Time series indicators are widely used in ecosystem-based management. A suite of indicators is typically calculated for a static region or multiple subregions and presented in an ecosystem assessment (EA). These are used to guide management decisions or determine environmental status. Yet, few studies have examined how the spatial scale of an EA influences indicator behavior. We explore this question using the Northwest Atlantic continental shelf ecosystem (USA). We systematically divided the ecosystem at six spatial scales (31 unique units), covering spatial extents from 250,000 km2 to 20,000 km2. The same 22 indicators were calculated for each unit, assessed for trends, and evaluated as 31 independent EAs. We found that the detected signals of indicator trends depended on the spatial scale at which the ecosystem was defined. A single EA for the whole region differed by 23% (in terms of the 22 indicator trend tests) relative to ones for spatially nested 120,000 km2 subunits, and by up to 36% for EAs at smaller scales. Indicator trend disagreement occurred because (most common) a localized trend was perceived as widespread, (common) a local trend was obscured by aggregating data over a large region, or (least common) a local trend switched direction when examined at a broader scale. Yet, there was variation among indicators in their scale sensitivity related to trophic level. Indicators of temperature, chlorophyll-a, and zooplankton were spatially coherent: trends portrayed were similar regardless of scale. Mid-trophic level indicators (fish and invertebrates) showed more spatial variation in trends. We also compared trend magnitude and indicator values to spatial extent and found relationships consistent with scaling theory. Indicators at broad scales produced subdued trends and values relative to indicators developed at smaller spatial scales, which often portrayed ‘hotspots’ of local abundance or strong trend. Our results imply that subsequent uses of indicators (e.g., determining environmental status, risk assessments, management decisions) are also sensitive to ecosystem delineation and scale. We suggest that indicators and EAs should be done at multiple spatial scales and complimented with spatially explicit analysis to reflect the hierarchical structure of ecosystems. One scale is not best, but rather we gain a new level of understanding at each scale examined that can contribute to management decisions in a multiscale governance framework characterized by goals and objectives with relevance at different scales.
Hydropower plays a key role in maintaining grid reliability, but there is uncertainty regarding the ecological implications of using hydropower to balance variability from high penetration of intermittent renewable resources, such as solar and wind. Hydropower can offer advantages at the macro-ecological level (e.g., reduced greenhouse gas emissions), however it may have significant environmental impact on a local level (e.g., increased risk to fish species during migration and breeding periods). Using the New England region as a case study, we use an electricity model to estimate how hydropower operation changes as offshore wind capacity increases at a system level. We then tie alterations in hydropower energy production to local impacts on riverine ecosystems and the lifecycle of migratory fish. We find that increasing offshore wind capacity from 1600 to 10,000 MW more than doubles the average hourly hydropower ramping need and the associated river flowrate during April. This increased flowrate aligns with the migration timing of the lone endangered fish species on the Connecticut River, the shortnose sturgeon. Alternatively, the majority of months in which hydropower operation is most strongly impacted by the addition of offshore wind capacity do not coincide with key fish lifecycle events. Other sustainability benefits, including reduced air pollution and water consumption, can be achieved through deployments of offshore wind. Our results suggest that in order to balance global (i.e., CO2 mitigation) and local (i.e., fish migration) environmental issues, a portfolio of solutions is needed to address grid integration of renewables.
Sustainable tourism involves increasingly attracting visitors while preserving the natural capital of a destination for future generations. To foster tourism while protecting sensitive environments, coastal managers, tourism operators, and other decision-makers benefit from information about where tourists go and which aspects of the natural and built environment draw them to particular locations. Yet this information is often lacking at management-relevant scales and in remote places. We tested and applied methods using social media as data on tourism in The Bahamas. We found that visitation, as measured by numbers of geolocated photographs, is well correlated with counts of visitors from entrance surveys for islands and parks. Using this relationship, we predicted nearly 4 K visitor-days to the network of Bahamian marine protected areas annually, with visitation varying more than 20-fold between the most and least visited parks. Next, to understand spatial patterns of tourism for sustainable development, we combined social media-based data with entrance surveys for Andros, the largest island in The Bahamas. We estimated that tourists spend 125 K visitor-nights and more than US$45 M in the most highly visited district, five times that of the least visited district. We also found that tourists prefer accessible, natural landscapes—such as reefs near lodges—that can be reached by air, roads, and ferries. The results of our study are being used to inform development and conservation decisions, such as where to invest in infrastructure for visitor access and accommodation, siting new marine protected areas, and management of established protected areas. Our work provides an important example of how to leverage social media as a source of data to inform strategies that encourage tourism, while conserving the environments that draw visitors to a destination in the first place.
Sublittoral rocky reef habitats host important ecological communities in UK waters, but their ecological condition is difficult to monitor. Monitoring methods based on seabed imagery data are prone to inconsistencies in both the identification and enumeration of species, which is a major hurdle in detecting meaningful ecological change. To overcome this problem, our study used a single monitoring dataset, collected using one standard method at the Pisces Reef Marine Protected Area (MPA) in 2016. We identified which method of data extraction from seabed imagery is best able to detect change along a gradient of anthropogenic resuspended sediments, which represents a pressure on the epifaunal community. We modelled the spatial distribution of the pressure, caused by nearby fishing activity, using an approach based on individual Vessel Monitoring System (VMS) ping data, rather than spatially homogenised data aggregated to a grid cell. We found that up to 22% of the biological variability across the three reef areas within the MPA is explained by the measured and derived environmental variables. The response of the epibenthic community at Pisces Reef MPA to the resuspended sediments pressure gradient is masked by commonly used univariate metrics such as species diversity and abundance of individuals. Conversely, a Threshold Indicator Taxa Analysis (TITAN) identifies community-level change caused by a low level of modelled resuspended sediments pressure. We found that a 0.05 decimal degree grid cell of seabed within 1 km of the MPA boundary, swept by demersal fishing gear as little as five times per year on average, can elicit such a community response. The data extraction metric best able to detect this change in the sublittoral rock community is the frequency of occurrence of taxa in images with an average field of view of 0.7 m2, using a 25-cell grid. More traditional metrics extracted from seabed imagery, such as raw counts and percentage cover estimates, are less sensitive to detecting such community change. The TITAN also identified taxon-level responses to the pressure gradient that could be considered for future monitoring programmes. The solitary coral genus Caryophyllia and cup-like sponges show a sharp and strong negative response to pressure exposure, and could represent a starting point for a future monitoring programme of UK sublittoral rock habitats. The implications for future monitoring are discussed, including survey design, environmental and biological data collection and improved pressure modelling.
In this study, the effects of sea ice and wind speed on the timing and composition of phytoplankton spring bloom in the central and southern Baltic Sea are investigated by a hydrodynamic–biogeochemical model and observational data. The modelling experiment compared the results of a reference run in the presence of sea ice with those of a run in the absence of sea ice, which confirmed that ecological conditions differed significantly for both the scenarios. It has been found that diatoms dominate the phytoplankton biomass in the absence of sea ice, whereas dinoflagellates dominate the biomass in the presence of thin sea ice. The study concludes that under moderate ice conditions (representing the last few decades), dinoflagellates dominate the spring bloom phytoplankton biomass in the Baltic Sea, whereas diatoms will be dominant in the future as a result of climate change i.e. in the absence of sea ice.
Climate change is already affecting the distributions of marine fish, and future change is expected to have a particularly large impact on small islands that are reliant on the sea for much of their income. This study aims to develop an understanding of how climate change may affect the distribution of commercially important tuna in the waters around the United Kingdom’s Overseas Territories in the South Atlantic. The future suitable habitat of southern bluefin, albacore, bigeye, yellowfin and skipjack tunas were modelled under two future climate change scenarios. Of all the tunas, the waters of Tristan da Cunha are the most suitable for southern bluefin, and overall, the environmental conditions will remain so in the future. Tristan da Cunha is not projected to become more suitable for any of the other tuna species in the future. For the other tuna species, Ascension Island and Saint Helena will become more suitable in the future, particularly so for skipjack tuna around Ascension Island, as the temperature and salinity conditions change in these areas. Large marine protected areas have been designated around the territories, with those in Ascension and Tristan da Cunha closed to tuna fishing. Although these areas are small relative to the whole Atlantic, these model projections could be useful in understanding whether this protection will benefit tuna populations into the future, particularly where there is high site fidelity.
In many parts of the world, particularly remote and underdeveloped regions, reports of fisheries catch, effort, and landing data are limited. In order to implement effective fishing regulations to protect natural stocks, understanding fishing pressure, key target species, catch composition, and value of each species is vital. In regions where published data is limited, and the sampling of numerous small boats and landing sites is not feasible, fish market surveys represent an opportunity to obtain key fisheries data. This study therefore aims to obtain species-specific prices and market composition for fish landed in the central Red Sea by surveying local fish markets. We conducted 11 surveys at two major Red Sea fish markets to ascertain key fisheries metrics using market data as a proxy for catch data. Results indicate that a high proportion of the market composition is generated by 46 species from six family-level groups, Serranidae, Labridae, scarine labrids, Carangidae, Lethrinidae, and Lutjanidae, contributing to 87 % of the total market biomass. Species-specific values ranged from 4.50 USD/kg to 26.44 USD/kg, with market surveys highlighting the economic value of three local serranid species: Plectropomus pessuliferus marisrubri, Plectropomus areolatus and Variola louti, all valued at more than 25 USD/kg, and a labrid: Cheilinus undulatus, valued at 26.44 USD/kg. The Serranidae family represents 47 % of the total biomass and 55 % of the potential revenue in the market, while also indicating potentially overfished reefs due to the high occurrence of smaller species and undersized individuals of higher priced serranid species. Many of the high-valued serranids were below the size at sexual maturity. Target species exhibited small body size and decreasing abundance, potentially indicating a “shrinking baseline” scenario occurring in the Saudi Arabian artisanal coral reef fishery. These results indicate that introducing effective fisheries legislation and management is necessary for the longevity and sustainability of the reef-based fishery in the Saudi Arabian Red Sea. Implementing catch quotas, size limits, and seasonal restrictions are potential mechanisms that could be used to facilitate positive change within this vulnerable fishery.
Artificial Reefs (AR) show a wide diversity and vary in their construction materials, shape and purpose, as illustrated by the present analysis of 127 scientific papers. AR have been deployed for different purposes, including fisheries improvement, ecological restoration of marine habitats, coastal protection or purely scientific research. Statistical analyses using 67 variables allow us to characterize the design, objectives and monitoring strategies used for AR. An effectiveness indicator comprised of three categories (low, moderate and high) was adapted from previous studies and applied to the present dataset in terms of the objectives defined in each scientific paper. The effectiveness of various monitoring approaches was investigated and recommendations were formulated regarding environmental parameters and the assessment of ecological processes as a function of AR type. These analyses showed that inert materials like concrete associated with biomimetic designs increase the benefits of reefs to the local environment. This study also compared effectiveness between the different economic, ecological or scientific objectives of AR projects and reveals that fisheries projects showed the highest efficiencies but points out the weakness of environmental assessments for this type of project. In conclusion, the analyses presented here highlight the need to use a panel of complementary monitoring techniques, independently of the initial purpose of the artificial structures, to properly assess the impact of such structures on the local environment. It is recommended to adopt approaches that associate structural and functional ecology. An improved characterization of the role of AR should be integrated into future assessments, taking into account the complex framework of ecosystem structure and trophic relationships.
Sea turtle scute abnormalities are observed in higher proportion in hatchlings compared to adults, suggesting that hatchlings with a non-modal scute pattern (NMSP) have a lower chance of surviving to adulthood. In this study, we collected 732 newly emerged hatchlings from Redang Island, Malaysia, and compared their scute classification, size, and mass to fitness correlates (self-righting ability, crawling speed, and swimming speed). We investigated the proportion of hatchlings from each nest with NMSP to determine if there was a correlation with incubation duration or clutch relocation. We found relocated clutches at Chagar Hutang Turtle Sanctuary had a significantly shorter incubation duration with a higher proportion of NMSP compared to in situ clutches. Hatchlings’ mass were significantly heavier from in situ clutches compared to relocated clutches, although there were no significant differences of hatchling speed based on scute classification or clutch type. The difference of hatchling mass between in situ and relocated clutches could affect predation and mortality rates on recently emerged hatchlings. These findings have important conservation implications, suggesting that relocation should only be implemented on clutches with a high potential to be disrupted or with a low chance of survival if left in situ. Our findings highlight the need for a standard procedure when clutch relocation is used as a conservation strategy. Relocation should replicate natural nest dimensions by duplicating both nest width and depth, and clutches should be relocated to similar shade conditions as the natural nest.
The human ingestion of mercury (Hg) from sea food is of big concern worldwide due to adverse health effects, and more specifically if shark consumption constitutes a regular part of the human diet. In this study, the total mercury (THg) concentration in muscle tissue were determined in six sympatric shark species found in a fishing vessel seized in the Galapagos Marine Reserve in 2017. The THg concentrations in shark muscle samples (n = 73) varied from 0.73 mg kg-1 in bigeye thresher sharks (Alopias superciliosus) to 8.29 mg kg-1 in silky sharks (Carcharhinus falciformis). A typical pattern of Hg bioaccumulation was observed for all shark species, with significant correlation between THg concentration and shark size for bigeye thresher sharks, pelagic thresher sharks (Alopias pelagicus) and silky sharks. Regarding human health concerns, the THg mean concentration exceeded the maximum weekly intake fish serving in all the studied species. Mass-Dependent Fractionation (MDF, δ202Hg values) and Mass-Independent Fractionation (MIF, Δ199Hg values) of Hg in whitetip sharks (Carcharhinus longimanus) and silky sharks, ranged from 0.70‰ to 1.08‰, and from 1.97‰ to 2.89‰, respectively. These high values suggest that both species are feeding in the epipelagic zone (i.e. upper 200 m of the water column). While, blue sharks (Prionace glauca), scalloped hammerhead sharks (Shyrna lewini) and thresher sharks were characterized by lower Δ199Hg and δ202Hg values, indicating that these species may focus their foraging behavior on prey of mesopelagic zone (i.e. between 200 and 1000 m depth). In conclusion, the determination of THg concentration provides straight-forward evidence of the human health risks associated with shark consumption, while mercury isotopic compositions constitute a powerful tool to trace the foraging strategies of these marine predators.
A double approach combining Hg concentrations with stable isotopes ratios allowed to assess ontogeny in common shark species in the area of the Galapagos Marine Reserve and the human health risks concern associated to their consumption.
Given the current natural and anthropogenic threats facing Qatar's marine environment and the consequential expected decline in ecosystem services, this paper examines the potential application of the Ecosystem Services-EBM framework developed by Granek et al. (2010) to sustainably manage Qatar's coral reef and seagrass bed ecosystems. Using interviews with stakeholders and field-collected data from sixteen coral reef sites and 6 seagrass meadows as well as secondary data, the paper presents new knowledge regarding the status of these ecosystems and the benefits they provide that are most valued by stakeholders. The research identifies existing and missing ecological and socio-economic data, as well as the processes and management strategies required to implement the five-step framework within a Qatari context. Key goals for implementing EBM identified by stakeholders include: adoption of scientific planning and valuation of marine environment, contextualizing and drafting legislation, regulations and policies in support of EBM; monitoring and enforcement of laws; and, promotion of public awareness and engagement. The article concludes with recommendations for filling remaining data gaps and highlights opportunities available to Qatar to become a leader in implementing EBM. These include maximizing the increasing role that stakeholders can play in mitigating further decline of the country's coastal ecosystems and leveraging mega events planned in Qatar, such as FIFA World Cup 2022.
We develop a methodology to derive a global medium resolution (250 m) land mask from several existing data sources. In particular, a number of improved land mask data sets have been developed from satellite measurements recently, though some artifacts and omissions still remain. We show how combining global land mask data from multiple independent data sources can decrease the frequency of artifacts, and improve the data consistency and quality. We use the ocean color product imagery derived from measurements of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) to evaluate and validate the new global land mask implemented in the Multi-Sensor Level-1 to Level-2 (MSL12) ocean color data processing system, and demonstrate the improvements in the derived global ocean color data coverage. Results show that when using the new proposed land mask the accuracy of global ocean color data coverage is significantly improved over coastal and inland waters. The new land mask more accurately represents the current global land coverage status, providing more complete and consistent global land/water coverage data set for ocean color remote sensing and for various other satellite Earth observing applications.
Humans have been exploiting marine resources along the Levantine coast for millennia. Advances in biomolecular archaeology present novel opportunities to understand the exploitation of these taxa in antiquity. We discuss the potential insights generated by applying collagen peptide fingerprinting, ancient DNA analysis, and stable isotope analysis to groupers (Serranidae) and sea turtles (Chelonia mydas and Caretta caretta) in the Levant. When combined with traditional zooarchaeological techniques, biomolecular archaeology offers utility to further investigate human impacts on marine ecosystems.
Coastal zone management is a pressing matter, especially in developing countries, which are highly vulnerable to the effects of climate change. Human systems are underrepresented in the vast array of indicators aimed at assisting coastal zone management decisions. Clearly, there is room to better capture natural and human system relationships and interactions in coastal area assessments. A case in point is the well-known Coastal Hazard Wheel (CHW). Hence three main objectives guide this paper: (i) Analysing the existing set of indicator themes and categories in coastal areas; (ii) Contrasting this set of indicators with the perceived needs of local coastal stakeholders from a developing country; and (iii) Proposing indicator categories to be included as part of a systemic coastal zone management framework. To this end, we undertook an automated content analysis of 1116 peer-reviewed articles on the subject matter. The analysis and a stringent set of criteria led to 40 articles that were reviewed to identify suitable indicators. In parallel, field research in Ghana allowed for a set of indicators from the quadruple helix stakeholders operating in coastal zones to be elicited. Contrasting the two sets of indicators resulted in three situations. The first involves 14 indicator categories that co-occur in the literature and the detected needs from local coastal stakeholders. In the second situation, the categories mentioned in the literature were those not mentioned at local level. A third situation appeared when the local coastal stakeholders mentioned categories of indicators that were not identified in the reviewed literature. After examining each case, we advocate for the indicators in the first situation to be incorporated into the current coastal indicator monitoring frameworks (for example by upgrading the CHW). The unique contribution of this paper is the combination of literature and stakeholder-based indicator sub-categories that should be added to the current set of coastal monitoring frameworks.
Marine heatwaves (MHWs) are prolonged extreme oceanic warm water events. Globally, the frequency and intensity of MHWs have been increasing in recent years, and it is expected that this trend is reflected in the Kerguelen Plateau region. MHWs can negatively impact the structure of marine biodiversity, marine ecosystems, and commercial fisheries. Considering that the KP is a hot-spot for marine biodiversity, characterizing MHWs and their drivers for this region is important, but has not been performed. Here, we characterize MHWs in the KP region between January 1994 and December 2016 using a combination of remotely sensed observations and output from a publicly available model hindcast simulation. We describe a strong MHW event that starts during the 2011/2012 austral summer and persists through winter, dissipating in late 2012. During the winter months, the anomalous temperature signal deepens from the surface to a depth of at least 150 m. We show that downwelling-favorable winds occur in the region during these months. At the end of 2012, as the MHW dissipates, upwelling-favorable winds prevail. We also show that the ocean temperature on the KP is significantly correlated with key modes of climate variability. Over the KP, temperature at both the ocean surface and at a depth of 150 m correlates significantly with the Indian Ocean Dipole. To the south of the KP, temperature variations are significantly correlated with the El Niño Southern Oscillation, and to both the north and south of the KP, with the Southern Annular Mode. These results suggest there may be potential predictability in ocean temperatures, and their extremes, in the KP region. Strong MHWs, like the event in 2012, may be detrimental to the unique ecosystem of this region, including economically relevant species, such as the Patagonian Toothfish.
Chile is the second largest global producer of farmed salmon. The growth of salmon production has not been free of environmental challenges, such as the increasing use of pesticides to control the parasitic load of the sea lice Caligus rogercresseyi. The lack of the specificity of pesticides can potentially affect non-target organisms, as well as the structure and functioning of aquatic ecosystems. The aim of this study, was to understand the effect of pesticides on natural microbial communities to the addition of the anti-lice pesticide azamethiphos, deltamethrin and emamectin benzoate, and their potential impact in ammonium uptake rates in the coast off central-southern Chile and Northern Patagonia. The addition of pesticides on natural microbial communities resulted in a rapid response in ammonium uptake, which was significant for the single use of pesticide, azamethiphos and emamectin benzoate, as well as the combination, azamethiphos, deltamethrin and emamectin benzoate. In northern Patagonia, azamethiphos addition produced a 53% decrease in photoautotrophic uptake. However, an increase, although variable, was observed in chemoautotrophic uptake. Emamectin benzoate produced a 36 to 77% decrease in chemo and photoautotrophic ammonium uptake, respectively. The combined use of pesticides, also produced up to 42% decrease in both photo and chemoautotrophic assimilation. We conclude that the use of pesticides in salmon farming produces diverse responses at the microbial level, stimulating and/or inhibiting microbial communities with subsequent impact on nitrogen budgets. Further studies are necessary to understand the impact of pesticides in the ecology of central-southern and northern Patagonia, Chile.
The recent establishment of the “landing obligation” under the reformed EU Common Fishery Policy has the twofold objective of reducing the excessive practice of discarding unwanted catch at sea and encouraging more selective and sustainable fisheries. Within this context, the awareness of the spatial distribution of potential unwanted catches is important for devising management measures aimed to decrease discards. This study analyzed the distribution of Hot Spot density areas of demersal fish and crustaceans below the Minimum Conservation Reference Size (MCRS) in four different southern European seas: continental Portuguese coast, Catalan Sea, South of Sicily, Liguria and northern Tyrrhenian Seas using both bottom trawl survey data and information on the spatial distribution of commercial fisheries. Critical areas for discarding were identified as zones where the highest densities of individuals below MCRS were consistently recorded throughout a series of years. Results clearly showed a patchy distribution of undersized individuals in each investigated area, highlighting the overlap between high density patches of both discards and fishing effort. The present findings provide a relevant knowledge for supporting the application of spatial-based management actions, such as the designation of Fisheries Restricted Areas (FRAs), in order to minimize the by-catch of undersized specimens and improve the sustainability of demersal fisheries.
Although research into the ecology and impacts of invasive species is prevalent, there are knowledge gaps relating to the role of invasive species in parasite transmission. This work synthesises invasive host–parasite interactions and impacts, using marine bivalves as a model group, to consider how global movement of shellfish consignments for aquaculture purposes facilitates the unintentional transfer of invasives. We discuss how invasive species can act as both hosts or parasitic organisms themselves, and introductions may lead to diseases within the bivalve aquaculture sector. This review highlights the importance of interdisciplinary research, with particular regard to the fields of parasitology and invasion ecology. We suggest that further integrating these fields will enhance critical knowledge of marine diseases, parasite-invasive-bivalve interplay dynamics, and potential mitigation strategies, including temperature-based disease surveillance models. We also address how climate change might impact invasive species, again with a focus on marine bivalves, and the potential outcomes for parasite transmission, including changes in host/parasite distribution, life-history and virulence. We acknowledge the importance of horizon scanning for future invasive host–parasite introductions and note that increased screening of invasive species, both in their native and invaded ranges, will provide clarity on invasion dynamics and potential impacts.
As the growth of the whale-watching activity increases rapidly around the world, the challenge of responsible management and sustainability also rises. Without suitable management, operators may try to maximize their own profits by breaking the rules, which may negatively affect cetaceans. In this paper, the applicability of conditions for sustainability governance in humpback whale-watching was evaluated. To achieve this purpose, semi-structured interviews were conducted in Uramba Bahía Málaga National Natural Park, Colombia. Results of this study showed that humpback whale-watching is characterized by unevenness in connections with markets, income inequality and the distribution of operators across several villages and cities. The combination of which restricts cooperation between operators. Nevertheless, there are informal agreements among the operators, and some operators are motivated to form associations. Besides, environmental entities have been responsible of regulation in lack of community-based management. However, this still does not achieve effective enforcement of the rules. Stakeholders (communities and government authorities) must mediate trust and reciprocity among operators to improve the situation. It is important to involve all operators to fill gaps in the limited government monitoring capacity and absence of sanctions. This is relevant to continue monitoring the evolution of the whale-watching in this and other Marine Protected Areas, so that the sustainability of the activity is not affected in the future.
Direct interactions with fisheries are broadly recognized as the leading conservation threat to small cetaceans. In open-ocean environments, one of the primary gear types implicated in these interactions is the pelagic longline. Unlike accidental entanglement in driftnets or deliberate entrapment by purse-seines, interactions between cetaceans and longlines are often driven by attraction of the animals to feed on bait or fish secured on the gear, a behavior known as depredation. Many small and medium-sized delphinid species have learned to exploit such opportunities, leading to economic costs to fisheries and a risk of mortality to the animals from either retaliation by fishermen or hooking or entanglement in fishing gear. Two pelagic longline fisheries in the United States experience depredation and bycatch by odontocete depredators: the Hawai‘i deep-set longline fishery, which is depredated primarily by false killer whales (Pseudorca crassidens), and the Atlantic pelagic longline fishery depredated primarily by short-finned pilot whales (Globicephala macrorhynchus). These fisheries are among the most intensively documented and managed pelagic longline fisheries in the world, with high levels of observer coverage, and bycatch mitigation measures required to reduce the mortality of seabirds, sea turtles and cetaceans. Both fisheries have active, multi-stakeholder “Take Reduction Teams,” enacted under the U.S. Marine Mammal Protection Act (MMPA), that are tasked to develop measures to reduce the bycatch of cetaceans below statutory reference points. Consequently, these two Teams represent model processes within which to address depredation and bycatch, having access to detailed, high-quality data on the nature and frequency of interactions with cetaceans, meaningful stakeholder involvement, resources to test potential solutions, and the institutional will to improve outcomes. We review how mitigation strategies have been considered, developed, and implemented by both Teams and provide a critical analysis of their effectiveness in addressing these problems. Notably, in the absence of straightforward avoidance or deterrence strategies, both Teams have developed gear and handling strategies that depend critically on comprehensive observer coverage. Lessons offered from these Teams, which have implemented consensus-driven management measures under a statutory framework, provide important insights to managers and scientists addressing other depredation problems.