trammel nets during summer over the 10‐year period. In addition, the model estimated a total of 916 by‐catch if the entire small‐scale fleet was to use trammel nets in the study area in the summers between 1992 and 2001, with a direct mortality rate of 69%.
• 4. The probability of immediate survival for sea turtles caught in trammel nets seems to be directly related to the size of the specimens caught; however, this relationship is plausible only when incidental capture in the net occurs shortly before gear retrieval.
• 5. The study area represents a region where the abundance of sea turtle by‐catch per vessel in trammel nets was much higher in July and August than in June and could represent a potential hot spot for the presence of juvenile loggerhead turtles, with high levels of interactions between the species and this fishing gear. Further research should better characterize the incidents of by‐catch and assess potential innovative solutions that allow small‐scale fisheries to coexist alongside sea turtles. Copyright © 2010 John Wiley & Sons, Ltd.

     

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

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Understanding fisheries credit systems: potentials and pitfalls of managing catch efficiency

Following implementation in a range of other resource sectors, a number of credit‐like systems have been proposed for fisheries. But confusion exists over what constitutes these nascent ‘fisheries credit’ systems and how they operate. Based on a review of credit systems in other sectors, this study fills this gap by defining how credit systems function and what credits add to prevailing fisheries management. In doing so, we distinguish ‘mitigation’ and ‘behavioural’ fishery credits. Mitigation credits require resource users to compensate for unsustainable catches of target species, by‐catch species or damaging practices on the marine environment by investing in conservation in a biologically equivalent habitat or resource. Behavioural credit systems incentivize fishers to gradually change their fishing behaviour to more sustainable fishing methods by rewarding them with, for instance, extra fishing effort to compensate for less efficient but more sustainable fishing methods. The choice of credit system largely depends on the characteristics of specific fisheries and the management goals agreed upon by managers, scientists and the fishing industry. The study concludes that fisheries credit systems are different but complimentary to other forms of management by focusing on ‘catchability’ or gear efficiency in addition to effort or catch quota, affecting overall economic efficiency by setting specific goals as to how fish are caught. Credit systems therefore incentivize specific management interventions that can directly improve stock sustainability, conserve habitat and endangered species, or decrease by‐catch.     

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.     

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。     

Voluntary angler logbooks reveal long‐term changes in a lentic pike,Esox lucius,population

Sixty‐two years of voluntarily collected angling logbook data from a large natural Danish lake were used to study variation in pike, Esox lucius L., CPUE (catch per unit effort), expressed as no. of captured pike per boat trip, as an index of stock size. Pike CPUE was positively related to pike release rate by anglers and negatively affected by certain commercial fishers. The stocking of young‐of‐the‐year pike and a fishery‐dependent index of perch, Perca fluviatilis L., abundance (which may be pike prey or predator depending on size) did not correlate with pike CPUE. Analyses of the size distribution of pike, based on sizes of annual record trophy pike captured by anglers, confirmed the negative impact of commercial pike fishing and revealed a positive influence of air temperature. It is concluded that high‐quality angler logbooks that record effort and catch can be a cost‐effective tool to inform lake fisheries management by revealing long‐term population trends. Further, state space modelling, a statistical technique not yet seen in recreational fisheries science, is recommended as a tool to model proxies for population dynamics from angler logbook data.     

Impacts of fishing,river flow and connectivity loss on the conservation of a migratory fish population

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