Marine Megafauna Research Articles

Necrophagy and Marine Megafauna Predation By Sharks in a Hotspot in the Southwest Atlantic Ocean

Necrophagy and Marine Megafauna Predation By Sharks in a Hotspot in the Southwest Atlantic Ocean

Temporal and Spatial Distribution of Harbor Seal (Phoca vitulina) Risk of Entanglement in Gillnets Along the Norwegian Coast

Incidental capture of non-target species by fisheries, also referred to as bycatch, is a major concern for the management of marine megafauna species. In Norway, it has been estimated that 555 harbor seals (Phoca vitulina) get entangled and drown in gillnets every year. The majority of these bycatch events occur in large-mesh gillnet fisheries targeting cod (Gadus morhua) and monkfish (Lophius piscatorius). Young-of-the-year individuals represent the largest proportion of bycaught harbor seals. To increase our understanding of harbor seal bycatch events along the Norwegian coast, times and areas of potential bycatch risk were identified. Seasonal variation in the at-sea distribution of harbor seals was simulated based on movement from their molting site to predicted at-sea locations. Relative age-specific bycatch abundances were used to weigh the different seasons (times of the year) based on harbor seal age. The overlap in the distribution of harbor seals and the documented distribution of fishing effort was then used to estimate the relative bycatch risks between harbor seals and fisheries in defined Statistical Sea Locations (SSLs) in each of the four seasons. The method used here provides a general framework for understanding temporal and spatial interaction between harbor seals and coastal gillnet fisheries. The times and areas of high interaction risk that were identified can be used in management practices to increase our understanding of bycatch events, and to ultimately reduce unwanted bycatch of harbor seals in coastal fisheries along the Norwegian coast.

Overcoming challenging telemetry data of giant sunfish Mola alexandrini (Molidae) in Bali, Indonesia

The ocean sunfishes Mola spp. (Family Molidae) are charismatic marine megafauna that are difficult for nature-based tourism operators to target due to their sporadic occurrence. However, the giant sunfish M. alexandrini is seasonally important for the SCUBA tourism industry in Bali, Indonesia, where these molids seek cleaner-fish interactions on the reefs of the local Nusa Penida Marine Protected Area (MPA) in the Lombok Strait. Little is known of their movements, including their apparent seasonal affinity to the Nusa Penida MPA. We tagged 8 fish with Fastloc GPS tags; however, intermittent surface visits and crepuscular diving habits, combined with early tag dislodgment and tag transmission failures, yielded a challenging data set to analyze. We overcame this difficulty with a geolocation model (HMMoce) that was parameterized to leverage the complex topography of the study region, be robust to data sparsity, and accommodate switching between distinct resident and migrant behaviour states. The results revealed small-scale movements whereby the fish exhibited particular affinity to bathymetrically complex, intense upwelling areas around Nusa Penida, the east coast of Bali, and an inter-basin trough to the north. Dive patterns suggested that the molids were foraging in these oceanographically dynamic areas. Our findings suggest that the Lombok Strait is at least of seasonal importance to this species, and the local SCUBA tourism industry likely relies on individual fish that re-visit the reefs of the Nusa Penida MPA multiple times during the sunfish season.

Marine megafauna interactions with the Peruvian artisanal purse-seine fleet

Bycatch is a global problem for marine megafauna. Peru is a major fishing nation known in particular for its industrial purse-seine fishery for the Peruvian anchovy (Engraulis ringens). However, Peru also has an artisanal purse-seine fishery for this same resource and other species such as Pacific bonito (Sarda chiliensis), Pacific chub mackerel (Scomber japonicus) and Chilean jack mackerel (Trachurus murphyi) used for human consumption. While there is limited documentation of bycatch of megafauna by the industrial purse-seine fishery, there is no similar information for the artisanal purse-seine fishery. Therefore, this study aimed to assess the marine megafauna (small-cetaceans, seabirds, sea turtles, and elasmobranchs) bycatch interactions of the Peruvian artisanal purse-seine fishery for consumption for the year 2019 (before the COVID-19 pandemic) through interviews with artisanal fishers in 5 landing ports (San Jose, Santa Rosa, Callao, Pucusana, and San Andres). We found that these fisheries had bycatch with all taxa groups, with dusky dolphins (Lagenorhynchus obscurus), guanay cormorants (Leucocarbo bougainvilliorum) and eagle rays (Myliobatis spp.) having the highest quantity and most frequently reported bycatch. Multiple correspondence analysis (MCA) indicated an association between the bycatch of 1–3 common dolphins (Delphinus spp.) per set from the northern ports (San Jose and Santa Rosa) and vessels of 20–36 MT. Likewise, a relationship was found between smooth hammerhead sharks (Sphyrna zygaena) and vessel storage capacity, with a similar result reported for the bycatch of humpback smoothhounds (Mustelus whitneyi). In addition, a relationship of eagle ray (Myliobatis spp.) bycatch with a landing port was identified, and several respondents mentioned catching more than 1 MT per set. Fifty-three percent of fishers considered bycatch to be a problem, mainly because it wastes their time during fishing operations. This preliminary study is the first research that demonstrates bycatch in artisanal purse-seine in Peru and can serve as a baseline for future research. We also highlight the need to quantify bycatch rates of marine megafauna using additional methodologies, such as monitoring with onboard observers.

Is the demand for fish swim bladders driving the extinction of globally endangered marine wildlife?

Abstract International trade in croaker swim bladders or maws and incidental catches in fisheries targeting croakers for their maws pose a global problem that needs addressing to protect target croakers and globally threatened small cetaceans, sharks, rays and marine turtles. The lesson of the likely imminent extinction of the vaquita porpoise (Phocoena sinus) in the Gulf of California, Mexico, owing to entanglement in gillnets targeting the totoaba croaker for its maw, is that the underlying threats to marine species must be addressed well before precipitous declines make their extinction inevitable. Opportunistic interviews with fishers and fish traders in Bangladesh indicate that the increasing demand for fish maws, selling for as much as 5,000 USD per kg, may be intensifying small‐scale coastal fisheries and bycatches of globally threatened marine wildlife, especially due to the potential for a windfall profit. In 137 croaker catches made in gillnets, sharks were bycaught in 22%, marine turtles in 8% and rays in 3% of catches. Of particular concern were six bycatches of 125 Critically Endangered scalloped hammerhead sharks (Sphyrna lewini), 11 bycatches of 20 Vulnerable (VU) olive ridley turtles (Lepidochelys olivacea) and two bycatches of 13 VU longtail butterfly rays (Gymnura poecilura). A recent IUCN Motion for ‘Controlling and monitoring trade in croaker swim bladders to protect target croakers and reduce incidental catches of threatened marine megafauna’ recommends conducting an analysis on the impacts of the demand for and trade in fish maws on croaker species and threatened marine megafauna, regulating trade in fish maws through national laws and developing a potential proposal to list croaker species in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). To prevent species extinctions, additional measures focusing on fishery management will be needed.

Cetacean‐mediated vertical nitrogen transport in the oceanic realm

AbstractIn natural systems, animal‐mediated nutrient transport can be a major driver of primary productivity, but the role of marine megafauna such as cetaceans in mediating the transfer and recycling of nutrients has been overlooked. Here, we developed a spatially resolved, stochastic, nutrient‐transport model for cetaceans in the oceanic Gulf of Mexico using species−specific foraging depths, distributions, and diets. An estimated 6.4 × 108 mmol N d−1, or 0.06 mt N yr−1 ind−1, is transported to the surface from depths below 100 m by the 19 cetacean species that occur in the oceanic Gulf of Mexico; 75% of this transport occurs seaward of the continental slope, but the per area transported nitrogen is greater on the continental slope (200–1000 m) than in the ocean basin. Benthos to surface transport comprised 6.0 × 107 mmol N d−1 and was much more common on the continental slope than the open basin. Compared to an existing physical‐biogeochemical model, the transported nutrients add 8% N d−1 to the estimated ammonium concentration above the nutricline and could add 16% N d−1 to the surface ammonium concentration if expelled nutrients remain at the surface. Through feeding on diel vertical migrants, cetaceans retain an additional 2.7 × 107 mmol N d−1 in the surface waters that would otherwise return to depth via downward diel vertical migration. Cetaceans contribute to nutrient movements and recycling in the oceanic Gulf of Mexico, and may provide one of the few allochthonous sources of nutrients for primary producers in oligotrophic ecosystems.

An interview-based investigation of marine megafauna bycatch in the northern South China Sea

There is still limited information available regarding the patterns and extent of bycatch mortality in heavily-fished marine systems. To address this gap, we conducted an interview-based study to investigate the bycatch of five marine megafaunal species/categories in the northern South China Sea. Approximately two-thirds of the interviewed fishers reported encountering bycatch events, with sea turtles being the most commonly reported megafauna (33.6 % of respondents), followed by Indo-Pacific finless porpoises and whale sharks (both 12.4 %), and Indo-Pacific humpback dolphins (8.5 %). Dugongs were only reported by one respondent. Bycatch of these taxa was mainly associated with gillnets, trawl nets, and seine nets. Our estimates indicated a total of 7464 bycatch events annually, resulting in 1391 deaths for these five taxa. These numbers underscore the alarming impact of fisheries on marine megafauna, particularly on small cetaceans, which accounted for 66.1 % of the reported annual deaths, including 690 finless porpoises and 230 humpback dolphins. Lower bycatch levels were reported for all taxa in winter, potentially due to temporary reductions in fishery activity and/or animal migrations. Random forest model revealed that bycatch of humpback dolphins, finless porpoises, and sea turtles was primarily influenced by water depth and distance from the coast, while whale shark bycatch was influenced by administrative region. This study demonstrates that local ecological knowledge can provide a rapid means of obtaining basic information on the bycatch of marine megafauna, and serves as a sobering reminder that fisheries-related mortality contributes to the population declines of coastal small cetaceans.

Spatiotemporal variations in the acoustic presence of dugongs and vessel traffic around Talibong Island, Thailand: Inputs for local coastal management from passive acoustical aspects

Examining the spatiotemporal habitat use by marine megafauna and human activities at a fine scale is important to achieve harmonised management of coastal areas. Passive acoustic monitoring (PAM) can provide this information by observing animal vocalisations and the sounds generated by motorised vessels. Dugongs (Dugong dugon), which are endangered herbivorous mammals inhabiting coastal seas, communicate through social calls. Although their spatiotemporal acoustic presence on a fine scale could assist in prioritizing local marine spatial planning, such knowledge is limited. To address this gap, we examined the spatiotemporal pattern of the acoustic presence of dugongs and its correlation with environmental and anthropological factors; additionally, the overlap of these areas with vessel traffic was illustrated. Underwater recorders were deployed at 11 locations around Talibong Island, Thailand, for one month in both rainy and dry seasons. Based on the recorded sound stream, dugong calls and vessel sounds were automatically detected using custom-made software, and false detections were removed by manual examinations. In 2019 and 2020, 1933 h and 2719 h of recordings, respectively, revealed that while dugongs had a clear spatial preference for vocal communication at some locations, their temporal patterns varied among locations. Further, their acoustic presence was significantly correlated with environmental and anthropological factors at some locations, while these factors varied among other locations. However, the distribution of vessel traffic was spatially and temporally stable. These results suggested that (1) spatial management of vocalisation areas can effectively conserve dugongs by protecting their social behaviour and (2) temporal planning may reduce the potential disturbance risk to dugongs. Moreover, to achieve harmonised marine spatial planning in coastal areas, the PAM approach for social calls can be effectively employed to provide a unique layer of habitat use for vocalising species and vessel traffic on a fine scale.

Impact of climate change on the distribution and habitat suitability of the world’s main commercial squids

Climate change is expected to have major negative effects on marine life across phylogenetic groups. Cephalopods, however, have life history characteristics that suggest they may benefit from certain climate change scenarios. Of all cephalopods, squids reach the greatest biomasses; as a result, they are of substantial importance for human and predator consumption. To test the hypothesis that the effects of climate change are beneficial for commercial squid, we used species distribution models on climate scenarios for the period between 2000 and 2014, as well as the years 2050 and 2100 (RCP [representative concentration pathway] 2.6, 4.5, 6.0, and 8.5; CMIP5). Our results suggest that consequences of climate change scenarios are species specific. In the North Pacific and Northwest Atlantic, squid’s habitat suitability may increase (from + 0.83% [Doryteuthis pealeii] to + 8.77% increase [Illex illecebrosus]), while it is predicted to decrease in other regions (from − 1.03% [Doryteuthis opalescens] to − 15.04% decrease [Loligo reynaudii]). Increases in habitat suitability occurred mostly at higher latitudes (north of 50° N), while suitable habitat decrease was predicted for the tropical regions. These shifts in future habitat suitability were stronger under harsher emission scenarios. Starting in 2050 (with RCP scenarios 4.6, 6.0 and 8.5), as a result of warming of the Arctic, squid habitat may increase along both coasts of North America. In the Southern Hemisphere, squids may lose habitat with no poleward habitat alternatives to move into. Contrary to our hypothesis, these commercial squid do not stand to benefit from climate change. Since these squid are an important food source for marine megafauna and humans, it is imperative that climate change biogeographic impacts are considered for a sustainable management of this important group of molluscs.

Improving Marine Megafauna Knowledge with eDNA: A French Story

In the current context of large-scale biodiversity loss (Díaz et al. 2019), it is urgent to carry out biodiversity inventories in order to investigate spatial and temporal variations. Among the available methods, environmental DNA (eDNA) (Taberlet et al. 2018) combined with molecular metabarcoding (Valentini et al. 2009) bring new insights in drafting inventories of taxa present in an environment. Approaches based on eDNA facilitate the study of remote ecosystems and the detection of rare, cryptic or invasive species in a non-invasive way (Bohmann et al. 2014). In the marine realm, the study of mobile fauna, including mammals particularly, can greatly benefit from these new techniques. Here, we present a case study carried out in the northeast and northwest Atlantic, within the boundaries of marine protected areas. The Iroise Natural Marine Park*1 was the first French marine natural park created in France in 2007 (Fig. 1). The first campaign in the Iroise Natural Marine Park successfully detected several species of cetacean (e.g., Lagenorhynchus albirostris, Lagenorhynchus obliquidens) and four species of elasmobranchs (e.g., Scyliorhinus canicula, Torpedo marmorata, Raja undulata and Mustelus asterias). This study was extended to the Martinique Natural Marine Park*2, where similar analyses identified three cetacean species (Stenella attenuata, Lagenodelphis hosei and Tursiops truncatus) and 193 teleost taxa (Riou 2022), representing more than half of the species expected in Martinique. The analyses carried out in Martinique highlighted several remarkable sites for fish biodiversity. In Guadeloupe, in the heart of the Agoa Marine Mammals Sanctuary*3 (corresponding to the French Antilles exclusive economic zone), the taxonomic composition of different eDNA samples made in 2021 and 2022 was compared. The samples were analyzed using different primer sets, specific to vertebrates, teleosts and mammals. Comparison of the results obtained with vertebrate-specific primers and those specific to teleosts showed complementary results. For cetaceans, the analyses distinguished ten distinct cetacean taxonomic units and at least 3 distinct species from four samples. In addition, the eDNA samples were used to discriminate between the two recently recognised bottlenose dolphin ecotypes, based on the observation of a fixed nucleotide difference on the barcode targeted by the mammal-specific primers. New primers are currently being developed to make it easier to distinguish species of Delphinidae, which are still complex to identify. Environmental DNA and metabarcoding offer new possibilities for the inventories of marine megafauna and support adequate conservation decision-making processes. It is a major step towards better monitoring of marine mammal populations of the Atlantic Ocean. Moreover, our datasets will be freely available through open platforms following the FAIR (Findable, Accessible, Interoperable, and Reusable) principles.

Drone-Based Assessment of Marine Megafauna off Wave-Exposed Sandy Beaches

The wave-impacted waters off exposed sandy beaches support marine megafauna, including dolphins, whales, sharks, rays and turtles. To characterise variation in megafaunal assemblages in this challenging habitat, we used drone-based remote sensing to survey marine megafauna off 23 beaches along 1050 km of the New South Wales (NSW, Australia) coast from 2017 to 2020. The surveys occurred from September to May and included 17,085 drone flights, with megafaunal abundances standardised by flight hours. In total, we identified 3838 individual animals from 16 taxa, although no megafauna was observed off 5 of the 23 beaches surveyed. Bottlenose dolphins were the most commonly sighted taxa and accounted for 82.3% of total megafaunal abundance. Cownose (6.7%) and eagle (3.4%) rays were the next most abundant taxa, with potentially dangerous sharks being rarely sighted (<1% of total megafauna). The megafaunal assemblages off wave-exposed beaches in northern NSW significantly differed from those in the central region, whereas the assemblages off the central region and southern NSW did not differ significantly. Wave exposure and water temperature were the best predictors of megafaunal assemblage structure. The richness of marine megafauna off ocean beaches was significantly greater in northern than southern NSW, and turtles were only observed off beaches in the northern region. However, variation in megafaunal richness, as well as the abundances of total megafauna, dolphins, rays, sharks and turtles were not significantly explained by water temperature, wave height, distance to estuary, or proximity to the nearest reef. Overall, drone-based surveys determined that megafaunal assemblages off wave-exposed beaches are characterised by sparse individuals or small groups of sharks, turtles and rays, punctuated by occasional large aggregations of dolphins, cownose rays and schooling sharks. The exception to this pattern was bottlenose dolphins, which routinely patrolled some beaches in northern NSW.

Marine megafauna catch in Thai small‐scale fisheries

Abstract Small‐scale fisheries are a global conservation threat to marine megafauna (marine mammals, sea turtles, and elasmobranchs). There is currently limited information about marine megafauna catch in Thailand's small‐scale fisheries, which is required for effective management. This study represents the first independent catch assessment of marine megafauna in Thai small‐scale fisheries. Data on catch and fisheries effort across 1 year (2016–2017) were collected from questionnaire interviews with 535 fishers in 17 provinces along the Gulf of Thailand and the Andaman Sea coasts. Catch per unit effort was calculated for marine megafauna by fishing gear types and extrapolated to estimate annual catches using Thai official fisheries statistics. The annual estimated catches were 5.66 million (95% confidence interval, CI: 4.10–7.82 million) rays, 457,864 (95% CI: 192,352–969,166) sharks, 2,400 (95% CI: 1610–3,537) sea turtles, 790 (95% CI: 519–1,167) small cetaceans, and 72 (95% CI: 19–194) dugongs in Thai small‐scale fisheries. Gillnets had the highest catch per unit effort for all megafauna groups in both sea areas except for sea turtles, where pound nets had the highest catch per unit effort in the Gulf of Thailand. Further, among gillnets, crab gillnets had the highest catch per unit effort for all groups except dugongs, where ray gillnets had the highest catch per unit effort. Accounting for effort, crab gillnets and shrimp trammel nets were responsible for most of the megafauna catch, where crab gillnets contributed 72%–95% of the annual estimated marine megafauna catch. Crab gillnets and shrimp trammel nets were used by 46% and 40% respectively of the interviewed fishers and by 27% and 15% respectively of all small‐scale fishers operating in Thai waters. Restrictions for gillnet fishing effort (crab gillnets specifically) are needed to prevent extirpation of threatened megafauna species that are important for ecosystem resilience and productivity.

A Systematic Review on Challenges and Conservation Strategies for Marine Megafauna

Marine megafauna play pivotal roles in oceanic ecosystems, contributing to their health, functionality, and biodiversity. These species are facing escalating threats, from direct harms such as overhunting to indirect pressures like habitat degradation and climate change. This systematic review explores the challenges confronting marine megafauna, examines current conservation strategies, and explores innovative future strategies. Current efforts, while beneficial, often fail to address socio-economic factors and cumulative threat impacts, and lack robust long-term outcome evaluations. Potential strategies, leveraging emerging technologies, climate-smart conservation, sustainable blue economies, and rights-based approaches, are discussed. Despite their potential, these strategies present challenges, necessitating further interdisciplinary, social, cumulative impact, and long-term monitoring research. Understanding and addressing these aspects is essential for the development of holistic, effective, and sustainable marine megafauna conservation strategies. Future research should address gaps in species-specific knowledge, socio-economic understanding, cumulative threat assessments, and long-term conservation outcomes to provide a more comprehensive approach towards the protection of these vital species.

The fate of plastic-wearing sharks: Entanglement of an iconic top predator in marine debris

Plastic waste is currently a major threat to marine ecosystems, and the ever-growing production of plastic materials suggests that this scenario will not change soon. Understanding cryptic effects of plastic debris on keystone marine species is warranted to address ecosystem-level impacts caused by plastic pollution. This study reports on plastic entanglement in top predator tiger sharks, Galeocerdo cuvier, from the western South Atlantic Ocean. Circular plastic straps produced severe trauma in 3 % of all tiger sharks sampled and led to abnormal anatomical development, indicating worrisome incidence and consequences of plastic entanglement in this species. Removing the plastic strap from one shark which had been entangled for at least 9 months was probably the cause for the shark having experienced post-release mortality. This suggests that, in some circumstances, strap removal is not effective to promote the survival of entangled sharks. Eliminating the circular integrity of plastic materials at first use should contribute to mitigate some of the impacts of plastic pollution on marine megafauna since this shape might be determinant in the process of shark entanglement.

Artisanal fishery with surface gillnets and megafauna strandings

Bycatch is an issue of worldwide relevance involving conflicts between conservation and fishery interests. In Brazil, this conflict has been highlighted in relation to the regulation of small-scale fishery with surface gillnets. To promote management and transformation of this conflict, we analyzed the relationship between catch unloadings from small-scale fishing with surface gillnets and strandings of marine megafauna. We used fishery monitoring data and beach monitoring data in São Paulo between 2015 and 2021, relating to Chelonia mydas, Caretta caretta, Lepidochelys olivacea, Pontoporia blainvillei and Sotalia guianensis. The analyses included (i) overview of catches unloadings from small-scale fishing with surface gillnets and strandings that resulted in the death of each of these species over the course of the year; (ii) correlation tests between those variables for the northern, central, and southern regions; and (iii) performing regression analyses for municipalities within these regions, exhibiting statistically significant positive correlations. The fisheries harvest period was found not to overlap with the stranding distribution. In correlation tests, only strandings of C. mydas in the northern and southern regions, S. guianensis in the southern region and P. blainvillei in the central region showed relationships with fishing landings. The regression analysis was significant for C. mydas and S. guianensis. At the municipal level, the results were statistically significant for C. mydas in São Sebastião, Ubatuba, Ilha Comprida and Cananéia and for S. guianensis in Cananéia. However, the regression explained a small part of the mortality and other impact factors were pointed out. Non-prohibitive management measures, participatory studies, and direct methods for evaluating the interaction between fisheries and megafauna associated with environmental factors should be implemented, along with analyses on other impacts on megafauna.

The Economic Value of Sea Otters and Recreational Tourism in a California Estuary

The recovery of marine megafauna can lead to improved ecosystem function and services, but not all stakeholders may benefit equally. Quantifying the local economic value of a species’ presence may appeal to broader range of stakeholders when developing conservation strategies. This study aims to examine the economic effect recreational activities can have on a local region, and to determine what role the presence of southern sea otters (Enhydra lutris nereis) had on the value visitors placed on the visit and the area’s preservation. We surveyed visitors to Elkhorn Slough, a small estuary in California known for diverse wildlife, modeled direct and indirect economic contributions to local economics, and evaluated perceptions and value placed on the area and wildlife. Annually, visitors contributed approximately $3.2 million (USD) in direct spending, with an additional $1.85 million in indirect economic gains, which could support over 300 full-time, part-time, and seasonal jobs to the region. Whether sea otters were observed during a trip influenced how visitors ranked their importance, and the perceived value of the estuary and sea otters. Combined, this study quantified what recreational visitors could contribute to local economies and that sea otters play a role in what visitor’s value about their visit. These results provide additional support to the benefits of species presence at a local scale. We discuss how these types of studies can be used as part of larger species and ecosystem management plans, particularly considering species recovery and range expansion.

First record of bottom-feeding behaviour in the whale shark (Rhincodon typus).

Despite being the world's largest fish, many questions remain regarding the ecology and behaviour of the whale shark (Rhincodon typus). We present the first direct evidence of whale sharks engaging in bottom-feeding behaviour and provide potential explanations for this foraging strategy. We suggest that whale sharks actively feed on benthic prey, either predominantly in deepwater environments or where the abundance of such prey exceeds that of planktonic food sources. We also highlight the potential for ecotourism and citizen science projects to contribute to our understanding of marine megafauna behavioural ecology.

Fine-scale intraspecific niche partitioning in a highly mobile, marine megafauna species: implications for ecology and conservation.

A species may partition its realized ecological niche along bionomic and scenopoetic axes due to intraspecific competition for limited resources. How partitioning manifests depends on resource needs and availability by and for the partitioning groups. Here we demonstrate the utility of analysing short- and long-term stable carbon and nitrogen isotope ratios from imperiled marine megafauna to characterize realized niche partitioning in these species. We captured 113 loggerhead sea turtles (Caretta caretta) at a high-use area in the eastern Big Bend, Florida, between 2016 and 2022, comprising 53 subadults, 10 adult males and 50 adult females. We calculated trophic niche metrics using established and novel methods, and constructed Bayesian ellipses and hulls, to characterize loggerhead isotopic niches. These analyses indicated that loggerheads partition their realized ecological niche by lifestage, potentially along both bionomic (e.g. trophic) and/or scenopoetic (e.g. habitat, latitude or longitude) axes, and display different characteristics of resource use within their niches. Analysis of stable isotopes from tissues with different turnover rates enabled this first characterization of intraspecific niche partitioning between and within neritic lifestages in loggerhead turtles, which has direct implications for ongoing research and conservation efforts for this and other imperiled marine species.

Marine protected areas in the southern south‐west Atlantic: Insights from marine top predator communities

AbstractThe marine ecosystem provides numerous goods and services, dampens the impacts of floods and storms, and provides climate control, through the regulation of carbon fluxes, nutrient cycling, and the bioremediation of human waste and tourism. However, the ocean is vulnerable to anthropogenic threats and has been severely altered by humans.Seabirds and marine mammals are long lived, highly mobile, easily identifiable, and occupy the upper levels of trophic webs. These ecological features make them suitable as sentinels of the marine ecosystem.Sighting data collected during eight oceanographic surveys were analysed to describe and compare the biodiversity of the communities of top predators within the marine protected areas (MPAs) of Namuncurá/Burdwood Bank I and II and the surrounding areas in two contrasting seasons (summer and winter). Data were grouped into six zones based on depth and geographic position.Twenty‐five species of seabirds and 13 species of marine mammals were recorded in 113 days of surveys between 2014 and 2018. Top predator community composition varied seasonally in the different zones.A suite of indicator species was identified according to their specificity and fidelity to a particular zone. Most of the species identified as potentially useful indicators differed between summer and winter, highlighting the importance of conducting systematic surveys in both periods.The MPAs Namuncurá/Burdwood Bank I and II are key areas for top predator communities in the region, mainly in summer when the number and abundance of species increase. However, the waters around Isla de los Estados and the channel between Isla de los Estados and Burdwood Bank were also identified as a relevant habitat for many species. This knowledge should be included to create a regional network of areas under special management considerations that connect the established MPAs with other key pelagic and coastal areas (as found in this study) for the conservation of subantarctic marine megafauna.

Solid waste ingestion by marine megafauna on Southeast Brazilian coast

The disparities in the ecology and behavior of marine megafauna may influence their susceptibility to solid waste ingestion; however, this relationship has been underestimated along the Brazilian coast. We analyzed a dataset of 7261 marine megafauna (45 species) necropsied to investigate the influence of their foraging strategies on solid waste ingestion. A total of 1240 specimens ingested solid waste with over 55 % (689) that ingested plastic. Sea turtles were the most impacted taxa, while cetaceans present the lowest frequency. Some characteristics such as regurgitation (e.g., Suliformes and Charadriiformes seabirds) or possess complex foraging strategies (e.g., cetaceans echolocation) may mitigate the negative effects of solid waste ingestion. Also, the variability over the monitoring program likely was influenced by the volume of pollutants transported to the ocean during flood periods, and level of staff training. This study serves as a valuable baseline for solid waste management actions and marine megafauna conservation efforts.