Time-area Closures Research Articles

Using vessel surveillance data to estimate spatiotemporal patterns in the short mackerel purse-seine fishery: Implications for time–area closure management in Thai waters

Mapping fishing effort and fish abundance across management areas is required to adjust and enforce time–area management measures. Seasonal closures are imposed in Thai waters to mitigate the overexploitation of short mackerel (Rastrelliger brachysoma), one of Southeast Asia’s most economically important pelagic species. This study applied machine learning to fishing vessel surveillance data to estimate spatiotemporal distributions of fishing effort and fish abundance in the Gulf of Thailand (GOT) and the Andaman Sea (ADS) to provide reliable and near real-time information to support seasonal closures. Data collected between 2018 and 2020 from Thai purse seiners targeting short mackerel included VMS data, fishing trip records, and landing information. Spatiotemporal patterns in fishing effort and catch per unit effort (CPUE) were then visualized in relation to the closures in different statistical management zones. The results show that fishing effort in the ADS increased in 2020 from 2018 and 2019, and peaked in 2019 in the GOT. No significant spatiotemporal trend in the distribution of CPUE was identified over the 3 years. Notably, the results reveal spatiotemporal adjustments to fishing effort and CPUE following the implementation of seasonal closures. This study is the first to present a practical approach to using vessel surveillance data to examine seasonal patterns in fishing effort and estimated fish distribution in Thai waters. The findings improve our understanding of fishing effort in response to area closures. The information generated here supports the time–area management of an intensively exploited migratory fish species, given timely and accurate information.

Juvenile survival and movements of two threatened oceanic sharks in the North Atlantic Ocean inferred from tag-recovery data.

Understanding population dynamics, movements, and fishing mortality is critical to establish effective shark conservation measures across international boundaries in the ocean. There are few survival and dispersal estimates of juveniles of oceanic shark species in the North Atlantic despite it being one of the most fished regions in the world. Here we provide estimates of dispersal, survival, and proportion of fishing mortality in the North Atlantic for two threatened oceanic sharks: the blue shark (Prionace glauca) and the shortfin mako shark (Isurus oxyrinchus). Our results are based on multi-event models applied to tag-recovery data of 700 blue sharks and 132 shortfin makos tagged over a decade. A total of 60 blue sharks (8.57% of tagged) and 30 makos (22.73%) were recovered by the longline fishery between 2009 and 2017. Tag-reporting rate (percentage of returned information when a tagged shark was caught) was estimated to be high (0.794 ± 0.232 SE). Mean annual survival, as predicted from the models, was higher for blue shark (0.835 ± 0.040 SE) than for shortfin mako (0.618 ± 0.189 SE). Models predicted that fishing caused more than a half of total mortality in the study area for both species (0.576 ± 0.209), and more than a third of tagged individuals dispersed from the study area permanently (0.359 ± 0.073). Our findings, focused mainly on juveniles from oceanic areas, contribute to a better understanding of shark population dynamics in the North Atlantic and highlight the need for further conservation measures for both blue shark and shortfin mako, such as implementing efficient bycatch mitigation measures and static/dynamic time-area closures in the open ocean.

Comparing spatial management tools to protect highly migratory shark species in the Eastern Mediterranean Sea hot spots

Bycatch of non-target species is a pressing problem for ocean management. It is one of the most concerning issues related to human-wildlife interactions and it affects numerous species including sharks, seabirds, sea turtles, and many critically endangered marine mammals. This paper compares different policy tools for ocean closure management around a unique shark aggregation site in Israel's nearshore coastal waters. We provide a set of recommendations based on an optimal management approach that allows humans to enjoy marine recreational activities such as fishing, while maintaining safe conditions for these apex predators which are vital to the local marine ecosystem. To learn more about recreational fishers' derived benefits, we use a benefit transfer method. Our main conclusion is that dynamic time-area closures offer sustainable and effective management strategies. Since these closures are based on near real-time data, they might successfully preserve specific species in limited areas (i.e., small areas).

Emergent interactions in the management of multiple threats to the conservation of harbour porpoises

Human activities at sea are intensifying and diversifying. This is leading to more complex interactions of anthropogenic impacts requiring adaptable management interventions to mitigate their cumulative effects on biodiversity conservation and restoration objectives. Bycatch remains the dominant conservation threat for coastal cetaceans. Additionally, the indirect impact of repeated exposure to disturbances, particularly acoustic disturbances, can affect cetacean population growth and therefore conservation objectives. Pingers are used to ensonify nets to provide an effective mitigation of bycatch risk. As those become more prevalent across fisheries at risk to catch for example harbour porpoises, pingers become contributors to the anthropogenic noise landscape which may affect the vital rates of this species as well. Currently, we do not know how to best balance pinger prevalence to minimise both bycatch rate and the population consequences of acoustic disturbance (PCoD). Here we use an agent-based model to determine how pinger prevalence in nets can be adjusted to minimise bycatch rate and noise disturbance propagating to affect population growth for harbour porpoises. We show that counter-intuitively bycatch rate can increase at lower pinger prevalence. When ecological conditions are such that PCOD can emerge, higher prevalence of pingers can lead to indirect effects on population growth. This would result from condition-mediated decreased reproductive potential. Displacing fishing effort, via time-area closure, can be an effective mitigation strategy in these circumstances. These findings have important implications for current management plans which, for practical consideration, may lead to lower overall pinger prevalence at sea. This study also shows that estimating the reproductive potential of the species should be incorporated in bycatch monitoring programmes. We now need to better understand how physiological condition affect reproductive decisions and behavioural responses to noise in cetaceans to better appraise and estimate the cumulative impacts of bycatch and its mitigations.

Spatio-Temporal Distribution of Juvenile Oceanic Whitetip Shark Incidental Catch in the Western Indian Ocean

Oceanic whitetip shark (Carcharhinus longimanus) is an important top predator in pelagic ecosystems currently classified as globally Critically Endangered by the International Union for the Conservation of Nature. This species is incidentally caught by fisheries targeting highly migratory tunas and billfishes throughout the Indian Ocean. Understanding the temporal, spatial and environmental factors influencing the capture of this species is essential to reduce incidental catches. In this study, we used generalized additive models to analyze the spatio-temporal distributions of the juvenile oceanic whitetip shark catches and the environmental conditions in the western Indian Ocean using observer data from 2010 to 2020 of the European Union and associated flags purse seine fishery. We found sea surface temperature and nitrate concentration to be the most important environmental variables predicting the probability of catching an oceanic whitetip shark. A higher probability of capture was predicted in areas where sea surface temperature was below 24°C and with low nitrate concentrations close to zero and intermediate values (1.5-2.5 mmol.m-3). We also found a higher probability of capture in sets on fish aggregating devices than in sets on free schools of tuna. The Kenya and Somalia basin was identified to have higher probabilities of capture during the summer monsoon (June to September) when upwelling of deep cold waters occurs. We provide the first prediction maps of capture probabilities and insights into the environmental preferences of oceanic whitetip shark in the western Indian Ocean. However, the causal mechanisms behind these insights should be explored in future studies before they can be used to design spatial management and conservation strategies, such as time-area closures, for bycatch avoidance.

Assessing the effectiveness of dFADs fishing moratorium in the Eastern Atlantic Ocean for conservation of juvenile tunas from AOTTP data

Targeting tunas associated with drifting Fish Aggregating Devices (dFADs) raises questions on the sustainability of tropical tuna fisheries. To limit catches of juvenile tunas, multiple time-area dFADs-fishing moratoria have been implemented by ICCAT since 1998. In this study we assessed the effectiveness of two different dFADs time-area closures implemented for the protection of both bigeye and yellowfin tuna juveniles. Using Atlantic Ocean Tunas Tagging Program (AOTTP) data from 2016 to 2019, we estimated the relative risk for individuals tagged inside the moratorium strata to be recaptured inside in comparison to the recapture rate outside the spatio-temporal strata. AOTTP releases were not homogeneously distributed in terms of areas and school type, therefore to assess the effect of the moratorium without potential bias a matching procedure was used to rebalance the release areas. As a result of the matching procedure and subsequent filtering applied to the dataset, the number of bigeyes recaptures retained inside and outside the time-area closure were below the threshold from which any conclusion could be drawn. In contrast, our results show that a majority of yellowfin and skipjack tunas tagged within the closed area stayed within the closed area during the moratorium period. Consequently, the last moratorium can be considered as effective for these two species, at least during the months of fishing ban on dFADs.

Using movement models and systematic conservation planning to inform marine protected area design for a multi-species predator community

Marine protected areas (MPAs) are increasingly applied to regulate fishing and conserve marine biodiversity. Yet, MPAs are often designed without sufficient ecological knowledge of the species they are intended to protect. This is particularly relevant to large and wide-ranging marine predators including many elasmobranchs (sharks and rays), for which region-specific space-use information is limited. Further, uncertainty remains in how to integrate movement datasets with systematic conservation planning frameworks to meet explicit conservation objectives. We addressed these knowledge gaps by combining movement models, constructed from passive acoustic telemetry data for eight elasmobranch species, and systematic conservation planning to investigate the design and adequacy of MPAs in Bimini, The Bahamas. Currently, there is a proposal for a no-take MPA in North Bimini (NBMPA), although it is unclear how this MPA would benefit elasmobranch communities if or when implemented. Our results show that although the NBMPA would contribute to elasmobranch conservation, the supplementation with an additional MPA southwest of Bimini would be necessary to protect important habitats for multiple elasmobranch species. This southwestern area was highlighted as a conservation priority area of both permanent MPA designs as well as seasonal time-area closures, regardless of NBMPA implementation status and conservation targets considered in this study. Our integrative approach also demonstrates its ability to optimize MPA designs for marine predator communities, combining multi-species movement models, constructed from acoustic telemetry datasets that include space-use estimates over multiple years, with MPA optimization tools.

Investigating Spinner Dolphin (Stenella longirostris) Occurrence and Acoustic Activity in the Maui Nui Region

Hawaiian spinner dolphins (Stenella longirostris) rest during the day in the islands’ coastal waters where they are susceptible to human disturbance. Due to concerns over the negative impacts of human activity, the Pacific Islands Regional Office of the National Oceanic and Atmospheric Administration (NOAA) has proposed a 50-yard approach rule for spinner dolphins and is also considering time-area closures of certain important spinner dolphin resting areas. However, gaps still persist in the understanding of how spinner dolphin populations on different Hawaiian Islands use coastal waters, raising questions about the efficacy of the proposed rules. To better understand how spinner dolphins use the waters in the Maui Nui region (Maui, Moloka‘i, Lāna‘i, and the ‘Au‘au channel), a study was conducted using a combination of passive acoustic monitoring and vessel surveys to document spinner dolphin occurrence and movements. Bottom-moored acoustic recorders were deployed at eight locations in Maui Nui, and at one previously established resting bay off west O‘ahu for comparison. The amount of whistles, clicks, and burst pulses at each location was quantified and averaged by the hour of the day. Acoustic activity was greater at the O‘ahu site than at any of the Maui Nui sites, and was greatest between sunrise and noon. Acoustic activity and vessel surveys both reveal that spinner dolphins occur and exhibit resting behaviors in the ‘Au‘au channel between Maui and Lāna‘i, and also along west Maui and southeast Lāna‘i. Spinner dolphins resting in a channel between islands appears to be unique to Maui Nui and differs from resting patterns described along Hawai‘i Island and O‘ahu. Because spinner dolphins appear to use both the coastlines and the channel to rest in Maui Nui, the 50-yard approach rule appears to be a more suitable management option for the region than time-area closures.

Horizontal and vertical movements of immature dusky sharks Carcharhinus obscurus in relation to commercial longline fisheries in the western North Atlantic Ocean

BackgroundMany species of sharks, including the dusky shark Carcharhinus obscurus, are often incidentally captured in commercial pelagic and bottom longline fisheries. Incidental capture can lead to at-vessel or post-release mortality and can be detrimental to populations of threatened, endangered, or prohibited species. The estimated at-vessel mortality for dusky sharks can be high in longline fisheries and, to minimize mortality, time–area closures have been designated in the western North Atlantic Ocean to mitigate interactions with longline fisheries, yet incidental capture of dusky sharks is still common. We compared the vertical and horizontal movements of dusky sharks to the overall fishing effort and depth fished of commercial pelagic and bottom longline fisheries to determine when and where overlap is present that could lead to incidental capture.ResultsTwenty-one (n = 21) dusky sharks were tagged with pop-up archival transmitting satellite tags and all were immature animals (123–200 cm FL) apart from two individuals (230 and 300 cm FL). Sharks were tagged off the coasts of North Carolina (71%) and Florida (29%). Twenty tags (95%) reported and provided tracks between 1 and 107 days (median 15 days) and 10 tags (50%) remained on sharks for > 4 days. Most individuals remained within the bottom longline closed area off the coast of North Carolina during their time at liberty. Dusky sharks primarily occupied the 20–40 m depth range 26% of the time, and overlapped with bottom and pelagic longline gears 41% and 59% of the time, respectively. Overlap was highest in the winter and spring for both commercial fisheries.ConclusionsThe use of archival satellite telemetry in this study has provided valuable preliminary information on vertical and horizontal movements of immature dusky sharks in western North Atlantic Ocean. Dusky sharks may be more vulnerable to incidental capture in the pelagic longline fishery due to the high fishing effort, larger areas of horizontal overlap, and greater percentage of vertical overlap. This information will inform mitigation measures of commercial longline fisheries, which can work toward population rebuilding of the species.

Effects of time-area closures on the distribution of snow crab fishing effort with respect to entanglement threat to North Atlantic right whales

AbstractTime-area closures are increasingly used to mitigate cetacean entanglement by temporarily excluding fishing effort from areas where high densities of cetaceans and fishing overlap. The effort displaced by these closures can be redistributed to the areas that remain open, changing the distribution and density of fishing effort outside the closures. These patterns were evaluated for the southern Gulf of St. Lawrence snow crab fishery by comparing recent years (2015–2017) with 2018 when time-area closures were implemented to protect North Atlantic right whales. A predictive model framework was created to test how well we could predict the response of fishers to closures. Approximately 29% of the total fishing effort was displaced by the 2018 closures, increasing effort density outside the closures by 41%. Displaced fishing effort shifted farther from the closures than predicted, into areas which, prior to 2018, had low effort density, producing a higher threat of entanglement in these new areas. Fishing effort in 2018 remained as high as 2017, despite a lower quota and reduced trap limit. Consequently, the resulting effects of time-area closures on fishing patterns outside of the closures cannot be discounted if entanglement threat to whales is to be successfully mitigated.

Comparing Dynamic and Static Time-Area Closures for Bycatch Mitigation: A Management Strategy Evaluation of a Swordfish Fishery

Time-area closures are a valuable tool for mitigating fisheries bycatch. There is increasing recognition that dynamic closures, which have boundaries that vary across space and time, can be more effective than static closures at protecting mobile species in dynamic environments. We created a management strategy evaluation to compare static and dynamic closures in a simulated fishery based on the California drift gillnet swordfish fishery, with closures aimed at reducing bycatch of leatherback turtles. We tested eight operating models that varied swordfish and leatherback distributions, and within each evaluated the performance of three static and five dynamic closure strategies. We repeated this under 20 and 50% simulated observer coverage to alter the data available for closure creation. We found that static closures can be effective for reducing bycatch of species with more geographically associated distributions, but to avoid redistributing bycatch the static areas closed should be based on potential (not just observed) bycatch. Only dynamic closures were effective at reducing bycatch for more dynamic leatherback distributions, and they generally reduced bycatch risk more than they reduced target catch. Dynamic closures were less likely to redistribute fishing into rarely fished areas, by leaving open pockets of lower risk habitat, but these closures were often fragmented which would create practical challenges for fishers and managers and require a mobile fleet. Given our simulation’s catch rates, 20% observer coverage was sufficient to create useful closures and increasing coverage to 50% added only minor improvement in closure performance. Even strict static or dynamic closures reduced leatherback bycatch by only 30–50% per season, because the simulated leatherback distributions were broad and open areas contained considerable bycatch risk. Perfect knowledge of the leatherback distribution provided an additional 5–15% bycatch reduction over a dynamic closure with realistic predictive accuracy. This moderate level of bycatch reduction highlights the limitations of redistributing fishing effort to reduce bycatch of broadly distributed and rarely encountered species, and indicates that, for these species, spatial management may work best when used with other bycatch mitigation approaches. We recommend future research explores methods for considering model uncertainty in the spatial and temporal resolution of dynamic closures.

Evaluating socio-economic and conservation impacts of management: A case study of time-area closures on Georges Bank.

Globally, economies and marine ecosystems are increasingly dependent on sustainable fisheries management (SFM) to balance social, economic, and conservation needs. The overarching objectives of SFM are to maximize both conservation and socio-economic benefits, while minimizing short-term socio-economic costs. A number of tools have been developed to achieve SFM objectives, ranging from fishery specific to ecosystem-based strategies. Closures are a common SFM tool used to balance the trade-off between socio-economic and conservation considerations; they vary in scope from small-scale temporary closures to large-scale permanent networks. Unfortunately, closures are frequently implemented without a plan for monitoring or assessing whether SFM objectives are met. In situations in which a monitoring plan is not in place we propose that commonly available fishery data can often be used to evaluate whether management tools are effective in meeting SFM objectives. Here, we present a case study of closures on Georges Bank that shows how fishery data can be analyzed to perform such an assessment. Since 2006, on the Canadian side of Georges Bank, seasonal scallop fishery closures have been implemented with the aim of reducing by-catch of Atlantic cod (Gadus morhua) and yellowtail flounder (Pleuronectes ferruginea) during spawning. In lieu of data from a dedicated monitoring program, we analyzed data from Vessel Monitoring Systems (VMS), fishery logbooks, and a scallop survey to assess the impact of these closures on the scallop fishery, and use observer data (i.e. by-catch) to assess the effectiveness of these closures in meeting their conservation objective. While compliance for these time-area closures was high, the closures did not significantly displace fishing activity and overall there was limited evidence of an impact on the scallop fishery. Further, the discard rates for both cod and yellowtail were above average when their respective closures were active. These results suggest that improvements to the closures design and/or other measures may be required to achieve the desired SFM objectives.

Beyond static spatial management: Scientific and legal considerations for dynamic management in the high seas

Natural and human stressors in the high seas act across a wide range of spatial and temporal scales. These include direct interaction such as fisheries bycatch or indirect interaction like warming oceans and plastic ingestion. Area-based management tools (ABMTs), such as marine protected areas and time-area closures, are a widely accepted and a broadly successful form of management used to mitigate localized human impacts on marine species and ecosystems. Protection provides an opportunity for population recovery, which can then propagate outside of the closure. As the United Nations negotiates a new treaty on the conservation and sustainable use of biodiversity beyond national jurisdiction, efforts to design and implement high seas ABMTs at appropriate scales are critical to ensure that these spatial protection measures are most effective and climate-ready in the face of changing oceans. Here we identify the four most important temporal scales – contemporary, intra-annual, multi-annual and multidecadal – for aligning high seas ABMTs to relevant ecological, oceanographic and atmospheric processes. From this, we explore how managers and decision-makers can integrate this knowledge when implementing a new treaty.

Population ecology and the management of whale watching operations on a data-deficient dolphin population.

Whale watching is a popular commercial activity, producing socio‐ecological benefits but also potential long‐term effects on the targeted cetacean population. This industry is currently developing in data‐deficient contexts in a largely unregulated fashion. Management schemes should adopt precaution and be informed by the relevant literature, but would be more effective if the assessment of the target population vulnerability, biological impacts, and management implications was drawn from site‐specific data.This paper focuses on a reef‐associated, data‐deficient population of spinner dolphins in the Egyptian Red Sea. In Satayah Reef, new information on population size and dynamic parameters were documented using visual observation and photo‐identification‐based capture–recapture methods (Cormack–Jolly–Seber time‐since‐marking model).Dolphins occurred on 98% of the survey days. Average school size was 66 individuals (±42.1 SE), with most groups including calves. The population was equally divided into recurrent and transient individuals. An “emigration + mortality” model best described residence at the site. Five recurrent males (5% of the Satayah population) provided connectivity between this and the geographically close population of Samadai Reef.Average annual survival probability was 0.83 (±0.06 SE) in the year following first capture and 0.99 (±0.06 SE) for recurrent individuals. Mean yearly population sizes ranged 143–207 individuals.The study had the power to detect a 30% decline in the population, but not the rate of change in abundance estimated from the data (r = 0.018 ± 0.04), which would have required a 3‐ to 5‐times longer study. Synthesis and application: These findings advance the assessment of the Satayah population's intrinsic vulnerability and have three major management applications: (a) the delineation of management units; (b) the identification of key indicators for future impact monitoring and assessment; and (c) realistic estimates of the statistical power for trend detection. Based on our results, we recommend supporting future research, devising site‐specific time–area closure plans, and integrating them in a regional scheme. Approaches employed in this case study can inform the management of whale watching industries targeting other data‐deficient populations.

Using individual-based movement information to identify spatial conservation priorities for mobile species.

The optimal design of reserve networks and fisheries closures depends on species occurrence information and knowledge of how anthropogenic impacts interact with the species concerned. However, challenges in surveying mobile and cryptic species over adequate spatial and temporal scales can mask the importance of particular habitats, leading to uncertainty about which areas to protect to optimize conservation efforts. We investigated how telemetry-derived locations can help guide the scale and timing of fisheries closures with the aim of reducing threatened species bycatch. Forty juvenile speartooth sharks (Glyphis glyphis) were monitored over 22 months with implanted acoustic transmitters and an array of hydrophone receivers. Using the decision-support tool Marxan, we formulated a permanent fisheries closure that prioritized areas used more frequently by tagged sharks and considered areas perceived as having high value to fisheries. To explore how the size of the permanent closure compared with an alternative set of time-area closures (i.e., where different areas were closed to fishing at different times of year), we used a cluster analysis to group months that had similar arrangements of selected planning units (informed by shark movements during that month) into 2 time-area closures. Sharks were consistent in their timing and direction of migratory movements, but the number of tagged sharks made a big difference in the placement of the permanent closure; 30 individuals were needed to capture behavioral heterogeneity. The dry-season (May-January) and wet-season (February-April) time-area closures opened 20% and 25% more planning units to fishing, respectively, compared with the permanent closure with boundaries fixed in space and time. Our results show that telemetry has the potential to inform and improve spatial management of mobile species and that the temporal component of tracking data can be incorporated into prioritizations to reduce possible impacts of spatial closures on established fisheries.

Reproductive philopatry in a coastal shark drives age-related population structure

The cosmopolitan lamniform shark Carcharias taurus (commonly known as the ragged-tooth, grey nurse or sand tiger shark) is threatened by overexploitation in parts of its range. Return migrations of females to specific nursery areas suggest that females exhibit reproductive philopatry, a behaviour that over time might lead to genetically isolated subpopulations over various spatial scales. To investigate genetic evidence for reproductive philopatry, genetic data from mitochondrial and microsatellite markers were generated for 104 young-of-the-year and juvenile sharks. Comparing the smallest versus the largest young sharks revealed a pattern of size-related differentiation between nurseries that was only found in the smaller size class. This not only confirms reproductive philopatry of their mothers, but is also in line with previous observations of larger juvenile sharks increasing their migration range and moving between sites. Our results highlight the need to target young-of-the-year sharks when investigating reproductive philopatry to exclude roaming individuals that obscure size-related signals of genetic differentiation. Given the species’ high susceptibility to overexploitation, the evidence for reproductive philopatry is of direct importance to the management and conservation of C. taurus worldwide. As many nursery areas as possible should be protected to ensure that the number of locally resident juveniles and the pool of the returning females remain stable in the long term. This may warrant protected areas, or time-area closures, prohibiting exploitation in the nursery areas during pupping season.

Fisheries management in the face of uncertainty: Designing time-area closures that are effective under multiple spatial patterns of fishing effort displacement in an estuarine gill net fishery.

A commonly cited reason for the failure of time-area closures to achieve fisheries management goals is the displacement of fishing effort from inside the closure into the surrounding area still open to fishing. Designing time-area closures that are predicted to achieve management goals under multiple spatial patterns of effort redistribution will increase chances of success. Using data from an estuarine gill net fishery, we tested if there are time-area closures predicted to reduce bycatch of two protected species groups while maintaining target catch under four simulated effort redistribution patterns. We found that the pattern of effort redistribution had a substantial impact on the amount of predicted bycatch in each closure scenario. Multiple closures were predicted to reduce bycatch of these species under all four simulations of effort redistribution. However, some combinations of closure and effort redistribution pattern resulted in estimated bycatch being higher than without a closure. We did not find any time-area closures that resulted in a predicted reduction in bycatch while maintaining target catch at original levels. We demonstrate a simple way for fisheries managers to account for the uncertainty in fishers' behavior by designing time-area closures that are predicted to reduce bycatch under multiple potential patterns of spatial redistribution of fishing effort.

Behavioural responses of spinner dolphins to human interactions.

There is increasing evidence that whale and dolphin watching activities have detrimental effects on targeted cetacean populations. In Egypt, spinner dolphins regularly occur in the resting areas of Samadai, Satayah and Qubbat'Isa reefs. In-water human interactions with dolphins are regulated with a time-area closure system at Samadai, unregulated at Satayah and non-existent at Qubbat'Isa. This provided an ideal experimental setting to advance our understanding of the effects of tourism on a species highly sensitive to disturbances. Our study confirmed that the intensity and duration of interactions, and therefore, dolphin exposure to tourism, differed among the study sites. Compared with the Qubbat'Isa control site, behavioural reactions to boats and swimmers at the two tourism sites suggested that dolphin rest was disrupted, especially around the middle of the day and especially at Satayah, where dolphin tourism is unregulated. Our results indicate also that the dolphin protection measures at Samadai reduce the level of disturbance. We recommend that similar measures be implemented at other dolphin tourism locations, and that no new operations be initiated until the long-term impacts on dolphin populations are better understood. Our experience emphasizes the need to adopt precautionary approaches in research and management of whale and dolphin watching.

Effects of variation in the abundance and distribution of prey on the foraging success of central place foragers

Summary Seabirds and pinnipeds are vulnerable to reductions in prey availability, especially during the breeding season when spatial constraints limit their adaptive capacity. There are growing concerns about the effects of fisheries on prey availability in regions where large commercial fisheries target forage fish. For breeding seabirds and pinnipeds, prey availability depends on a combination of abundance, accessibility, patchiness and distance from the colony. An understanding of the aspects of prey availability that determine foraging success is essential for the design of effective management responses. We used a mechanistic individual‐based foraging model based on observed data for two seabird species, the Peruvian Booby Sula variegata and Guanay Cormorant Phalacrocorax bougainvilliorum, to simulate the foraging patterns of seabirds feeding on schooling fish. We ran the model over simulated prey fields representing eight possible combinations of high or low prey abundance, shallow or deep prey, and broadly distributed or spatially concentrated prey. The results highlight the importance of the accessibility of prey. Depth distribution was the primary factor determining modelled foraging success for both species, followed by abundance, and then spatial configuration. Synthesis and applications. The individual‐based foraging model provides a spatially explicit framework for assessing the effects of fisheries on the foraging success of seabirds and other central place foragers, and for evaluating the potential effectiveness of marine‐protected areas and other fisheries management strategies for safeguarding central place foragers in dynamic ecosystems. Our analysis indicates that broad‐scale fisheries management strategies that maintain forage fish above critical biomass levels are essential, but may need to be supplemented by targeted actions, such as time–area closures, when environmental conditions lead to low prey abundance or reduce prey accessibility for seabirds or pinnipeds of conservation concern. The individual‐based foraging model is adaptable and could be reconfigured for application to other species and systems.

Dynamic ocean management increases the efficiency and efficacy of fisheries management

In response to the inherent dynamic nature of the oceans and continuing difficulty in managing ecosystem impacts of fisheries, interest in the concept of dynamic ocean management, or real-time management of ocean resources, has accelerated in the last several years. However, scientists have yet to quantitatively assess the efficiency of dynamic management over static management. Of particular interest is how scale influences effectiveness, both in terms of how it reflects underlying ecological processes and how this relates to potential efficiency gains. Here, we address the empirical evidence gap and further the ecological theory underpinning dynamic management. We illustrate, through the simulation of closures across a range of spatiotemporal scales, that dynamic ocean management can address previously intractable problems at scales associated with coactive and social patterns (e.g., competition, predation, niche partitioning, parasitism, and social aggregations). Furthermore, it can significantly improve the efficiency of management: as the resolution of the closures used increases (i.e., as the closures become more targeted), the percentage of target catch forgone or displaced decreases, the reduction ratio (bycatch/catch) increases, and the total time-area required to achieve the desired bycatch reduction decreases. In the scenario examined, coarser scale management measures (annual time-area closures and monthly full-fishery closures) would displace up to four to five times the target catch and require 100-200 times more square kilometer-days of closure than dynamic measures (grid-based closures and move-on rules). To achieve similar reductions in juvenile bycatch, the fishery would forgo or displace between USD 15-52 million in landings using a static approach over a dynamic management approach.