Analysis of bycatch in the South African midwater trawl fishery for horse mackerel Trachurus capensis based on observer data

The South African midwater trawl fishery targets adult horse mackerel Trachurus capensis. The bulk of the catch is taken by a single freezer-trawler, the biggest fishing vessel operating in South African waters. As fishing takes place off the south coast in ecologically sensitive areas, there are concerns about the potential impacts of this fishing operation on non-target species. Fishing behaviour and bycatch of this fishery from 2004 to 2014 were investigated by analysing observer records with regard to catch composition, volume and temporal and spatial patterns. The midwater trawl fishery was estimated to have caught 25 415 tonnes annually, with a bycatch of 6.9% of the total catch, by weight. There are species overlaps with various fisheries, namely the demersal trawl, small-pelagic, line, shark longline and squid fisheries, yet the total bycatch estimates from this fishery are generally small relative to catches taken in the target fisheries. Bycatch species with the highest average annual catches were chub mackerel Scomber japonicus, redeye roundherring Etrumeus whiteheadi, ribbonfish Lepidopus caudatus and hake Merluccius spp. Large-fauna bycatch species included sunfish Mola mola as well as a number of CITES II- and IUCN-listed species, such as Cape fur seal Arctocephalus pusillus, dusky shark Carcharhinus obscurus, smooth hammerhead shark Sphyrna zygaena and thresher sharks Alopias spp. The 97.9% observer coverage is high and the 6.9% bycatch rate low compared to other South African fisheries; however, due to the large size of the individual hauls (average of 46.3 t), the average sampling rate of 1.56% is low. Our analyses suggest that bycatch in the South African midwater trawl fishery has been lower than in other South African fisheries and similar fisheries elsewhere, but due to the combination of high catch volumes and low sampling rates, estimation errors for rare species are high and there is a substantial risk of incidental unmonitored bycatch of rare large fauna and aggregations of small fauna. This could be mitigated by spatio-temporal management of this fishery, to avoid fishing in high-risk areas, and the introduction of an electronic monitoring programme.     

Generating the evidence for marine fisheries policy and management

The uptake of research in marine fisheries management and policy making depends on how effectively fisheries managers, researchers and scientific advisers communicate the needs for evidence, and the results and policy implications of research. The MariFish network of the major European funders of marine fisheries has therefore undertaken a study of current practices relating to communication of research needs and results, identifying strengths and weaknesses, and consequently how two-way communications, and hence the effectiveness of generating evidence for marine fisheries policy making and management, can be improved. Conclusions and recommendations for ‘good practice’ include the importance of building good relationships and trust between researchers and fisheries managers, the need for fisheries ministries to have sufficient inhouse scientific capacity to act as ‘intelligent customers’, and the key role of interpreters of research whose skills and career paths need to be carefully developed.     

Bridges to best management: Effects of a voluntary bycatch avoidance program in a mid-water trawl fishery

The catch of non-target species or discarding of target species (bycatch) in commercial fisheries can result in negative species level and ecosystem wide impacts as well as adverse social and economic effects. Bycatch has become one of the foremost, global issues of fishery managers and conservationists, especially when the non-target species is from a protected or threatened population. However, the impact and spatial distribution of bycatch is frequently unknown making it difficult to develop effective, justifiable mitigation regulations. This challenge is exemplified by the bycatch of river herring (alewife, Alosa pseudoharengus, and blueback herring, A. aestivalis) and American shad (A. sapidissima) in the northwest Atlantic mid-water trawl fishery targeting Atlantic herring (Clupea harengus) and Atlantic mackerel (Scomber scombrus). As an alternative to immediate management action, a voluntary bycatch avoidance program was established through an industry, state government, and university partnership. Here the program is described and its impact is evaluated by comparing fleet behavior and bycatch prior to and during the program. The combined results suggest that consistent communication, facilitated by the avoidance program, positively influenced fishing habits and played a role in the approximately 60% decrease in total bycatch and 20% decrease in the bycatch ratio observed during the program. However, the success of small scale move-along strategies to reduce bycatch ratios varied greatly in different areas of the fishery and years. This suggests the program is best viewed as an intermediate or complimentary solution. Overall, this project exemplifies of how collaborative programs can help alleviate difficult management scenarios.     

War,fish, and foreign fleets: The marine fisheries catches of Sierra Leone 1950–2015

In countries like Sierra Leone, where stock assessments based on fisheries-independent data and complex population models are financially and technically challenging, catch statistics may be used to infer fluctuations in fish stocks where more precise data are not available. However, FAO FishStat, the most widely-used time-series data on global fisheries ‘catches’ (actually ‘landings’), does not account for Illegal, Unreported, and Unregulated (IUU) catches and relies on statistics provided by the national agencies of each member country. As such, reported FishStat data is vulnerable to changes in monitoring capacity, governmental transitions, and budgetary constraints, and may substantially underestimate the measure of extracted marine resources. In this report, Sierra Leone's total catches by all marine fishing sectors were estimated for the period 1950–2015, using a catch reconstruction approach incorporating national data, expert knowledge, and both peer-reviewed and grey literature. Results demonstrate that a substantial amount of marine resource exploitation is not represented in official statistics, and reconstructed catches represent more than 2.25 times the recorded FAO Fishstat values. Notably, foreign fleets take the vast majority of industrial catch in Sierra Leone's EEZ, indicating that most of the resource catch and revenue is diverted to foreign companies and export markets. While foreign actors dominate the industrial sector, the small-scale sector represents the majority of domestic catch. Illegal fishing is also a substantial challenge in Sierra Leone, and extracts a large amount of the country's marine fish resources. Reconstructing catches in Sierra Leone also highlights the impacts of various historical events such as Sierra Leone's civil war and post-war reconstruction on the development of the fisheries sector. The results found in the reconstruction present a large discrepancy from FishStat data, with considerable implications for assessment of stocks and management of Sierra Leone's marine resources.     

Comments on FAO's State of Fisheries and Aquaculture, or ‘SOFIA 2010’

Comments are provided on a few sections of the FAO's 2010 edition of the bi-annual ‘State of the World's Fisheries and Aquaculture’ (SOFIA), i.e., its characterization of the present as a period of ‘stability’, the peculiar role of China's fisheries statistics, the under-reporting of much of the small-scale fisheries catch from developing countries as a key aspect of the deteriorating quality of statistical data submitted to the FAO by member countries, and some other minor topics (but not aquaculture). Overall, this SOFIA report, like its predecessors, provides an excellent starting point for debates about the status of global fisheries, rather than settling them, and a few vignettes are presented, which illustrate this. Moreover, this debate should be broader, e.g., involve more university- and civil society-based researchers, to provide the wide variety of views and analyses required to strengthen FAO in its laudable mission of providing dependable information on the state of global fisheries.     

Ghost fishing in European waters: Impacts and management responses

In this paper we review levels of net loss, what happens to the gear once it has been lost, and the resulting levels of ‘ghost catches’ made in passive net fisheries in the EU. We also consider ghost catches resulting from lost gear in other types of fisheries, and the extent to which the value of ghost catches has been quantified. We consider why fishing gear is lost, and profile common management responses. We present a cost benefit model to assess the relative cost effectiveness of different management measures, and suggest that gear retrieval programmes may provide less value for money than other management responses.     

Few data but many fish: marine small-scale fisheries catches for Mozambique and Tanzania

The fisheries data supplied to the Food and Agriculture Organization of the United Nations (FAO) by national agencies have served as the primary tool for many global and regional studies. However, it is recognised that these data are incomplete and often underestimate actual catches, particularly for small-scale fisheries. This study reconstructed total marine fisheries catches from 1950 to 2005 for Mozambique and the United Republic of Tanzania, by applying an established catch reconstruction approach utilising all available quantitative and qualitative data, combined with assumption-based estimations and interpolations. Since the 1950s, Mozambique has reported primarily industrial catches and has substantially under-reported the country's small-scale fishing sector due to lack of resources and civil war. In Tanzania, Zanzibar's recorded fisheries statistics prior to 2000 are absent from Tanzania's marine fisheries catches reported to FAO, and total mainland catches are at least one-third larger than officially reported. Based on our reconstruction, since 2000, Mozambique caught between 150 000 and 172 000 t y^?1, while the United Republic of Tanzania caught at least 95 000 t y^?1. For the period 1950–2005, reconstructed total marine catches were 6.2 and 1.7 times greater than data supplied to FAO by Mozambique and Tanzania respectively. The reliance on incomplete and substantially under-reported national data puts authorities under serious risk of over-licensing fishing access and mismanaging marine ecosystems and national food security.     

A knowledge base for management of the capital-intensive fishery for small pelagic fish off South Africa

As a contribution to South Africa's move towards an ecosystem approach to fisheries management, this study explores the existence of common perceptions about South Africa's pelagic fishery between resource users and scientists. It represents a collaborative research effort of social and natural scientists. A brief overview is given of the southern Benguela upwelling ecosystem and small pelagic fish resources, the fishery, and management of the fishery. Stakeholder knowledge and views were determined by conducting open-ended qualitative local knowledge interviews. Candidate indicators to address five major issues raised in the interviews were selected: length-at-50% maturity, total mortality, exploitation rate, proportion of bycatch, mean length of catch, and centre of gravity of catches. The indicator approach is shown to be a useful tool to manage the South African small pelagic fishery, and can be made compatible with existing management approaches. The foundation of a good adaptive fisheries management system is a data collection system that enables multi-disciplinary analysis and provides a basis on which decisions can be made.     

Bycatch governance and best practice mitigation technology in global tuna fisheries

Overexploitation of bycatch and target species in marine capture fisheries is the most widespread and direct driver of change and loss of global marine biodiversity. Bycatch in purse seine and pelagic longline tuna fisheries, the two primary gear types for catching tunas, is a primary mortality source of some populations of seabirds, sea turtles, marine mammals and sharks. Bycatch of juvenile tunas and unmarketable species and sizes of other fish in purse seine fisheries, and juvenile swordfish in longline fisheries, contributes to the overexploitation of some stocks, and is an allocation issue. There has been substantial progress in identifying gear technology solutions to seabird and sea turtle bycatch on longlines and to direct dolphin mortality in purse seines. Given sufficient investment, gear technology solutions are probably feasible for the remaining bycatch problems. More comprehensive consideration across species groups is needed to identify conflicts as well as mutual benefits from mitigation methods. Fishery-specific bycatch assessments are necessary to determine the efficacy, economic viability, practicality and safety of alternative mitigation methods. While support for gear technology research and development has generally been strong, political will to achieve broad uptake of best practices has been lacking. The five Regional Fisheries Management Organizations have achieved mixed progress mitigating bycatch. Large gaps remain in both knowledge of ecological risks and governance of bycatch. Most binding conservation and management measures fall short of gear technology best practice. A lack of performance standards, in combination with an inadequate observer coverage for all but large Pacific purse seiners, and incomplete data collection, hinders assessing measures' efficacy. Compliance is probably low due to inadequate surveillance and enforcement. Illegal, unreported and unregulated tuna fishing hampers governance efforts. Replacing consensus-based decision-making and eliminating opt-out provisions would help. Instituting rights-based management measures could elicit improved bycatch mitigation practices. While gradual improvements in an international governance of bycatch can be expected, market-based mechanisms, including retailers and their suppliers working with fisheries to gradually improve practices and governance, promise to be expeditious and effective.     

Emerging fisheries,emerging fishery interactions with sea turtles: A case study of the large-mesh gillnet fishery for flounder in Pamlico Sound,North Carolina,USA

Emerging fisheries and changes in fishery practices are not always readily apparent, nor are their impacts on non-target species such as seabirds, sea turtles, and marine mammals. Data from several different sources led managers to discover high rates of sea turtle bycatch in an inshore large-mesh gillnet fishery in North Carolina, USA, particularly the emerging deep-water gillnet fishery. This paper reviews the history of how increased numbers of observed stranded sea turtles in 1999 led to the discovery that turtles were becoming entangled in the large-mesh gillnet fishery in Pamlico Sound, North Carolina. It also demonstrates how a variety of data sets from fisheries observers, aerial surveys, and fisheries statistics programs contributed to shaping management of the large-mesh gillnet fishery in Pamlico Sound to decrease turtle bycatch and now point towards the need of additional assessment of gillnet bycatch in other parts of North Carolina. Finally, potential approaches are discussed for a more timely detection of future fishery conflicts and development of a plan to reduce otherwise inevitable bycatch and disruptions to fishing effort.     

Fleet communication to abate fisheries bycatch

Fleet communication systems report near real-time observations of bycatch hotspots to enable a fishery to operate as a coordinated “One Fleet” to substantially reduce fleet-wide capture of protected bycatch species. This benefits the bycatch species per se, reduces waste, and can provide economic benefits to industry by reducing risk of exceeding bycatch thresholds and causing future declines in target species catch levels. We describe case studies of fleet communication programs of the US North Atlantic longline swordfish fishery, US North Pacific and Alaska trawl fisheries, and US Alaska demersal longline fisheries, and identify alternative fleet communication program designs to reduce fisheries bycatch. Evidence supports the inference that these three fleet communication programs substantially reduced fisheries bycatch and provided economic benefits that greatly outweighed operational costs. Fleet communication may be appropriate in fisheries where there are strong economic incentives to reduce bycatch, interactions with bycatch species are rare events, adequate onboard observer coverage exists, and for large fleets, vessels are represented by a fishery association.     

Bycatch in the gillnet and beach-seine fisheries in the Western Cape,South Africa,with implications for management

Interview questionnaires and access point surveys were conducted in order to describe and quantify the catch composition of the inshore net-fisheries in the Western Cape, South Africa. A total of 138 562 fish, representing 29 species from 20 families, was recorded in 141 monitored commercial gillnet fishing operations between February 1998 and October 1999. Numerically, the legal target species, harders Liza richardsonii, dominated the catches, contributing 94.87% of the total gillnet catch. Elf, Pomatomus saltatrix, horse mackerel Trachurustrachurus capensis, gurnard Chelidonichthys capensis and barbel Galeichthys feliceps were the most common bycatch species, and contributed 4.2% to the total catch numerically and occurred in 12–47% of the marine 44–64-mm gillnet catches that were monitored. Five species most frequently targeted by shore-anglers on the West Coast: galjoen Dichistius capensis, white stumpnose Rhabdosargus globiceps, hottentot Pachymetopon blochii, silver kob Argyrosomus inodorus and white steenbras Lithognathus lithognathus, also occurred in gillnet catches. Most of the bycatch consisting of immature, undersized fish that were often injured during entanglement and were not released alive. L. richardsonii also numerically dominated the beach-seine hauls that were monitored (>99%) with only four bycatch species being recorded in low numbers. Beach-seine questionnaire respondents, however, reported sporadic catches of at least 17 bycatch species, including occasional appreciable catches of the important linefish species L. lithognathus and A. inodorus.     

Ecological footprint and vulnerability of marine capture fisheries in China

China(herein referred as China’s mainland,and excluding Hong Kong,Macao and Taiwan)ranks as the world’s leading fishing nation,with approximately 11.1 million tons of domestic marine catch acquired in 2017.Marine fisheries resources in China are mainly exploited by its 11 coastal provinces and municipalities,and the development of fishing industry varies among them.However,few studies have examined the exploitation history of the 11 coastal provinces and municipalities.In this paper,we systematically quantified the exploitation history of marine fishery resources in China and then measured the vulnerability of the 11 coastal provinces and municipalities of China to a reduction in marine catches.Our analysis suggested that Chinese marine fisheries experienced rapid growth from the mid-1980 s to the end of the 20 th century,and this rapid increase in marine catches were mainly promoted by increased fishing effort.The total primary production required level amounted to approximately 80%of the average primary productivity in 2017,and Zhejiang,Fujian,Shandong,Hainan and Guangdong provinces were the main fishing provinces in China.By assessing three dimensions of vulnerability(exposure,sensitivity and adaptive capacity)to the impacts of a reduction in marine catches in the 11 coastal provinces and municipalities,we found that Hainan,Guangxi,Zhejiang and Fujian provinces had high or very high vulnerability,while the municipalities of Shanghai and Tianjin had low vulnerability.Identifying suitable adaptation policies and management plans based on the differences in vulnerability among coastal provinces is important in sustainable fisheries management.     

The tower of Babel: Different perceptions and controversies on change and status of North Sea fish stocks in multi-stakeholder settings

Fishermen, scientists, national policy makers, and staff of environmental NGOs (ENGOs) hold different perceptions about temporal patterns in fish stocks. Perception differences are problematic in multi-stakeholder settings, because they elicit controversies and unbalanced disputes. These hinder effective participation, a prerequisite for ‘good governance’ and effective management of sustainable fisheries. This study shows that perceptions of change (‘does the stock increase or decrease?’) and of current status of a fish stock (‘is it doing well or not?’) are influenced by the capturing and processing of information, rather than by interests alone. We focused on the Dutch North Sea fishery on plaice and sole and examined (1) availability and accessibility of information on temporal patterns of these stocks and (2) perception differences between all parties. A first explanation for these differences is the use of different parameters as a measure for stock size. Fishermen focus on catch rates or catch-per-unit-effort (relative stock size), whereas scientists, policy makers, and ENGO-staff mainly use scientific assessments of spawning stock biomass (absolute stock size). Between-group perception differences are further explained by spatial aggregation levels of information, lengths of time series evaluated, and by modes of comparison to qualify the current status of fish stocks. Awareness of information differences and the development of shared information use and processing may release some of the tensions in multi-stakeholder settings debating fisheries management. However, comprehension problems amongst all parties on how spawning stock biomass is reconstructed and how it relates to catch rates in the fishery may pose an enduring barrier.     

Unsuitability of TAC management within an ecosystem approach to fisheries: An ecological perspective

Fisheries management in European waters is gradually moving from a single-species perspective towards a more holistic ecosystem approach to management (EAM), acknowledging the need to take all ecosystem components into account. Prerequisite within an EAM is the need for management processes that directly influence the ecological effects of fishing, such as the mortality of target and non-target species. Up until recently, placing limits on the quantities of fish that can be landed, through the imposition of annual total allowable catches (TACs) for the target species, has been the principal management mechanism employed. However, pressure on non-target components of marine ecosystems is more closely linked to prevailing levels of fishing activity, so only if TACs are closely related to subsequent fishing effort will TAC management serve to control the broader ecosystem impacts of fishing. We show that in the mixed fisheries that characterise the North Sea, the linkage between variation in TAC and the resulting fishing effort is in fact generally weak. Reliance solely on TACs to regulate fishing activity is therefore unlikely to mitigate the impacts of fishing on non-target species. Consequently, we conclude that the relationship between TACs and effort is insufficient for TACs to be used as the principal management tool within an EAM. The implications, and some alternatives, for fisheries management are discussed.     

The justification,design and implementation of Ecological Risk Assessments of the effects of fishing on seabirds

Many marine species are threatened by high levels of incidental mortality in fisheries. This paper reviews the design of selected recent, detailed Ecological Risk Assessments (ERAs) of the effects of fishing on seabirds. Several aspects of ERA methodology for seabirds are still in development, including the most appropriate ways to: predict seabird distribution and fisheries overlap; handle data gaps; compare productivity and susceptibility among species; and incorporate data on bycatch. Nor is there consensus on rules for selecting species or populations for inclusion in assessments, the appropriate spatial and temporal resolution for the analyses, and the definition of risk. Despite these uncertainties, the clear benefits of undertaking quantitative or semi-quantitative ERAs include the identification of particularly vulnerable species or populations and of key areas and seasons in which bycatch may be occurring, and the highlighting of data gaps and priorities for future monitoring. ERAs are likely to be particularly effective where explicit links are established at the outset between the outcomes or conclusions of the ERA and management responses. A precautionary approach to bycatch mitigation can then be embedded in the broader fisheries management framework. However, this requires that the ERA process is not overly complex or is prolonged to the extent that it draws attention away from existing responsibilities and commitments to reduce bycatch per se. When selecting the best approach, it is vital to balance desired outputs against the availability of data for the assessment, and to deal with data gaps in a precautionary manner.     

Extent and implications of IUU catch in Mexico's marine fisheries

It is well recognized that not all fisheries catches are reported or recorded properly by either government or non-government agencies. These unreported catches can be illegal, of unregulated species, or simply not monitored due to logistical barriers. In Mexico, these barriers are an extensive and often not easily accessible coastline, mostly de facto open access fisheries, poor administrative practices and generalized corruption in the fishing sector as a whole. These conditions were likely promoted early in the last century through the government's largely successful policies to increase fisheries catches and stimulate employment and economic growth. Many years later and amid declines in fish stocks and subsequent economic benefits, most notably at local scales, it is evidently time for a fundamental change in strategy away from expansion of fishing effort and toward ecological and economic sustainability. An important step in this endeavor is to provide a quantitative pre-mortem analysis of Mexico's total marine fisheries catches during the last half-century. Results suggest that from 1950 to 2010, total catches were nearly twice as high as the official reports, with an average annual catch of 1.5 million tonnes (t) compared to 796 thousand t in official statistics. In the last year of available data, 2010, official and total estimated catches were 1.5 million and 2.2 million t, respectively. While these results may be perceived as a criticism of the status quo and ante, this study actually does not single out a responsible party, but is, rather, a call to the many sectors of society who contribute to a lack of control, to help overcome these conditions, and increase and sustain the benefits from Mexico's marine fisheries.     

A review of marine mammal,sea turtle and seabird bycatch in USA fisheries and the role of policy in shaping management

This paper reviews the available information (observer programs, estimates, statutes, regulations) for bycatch of marine mammals, sea turtles, and seabirds in fisheries of the United States. Goals of the review were to evaluate the state of knowledge of bycatch and the role of existing protective legislation in shaping bycatch management for different taxa. Pressing issues are identified, as well as knowledge gaps and policy limitations that hinder multi-species bycatch reduction. The USA has made important progress toward reducing bycatch in its fisheries, but the efficacy of its management has been limited somewhat by a focus on taxon- and fishery-specific regulation and the lack of consistent mandate across taxa for taking a cumulative perspective on bycatch. Applying consistent criteria across taxa for setting bycatch limits (e.g., extending the approach used for marine mammals to sea turtles and seabirds) would be the first step in a multi-species approach to bycatch reduction. A population-based multi-species multi-gear approach to bycatch would help identify priority areas where resources are needed most and can be used most effectively.     

过度捕捞造成全球海洋渔业的产量损失评估

Many fish stocks in the world are depleted as a result of overexploitation, which reduces stock productivity and results in loss of potential yields. In this study we analyzed the catch trends and approximate thresholds of sustainable fishing for fished stocks to estimate the potential loss of catch and revenue of global fisheries as a result of overexploitation during the period of 1950–2010 in 14 FAO fishing areas. About 35% of stocks in the global marine ocean have or had suffered from overexploitation at present. The global catch losses amounted to 332.8 million tonnes over 1950–2010, resulting in a direct economic loss of US$298.9 billion(constant 2005 US$).Unsustainable fishing caused substantial potential losses worldwide, especially in the northern hemisphere.Estimated potential losses due to overfishing for different groups of resources showed that the low-value but abundant small-medium pelagics made the largest contribution to the global catch loss, with a weight of 265.0 million tonnes. The geographic expansion of overfishing not only showed serial depletion of world's fishery resources, but also reflected how recent trends towards sustainability can stabilize or reverse catch losses.Reduction of global fishing capacity and changes in fishery management systems are necessary if the long-term sustainability of marine fisheries in the world is to be achieved.