Plastic ingestion by odontocetes from the Western South Atlantic: A particular concern to a threatened species

The ingestion of debris by marine fauna is a growing threat to biodiversity. This study aimed to evaluate and characterize litter ingestion by odontocetes from the Western South Atlantic. Between 2018 and 2022, 154 stomachs from six species were collected from stranded individuals and incidental captures. Stomach contents were analyzed with the naked eye and items of anthropic origin found were counted and physically/chemically characterized. Generalized Linear Models were used to evaluate the influence of biological factors on the presence/absence of litter in stomachs, and for Pontoporia blainvillei only, the influence of these factors on the number of ingested items was also tested; additionally, a temporal analysis of ingestion was done for this species (1994-2022). A total of 156 items, mainly macro-sized plastics made of polypropylene, were found in 52 stomachs of four species: Tursiops spp. (FO% = 3.3%), Steno bredanensis (10.0%), Delphinus delphis (28.6%) and P. blainvillei (47.5%). The presence/absence of litter was explained only by species (χ2 = 28.29 and p < 0.001). For P. blainvillei, a threatened species in the region, the number of items was positively influenced by individual size (χ2 = 6.01 and p = 0.01) and sex (χ2 = 7.93 and p = 0.005). There was an increase in plastic ingestion by this species over the years (χ2 = 121.6 and p < 0.001) and it was estimated that 75% of P. blainvillei stomachs will contain plastic by 2040. The ingestion of litter by odontocetes from the Western South Atlantic was confirmed and the potential risks posed by this type of pollution were evidenced, especially since these species also face other anthropic pressures. These results further demonstrate the increasing threat of litter in the ocean and highlight the importance of circularity of plastics and proper waste management.

Assessing the vulnerability of Elasmobranch species in the Bay of Bengal: Insights from Lakkha gill net fishery of Bangladesh

The elasmobranch population is declining in the Bay of Bengal of Bangladesh due to large-mesh gill net fishing, locally known as the Lakkha net, which primarily targets Indian threadfin (Leptomelanosoma indicum). This study was the first attempt to identify megafaunal bycatch in Lakkha fishing and assess its vulnerability using Productivity Susceptibility Analysis. A total of 40 elasmobranch bycatch species were identified, with sharks comprising 13 species from three families, while 27 rays belonged to six families, with the majority belonging to the Myliobatiformes order (60 %). Productivity and susceptibility scores were assigned to all identified species, with values ranging from 1.27 to 2.73 and 1.50 to 2.63, respectively. The target Lakkha fish exhibited the highest susceptibility score, followed by several pelagic sharks and eagle rays. Vulnerability assessment revealed that 31.7 % (n = 13) of species were highly vulnerable, while 43.9 % (n = 18) were classified as moderate, and 24.4 % (n = 10) were considered to have low vulnerability. All the high-risk megafauna species (n = 13) are classified as threatened by the global IUCN Red List. Sensitivity analysis highlighted susceptibility as a major contributor to species' vulnerability. Alterations in susceptibility scores led to significant changes in the vulnerability status of many species. The overall data quality assessment indicated moderate data quality across species, with variability observed between productivity (76 % of species received a poor data quality score) and susceptibility attributes. However, vulnerability of these species can be reduced through adequate gear modification, shorter net deployment periods, adoption of safe discharge techniques, identification of critical habitats, and establishment of marine protected areas within this region. This study provides valuable insights into the species composition and vulnerability of elasmobranchs in the Lakkha gill net fishery, emphasizing the need for conservation measures to mitigate bycatch impacts on threatened species.

Current species protection does not serve its porpoise-Knowledge gaps on the impact of pressures on the Critically Endangered Baltic Proper harbour porpoise population, and future recommendations for its protection

Successful management requires information on pressures that threaten a species and areas where conservation actions are needed. The Baltic Proper harbour porpoise population was first listed as Critically Endangered by the International Union for the Conservation of Nature in 2008. Now, 16 years later, there is no change in conservation status despite ample conservation policy calling for its protection and an urgent need for management action to protect this population. Here, we provide an overview of the current status of the population, highlight knowledge gaps on the impact of pressures, and make recommendations for management of anthropogenic activities. Based on an exceeded limit for anthropogenic mortality, the high concentrations of contaminants in the Baltic Sea, combined with reductions in prey availability and increases in underwater noise, it is inferred that this population is likely still decreasing in size and conservation action becomes more urgent. As bycatch and unprotected underwater explosions result in direct mortality, they must be reduced to zero. Inputs of contaminants, waste, and existing and emerging noise sources should be minimised and regulated. Additionally, ecosystem-based sustainable management of fisheries is paramount in order to ensure prey availability, and maintain a healthy Baltic Sea. Stranding networks to routinely assess individuals for genetic population assignment and health need to be expanded, to identify rare samples from this population. Knowledge is still scarce on the population-level impact of each threat, along with the cumulative impact of multiple pressures on the population. However, the current knowledge and management instruments are sufficient to apply effective protection for the population now. While bycatch is the main pressure impacting this population, urgent conservation action is needed across all anthropogenic activities. Extinction of the Baltic Proper harbour porpoise population is a choice: decision-makers have the fate of this genetically and biologically distinct marine mammal population in their hands.

Ingestion of fishing gear and Anisakis sp. infection in a beached Indo-Pacific finless porpoise (Neophocaena phocaenoides) in the Jeju Island, Republic of Korea: findings from post-mortem computed tomography and necropsy

BACKGROUND

Human fishing activities have significantly affect environmental concern for marine ecosystems, conservation of marine mammals, and human health. Coastal cetaceans are highly vulnerable to ingestion of fishing gear, bycatching, or entanglement, all of which can be fatal for these animals. In particular, certain coastal dolphins and porpoises are heavily impacted by fishing gear such as angling gear or stownet, as their food often overlap with the target fish species of human fisheries.

CASE PRESENTATION

This study presents a case of an Indo-Pacific finless porpoise (Neophocaena phocaenoides) beached on the coast of Jeju Island, Republic of Korea, with ingestion of fishing gear and severe Anisakis infection. Although this species inhabits waters ranging from the Persian Gulf to Taiwan, several stranded carcasses have been reported on Jeju Island in recent years. Post-mortem computed tomography revealed a bundle of four fishing hooks in the forestomach, along with nylon lines and steel lines with connectors, which were assumed to be angling gear for Jeju hairtail (Trichiurus lepturus). Further necroscopic investigation revealed that the forestomach contained a large number of Anisakis spp. (Nematoda: Anisakidae). Histological examination revealed a thickened forestomach wall with pinpoint and volcanic ulcerations, a thickened layer of stratified squamous epithelium, and infiltrated stroma in the squamous epithelium.

CONCLUSIONS

This study emphasizes the urgent need to address the impact of fishing activities on marine mammals, marine litter pollution, and the bycatch problem in Korean seawater. In addition, the occurrence of N. phocaenoides in seawater around Jeju Island should be raised in future geographical ecology or veterinary pathology studies and when its distribution is updated.

Management and research efforts are failing dolphins, porpoises, and other toothed whales

Despite being subject to intensive research and public interest many populations of dolphins, porpoises, and other toothed whales (small cetaceans) continue to decline, and several species are on the verge of extinction. We examine small cetacean status, human activities driving extinction risk, and whether research efforts are addressing priority threats. We estimate that 22% of small cetaceans are threatened with extinction, with little signs of improvement in nearly thirty years. Fisheries and coastal habitat degradation are the main predictors of extinction risk. Contrary to popular belief, we show that the causal impact of small-scale fisheries on extinction risk is greater than from large-scale fisheries. Fisheries management strength had little influence on extinction risk, suggesting that the implementation of existing measures have been largely ineffective. Alarmingly, we find research efforts for priority threats to be vastly underrepresented and so a major shift in research focus is required. Small cetaceans are among the lower hanging fruits of marine conservation; continued failure to halt their decline bodes poorly for tackling marine biodiversity loss and avoiding an Anthropocene mass extinction.

Development of a new control rule for managing anthropogenic removals of protected, endangered or threatened species in marine ecosystems

Human activities in the oceans are increasing and can result in additional mortality on many marine Protected, Endangered or Threatened Species (PETS). It is necessary to implement ambitious measures that aim to restore biodiversity at all nodes of marine food webs and to manage removals resulting from anthropogenic activities. We developed a stochastic surplus production model (SPM) linking abundance and removal processes under the assumption that variations in removals reflect variations in abundance. We then consider several 'harvest' control rules, included two candidate ones derived from this SPM (which we called 'Anthropogenic Removals Threshold', or ART), to manage removals of PETS. The two candidate rules hinge on the estimation of a stationary removal rate. We compared these candidate rules to other existing control rules (e.g. potential biological removal or a fixed percentage rule) in three scenarios: (i) a base scenario whereby unbiased but noisy data are available, (ii) scenario whereby abundance estimates are overestimated and (iii) scenario whereby abundance estimates are underestimated. The different rules were tested on a simulated set of data with life-history parameters close to a small-sized cetacean species of conservation interest in the North-East Atlantic, the harbour porpoise (Phocoena phocoena), and in a management strategy evaluation framework. The effectiveness of the rules were assessed by looking at performance metrics, such as time to reach the conservation objectives, the removal limits obtained with the rules or temporal autocorrelation in removal limits. Most control rules were robust against biases in data and allowed to reach conservation objectives with removal limits of similar magnitude when averaged over time. However, one of the candidate rule (ART) displayed greater alignment with policy requirements for PETS such as minimizing removals over time.

Red-list status and extinction risk of the world's whales, dolphins, and porpoises

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2-3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.

Assessment of Harbour Porpoise Bycatch along the Portuguese and Galician Coast: Insights from Strandings over Two Decades

The Iberian harbour porpoise population is small and fisheries bycatch has been described as one of its most important threats. Data on harbour porpoise strandings collected by the Portuguese and Galician stranding networks between 2000 and 2020 are indicative of a recent mortality increase in the western Iberian coast (particularly in northern Portugal). Overall, in Portugal and Galicia, individuals stranded due to confirmed fishery interaction represented 46.98% of all analysed porpoises, and individuals stranded due to probable fishery interaction represented another 10.99% of all analysed porpoises. Considering the Portuguese annual abundance estimates available between 2011 and 2015, it was possible to calculate that an annual average of 207 individuals was removed from the population in Portuguese waters alone, which largely surpasses the potential biological removal (PBR) estimates (22 porpoises, CI: 12-43) for the same period. These results are conservative and bycatch values from strandings are likely underestimated. A structured action plan accounting for new activities at sea is needed to limit the Iberian porpoise population decline. Meanwhile, there is an urgent need for a fishing effort reorganization to directly decrease porpoise mortality.

Potential biases in dietary interpretation derived from stable isotope analysis of small dolphin teeth

We analyzed δ¹³C and δ¹⁵N values in different tooth portions (Growth Layer Groups, GLGs) of franciscanas, Pontoporia blainvillei, to investigate their effect on whole tooth (WT) isotopic values and the implications for dietary estimates. Tooth portions included the dentin deposited during the prenatal development (PND), the first year of life (GLG₁) deposited during the nursing period and the central part of the tooth with no distinction amongst subsequent GLGs (Center). Isotopic mixing models estimating the contribution of PND, GLG₁ and Center to WT showed that GLG₁ has a strong effect on WT isotope values in juveniles, while Center only starts to affect WT isotopic values from age four. Isotopic mixing models estimating prey contribution to the diet of juveniles using WT vs Center tooth portions significantly differed in dietary outputs, demonstrating that GLG₁ influence on WT isotope values affects dietary estimates in young franciscanas. As the small tooth size and narrowness of the last GLGs hinder the analysis of individual layers, we recommend excluding GLG₁ in studies based on teeth isotope composition in franciscanas and caution when interpreting isotopic values from the WT of other small cetaceans.

Spatiotemporal relationships of threatened cetaceans and anthropogenic threats in the lower Yangtze system

The impacts of fisheries interactions on cetaceans can be challenging to determine, often requiring multiple complementary investigative approaches. The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), one of the few Critically Endangered cetaceans, is endemic to the middle-lower Yangtze drainage, a system impacted by multiple anthropogenic pressures. Bycatch mortality is implicated in regional porpoise decline, but the significance and dynamics of porpoise interactions with fishing activities and other threats remain poorly understood. We conducted boat-based surveys to map seasonal distributions and spatial congruence of porpoises and two potential threats (fishing and sand-mining), and an interview survey of fishing communities to understand temporal patterns and drivers of regional fishing activity, across Poyang Lake and the adjoining Yangtze mainstem. Variation in harmful and non-harmful gear use (non-fixed nets versus static pots and traps) between these landscapes might be an important factor affecting local porpoise status. Within Poyang Lake, spatial correlations between porpoises and threats were relatively weak, seasonal porpoise and threat hotspots were located in different regions, and two protected areas had higher porpoise encounter rates and densities than some unprotected sections. However, porpoise hotspots were mostly in unprotected areas, threats were widely observed across reserves, and more fishing and sand-mining was seasonally observed within reserves than within unprotected areas. Compared to null distributions, porpoises were detected significantly closer to fishing activities in summer and further from sand-mining in winter, indicating possible spatial risks of gear entanglement and disturbance. Reported porpoise bycatch deaths are associated with fixed and non-fixed nets, hook-based gears, and electrofishing. Longitudinal patterns in reported gear use indicate that hook-based fishing has decreased substantially and is generally conducted by older fishers, and significantly fewer respondents now practice fishing as their sole source of income, but electrofishing has increased. This combined research approach indicates a continued potential risk to porpoises from changing fisheries interactions and other threats, highlighting the importance of fishing restrictions and appropriate support for fishing communities impacted by this legislation. A potential “win–win” for both biodiversity and local livelihoods could be achieved through wider use of static pots and traps, which are not associated with bycatch deaths.

Geographic range size, water temperature, and extrinsic threats predict the extinction risk in global cetaceans

Despite the fact that cetaceans provide significant ecological contributions to the health and stability of aquatic ecosystems, many are highly endangered with nearly one-third of species assessed as threatened with extinction. Nevertheless, to date, few studies have explicitly examined the patterns and processes of extinction risk and threats for this taxon, and even less between the two subclades (Mysticeti and Odontoceti). To fill this gap, we compiled a dataset of six intrinsic traits (active region, geographic range size, body weight, diving depth, school size, and reproductive cycle), six environmental factors relating to sea surface temperature and chlorophyll concentration, and two human-related threat indices that are commonly recognized for cetaceans. We then employed phylogenetic generalized least squares models and model selection to identify the key predictors of extinction risk in all cetaceans, as well as in the two subclades. We found that geographic range size, sea surface temperature, and human threat index were the most important predictors of extinction risk in all cetaceans and in odontocetes. Interestingly, maximum body weight was positively associated with the extinction risk in mysticetes, but negatively related to that for odontocetes. By linking seven major threat types to extinction risk, we further revealed that fisheries bycatch was the most common threat, yet the impacts of certain threats could be overestimated when considering all species rather than just threatened ones. Overall, we suggest that conservation efforts should focus on small-ranged cetaceans and species living in warmer waters or under strong anthropogenic pressures. Moreover, further studies should consider the threatened status of species when superimposing risk maps and quantifying risk severity. Finally, we emphasize that mysticetes and odontocetes should be conserved with different strategies, because their extinction risk patterns and major threat types are considerably different. For instance, large-bodied mysticetes and small-ranged odontocetes require special conservation priority.

The first study of genetic diversity and population structure of Indo-Pacific bottlenose dolphin (Tursiops aduncus) and pantropical spotted dolphin (Stenella attenuata) in the Thai Andaman Sea based on ISSR

Background and Aim

The Indo-Pacific bottlenose dolphin, Tursiops aduncus, and the pantropical spotted dolphin, Stenella attenuata, are protected marine mammals in Thailand; however, knowledge regarding the populations of both species in Thai seas is minimal. We aimed to reveal the genetic diversity and population structure of two species, T. aduncus, and S. attenuata, based on inter-simple sequence repeats (ISSRs).

Materials and Methods

Samples of stranded T. aduncus (n = 30) and S. attenuata (n = 23) found along Thai Andaman Sea coasts from 1998 to 2018 were used in this study. A total of 17 and 16 ISSR primers that produced clear and polymorphic bands were selected for T. aduncus and S. attenuata, respectively.

Results

The highest percentages of polymorphic bands for T. aduncus and S. attenuata were 93.750% and 92.857%, respectively. Phylogenetic dendrograms indicated that the population of each species was clustered into three groups. This outcome was consistent with the genetic population structure, as both suggested three genetic clusters (DK = 3). Genetic diversity analysis revealed that the average Shannon's information index (I) was 1.926 ± 0.066 for T. aduncus and 1.714 ± 0.090 for S. attenuata, which indicate a high level of genetic variation. Further, low fixation index (F) values were observed for T. aduncus and S. attenuata at -0.231 ± 0.024 and -0.312 ± 0.042, respectively, suggesting that inbreeding is unlikely to have occurred for both species over the past decades.

Conclusion

At least three genetic clusters of both species were found in the Thai Andaman Sea, and the diversity indices of each species indicated that these species are not at a critical level for extinction. However, monitoring their population status should be prioritized to observe any future changes in the level of diversity.

A global horizon scan of issues impacting marine and coastal biodiversity conservation

The biodiversity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal biodiversity over the next 5-10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for example the impact of wildfires and the effect of poleward migration on equatorial biodiversity; resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens; and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal biodiversity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems.

Eco-Crimes and Ecocide at Sea: Toward a New Blue Criminology

This essay adopts an interdisciplinary approach to consider the meaning of "eco-crime" in the aquatic environment and draws on marine science, the study of criminal law and environmental law, and the criminology of environmental harms. It reviews examples of actions and behaviors of concern, such as offences committed by transnational organized crime and the legal and illegal over-exploitation of marine resources, and it discusses responses related to protection, prosecution and punishment, including proposals for an internationally accepted and enforced law of ecocide. One key element of the policy and practice of ending ecocide is the call to prioritize the adoption of technologies that are benign and renewable. Our essay concludes with a description of the "Almadraba" method of fishing to illustrate that there are ways in which the principles of sustainability and restoration can be applied in an ethical and just way in the context of modern fisheries.

Causes of Death and Pathological Findings in Stranded Harbour Porpoises (Phocoena phocoena) from Swedish Waters

Simple Summary

Disease factors and mortality etiologies of free ranging wild cetaceans such as the harbour porpoise (Phoceona phocoena) are difficult to study. However, stranded animals and carcasses can provide invaluable information on the health and biology of this species. Post-mortem examinations performed on 128 stranded harbour porpoises collected over 15 years from Swedish waters examined general health, disease findings and cause of death. The main cause of death was bycatch in fishing gear (31%, confirmed or suspected). Disease, most often pneumonia, was also a frequent cause of death (21%). Porpoise population health may mirror the overall health and stability of marine ecosystems and the effects of human activities on coastal environments. Monitoring health, diseases and causes of death of porpoises allows for identification of threats to these animals, to other animals, to humans and to the environment.

Abstract

Harbour porpoises (Phocoena phocoena) are useful indicators of the health of their wild populations and marine ecosystems, yet their elusive nature makes studying them in their natural environment challenging. Stranded porpoises provide an excellent source of data to study the health and biology of these animals and identify causes of death, diseases and other threats. The aim of this study was to document pathology, and where possible, cause of death in porpoises from Swedish waters. Post-mortem examinations were performed on 128 stranded porpoises collected from 2006 to 2020. Overall, bycatch including definitive and probable cases was the most common cause of death (31.4%), followed by disease (21.3%), predominantly pneumonia. In adults, infectious disease was the most common cause of death. Bacteria with zoonotic potential such as Erysipelothrix rhusiopathiae and Brucella sp. were documented for the first time in porpoises from Swedish waters, as was the porpoise-adapted group B Salmonella enterica ST416/ST417. Three of four deaths from non-infectious diseases involved parturition complications. Four cases of suspected predation were documented, but further analyses are required to confirm these findings. Our results are consistent with those from other regions in Europe and serve as a reference for future monitoring for changing patterns of health and disease of porpoises and their environments.

Trade-offs between bycatch and target catches in static versus dynamic fishery closures

The incidental catch of threatened species is still one of the main barriers to fisheries sustainability. What would happen if we closed 30% of the ocean to fishing with the goal of reducing bycatch? Analyzing 15 different fisheries around the globe, we found that under static area management, such as classic no-take marine area closures, observed bycatch could be reduced by 16%. However, under dynamic ocean management based on observed bycatch and closing the same total area but fragmented in smaller areas that can move year to year, that reduction can increase up to 57% at minimal or no loss of target catch.

While there have been recent improvements in reducing bycatch in many fisheries, bycatch remains a threat for numerous species around the globe. Static spatial and temporal closures are used in many places as a tool to reduce bycatch. However, their effectiveness in achieving this goal is uncertain, particularly for highly mobile species. We evaluated evidence for the effects of temporal, static, and dynamic area closures on the bycatch and target catch of 15 fisheries around the world. Assuming perfect knowledge of where the catch and bycatch occurs and a closure of 30% of the fishing area, we found that dynamic area closures could reduce bycatch by an average of 57% without sacrificing catch of target species, compared to 16% reductions in bycatch achievable by static closures. The degree of bycatch reduction achievable for a certain quantity of target catch was related to the correlation in space and time between target and bycatch species. If the correlation was high, it was harder to find an area to reduce bycatch without sacrificing catch of target species. If the goal of spatial closures is to reduce bycatch, our results suggest that dynamic management provides substantially better outcomes than classic static marine area closures. The use of dynamic ocean management might be difficult to implement and enforce in many regions. Nevertheless, dynamic approaches will be increasingly valuable as climate change drives species and fisheries into new habitats or extended ranges, altering species-fishery interactions and underscoring the need for more responsive and flexible regulatory mechanisms.

Age and lunar cycle predict harbor porpoise bycatch in the south-western Baltic Sea

The harbor porpoise, Phocoena phocoena, is the only cetacean regularly occurring in the Baltic Sea. During the last decades, several anthropogenic activities have affected porpoises in the Baltic region. Most notably is bycatch in static fishing gear, such as gill nets, which is the main human-induced cause of death in odontocetes. There is still considerable uncertainty about which factors influence the amount of bycatch. In the present study, we reviewed bycatch data collected from 1987 to 2016 from the south-western Baltic Sea. There was a significant difference in bycatch due to seasonality and region, and there was a higher bycatch rate in juveniles than in adults. The only abiotic factor associated with bycatch was the lunar cycle, with more animals bycaught during a full moon. These results improve our understanding of which biotic and abiotic factors are associated with bycatch of Baltic harbor porpoises, which can be used to strengthen conservation endeavors such as managing fishing efforts.

Small Scale Fisheries, Dolphins and Societal Challenges: A Case Study in the City of Volos, Greece

Existing literature on dolphin-fisheries interaction focused on Greece reveals both an undeveloped area for research, but also a lack of relevant data in this field. Although imperative, relevant research has been slow on innovation and cooperation among universities, official bureaus, and NGOs that are obliged to work together as European and national laws dictate. Most of the research in this new field focuses on the interaction between marine mammals and local fisheries, suggesting that this relationship may be problematic for both parties since the former are being treated (at least occasionally) with brutality, while the latter try to deal with economic loss. Dolphins and fishermen operate within the same ecological niches for their survival, the main area of conflict being nutritious fish. Anthropological research on ethnic identity has long dealt with antagonistic relationships over resources between adjacent groups of people. Marine biologists’ research in Greece focuses on the human factor, and some of its shortcomings may well be seen as the result of limited, or an absence of, training in social sciences. This article attempts to draw from anthropological theory to shed light on a particular symbiosis between humans and dolphins. Multidisciplinary approaches gain ground in a wide range of research interests and seem to be fruitful in terms of theoretical and practical results.

Marine mammal conservation: over the horizon

Marine mammals can play important ecological roles in aquatic ecosystems, and their presence can be key to community structure and function. Consequently, marine mammals are often considered indicators of ecosystem health and flagship species. Yet, historical population declines caused by exploitation, and additional current threats, such as climate change, fisheries bycatch, pollution and maritime development, continue to impact many marine mammal species, and at least 25% are classified as threatened (Critically Endangered, Endangered or Vulnerable) on the IUCN Red List. Conversely, some species have experienced population increases/recoveries in recent decades, reflecting management interventions, and are heralded as conservation successes. To continue these successes and reverse the downward trajectories of at-risk species, it is necessary to evaluate the threats faced by marine mammals and the conservation mechanisms available to address them. Additionally, there is a need to identify evidence-based priorities of both research and conservation needs across a range of settings and taxa. To that effect we: (1) outline the key threats to marine mammals and their impacts, identify the associated knowledge gaps and recommend actions needed; (2) discuss the merits and downfalls of established and emerging conservation mechanisms; (3) outline the application of research and monitoring techniques; and (4) highlight particular taxa/populations that are in urgent need of focus.

A DNA microarray assay for authenticating five important marine mammal species in food and feed

Material identification in processed and unprocessed food and feed is crucial for ensuring the safety and hygiene of food and feed products. Therefore, to identify possible marine mammal components in feed, we study developed a DNA microarray with species-specific oligonucleotide probes that enable the rapid identification of five important marine mammal species (dolphins, seals, sea lions, white whales, and finless porpoises). The assay was tested using five target marine mammal species, and the probe patterns were compared with those of three fish meals (for feed) to see if they contained traces of marine mammals. All five marine mammal species could be distinguished by the microarray, and no marine mammal-derived ingredients were detected in the three fish meals. This study indicates that DNA microarray-based detection is relatively easy and effective for identification of non-compliant marine mammal ingredients in seafood or feed.

Getting to the bottom of bycatch: a GIS-based toolbox to assess the risk of marine mammal bycatch

Marine mammal bycatch poses a particular challenge in developing countries, where data to document bycatch and its effects are often lacking. Using the Bycatch Risk Assessment (ByRA) toolkit, based on InVEST open-source models, we chose 4 field sites in Southeast Asia with varying amounts of data on marine mammals and fishing occurrence: Trat province in the eastern Gulf of Thailand, the Sibu-Tinggi Islands and Kuching Bay, Malaysia, and Kien Giang Biosphere Reserve in southwestern Vietnam. These field sites have similar species of coastal marine mammals, small-scale and commercial fisheries, and support for research from universities and/or management. In Thailand and Kuching, results showed changing patterns of fishing and Irrawaddy dolphin Orcaella brevirostris habitat use across seasons, showing how bycatch risk could change throughout the year. Risk maps for dugongs Dugong dugon in peninsular Malaysia highlighted patterns of bycatch risk concentrated around a mainland fishing pier, and revealed high risk in a northern subregion. In Vietnam, first maps of bycatch risk for the Irrawaddy dolphin showed the highest risk driven by intensive use of gillnets and trawling gear. ByRA pinpointed areas of spatial and seasonal bycatch exposure, and estimated the consequence of bycatch on local species, providing managers with critical information on where to focus bycatch mitigation and meet new global standards for US Marine Mammal Protection Act and other international regulation (e.g. Official Journal of the European Union 2019; Regulation 2019/1241) compliance. The toolbox, a transferable open-source tool, can be used to guide fisheries management, marine mammal conservation, spatial planning, and further research.