The Cuvier's beaked whale, Ziphius cavirostris, is a cosmopolitan species and the only beaked whale species commonly found in the Mediterranean Sea. Five strandings of Cuvier's beaked whale were reported along the Aegean/Mediterranean Seas coasts of Türkiye and northern coast of Cyprus in 2016–2017. Mitochondrial DNA (mtDNA) control region (430–444 bp) and cytochrome b (cytb) (382–424 bp) sequences each revealed two different haplotypes (four out of five individuals had the same haplotype for each locus) on these stranded animals. The control region haplotypes were identical to two previously identified haplotypes from the Ionian (Greece) and Adriatic (Croatia) Seas. Only one of the cytb haplotypes had previously been described from the Adriatic Sea (Italy) and the other one was detected for the first time. In a comparison of these haplotypes with Cuvier's beaked whale haplotypes previously reported from outside the Mediterranean Sea, the Mediterranean subpopulation shows genetic differentiation based upon the presence of two unique haplotypes. Additional mtDNA sequences from the Mediterranean Sea are needed for a better understanding of the genetic population structure of this species and to elaborate more concrete conservation measures.

Species distributions are predicted to change with future climate-associated ecosystem changes such that so-called ‘vagrant’ individuals may become established or re-establish in areas currently thought to be beyond their principle ranges. Survey data were collated for occurrences of pinniped (seal) species at very high latitudes of the Vestfold Hills, East Antarctica. Aside from Weddell seals (Leptonychotes weddellii) and southern elephant seals (Mirounga leonina), which aggregate annually at the Vestfold Hills to breed and/or moult, three other pinniped species were observed with the recession of the fast-ice edge. Leopard seal (Hydrurga leptonyx) occurrences increased with an increase in a seasonally abundant prey resource, and crabeater seals (Lobodon carcinophaga) were seen at a time that coincides with their moult period. Occurrences of sub-adult male Antarctic fur seals (Arctocephalus gazella) increase the known southward range for this species and may reflect population increases at source populations in the Kerguelen Plateau area. Although there were no direct sightings of Ross seals (Ommatophoca rossii), their presence close to the Vestfold Hills was detected by underwater passive acoustic monitoring. Sightings of obligate drift-ice species and sub-Antarctic fur seals may change at the Vestfold Hills with climate-mediated changes in sea-ice conditions.

A new record of a white humpback whale (Megaptera novaeangliae) was made off Papeete, Tahiti in July 2019. The individual was completely white, except for grey patterns on its body and on the ventral part of the fluke. The presence of different colourations indicates that this individual is not an albino but a leucistic individual. According to field observations, the individual was likely a juvenile or a subadult. It was seen breaching several times and travelled further north of Papeete, where the animal was recaptured off Arue. White individuals are rare and offer unique opportunities to understand whale movement patterns and potential population connectivity among humpback whale populations.

Changes in abundance and distribution of marine top predators can indicate environmental change or anthropogenic pressure requiring management response. Here, we used an extensive dataset (21 years) to conduct a spatial and temporal analysis of grey seal strandings in Cornwall and the Isles of Scilly, close to the southern edge of the breeding range of the species. A total of 2007 strandings were reported from 2000 to 2020, increasing by 474% from 35 to 201 individuals per year during this period. The continued rise in strandings was consistent across all life stages and timeframes (5, 10 and 20 years), underpinning the suggestion of increasing abundance in the region. The observed seasonality differed by life stage, coinciding with the increased presence of animals near the coast for key life phases such as breeding, moulting and pupping. Strandings are widely distributed across the coast of Cornwall and the Isles of Scilly; however, most strandings were recorded on the north coast of Cornwall (70%) where major pupping and haul out sites are found. Despite hosting several pupping and haul out sites, a small proportion was recorded on the Isles of Scilly (5%) where it is thought that strandings are particularly underreported. Describing baselines in magnitude of strandings and life-stage compositions across space and time allows future deviations in frequency, demographic composition or spatial distribution to be detected and investigated. We demonstrate the utility of long-term citizen science data to provide valuable and cost-effective information on the distribution and abundance of a highly mobile marine mammal.

Suckerfish attached to dolphin species have been extensively reported worldwide, yet such association has been rarely seen in the tropical and shallow waters of South America. In Brazil, the Guiana dolphin Sotalia guianensis is distributed along almost the entire extent of the coast and only one case of association with suckerfish has been published. Here we report on a sharksucker Echeneis naucrates associated with a young Guiana dolphin on the north-eastern coast of Brazil. The juvenile dolphin with an attached sharksucker was observed on two occasions separated by a 47-day period; we hypothesize the occurrence of host attachment fidelity. The present report adds information to better discuss the ecological interactions between echeneids and dolphins, and expands the baseline information on cetacean species serving as host to suckerfish.

We analysed 23 years of data on strandings of the Antillean manatee Trichechus manatus manatus in Belize, documented by the Belize Marine Mammal Stranding Network, to examine the threats to this population. A total of 451 stranding incidents were reported, of which 376 (83.4%) cases were verified. A total of 286 (63.4%) of the incidents occurred within Belize District, where the number of strandings has almost tripled since 2009. Watercraft collisions accounted for the highest number of strandings, with 131 confirmed cases, and is the leading cause of anthropogenic mortality for this population. Collision with watercraft is an emerging and major threat to manatees in Belize, and is correlated with increases in human activity, in particular associated with tourism. This finding of high levels of manatee deaths in Belize is consistent with trends previously reported for manatees in Florida and Puerto Rico. This work can provide guidance to detect and address similar patterns of mortality in other Antillean manatee populations across the species' range. There is a need for greater awareness of the threats facing the species and its habitat, for stakeholder partnerships to address these threats, implementation of legislation for the protection of manatees, and consistent enforcement of regulations to protect this population. Boating regulations, such as no-wake zones within areas of high manatee presence, as well as regulation of tourism boating activities, need to be implemented to reduce the threats to the species.

Once widespread throughout the Black and Mediterranean Seas and the coasts of north Africa, the Endangered Mediterranean monk seal Monachus monachus has disappeared throughout most of its original range. In Cyprus evidence suggests that the species became effectively extinct at the end of the 20th century. Following an increase of seal sightings around the island, a monitoring programme was established in 2009 to evaluate the status of the species. During 2009–2018, using field surveys, photographs from camera traps and an information network, we recorded an increasing number of seal sightings, and the birth of several pups, indicating the permanent presence of the species on the island. This is the first recorded re-establishment of a Mediterranean monk seal population in an area of its former range following near eradication.

Weddell seals are polar predators that must partition their time between many behaviours, including hunting prey at depth and breathing at the surface. Although they have been well studied, little is known about how foraging behaviour changes when access to breathing holes is restricted, such as in the isolated-hole paradigm. The current study took advantage of previously gathered data for seals diving at an isolated hole to compare with foraging behaviour of free-ranging seals that had access to multiple holes. We examined dive structure, hunting tactics, and allocation of time, locomotor activity and energy based on three-dimensional dive profiles and video imagery of prey encounters for two free-ranging and six isolated-hole seals. Midsummer foraging dives of free-ranging seals were remarkably similar to those of seals diving at an isolated hole, but there were differences in two behavioural states and the frequency of several behavioural transitions. Results indicate that seals employ an energetically more conservative foraging strategy when access to breathing holes is limited and prey are less abundant. These results highlight the importance of understanding the complex interactions between breathing hole access, prey abundance and other factors that may result in different Weddell seal foraging strategies under changing future conditions.

This paper presents results of a study conducted on the trawling industrial fishery fleet of Merluccius gayi in south-central Chile, and the resulting interactions with the South American sea lion (Otaria flavescens). This study is based on observations made during September 2004, when incidental sea lion catch in the trawls was 6.3 sea lions/working day (1.2 sea lions/trawl−1). A total of 82 animals were incidentally caught, of which 12 were found dead, and the 70 remaining suffered from internal bleeding and/or fractures as a result of their capture. 83.3% of the fatalities occurred during nocturnal trawls, which comprise 30% of all observed trawls. Possible mechanisms of sea lion take are discussed. This note presents the first records of sea lions incidental by-catch by the trawler fleet along the south-east Pacific coast of Chile.

Cetacean species and their habitats are under threat and effective marine management mitigation strategies require knowledge and understanding of cetacean ecology. This requires data that are challenging and expensive to obtain; incidental sightings/strandings data are potential underused resources. In this study, incidental cetacean sightings (N = 6631) and strandings (N = 1856) in coastal waters of Cornwall, south-west Britain (1991 to 2008) were analysed for evidence of spatial and temporal patterns or trends. Eighteen species were recorded sighted and/or stranded; key species were identified as bottlenose dolphin (Tursiops truncatus), harbour porpoise (Phocoena phocoena), common dolphin (Delphinus delphis), Risso's dolphin (Grampus griseus) and minke whale (Balaenoptera acutorostrata). There were significant decreases in bottlenose dolphin sightings and pod size but an increase in harbour porpoise and minke whale sightings. Cetacean strandings showed a recent decrease over time although there was a significant positive trend in harbour porpoise strandings that correlated with sightings. Incidence of sightings and strandings were both greater on the south coast than the north coast. When Marine Tour Operator data were analysed, distinct species-specific inshore and offshore habitat use was evident. With rigorous interrogation and editing, significant patterns and trends were gained from incidentally collected data, highlighting the importance of public engagement with such recording schemes and the potential of these underused resources.

A short term survey to quantify the number of marine mammals incidentally caught, and interviews to gain perceptions of local fishers towards issues of by-catch, were conducted. A total of 44 cetaceans was recorded as incidental catches at Chennai, Kakinada and Mangalore fishing harbours during 80 days of observation. Six species of dolphins and one species of porpoise were recorded. The spinner dolphin Stenella longirostris was the most frequently caught (38.6%), followed by the finless porpoise Neophocaena phocaenoides (31.8%). Gill-nets and purse seines operated from motorized boats accounted for the entire by-catch. It is estimated that 9000–10,000 cetaceans are killed by gill-nets every year along the Indian coast. The intricacies and possibilities of reducing cetacean kills by gill-nets are discussed in this paper.

This research was conducted to assess the location of population groups and conservation issues affecting dugongs Dugong dugon along the eastern Gulf of Thailand off Cambodia and Phu Quoc Island, Vietnam. Interviews in fishing communities in 2002 and 2004 along the Cambodian coast revealed that dugongs are sporadically found in fishing nets and their body parts are sold for a relatively large profit. During 4 days of aerial surveys in Cambodia in 2004 we saw no dugongs. We interviewed villagers in Phu Quoc Island, Vietnam, in 2002 and learnt that dugongs are regularly found and hunted, again for high profits. In both countries we recommend that legislation addressing threatened species be strengthened and enforced. In collaboration with the Cambodian and Vietnamese governments and NGOs, we propose the exploration of alternative non-destructive fishing methods and the initiation of an education campaign based on conservation of marine wildlife and the nearshore environment. National and transboundary management and community-based conservation are required in conjunction with strategies to address overfishing and poverty.

The sustainability of indigenous customary hunting and fishing in remote areas can be influenced by human factors operating at global as well as regional and local scales because of the hybrid nature and sectoral interactions of the local economic environment. The internationally significant population of dugongs (Dugong dugon or seacow) in Torres Strait between Australia and Papua New Guinea supports an important indigenous fishery. The economic, socio-cultural and environmental factors that influenced hunting activity in 1998 and 1999 by the members of the community of Mabuiag Island were investigated to inform the sustainable management of the fishery. The landed catch during the eight months March to October of 145 dugongs in 1998 and 170 dugongs in 1999 potentially provided the community with an average of 290 g of dugong meat per person per day. Fifty-seven per cent of adult males on the island participated in dugong hunting, but more than half the catch in each year was caught by only two hunters. The probability of at least one person from the community going dugong hunting in 1998 and 1999 was 0.59 ± 0.02 per day. This probability was influenced by local environmental factors, including the abundance of dugongs in the traditional hunting grounds (affected by wind speed, year, season and lunar day) and the size of the commercial crayfish catch (which is influenced by the global market price, as well as local conditions). Although dugong hunting remains a very important part of the islanders’ contemporary culture and customary economy, the capacity to hunt dugongs is facilitated by the ease with which some hunters move between the state, commercial and customary sectors of their local economy. The complexities of the economic, social and cultural environments need to be considered in planning for the sustainable harvesting of threatened species by remote indigenous communities.

Assessment of pinniped predation most often relies on analysis of the hard, undigested prey remains evident in faecal (scat) samples. For many prey species this method can yield valuable information on predator–prey interactions. For some genera, however, species diagnostic characteristics are lost during the process of prey digestion, thereby preventing morphological identification of fish prey species. Here, the feasibility of using faecal DNA to detect the presence of salmonids in pinniped scat samples and to distinguish reliably between sea trout Salmo trutta and Atlantic salmon S. salar was assessed. Novel salmonid mitochondrial DNA (mtDNA) primers were designed to amplify 162 bp of the 16S rDNA and a 327 bp section of the cytochrome b gene. Species-specific banding patterns were obtained by digestion of the cytochrome b PCR product with the restriction endonuclease AluI, and confirmed by the species-specific amplification of the 16S rDNA fragment from Atlantic salmon. Scats collected from captive grey seals Halichoerus grypus fed on known monospecific diets used to validate the PCR-RFLP assay indicated a probability of at least 95.8% (23 of 24 faecal extracts) of detecting salmonids using DNA extracted from the scat matrix. Implemented alongside conventional prey remains analyses, this technique presents a promising new method for examining prey composition and assessing pinniped predation on salmonids.

This study provides an overview of the conservation status of the West Indian manatee Trichechus manatus in Nicaragua, including data on habitat availability, manatee distribution and relative abundance, and current threats. The data is based on surveys from boats and extensive interviews with local people. Nicaragua harbors one of the largest areas of habitat suitable for manatees in Central America. The species has an almost continuous distribution along the country's eastern, Caribbean coast and inland in some watercourses. There are larger groups of manatees in brackish lagoons than in freshwater rivers. Seasonal migrations and lengthy daily travels influenced by tides have been reported. The main threats to these manatees include poaching and incidental drowning in fishing nets, while boat traffic, pollution and habitat loss presently seem to be negligible factors in Nicaragua. Poaching is widespread along the coast and it is estimated that c. 40 manatees are killed annually throughout the country. Enforcement of hunting laws and protected areas is almost non-existent, with the exception of the Southeastern Nicaragua Biosphere Reserve. This may explain why manatees have disappeared from a few areas and become rare in others. Unless restrictions are imposed on poaching and on the use of gill nets within inland wetlands, the West Indian manatee may become rare throughout Nicaragua in the near future.

It has been observed that deep-foraging marine mammals have visual pigments that are blue shifted in terms of their wavelength of maximal absorbance (λmax) when compared to analogous pigments from terrestrial mammals. The mechanisms underlying the spectral tuning of two of these blue-shifted pigments have recently been elucidated and depend on three amino acid substitutions (83Asn, 292Ser, and 299Ser) in dolphin rhodopsin, but only one amino acid substitution (308Ser) in the dolphin long-wavelength-sensitive pigment. The objective of this study was to investigate the molecular basis for changes in the spectral sensitivity of rod visual pigments from seven distantly related marine mammals. The results show a relationship between blue-shifted rhodopsins (λmax ≤ 490 nm), deep-diving foraging behavior, and the substitutions 83Asn and 292Ser. Species that forage primarily near the surface in coastal habitats have a rhodopsin with a λmax similar to that of terrestrial mammals (500 nm) and possess the substitutions 83Asp and 292Ala, identical to rhodopsins from terrestrial mammals.