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1.
Time/area closures have been widely used in fisheries management to prevent overfishing and the destruction of marine biodiversity. To a lesser degree, such spatio‐temporal management measures have been used to reduce by‐catch of finfish or protected species. However, as ecosystem‐based management approaches are employed and more fisheries are managed through multispecies, multiobjective models, the management of by‐catch will likely become increasingly important. The elimination of by‐catch has become a primary goal of the fishing policies of many countries. It is particularly relevant in the United States, as the deadline for setting annual catch limits (ACLs) in all fisheries passes in 2011. This will result in a dramatic expansion of the number of catch and by‐catch quotas. Such catch measures may result in the early closure of otherwise sustainable fisheries when by‐catch quotas are exceeded. To prevent such closures and the consequent economic hardship to fishers and the economy, it is imperative that managers be given the tools necessary to reduce by‐catch and improve fishing selectivity. Targeted spatio‐temporal fishery closures are one solution open to managers. Here, we examine how the spatio‐temporal and oceanographic characteristics of by‐catch may be used by managers to design fishery closures, and place these methods within a decision tree to assist managers to identify appropriate management measures. We argue that the current movement towards marine spatial planning (MSP) presents an important impetus to examine how we manage fisheries spatially, and we offer a first step towards the objective participation of fisheries in the MSP process.  相似文献   

2.
A primary goal of ecosystem‐based fishery management is to reduce non‐target stock impacts, such as incidental harvest, during targeted fisheries. Quantifying incidental harvest has generally incorporated fishery‐dependent catch data, yet such data may be biased by gear non‐retention, observation difficulties, and non‐random harvest patterns that collectively lead to an impartial understanding of non‐target stock capture. To account for such issues and explicitly recognize the combined influence of ecological and harvest factors contributing to incidental capture within targeted fisheries, we demonstrate a probabilistic modelling framework that incorporates: (i) background rates of target and non‐target stock co‐occurrence as the primary ecological basis for incidental harvest; (ii) the probability of harvesting at localities exhibiting co‐occurrences; (iii) the probability of selecting for non‐target species with fishery gear; and, (iv) as a function of harvest effort, the overall probability of incidental capture for any non‐target stock contained in the species pool available for harvest. To illustrate application of the framework, simulation models were based on fishery‐independent data from a freshwater fishery in Ontario, Canada. Harvest simulations of empirical stock data indicated that greatest species‐specific capture values were over 4000 times more likely than for species with lowest values, indicating highly variable capture probabilities because of the combined influence of stock heterogeneity and harvest dynamics. Estimated bycatch–effort relationships will allow forecasting incidental harvest on the basis of effort to evaluate future shifts in fishing activity against specific ecosystem‐based fishery management objectives, such as reducing the overall probability of bycatch while maintaining target landings.  相似文献   

3.
Increasingly, fisheries are being managed under catch quotas that are often further allocated to specific permit holders or sectors. At the same time, serious consideration is being given to the effects of discards on the health of target and non‐target species. Some quota systems have incorporated discard reduction as an objective by counting discards (including unmarketable fish) against the overall quota. The potential effect of the introduction of a quota system that includes accountability for discards on the fishing strategies employed by fishermen is enormous. This is particularly true for multispecies fisheries where healthy and depleted stocks co‐exist; resulting in a trip's catch being applied to very large and very small stock quotas simultaneously. Under such a scenario, fishermen have a strong incentive to minimize (i) catch of low‐quota or ‘choke’ stocks, (ii) regulatory discards due to minimum size limits and (iii) catch partially consumed by predators. ‘Move‐on’ rules (i.e. event‐triggered, targeted, temporary closure of part of a fishery when a catch or bycatch threshold is reached) have been employed in a variety of fisheries. However, their efficacy has been limited by a lack of empirical analyses underpinning the rules. Here, we examine the utility of spatiotemporal autocorrelation analyses to inform ‘move‐on’ rules to assist a sector of the New England Multispecies Fishery to reduce discards and maximize profits. We find the use of empirical move‐on rules could reduce catch of juvenile and choke stocks between 27 and 33%, and depredation events between 41 and 54%.  相似文献   

4.
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.  相似文献   

5.
Managing fisheries using length‐based harvest regulations is common, but such policies often create trade‐offs among conservation (e.g. maintaining natural age‐structure or spawning stock biomass) and fishery objectives (e.g. maximizing yield or harvest numbers). By focusing harvest on the larger (older) fish, minimum‐length limits are thought to maximize biomass yield, but at the potential cost of severe age and size truncation at high fishing mortality. Harvest‐slot‐length limits (harvest slots) restrict harvest to intermediate lengths (ages), which may contribute to maintaining high harvest numbers and a more natural age‐structure. However, an evaluation of minimum‐length limits vs. harvest slots for jointly meeting fisheries and conservation objectives across a range of fish life‐history strategies is currently lacking. We present a general age‐ and size‐structured population model calibrated to several recreationally important fish species. Harvest slots and minimum‐length limits were both effective at compromising between yield, numbers harvested and catch of trophy fish while conserving reproductive biomass. However, harvest slots consistently produced greater numbers of fish harvested and greater catches of trophy fish while conserving reproductive biomass and a more natural population age‐structure. Additionally, harvest slots resulted in less waste in the presence of hooking mortality. Our results held across a range of exploitation rates, life‐history strategies and fisheries objectives. Overall, we found harvest slots to represent a valuable option to meet both conservation and recreational fisheries objectives. Given the ubiquitous benefits of harvest slots across all life histories modelled, rethinking the widespread use of minimum‐length limits is warranted.  相似文献   

6.
Small‐scale fisheries in the southern Gulf of Mexico that catch Rhizoprionodon terraenovae (Richardson) are heterogeneous and data‐poor. Fishery‐dependent monitoring was conducted from 2010 to 2017, including a target season during an aggregation of this species to estimate data‐poor fishery indicators. During the target season, the average sizes for females and males (95.3 and 89.8 cm total length, respectively) were recorded, a global male sex bias (1:1.7), the highest percentage of mature sharks for all years (>89%), the highest values of CPUE (20.1 sharks/day) and size‐selectivity higher than the size at maturity. The spawning potential ratio was over 0.6 (reference point of 0.71) in the combined (target and non‐target) and target seasons for all years, which suggests that the fishery stock is not healthy. Annual assessment of this fishery can be carried out through monitoring during the target season, where management is more feasible to implement.  相似文献   

7.
Marine protected areas (MPAs) are often promoted as tools for biodiversity conservation as well as for fisheries management. Despite increasing evidence of their usefulness, questions remain regarding the optimal design of MPAs, in particular concerning their function as fisheries management tools, for which empirical studies are still lacking. Using 28 data sets from seven MPAs in Southern Europe, we developed a meta‐analytical approach to investigate the effects of protection on adjacent fisheries and asking how these effects are influenced by MPA size and age. Southern European MPAs showed clear effects on the surrounding fisheries, on the ‘catch per unit effort’ (CPUE) of target species, but especially on the CPUE of the marketable catch. These effects depended on the time of protection and on the size of the no‐take area. CPUE of both target species and the marketable catch increased gradually by 2–4% per year over a long time period (at least 30 years). The influence of the size of the no‐take area appeared to be more complex. The catch rates of the entire fishery in and around the MPA were higher when the no‐take areas were smaller. Conversely, catch rates of selected fisheries that were expected to benefit most from protection increased when the no‐take area was larger. Our results emphasize the importance of MPA size on its export functions and suggest that an adequate, often extended, time frame be used for the management and the evaluation of effectiveness of MPAs.  相似文献   

8.
Individual quota (IQ) management systems in commercial marine fisheries are highly diverse, differing in the security, durability and exclusivity of the harvesting privilege and the transferability of quota units. This diversity in the degree of harvest rights may influence the effectiveness of IQ fisheries to meet management objectives. We conducted a global meta‐analysis of 167 stocks managed under IQs to test whether the strength of harvest rights impacts the conservation status of stocks in terms of catch, exploitation rate and biomass relative to management targets. We used non‐parametric methods to assess non‐linear relationships and linear regression models to explicitly consider interactions among predictors. Most IQ fisheries consistently met fleet‐wide quota limits (94% of stocks had recent catches below or within 10% of quotas), but only 2/3 of IQ fisheries adhered to sustainable management targets for biomass and exploitation rate (68% of stocks had exploitation rates below or within 10% of targets and 63% of stocks had biomass above or within 10% of biomass targets). Strikingly, when exclusivity of the harvesting privilege was low, exploitation rates depended on whether IQ implementation was industry‐driven (exploitation below targets) or government‐mandated (exploitation above targets). At high levels of exclusivity, exploitation rates converged to just below management targets. Transferability of quota units was associated with stock biomass closer to and slightly above target levels than stocks with non‐transferable quota. However, regional differences had the strongest effect on biomass, suggesting that other management or biological attributes of regional fishery systems have greater influence on marine populations.  相似文献   

9.
Wasted fishery resources: discarded by-catch in the USA   总被引：1，自引：0，他引：1  
Fishery by‐catch, especially discarded by‐catch, is a serious problem in the world's oceans. Not only are the stocks of discarded species affected, but entire trophic webs and habitats may be disrupted at the ecosystem level. This paper reviews discarding in the marine fisheries of the USA; however, the type, diversity and regulatory mechanisms of the fisheries are similar to developed fisheries and management programmes throughout the world. We have compiled current estimates of discarded by‐catch for each major marine fishery in the USA using estimates from existing literature, both published and unpublished. We did not re‐estimate discards or discard rates from raw data, nor did we include data on protected species (turtles, mammals and birds) and so this study covers discarded by‐catch of finfish and fishable invertebrates. For some fisheries, additional calculations were required to transform number data into weight data, and typically length and weight composition data were used. Specific data for each fishery are referenced in Harrington et al. (Wasted Resources: Bycatch and discards in US Fisheries, Oceana, Washington, DC, 2005). Overall, our compiled estimates are that 1.06 million tonnes of fish were discarded and 3.7 million tonnes of fish were landed in USA marine fisheries in 2002. This amounts to a nationwide discard to landings ratio of 0.28, amongst the highest in the world. Regionally, the southeast had the largest discard to landings ratio (0.59), followed closely by the highly migratory species fisheries (0.52) and the northeast fisheries (0.49). The Alaskan and west coast fisheries had the lowest ratios (0.12 and 0.15 respectively). Shrimp fisheries in the southeast were the major contributors to the high discard rate in that region, with discard ratios of 4.56 (Gulf of Mexico) and 2.95 (South Atlantic). By‐catch and discarding is a major component of the impact of fisheries on marine ecosystems. There have been substantial efforts to reduce by‐catch in some fisheries, but broadly based programmes covering all fisheries are needed within the USA and around the world. In response to international agreements to improve fishery management, by‐catch and discard reduction must become a regular part of fishery management planning.  相似文献   

10.
There is international recognition for greater inclusion of recreational fisheries catch data in species, fisheries and ecosystem assessments. Recreational charter fisheries provide important social services and contribute to total species catches. This study compares and validates industry logbook catch and effort data (1,357 trips) against observer data (154 trips) across six ports in a recreational charter fishery in eastern Australia. The mean numbers of clients and fishing effort (hours) per trip varied inconsistently between data sources and among ports. Logbooks did not adequately report released catches, and the mean number of species retained per trip was consistently underestimated in logbooks compared to observer data. For both data sources, catch rates of total individuals and key species displayed similar trends across different units of effort; catch per hour, client, client/hour and trip. The mean catch rates of total individuals and most key species, except those retained for bait, were similar across data sources, as were estimates of total fleet harvests. The length compositions of retained catches of some key species displayed truncation of larger organisms in the observer data whereas other species did not. Despite the shortcomings of the logbook data, future fishery and species monitoring strategies could include industry and observer data sources.  相似文献   

11.
We conducted a meta‐analysis of literature reporting on the use of circle hooks and J‐hooks in pelagic longline fisheries. Our study included more data than previous meta‐analyses of the effects of hook type, due to both a larger number of relevant studies available in recent years and a more general modelling approach. Data from 42 empirical studies were analysed using a random effects model to compare the effects of circle hooks and J‐hooks on catch rate (43 species) and at‐vessel mortality (31 species) of target and bycatch species. Catch rates with circle hooks were greater for 11 species, including four tuna species, six shark species and one Istiophorid billfish. Catch rates on circle hooks were lower for seven species, including two Istiophorid billfishes and two species of sea turtle. At‐vessel mortality was significantly lower with circle hooks in 12 species, including three tuna species, three Istiophorid billfishes, swordfish (Xiphias gladius) and three shark species. No species had significantly greater at‐vessel mortality when captured with a circle hook rather than a J‐hook. While our general approach increased model variability compared to more detailed studies, results were consistent with trends identified in previous studies that compared the catch rates and at‐vessel mortality (between hook types) for a number of species. Our results suggest that circle hooks can be a promising tool to reduce mortality of some bycatch species in pelagic longline fisheries, although the effects depend on the species and the metric (catch rate or at‐vessel mortality), emphasizing the need for fishery‐specific data in conservation and management decisions.  相似文献   

12.
It is important to consider the potential effectiveness of regulations for reducing total harvest levels when developing fishery management plans. A random forest (RF) modelling approach was used to examine how changing per‐angler harvest or minimum size limit regulations affected sport fishery harvest in US Atlantic coast recreational fisheries. Harvest limits per angler (i.e. bag limits) were typically high initially and subsequently reduced, whereas almost half of minimum length limits were initially below the length‐at‐maturity and subsequently increased. Across most fisheries examined, extreme reductions in harvest limits (e.g. from unlimited to catch‐and‐release) were largely ineffective at limiting total fishery harvest. Increasingly restrictive minimum length limits caused a greater average harvest reduction than per‐angler harvest limits. Some regulation changes were associated with higher angling effort and thus increased harvest, which suggests that when effort cannot be constrained, more direct harvest limitations should be considered.  相似文献   

13.
Guidelines for the assessment and management of developing swordfish fisheries are derived through an examination of five swordfish fisheries. As they develop, swordfish fisheries may be inclined to local depletion around underwater features, such as seamounts and banks. Few nations have applied the precautionary approach in managing their developing swordfish fisheries. Without controls, swordfish fisheries expand geographically and fishing effort increases, often overshooting optimum levels. However, it is difficult to distinguish clear evidence of fishery collapse; modern longliners harvest widely distributed tuna and swordfish and they are able to relocate to distant areas or switch between target species in response to fluctuations in species abundance and price. Furthermore, the wide distribution of swordfish combined with year‐round spawning and high growth rates amongst juveniles probably contribute to the apparent resilience of swordfish stocks to intensive harvesting. Over half the world’s swordfish catch is taken as an incidental catch of longliners fishing for tuna. In several areas, such as the North Atlantic, catch quotas have sometimes caused tuna longline fishers to discard swordfish. Minimum size limits have also resulted in discarding of swordfish in tuna fisheries and in dedicated swordfish fisheries. In addition to weakening the effectiveness of those management measures, bycatch and discarding add to the complexities of managing swordfish fisheries and to uncertainties in assessing the stocks. Longliners that target swordfish often fish at high latitudes where interactions with marine wildlife, such as seabird, are generally more frequent than at low latitudes. Concern over incidental catches of marine wildlife and other species is becoming a driving force in the management of several swordfish fisheries. Fishery management organisations will need to implement management measures to protect non‐target species and gather reliable data and information on the situation by placing observers on boats fishing for swordfish.  相似文献   

14.
Fisheries management based on catch shares – divisions of annual fleet‐wide quotas among individuals or groups – has been strongly supported for their economic benefits, but biological consequences have not been rigorously quantified. We used a global meta‐analysis of 345 stocks to assess whether fisheries under catch shares were more likely to track management targets set for sustainable harvest than fisheries managed only by fleet‐wide quota caps or effort controls. We examined three ratios: catch‐to‐quota, current exploitation rate to target exploitation rate and current biomass to target biomass. For each, we calculated the mean response, variation around the target and the frequency of undesirable outcomes with respect to these targets. Regional effects were stronger than any other explanatory variable we examined. After accounting for region, we found the effects of catch shares primarily on catch‐to‐quota ratios: these ratios were less variable over time than in other fisheries. Over‐exploitation occurred in only 9% of stocks under catch shares compared to 13% of stocks under fleet‐wide quota caps. Additionally, over‐exploitation occurred in 41% of stocks under effort controls, suggesting a substantial benefit of quota caps alone. In contrast, there was no evidence for a response in the biomass of exploited populations because of either fleet‐wide quota caps or individual catch shares. Thus, for many fisheries, management controls improve under catch shares in terms of reduced variation in catch around quota targets, but ecological benefits in terms of increased biomass may not be realized by catch shares alone.  相似文献   

15.
I summarize the total allowable catch (TAC) fishery management system, which forms part of the European Common Fisheries Policy (CFP) as complicated, inaccurate and ineffective. Total allowable effort (TAE), i.e. limits on fishing capacity and days‐at‐sea, provides a simpler, readily enforceable control to protect all species affected by a fishery. Fishing capacity of vessels in each region‐gear fleet could be capped through limits on engine power, gear, crew, and fittings, and/or reducing allowances of days‐at‐sea for large, powerful vessels. Two basic, fishery‐dependent indicators are put forward to assess sustainability of a fishery dependably even in the absence of fishery‐independent data. One is socio‐economic, the other is ecological. Fishery working groups within each marine region would recommend a TAE to sustain their fishery while also protecting the most critically affected species or processes. Regional working groups would supervise a consistent approach across the different fisheries in their region. A pan‐European group would set policy, implement external agreements, set rules for trading TAE if necessary and harmonize fishing opportunities across regions. To ease negotiations on TAEs with the fishing industry when an ecosystem needs to recover, I propose compensation payments funded by re‐direction of existing CFP subsidies that promote fishing.  相似文献   

16.
Overfishing may seriously impact fish populations and ecosystems. Marine protected areas (MPAs) are key tools for biodiversity conservation and fisheries management, yet the fisheries benefits remain debateable. Many MPAs include a fully protected area (FPA), restricting all activities, within a partially protected area (PPA) where potentially sustainable activities are permitted. An effective tool for biodiversity conservation, FPAs, can sustain local fisheries via spillover, that is the outward export of individuals from FPAs. Spillover refers to both: “ecological spillover”: outward net emigration of juveniles, subadults and/or adults from the FPA; and “fishery spillover”: the fraction of ecological spillover that directly benefits fishery yields and revenues through fishable biomass. Yet, how common is spillover remains controversial. We present a meta‐analysis of a unique global database covering 23 FPAs worldwide, using published literature and purposely collected field data, to assess the capacity of FPAs to export biomass and whether this response was mediated by specific FPA features (e.g. size, age) or species characteristics (e.g. mobility, economic value). Results show fish biomass and abundance outside FPAs was higher: (a) in locations close to FPA borders (<200 m) than further away (>200 m); (b) for species with a high commercial value; and (c) in the presence of PPA surrounding the FPA. Spillover was slightly higher in FPAs that were larger and older and for more mobile species. Based on the broadest data set compiled to date on marine species ecological spillover beyond FPAs' borders, our work highlights elements that could guide strategies to enhance local fishery management using MPAs.  相似文献   

17.
An assessment of vulnerability in Alaska groundfish   总被引：1，自引：0，他引：1  
Federal fishery management rules in the United States have recently changed, necessitating an examination of which fish stocks require annual catch limits and how appropriate stock complexes are formed. We used an analytical approach termed productivity-susceptibility analysis (PSA) to analyze the vulnerability of federally managed Alaska groundfish stocks to overfishing. The focus of the effort was non-target stocks that have limited data available for determining stock status and vulnerability. The PSA approach was originally created to assess risks to bycatch in Australian trawl fisheries and compares productivity attributes (e.g. life-history traits) to factors that determine a stock's susceptibility to fishing impacts, producing a combined score indicative of a stock's relative vulnerability to overfishing. We used a form of the PSA developed by a working group from the U.S. National Marine Fisheries Service specifically for use in assessing vulnerability in federally managed fisheries. Alaska groundfish displayed a wide range of vulnerability scores, and this result was mainly due to variability in productivity scores. Susceptibility scores varied less than productivity scores and were centered on an intermediate value. The inclusion of target stocks in the PSA was valuable for assessing the relative vulnerability of the non-target stocks. Sensitivity analyses indicated that PSAs respond differently to changes in attribute scores depending on their initial conditions, and managers should be careful in interpreting changes in PSA results when stocks are re-evaluated.  相似文献   

18.
The UK coastal trap fisheries target two key species, European lobster Homarus gammarus (L.) and brown crab Cancer pagurus L. Their stock status is assessed periodically using size‐based, yield‐per‐recruit analysis. Fishery trends are described using landings and, where available, effort data to estimate catch per unit of effort (CPUE), nominally proportional to abundance. Despite being caught together, assessments assume that concurrent capture of these species does not distort their individual CPUE estimates. Here, an in situ experiment tested impacts of inter‐specific and intra‐specific interactions by pre‐loading baited traps with different species and observing subsequent catches. Pre‐loaded European lobster significantly reduced brown crab catches, whereas, other species produced no such effects. The findings highlight the likely inconsistency of using CPUE as an index of abundance if landings data originate from a mixed‐species fishery in which species interactions and targeting behaviour of fishers are unknown or un‐quantified.  相似文献   

19.
Worldwide, most sea cucumber fisheries are ineffectively managed, leading to declining stocks and potentially eroding the resilience of fisheries. We analyse trends in catches, fishery status, fishing participation and regulatory measures among 77 sea cucumber fisheries through data from recent fishery reports and fishery managers. Critical gaps in fisheries biology knowledge of even commonly targeted species undermine the expected success of management strategies. Most tropical fisheries are small‐scale, older and typified by numerous (>8) species, whereas temperate fisheries are often emerging, mono‐specific and industrialized. Fisher participation data indicated about 3 million sea cucumber fishers worldwide. Fisher participation rates were significantly related to the average annual yield. permanova analysis showed that over‐exploited and depleted fisheries employed different sets of measures than fisheries with healthier stocks, and a non‐metric multidimensional scaling ordination illustrated that a broad set of regulatory measures typified sustainable fisheries. SIMPER and regression tree analyses identified that the dissimilarity was most related to enforcement capacity, number of species harvested, fleet (vessel) controls, limited entry controls and rotational closures. The national Human Development Index was significantly lower in countries with over‐exploited and depleted fisheries. Where possible, managers should limit the number of fishers and vessel size and establish short lists of permissible commercial species in multispecies fisheries. Our findings emphasize an imperative to support the enforcement capacity in low‐income countries, in which risk of biodiversity loss is exceptionally high. Solutions for greater resilience of sea cucumber stocks must be embedded within those for poverty reduction and alternative livelihood options.  相似文献   

20.
根据2014年5月在厦门白哈礁人工鱼礁拟投海域及对照海域开展的本底调查所获的渔业资源资料,对人工鱼礁拟投海域和对照区渔业生物的种类组成、数量分布、优势种和多样性等进行了分析研究。调查共鉴定出渔业生物23种,其中笼壶作业12种,刺网作业20种,渔获种类均以蟹类为主。笼壶作业平均生物量为16.34g/(h·10笼),刺网作业平均生物量为37.00g/(h·片)。综合笼壶作业和刺网作业的调查结果,拟建礁区及周边海域春季渔业资源经济种类少、渔获比重小,生物种类多样性水平低,渔业资源结构总体质量较低。  相似文献   

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