Effects of fish stocking and fishing pressure on fish community structures in French lakes

Fish stocking and regulation of fishing activities are widely implemented by freshwater fisheries authorities who have to protect aquatic communities. The effects of fish management on fish communities have not received sufficient attention. As a result of two datasets, one from EU Water Framework Directive (WFD) monitoring surveys, and one from a French survey targeting angler's associations, this study investigated the impacts of both fishing intensity and fish stocking on fish communities in French lakes. Both co-inertia analysis and community size spectra analysis, showed that: (i) stocking does not contribute to the standing stocks for five of the six most stocked fish species in France; and (ii) neither fishing intensity nor fish stocking lead to a change in the proportion of large and small fish. The results support alternative methods being promoted to enhance native fish populations.     

HIV and AIDS among fisherfolk: a threat to ‘responsible fisheries'?

Fishing communities are often among the highest‐risk groups in countries with high overall rates of HIV/AIDS prevalence. Vulnerability to HIV/AIDS stems from complex, interacting causes that may include the mobility of many fisherfolk, the time fishermen spend away from home, their access to daily cash income in an overall context of poverty and vulnerability, their demographic profile, the ready availability of commercial sex in fishing ports and the subcultures of risk taking and hypermasculinity among some fishermen. The subordinate economic and social position of women in many fishing communities in low‐income countries makes them even more vulnerable. HIV/AIDS in fishing communities was first dealt with as a public health issue, and most projects were conducted by health sector agencies and NGOs, focusing on education and health care provision. More recently, as the social and economic impacts of the epidemic have become evident, wider social service provision and economic support have been added. In the last 3 years, many major fishery development programmes in Africa, South/South‐East Asia and the Asia‐Pacific region have incorporated HIV/AIDS awareness in their planning. The HIV/AIDS pandemic threatens the sustainability of fisheries by eclipsing the futures of many fisherfolk. The burden of illness puts additional stresses on households, preventing them from accumulating assets derived from fishing income. Premature death robs fishing communities of the knowledge gained by experience and reduces incentives for longer‐term and inter‐generational stewardship of resources. Recent projects championing local knowledge and resource‐user participation in management need to take these realities into account. If the fishing communities of developing countries that account for 95% of the world's fisherfolk and supply more than half the world's fish are adversely impacted by HIV/AIDS, then the global supply of fish, particularly to lower‐income consumers, may be jeopardized.     

Identifying historical baseline at the onset of exploitation to improve understanding of fishing impacts

1. Marine communities have long been impacted by human activities, but the quantification of human‐driven changes often relies on recent data. This is because historical data on fish populations are lacking and are challenging to include in contemporary stock and ecological assessments. As a result, the impacts of early fishing pressure on marine communities are generally poorly documented worldwide.
2. Marine communities of Southeast Australia have a relatively short history of exploitation compared with other temperate systems and were sampled before and after the onset of commercial fishing. As such, they provide a rare opportunity to identify historical baselines and to understand ecological changes after the onset of commercial exploitation.
3. This study compares survey data collected around Tasmania, Southeast Australia, in 1909–1910 with data from the 1980s. The period considered precedes the establishment of a trawl fishery in Southeast Australia in 1915, of other important commercial fisheries in Tasmania, and of a fisheries data collection programme in 1984. Nominal catch rates are used to examine changes across all families of demersal fish recorded in catches and generalized linear models are used to estimate and compare standardized indices of abundance between the 1909–1910 and 1980s data for key commercial families.
4. Results show significant, and thus far unreported, fishing‐induced changes in marine communities after the establishment of commercial fishing in the region. Changes mostly relate to shifts in catch composition and steep declines in the abundance of the main commercial families.
5. This study illustrates a method for analysing low‐quality historical catch data and provides estimates of pre‐commercial fishing abundance that can be included in stock and ecological assessments. More broadly, this study demonstrates the significant role of early fishing in shaping marine communities and increases our understanding about general patterns of exploitation that have been difficult to identify with longer but less detailed fishing histories.

     

Response of benthic fauna to experimental bottom fishing: A global meta‐analysis

Bottom‐contact fishing gears are globally the most widespread anthropogenic sources of direct disturbance to the seabed and associated biota. Managing these fishing disturbances requires quantification of gear impacts on biota and the rate of recovery following disturbance. We undertook a systematic review and meta‐analysis of 122 experiments on the effects‐of‐bottom fishing to quantify the removal of benthos in the path of the fishing gear and to estimate rates of recovery following disturbance. A gear pass reduced benthic invertebrate abundance by 26% and species richness by 19%. The effect was strongly gear‐specific, with gears that penetrate deeper into the sediment having a significantly larger impact than those that penetrate less. Sediment composition (% mud and presence of biogenic habitat) and the history of fishing disturbance prior to an experimental fishing event were also important predictors of depletion, with communities in areas that were not previously fished, predominantly muddy or biogenic habitats being more strongly affected by fishing. Sessile and low mobility biota with longer life‐spans such as sponges, soft corals and bivalves took much longer to recover after fishing (>3 year) than mobile biota with shorter life‐spans such as polychaetes and malacostracans (<1 year). This meta‐analysis provides insights into the dynamics of recovery. Our estimates of depletion along with estimates of recovery rates and large‐scale, high‐resolution maps of fishing frequency and habitat will support more rigorous assessment of the environmental impacts of bottom‐contact gears, thus supporting better informed choices in trade‐offs between environmental impacts and fish production.     

Global fishing capacity and fishing effort from 1950 to 2012

Global marine wild‐capture landings have remained relatively stable for >20 years; however, there is a lack of credible fishing capacity and effort information required to assess the sustainability and efficiency of the global fleet. As such, we estimated global fishing capacity and effort from 1950 to 2012 using a relatively comprehensive database developed by the FAO, supplemented by other data sources. Using random sampling techniques, we estimated the uncertainty surrounding many of our estimates enabling the identification of deficiencies and limitations. Global fishing capacity and effort increased rapidly from the late 1970s through to around 2010 before stabilizing. The Asian fleet is more than an order of magnitude larger than any other region in both capacity and effort, and continues to increase. Most other regions have stabilized, and there have been considerable declines in Europe and, to a lesser extent, in North America. Developed nations, as a whole, have decreased in both measures in the recent years and are responsible for the stabilization of the global trend. Developing and undeveloped countries are still increasing with the former having the largest fleet and showing the greatest relative increase with the socioeconomic impacts of reversing these trends likely to be high. The efficiency of the global fleet, in terms of watt days of fishing effort per tonnage of wild marine catch, is now less than in 1950 despite the considerable technological advances, and expansion throughout the world's oceans, that has occurred during this period of time.     

Fish condition as an indicator of stock status: Insights from condition index in a food-limiting environment

Individual performance defines population dynamics. Condition index – a ratio of weight and some function of length – has been louded as an indicator of individual performance and recommended as a tool in fisheries management and conservation. However, insufficient understanding of the correlation between individual-level processes and population-level responses hinders its adoption. To this end, we use composite modelling to link individual's condition, expressed through the condition index, to population-level status. We start by modelling ontogeny of European pilchard (Sardina pilchardus, Clupeidae) as a function of food and constant temperature using Dynamic Energy Budget theory. We then provide a framework to simultaneously track the individual- and population-level statistics by incorporating the dynamic energy budget model into an individual-based model. Lastly, we explore the effects of fishing pressure on the statistics in two constant and food-limited environmental carrying capacity scenarios. Results show that, regardless of the species' environmental carrying capacity, individual condition index will increase with fishing mortality, that is, with reduction of stock size. Same patterns are observed for gilthead seabream (Sparus aurata, Sparidae), a significantly different species. Condition index can, therefore, in food-limited populations, be used to (i) estimate population size relative to carrying capacity and (ii) distinguish overfished from underfished populations. Our findings promote a practical way to operationally incorporate the condition index into fisheries management and marine conservation, thus providing additional use for the commonly collected biometric data. Some real-world applications, however, may require additional research to account for other variables such as fluctuating environmental conditions and individual variability.     

Fishers,dams, and the potential survival of the world's rarest turtle,Rafetus swinhoei,in two river basins in northern Vietnam

1. Next to cetaceans and megafishes, freshwater turtles are the most iconic endangered freshwater species.
2. A detailed questionnaire survey conducted with more than 100 individuals from fishing communities in northern Vietnam was used to investigate the current status of Southeast Asian turtles and provides new hope concerning the survival of Rafetus swinhoei, for which recent official records in the wild are limited to a single individual in Vietnam.
3. The survey included the entire Vietnamese portion of the Da River in Hoa Binh and Son La provinces, as well as the Chu and Ma river system in Thanh Hoa Province, as they are the last sites where the world's rarest and largest Asian softshell turtle has been seen. The questionnaire, conducted in Vietnamese, focused on demographic details, fishing intensity and gear, the status of fishing grounds, and the frequency of interaction with turtles.
4. The great majority of fishers could recognize different turtle species from photographs and describe their preferential breeding habitats; not all knew that they are protected. A few confirmed that more than once each year they still encounter freshwater turtles during their fishing activities.
5. This survey provides detailed information on sites where freshwater turtles are still seen in northern Vietnam and broadens our hope that wild individuals of the extremely rare R. swinhoei may still be present in the remaining riparian wetlands of these biodiverse, dammed, and controlled river basins in North Vietnam.

     

Fishing for biodiversity by balanced harvesting

Fisheries are damaging and seemingly incompatible with the conservation of marine ecosystems. Yet fish are an important source of food and support the lives of many people in coastal communities. This paper considers an idea that a moderate intensity of fishing, appropriately scaled across species, could help in maintaining biodiversity, rather than reducing it. The scaling comes from an intuition that rates of fishing mortality of species should be kept in line with production rates of the species, a notion known as balanced harvesting. This places species conservation and exploitation on an equal footing in a single equation, showing quantitatively the relative levels of fishing mortality that species of different abundance can support. Using a dynamic model of a marine ecosystem, we give numerical evidence showing for the first time that fishing, if scaled in this way, can protect rarer species, while allowing some exploitation of species with greater production. This works because fishing mortality rates, when scaled by production, are density-dependent. Such fishing, operating adaptively to follow species' production rates over time, contains a feedback that would help to protect species from overfishing in the presence of uncertainty about how marine ecosystems work.     

Confidentiality over fishing effort data threatens science and management progress

Understanding the effects of fishing fleets on both target and non‐target species and managing these effects are essential to achieve Good Environmental Status (GES) for marine ecosystems. The use of high resolution fishing effort data in environmental studies has allowed significant scientific progress with respect to the environmental impacts of real fishing fleets and provided a more realistic perspective on the wider ecological consequences of fishing disturbance. A new EU council regulation and its interpretation, aimed at protecting the confidentiality rights of individual fishers, are currently hampering scientific access to this high‐resolution effort data and thus are endangering the provision of management advice based on best available knowledge. This study argues that the withholding of this information will seriously undermine the quality and accuracy of scientific output and ultimately damage fishers' livelihoods through poorly advised management. Furthermore, the council regulation runs contrary to the EU's initiative for greater transparency and its commitment to implement an ecosystem approach to fisheries management and the preservation of ecosystem services. The interpretation of the new EU council regulation by local administrations can thus only be viewed as a significant step back from these aims. Ultimately, while trying to protect fishers' rights it may work to their disadvantage and that of society.     

Fishing operations and adaptive strategies of small‐scale fishers: insights for fisheries management in data‐poor situations

Small‐scale fisheries' management is complex given its multigear, multispecies nature; despite this, fishing effort has usually been controlled by nominal units, ignoring changes in effective fishing effort. This study aimed to understand the adaptive strategies of small‐scale fishers in San Felipe, Yucatan, Mexico through an analysis of their fishing operations. Minor changes in trip numbers among three seasons were observed, but increases in fishing time, depth and travel costs from one season to another at the operational level were found. It was also evident that high value species at the beginning of the season were gradually replaced by low‐value finfish as the season progresses. The results provide insights for new adaptive management strategies according to fisher's adaptive responses. For instance, using boats or fishing trips as fishing effort units in Yucatan may not be the most appropriated unit for management, as fishers adapt their strategies at different levels.     

Understanding fishing‐induced extinctions in the Amazon

相似文献   

Health in fishing communities: A global perspective

In resource‐dependent communities such as fishing communities, human health underpins the ability of individuals and families to maintain viable livelihoods. Fishing is a dangerous occupation, in which fishers are exposed to health risks both on and offshore. Many of these risks and associated health concerns also extend to fishing families and wider communities. Despite the importance of health, there is a lack of understanding of the breadth of health issues affecting people associated with fishing. This study presents the findings of a scoping review of peer‐reviewed literature that identifies the range of health issues and health determinants studied in fishing communities around the world. The findings reveal a wide variety of documented health issues, but with greater emphasis on physical health and occupational and behavioral factors, with limited attention paid to mental health. The majority of studies focused on fishers themselves, as opposed to other subgroups within fishing communities. Geographic differences in the health topics investigated highlight prevalent concerns and offer potential to share insights and solutions across contexts. The breadth of findings illustrates the complexity of health for people dependent on fishing, and the relevance of the many health determinants in maintaining viable fishing communities. We propose that a social well‐being approach offers an integrative lens through which a better understanding of human health in fisheries can be achieved and used to inform fisheries management that is ecologically and socially sustainable.     

Global constraints on rural fishing communities: whose resilience is it anyway?

Sustaining natural resources is regarded as an important component of ecological resilience and commonly assumed to be of similar importance to social and economic vitality for resource‐dependent communities. However, communities may be prevented from benefiting from healthy local resources due to constrained economic or political opportunities. In the case of Alaskan wild salmon, the fisheries are in crisis due to declining economic revenues driven by the proliferation of reliable and increasingly high‐quality products from fish farms around the world. This stands in contrast with many of the world's wild‐capture fisheries where diminished biological abundance has led to fishery collapse. Furthermore, increasing efficiency of salmon farm production, globalization, and dynamic consumer preferences, suggests that the wild salmon industry will continue to be challenged by the adaptability, price and quality of farmed salmon. Conventional responses to reduced revenues by the wild‐capture industry have been to increase economic efficiency through implementing a range of entry entitlement and quota allocation schemes. However, while these mechanisms may improve economic efficiency at a broad scale, they may not benefit local community interests, and in Alaska have precipitated declines in local ownership of the fishery. To be viable, economic efficiency remains a relevant consideration, but in a directionally changing environment (biological, social or economic), communities unable to procure livelihoods from their local resources (through access or value) are likely to seek alternative economic opportunities. The adopted strategies, although logical for communities seeking viability through transformation in a changing world, may not be conducive to resilience of a ‘fishing community’ or the sustainability of their wild fish resources. We use a theoretically grounded systems approach and data from Alaska's Bristol Bay salmon fishery to demonstrate feedbacks between global preferences towards salmon and the trade‐offs inherent when managing for the resilience of wild salmon populations and human communities at different scales.     

Tackling alcoholism and domestic violence in fisheries—A new opportunity to improve well‐being for the most vulnerable people in global fisheries

The UN Sustainable Development Goals (SDGs) principle of “leaving no one behind” focuses global attention on the poorest and most vulnerable people. As different sectors grapple to engage meaningfully with this principle, we posit that greater consideration of social problems in fishing‐dependent communities, such as alcoholism and domestic violence, presents an opportunity for fishery governors to contribute to the SDGs mandate. We further argue that governing marine resources in ignorance of these problems can risk harming some of the most vulnerable people in fisheries. Using subjective well‐being data from women living in two small‐scale fishing communities in India and Sri Lanka, we demonstrate the prevalence and impact of alcoholism and domestic violence in fishing households. We further highlight how policies which restrict access to marine resources can undermine important coping strategies, in particular, the ability of women to act as independent income earners, exacerbating harm to already vulnerable women. A scoping review of the literature reveals that alcoholism and domestic violence are reported in certain fisheries around the world, and we theorize how this may relate to the nature of fishing life and growing stresses regarding the future of fishing. Tackling the burdens of alcoholism and domestic violence in fisheries, where it is an issue, is an opportunity to improve well‐being for men, women and their families. The paper concludes with tangible actions which marine resource governors could adopt to contribute to the “leave no one behind” ethos.     

Floodplain fisheries as natural insurance for the rural poor in tropical forest environments: evidence from Amazonia

Abstract The findings of livelihood research on the role of artisanal fishing among rain forest communities in eastern Peru are reported. In‐depth household surveys conducted in three communities along the Ucayali River (n = 68 households) and four communities on the Marañón River (n = 87) provided data on resource use, income generation, asset holdings and household coping strategies in the face of two common shocks – illness and major floods. Results indicated the high economic importance of artisanal fishing, with considerable specialisation evident in fishing at the household and community levels. When faced with adversity, forest people in the Upper Amazon turn more to the floodplain (to fish) than to the rain forest (to hunt or extract forest products) to cope with major shocks. It appears that floodplain fisheries are an important safety net for forest people living along rivers in humid tropical environments.     

以VIIRS-DNB数据为基础的黄海渔船夜间灯光动态

将VIIRS/DNB卫星遥感夜间灯光图像作为研究渔业船舶动态的数据来源,使用黄海海域2016年间共719幅夜间灯光影像,根据黄海海域特点确定阈值,提取夜间作业船舶的灯光点位信息,结合中韩渔业协定区及黄海海域渔场划分对提取的船舶灯光点进行分析。结果显示,黄海海域夜间渔业灯光分布季节性变化显著,四季的渔船数量呈现秋季春季夏季冬季的态势。识别的灯光点数量韩方一侧水域最多,中方一侧水域次之,中韩协定区水域最少,结合灯光点密度分布图可看出,韩方一侧水域秋季作业强度高、分布范围广,而其他季节作业强度适中,常年有高等级密集区分布在沿岸海域;中方一侧水域春、秋季节作业强度高,夏、冬季节作业强度低,整体分布范围广阔但密集程度较低。在禁渔期,中方一侧水域灯光点数下降比例高达86.9%,且密度图像中的高等级密集区分布情况与黄海传统渔场位置相吻合,因此推断,识别的灯光点多数为渔业活动船只,本研究可以为黄海海域渔业活动监测和研究提供数据支撑。     

长江鱼类体长变化及其对资源变动的指征作用

本研究通过文献调研和野外调查相结合的方式, 对 20世纪 80年代以来部分代表性长江鱼类体长值变化进行了定量分析, 并探究了其变化对资源变动的指征作用。研究结果表明: (1) 对宜昌江段 7 种典型鱼类近 10~40 年体长变化的分析发现, 其种群体长特征值变化与生物学特性密切相关, 资源本底值高、食性广泛、性成熟年龄低且繁殖力强的鱼类在禁渔政策实施后体长增加较快, 反之则增加缓慢或不明显; (2) 对宜昌江段、金沙江、赤水河和洞庭湖 4 处水域近 20~40 年鱼类群落体长特征值的分析表明, 其变动大致可分为下降、波动上升和明显上升 3 个阶段, 与鱼类保护政策实施进程有较好的对应性; (3) 宜昌江段铜鱼和优势种鱼类群落的平均体长与单位捕捞努力量渔获量呈正相关关系(相关系数分别为 0.66 和 0.88), 表明鱼类体长特征值与资源丰度密切相关; (4) 基于 Logistic 曲线对宜昌江段鱼类群落体长特征值的分析预测表明, 2030 年该值将达 1.22, 与 20 世纪 80 年代鱼类群落体长特征值接近, 据此预测该江段鱼类资源在 2030 年可恢复到 20 世纪 80 年代水平。本研究发现天然水域鱼类体长特征值变动与种群、群落健康状况密切相关, 对资源丰度及其变动有较好的指示性作用, 可以作为长江鱼类资源常态化监测的一项重要参考指标。     

Fishing efficiency of competitive largemouth bass tournament anglers has increased since early 21st century

Tournament fishing has risen in popularity over the last half a century. As such, social and financial incentives combined with technological advancements are expected to drive changes in angler's capacity to exploit tournament‐eligible fish stocks, as has been observed in commercial fisheries. The aim of this study was to quantify temporal trends in angler efficiency and their ability to exploit a given fish stock relative to effort in largemouth bass fishing tournaments. A collective analysis across seven Illinois reservoirs comparing change through time in angler catch rates and relative population abundances indicated that angler efficiency has generally improved through time. For the decade from 2005 to 2015, a greater than threefold increase in the efficiency of anglers to exploit a static population of largemouth bass was estimated. Anglers have become more efficient at exploiting populations, which is likely to influence management decisions in the future, particularly in harvest‐orientated fisheries and those reliant upon fishery‐dependent surveys.