Multicriteria estimate of coral reef fishery sustainability

A holistic basis for achieving ecosystem‐based management is needed to counter the continuing degradation of coral reefs. The high variation in recovery rates of fish, corresponding to fisheries yields, and the ecological complexity of coral reefs have challenged efforts to estimate fisheries sustainability. Yet, estimating stable yields can be determined when biomass, recovery, changes in per area yields and ecological change are evaluated together. Long‐term rates of change in yields and fishable biomass‐yield ratios have been the key missing variables for most coral reef assessments. Calibrating a fishery yield model using independently collected fishable biomass and recovery data produced large confidence intervals driven by high variability in biomass recovery rates that precluded accurate or universal yields for coral reefs. To test the model's predictions, I present changes in Kenyan reef fisheries for >20 years. Here, exceeding yields above 6 tonnes km^?2 year^?1 when fishable biomass was ~20 tonnes/km² (~20% of unfished biomass) resulted in a >2.4% annual decline. Therefore, rates of decline fit the mean settings well and model predictions may therefore be used as a benchmark in reefs with mean recovery rates (i.e. r = 0.20–0.25). The mean model settings indicate a maximum sustained yield (MSY) of ~6 tonnes km^?2 year^?1 when fishable biomass was ~50 tonnes/km². Variable reported recovery rates indicate that high sustainable yields will depend greatly on maintaining these rates, which can be reduced if productivity declines and management of stocks and functional diversity are ineffective. A number of ecological state‐yield trade‐off occurs as abrupt ecological changes prior to biomass levels that produce MSY.     

Ecological indicators for coral reef fisheries management

Coral reef fisheries are of great importance both economically and for food security, but many reefs are showing evidence of overfishing, with significant ecosystem‐level consequences for reef condition. In response, ecological indicators have been developed to assess the state of reef fisheries and their broader ecosystem‐level impacts. To date, use of fisheries indicators for coral reefs has been rather piecemeal, with no overarching understanding of their performance with respect to highlighting fishing effects. Here, we provide a review of multispecies fishery‐independent indicators used to evaluate fishing impacts on coral reefs. We investigate the consistency with which indicators highlight fishing effects on coral reefs. We then address questions of statistical power and uncertainty, type of fishing gradient, scale of analysis, the influence of other variables and the need for more work to set reference points for empirical, fisheries‐independent indicators on coral reefs. Our review provides knowledge that will help underpin the assessment of the ecological effects of fishing, offering essential support for the development and implementation of coral reef fisheries management plans.     

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

相似文献   

Effects of cryptic mortality and the hidden costs of using length limits in fishery management

Fishery collapses cause substantial economic and ecological harm, but common management actions often fail to prevent overfishing. Minimum length limits are perhaps the most common fishing regulation used in both commercial and recreational fisheries, but their conservation benefits can be influenced by discard mortality of fish caught and released below the legal length. We constructed a computer model to evaluate how discard mortality could influence the conservation utility of minimum length regulations. We evaluated policy performance across two disparate fish life‐history types: short‐lived high‐productivity (SLHP) and long‐lived low‐productivity (LLLP) species. For the life‐history types, fishing mortality rates and minimum length limits that we examined, length limits alone generally failed to achieve sustainability when discard mortality rate exceeded about 0.2 for SLHP species and 0.05 for LLLP species. At these levels of discard mortality, reductions in overall fishing mortality (e.g. lower fishing effort) were required to prevent recruitment overfishing if fishing mortality was high. Similarly, relatively low discard mortality rates (>0.05) rendered maximum yield unobtainable and caused a substantial shift in the shape of the yield response surfaces. An analysis of fishery efficiency showed that length limits caused the simulated fisheries to be much less efficient, potentially exposing the target species and ecosystem to increased negative effects of the fishing process. Our findings suggest that for overexploited fisheries with moderate‐to‐high discard mortality rates, reductions in fishing mortality will be required to meet management goals. Resource managers should carefully consider impacts of cryptic mortality sources (e.g. discard mortality) on fishery sustainability, especially in recreational fisheries where release rates are high and effort is increasing in many areas of the world.     

Why have global shark and ray landings declined: improved management or overfishing?

Global chondrichthyan (shark, ray, skate and chimaera) landings, reported to the United Nations Food and Agriculture Organization (FAO), peaked in 2003 and in the decade since have declined by almost 20%. In the FAO's 2012 ‘State of the World's Fisheries and Aquaculture’ report, the authors ‘hoped’ the reductions in landings were partially due to management implementation rather than population decline. Here, we tested their hypothesis. Post‐peak chondrichthyan landings trajectories from 126 countries were modelled against seven indirect and direct fishing pressure measures and eleven measures of fisheries management performance, while accounting for ecosystem attributes. We found the recent improvement in international or national fisheries management was not yet strong enough to account for the recent decline in chondrichthyan landings. Instead, the landings declines were more closely related to fishing pressure and ecosystem attribute measures. Countries with the greatest declines had high human coastal population sizes or high shark and ray meat exports such as Pakistan, Sri Lanka and Thailand. While important progress had been made, country‐level fisheries management measures did not yet have the strength or coverage to halt overfishing and avert population declines of chondrichthyans. Increased implementation of legally binding operational fisheries management and species‐specific reporting is urgently required to avoid declines and ensure fisheries sustainability and food security.     

Human‐induced gradients of reef fish declines in the Hawaiian Archipelago viewed through the lens of traditional management boundaries

相似文献   

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.     

Factors influencing the scope and quality of science and management decisions

The lecture traces the historical path to overfishing of the world's fish and shellfish stocks, and provides an assessment of marine fish resources in the later half of the 1990s. The basis of overfishing as noted by various fishery scientists is reviewed. Four factors, including institutional paralysis, the rapidity of technological developments, uncertainty of science, and the inability to monitor and enforce regulations are identified as the major problems leading to overfishing. The failure of the world community to deal with extensive overfishing, appears to have motivated managers and scientists to promote a new fishery management paradigm that focuses on a broader set of problems resulting from fishing, and establishes a more conservative decision‐making process founded on precautionary principle and uncertainty. The author feels that the evolving paradigm will result in the rebuilding of a number of stocks in the United States, but is less certain of its adoption on a global scale, and whether or not science will play a more useful role in fisheries management. It is noted that the support for fisheries science and the status of fisheries have followed opposite courses. Over the past half century marine science has boomed, diversified and become intellectually and materially enriched, while the number of overfished stocks and ecological disasters has increased. Looking ahead it is expected that fisheries management will move into a more conservative era. The focus of fisheries has moved from full use of ocean resources to establishing yields that take into account the impacts of fisheries on target and non‐target species and the ecosystem in general. Although there has been wide‐spread abuse in the use of the world's fishery resources and condemnation of the fishing industries, the author feels that the government institutions must bear the primary responsibility for the historical course of fishery management and its failure.     

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.     

Reconstructing overfishing: Moving beyond Malthus for effective and equitable solutions

Inaccurate or incomplete diagnosis of the root causes of overfishing can lead to misguided and ineffective fisheries policies and programmes. The “Malthusian overfishing narrative” suggests that overfishing is driven by too many fishers chasing too few fish and that fishing effort grows proportionately to human population growth, requiring policy interventions that reduce fisher access, the number of fishers, or the human population. By neglecting other drivers of overfishing that may be more directly related to fishing pressure and provide more tangible policy levers for achieving fisheries sustainability, Malthusian overfishing relegates blame to regions of the world with high population growth rates, while consumers, corporations and political systems responsible for these other mediating drivers remain unexamined. While social–ecological systems literature has provided alternatives to the Malthusian paradigm, its focus on institutions and organized social units often fails to address fundamental issues of power and politics that have inhibited the design and implementation of effective fisheries policy. Here, we apply a political ecology lens to unpack Malthusian overfishing and, relying upon insights derived from the social sciences, reconstruct the narrative incorporating four exemplar mediating drivers: technology and innovation, resource demand and distribution, marginalization and equity, and governance and management. We argue that a more nuanced understanding of such factors will lead to effective and equitable fisheries policies and programmes, by identifying a suite of policy levers designed to address the root causes of overfishing in diverse contexts.     

Checking the pulse of the major commercial fisheries of lake Victoria Kenya,for sustainable management

The present study demonstrates the declining state of the major commercial fisheries of Lake Victoria, Kenya, a situation threatening sustainability of the lake's fishery. Data in the present study were derived from resource monitoring programmes that included hydro‐acoustics (2009–2018), trawl net fishing (2011–2018), frame surveys (2000–2016) and catch assessment surveys (2000–2015). The activities provided information on fish stocks and supported advice for fisheries management. The average fish stock densities for Tanzania, Uganda and Kenya of 8.92, 8.25 and 8.19 t/km², respectively, were relatively similar. Diplomatic and sustainable efforts for harmony in fish harvesting among the fishers of the riparian countries are encouraged given the interdependence of the lake. The Kenyan and River Kagera regions had a higher proportion (≈ 4% each) of big‐sized Nile perch (≥50 cm total length) in 2018, signifying the critical breeding areas for Nile perch. To sustain the fishery, there is need to enforce a 36%–44% effort reduction for all the major fisheries, and enforcement of gear limits to avoid harvesting of immature fish and destruction of the lake ecosystem.     

The barefoot ecologist goes fishing

Haliotid (abalone) fisheries are comprised of small‐scale (<5 km²) stocks and serve as a model for many such fisheries. Extremely valuable to local fishing communities in aggregate, these micro‐stocks are myriad and complex to study, monitor, assess and manage. Micro‐stocks need assessment and management at local scales to prevent small components from suffering the tragedy of commons. This paper asks how can we ever hope to address the research and management needs of so many small resources? Community‐based and territorial rights‐based systems may help in sustaining these resources, but servicing the technical needs of many small communities of stakeholders raises problems. A new generation of ‘barefoot ecologists’ is envisaged to perform this task.     

Coral reef fish communities in management systems with unregulated fishing and small fisheries closures compared with lightly fished reefs – Maldives vs. Kenya

• 1. This study presents a comparison of the benthic cover and fish communities in three widely different management systems: (1) a heavily utilized subsistence fishery (yields >5 Mg km^?2 yr^?1); (2) moderately sized and well enforced fisheries closures (～9% of the nearshore area) surrounded by heavy fishing; and (3) a more lightly used management system (yields <5 Mg km^?2 yr^?1).
• 2. The objective was to compare management systems of small to moderate‐sized closures surrounded by heavy use in Kenya with a large‐scale light‐use management system in the Maldives.
• 3. Gross level attributes of the fish community suggest that the Maldives reefs had higher numbers of individuals (30%) and species (15%) than the Kenyan closures.
• 4. Maldivian reefs had higher abundance of some carnivores such as emperors (Lethrinidae), jacks (Carangidae), triggerfish (Balistidae), and trumpetfishes (Aulostomidae). Half the biomass of fish in the Maldives was, however, composed of surgeonfish (Acanthuridae), which resulted in a higher abundance of herbivores/detritivores than found in Kenyan closures.
• 5. Apex predator species were not a large portion of the biomass (<10%) in any system and, if remote reefs of the Pacific are examples of undisturbed ecosystems, then neither management system has fully protected apex species.

Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Linking the biology and ecology of key herbivorous unicornfish to fisheries management in the Pacific

相似文献   

Ecologically and evolutionarily sustainable fishing of the pikeperch Sander lucioperca: Lake Oulujärvi as an example

Due to the multitude of participants and a diverse range of fishing gear used freshwater fisheries are often managed using minimum size limits (MSL) rather than regulations of total fishing effort. However, a concern has arisen whether attempts to improve ecological sustainability of fisheries by increasing MSLs would induce undesired adaptations to selective fishing. We examined the ecological and evolutionary impacts of varying fishing mortality rates under varying MSLs, with and without stockings, in an age-, size-, and maturity-structured evolutionary model which was parameterized for the Lake Oulujärvi pikeperch, Sander lucioperca. We found that at the current level of harvesting (fishing mortality rate, F = 0.7) and stockings (430 000 year⁻¹), and under the assumption of strongly density-dependent growth, the nation-wide MSL of 370 mm maximizes theoretical biomass yield in a deterministic model but does not prevent severe recruitment overfishing under further increased fishing pressures or stochasticity in recruitment success. The recently imposed, local MSL of 450 mm better ensures stable yields, and even increases them if individual growth is density-independent, but further increase of MSL to 500 mm would already reduce yield especially if there was discard mortality for undersized fish. Given density-dependent growth, equal survival between wild and stocked fish, and sustainable fishing mortality rate, stockings do not increase yield or significantly improve the stability of yields. Evolutionarily stable size at maturation decreases under strong fishing mortality, but increased MSLs reduce the magnitude of this undesired effect. Negatively size-dependent natural mortality was found to have a positive effect on the otherwise negative selection for length-at-age. Increased MSLs also reduce the total selection for decreased length-at-age. Our results support the intentions to increase MSLs in order to improve both ecological and evolutionary sustainability of recreational fisheries.     

Understanding fishing‐induced extinctions in the Amazon

相似文献   

Dependence of recruitment on parent stock of the spiny lobster,Panulirus argus,in Florida

Despite management practices to achieve sustainability, commercial landings for Florida spiny lobster (Panulirus argus) have experienced a drastic decline (57%) since 2000. This is cause for concern not only for economic reasons, but for issues of sustainability. An annual index of P. argus post‐larval (puerulus) abundance, estimated with a generalized linear model with significant mean sea‐level effects, shows a 36% decrease in annual puerulus supply since 1988. In addition, local Florida spawning stock biomass estimated from an age‐structured sequential population analysis decreased 57% since 1988. Puerulus abundance follows a highly correlated (R = 0.76) trend with a 12‐month delayed spawning stock abundance, which supports the contention that the Florida spawning population is a significant contributing factor to post‐larval recruitment in Florida. Residuals about the puerulus on spawning stock abundance function follow closely an interannual North Atlantic Oscillation Index signal. This residual effect is thought of as a secondary regional population effect on Florida puerulus recruitment. The Florida spiny lobster stock is exploited with no fishing mortality controls due to the Pan Caribbean recruitment concept adopted in Florida spiny lobster management. Therefore, the potential of recruitment overfishing exists if fishing mortality controls to protect local spawning stock abundance, such as catch quotas, are not introduced.     

Dynamics of floodplain fisheries in Bangladesh, results of 8 years fisheries monitoring in the Compartmentalization Pilot Project

Floodplain fisheries were monitored from 1992 until 2000 in the Compartmentalization Pilot Project in Tangail, Bangladesh. In permanent floodplains about 165 ± 28 kg ha^?1 of fish was caught annually. For seasonal floodplains, this figure was 83 ± 23 kg ha^?1 yr^?1. The fish catch exhibited a strong seasonal variation, with the highest catch in October, when the floodwater recedes towards the river, and the lowest catch during the dry season in April/May. The annual catch varied with the extent of flooding, with high catches in wet years and low catches in dry years. The extent of flooding was quantified through a Flood Index. Plotting the annual yields against this Flood Index provided a significant relation (P < 0.05), confirming the existence of a flood pulse. The fishing effort (f) and the catch‐per‐unit‐effort (CPUE) were significantly related (P < 0.05), whereby the fishing effort increased with increasing CPUE. The results are discussed within the frame of fisheries management in Bangladesh and highlight the need for long‐term data for proper evaluation of fisheries projects and the development of management schemes, and the difficulty of applying standard surplus production models in floodplain fisheries.     

The political ecology of gear bans in two fisheries: Florida's net ban and Alaska's Salmon wars

Parametric management in fisheries, which describes the management of how, where and when fishing occurs, is often essential for achieving sustainability. Changes to these parameters likely have impacts on stakeholders, however, for example through the costs and allocative consequences of spatial restrictions or gear changes. Here, I discuss two cases where gear bans have been implemented or proposed in response to conservation concerns: the commercial net ban enacted in Florida in 1995 and the failed ban on set gill‐nets in parts of Alaska. The two cases are remarkably similar, although the outcomes were quite different because of the social context of each fishery. Lessons from the Florida ban, which resulted in numerous negative social and ecological impacts, are informative regarding the impacts that likely would have accompanied the Alaska ban, had it proceeded. In both cases, the gear bans have had or were poised to have notable impacts on allocation, but scientific evidence for their necessity was limited. These cases show how ethical considerations can be inseparable from the ecological aspects of managing fisheries, and that when communities grapple with the sustainability of fisheries, they are simultaneously seeking to define the socially acceptable uses of those resources. I suggest a set of questions that can be asked when proposing parametric changes to fisheries, including how those changes will impact social well‐being and community resilience. These are questions that I argue must be addressed if both ethical and sustainable fisheries are the goal.