Search Results (316)

Effective species identification is crucial for the conservation and management of marine mammals, particularly in regions such as the Mediterranean Sea, where several cetacean populations are endangered or vulnerable. In this study, we developed and validated a High-Resolution Melting (HRM) analysis protocol for the rapid, cost-effective, and reliable identification of the four representative marine cetacean species that occur in the Mediterranean Sea: the bottlenose dolphin (Tursiops truncatus), the striped dolphin (Stenella coeruleoalba), the sperm whale (Physeter macrocephalus), and the fin whale (Balaenoptera physalus). Species-specific primers targeting mitochondrial DNA regions (cytochrome b and D-loop) were designed to generate distinct melting profiles. The protocol was tested on both tissue and fecal samples, demonstrating high sensitivity, reproducibility, and discrimination power. The results confirmed the robustness of the method, with melting curve profiles clearly distinguishing the target species and achieving a success rate > 95% in identifying unknown samples. The use of HRM offers several advantages over traditional sequencing methods, including reduced cost, speed, portability, and suitability for degraded samples, such as those from the stranded individuals. This approach provides a valuable tool for non-invasive genetic surveys and real-time species monitoring, contributing to more effective conservation strategies for cetaceans and enforcement of regulations against illegal trade. Full article

Bycatch is the most common cause of death of small delphinids worldwide, including the Mediterranean Sea. The diagnosis of bycatch as cause of death in stranded cetaceans depends on the cumulative presence of multiple findings, termed bycatch criteria. In this study, we retrospectively evaluated the presence of bycatch criteria in 138 necropsied cetaceans, 136 stranded and 2 confirmed bycaught, in the Catalan Mediterranean Sea across a 13-year period. With the aim of identifying the most specific and reliable bycatch criteria, the animals’ cause of death was classified as either bycaught or other causes. Animals were necropsied according to standard procedures with complete histopathological examination and ancillary diagnostic techniques. We reviewed the necropsy reports and photographs of 138 cetaceans of seven species. Bycatch had been determined as the cause of death/stranding in 40 (29%) necropsied cetaceans. Both sexes were equally represented in the bycatch group. Bycatch was diagnosed in the Mediterranean common bottlenose dolphin (10/14; 71.4%), striped dolphin (29/108; 26.9%), and Risso’s dolphin (1/11; 9.1%). Sixty-seven out of 98 (68.3%) cetaceans that had been classified as non-bycatch had one or two bycatch criteria. Cetaceans with two and three major criteria had an overlap of causes of death, as some animals were diagnosed with bycatch and others with other causes of mortality. Animals with four criteria were invariably diagnosed as being bycaught. Recent feeding, absence of disease, good nutritional status, marks of fishing gear, multiorgan intravascular gas bubbles, hyphema and amputations or sharp incisions presumably inflicted by humans were significantly more likely to result in a diagnosis of bycatch, while loss of teeth and cranial fractures were not. None of the dolphins diagnosed as bycatch had ingested fishing gear. Our results highlight the relevance of bycatch as the cause of death of dolphins in the Mediterranean and suggest that some criteria traditionally linked to bycatch are not specific for bycatch in our region. Full article

Semen collection is an important component of conservation and animal husbandry. Semen quality is generally improved using voluntary collection methods, particularly artificial vaginas (AVs). Most commercially available AVs are tube-shaped with few species-specific design augmentations. As genitalia are highly variable across taxa, incorporating species-specific genital morphologies into AV designs may enhance collected semen quality. We compared dolphin semen quality using: (1) silicone bioinspired artificial vaginas (BAVs) that reflect the internal shape of dolphin vaginas, and (2) manual stimulation. Sperm motility and kinematic parameters of five bottlenose dolphins (Tursiops sp.) were assessed using computer-aided sperm analysis (CASA). Sperm collected using BAVs showed non-significant increases in median progressive and rapid motility, and increases in median and mean linear motility, supporting a sexual selection functional hypothesis for the biodiverse vaginal folds unique to whales, dolphins, and porpoises. Sperm concentration decreased with BAV collection, while no consistent trends were detected in volume, pH, velocity, or plasma membrane integrity. Modifications to AVs for other species that incorporate genital morphologies may also optimize collected semen quality for application to artificial insemination. Full article

Humpback whales (Megaptera novaeangliae) are well known for their complex acoustic communication, which plays a critical role in social interactions and reproduction. Understanding the variability in humpback whale songs is crucial to deciphering their communication strategies and the factors that influence these changes, which may affect reproductive success and population dynamics. While most studies of humpback whale song behavior have focused on annual variation, intra-seasonal changes remain underexplored. This study investigates intra-seasonal song variation in the Colombian Pacific humpback whale population, a unique and diverse breeding stock. We analyzed 37 h of recordings collected during two distinct periods of the 2019 breeding season (July and August–September) in the northern Colombian Pacific. Song repertoires were compared between periods, and the acoustic structure of a common song unit (Unit1) was analyzed using spectrographic cross-correlation. Results revealed a decrease in repertoire diversity over the course of the season, along with an increase in the song rate and the acoustic consistency of Unit1 during the second period. These findings highlight the dynamic nature of humpback whale song production and suggest potential influences of social learning and hormonal modulation. Such insights may be useful for the conservation and monitoring of humpback whale populations in breeding areas. Full article

Imidazole dipeptides (IDPs), including anserine, carnosine, and balenine, are predominantly found in the skeletal muscles of vertebrates. Balenine is the major IDP in cetaceans. Serum amyloid A (SAA) is an acute phase protein released in response to damage or injury in various tissues, including skeletal muscles. A captive bottlenose dolphin (Tursiops truncatus) died due to rhabdomyolysis and subsequent acute kidney injury that probably originated from accidental muscle trauma. In this study, concentrations of IDPs and SAA were measured using stored serum collected from the affected dolphin with intermittent continuous damage of skeletal muscles to demonstrate the pathological relevance of these parameters and their usefulness as biomarkers for muscle damage in dolphins. The IDP concentration was measured using the high-performance liquid chromatography-ultraviolet method. The SAA concentration was measured using an enzyme-linked immunosorbent assay (ELISA) specific to dolphin SAA and a latex turbidimetric immunoassay (LTI) specific to human SAA. Herein, the IDP concentration was altered similarly to serum muscular enzymes, including creatinine kinase (CK) and aspartate aminotransferase (AST). However, IDP concentrations were elevated one day earlier than CK and AST levels at disease onset. Furthermore, IDP concentrations were similarly altered when assessed using both ELISA- and LTI-SAAs, and the change in IDP concentration coincided with that in LTI-SAA based on the statistical analysis. These data suggest that IDP concentration could detect muscle damage and injury, including necrosis and inflammation, in dolphins. Full article

This study estimated the density distribution of Antarctic krill inhabiting an area near the South Shetland Islands using two acoustic analysis methods recommended by the Commission for the Conservation of Antarctic Marine Living Resources, based on data collected using an echosounder installed on commercial fishing vessels. Mean Antarctic krill density for the entire survey area was estimated with two methods recommended by the Commission for the Conservation of Antarctic Marine Living Resources. The mean body length of krill collected using trawl gear was 49.06 ± 4.15 mm (range: 22.0–67.0 mm), with mode of krill observed at 50 mm body length. Using the swarm-based method and the frequency differences according to krill size, the mean densities of krill for stations and transects were 14.86 g/m² (CV = 47.09%) and 13.10 g/m² (CV = 41.16%), respectively. Furthermore, using the dB-difference method for the entire survey area, the average densities were 10.76 g/m² (CV = 43.83%) and 10.14 g/m² (CV = 53.48%), respectively, using the frequency difference based on krill size determined at all stations and per transect. Full article

The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis; YFP) is the only freshwater cetacean species that remains in the Yangtze River, China. Poyang Lake is connected to the main stream of the Yangtze River, and the number of YFPs in Poyang Lake constitutes approximately half of the total species population. To implement effective conservation measures and formulate scientific genetic management strategies for the YFPs in Poyang Lake, we conducted population genetic analyses on 125 blood samples from the Poyang population and 46 tissue samples from the Anqing population, utilizing mitochondrial DNA D-loop and microsatellite loci. The genetic diversity analysis revealed two haplotypes in the Poyang population, with mitochondrial genetic diversity indices of Hd = 0.481 ± 0.020 and Pi = 0.00078 ± 0.00030. Microsatellite markers further demonstrated indices of Ho = 0.610 and He = 0.655. The genetic differentiation analysis indicated that the two populations exhibited moderate genetic differentiation (0.05 < Fst < 0.15). Upon excluding the dead samples from the Anqing population, the genetic differentiation between the two populations increased and the gene flow diminished. This indicated that certain dead samples from the Anqing population might have originated from Poyang Lake or had a background of Poyang Lake–Yangtze River migration and gene exchange. This finding was further corroborated by STRUCTURE analysis, which revealed genetic admixture between the two populations. We assessed the current genetic diversity of the Poyang population and its genetic differentiation from the Anqing population. This study provides fundamental data for formulating a conservation program for YFPs in Poyang Lake. Full article

The presence of cetaceans along the Campania coast has always been documented. Between 2016 and 2022, out of 65 cetaceans stranded along the Campania coast, 46 were studied for bacteriological, virological, parasitological, and histopathological investigations. The results highlighted that for 59% (n = 27) of the specimens, the cause of death was of natural origin, while for only 2% (n = 1) of animals, the origin of death was ascribed to anthropic causes. Unfortunately, for 39% (n = 18) of the cetaceans, it was impossible to determine the cause of death. All the cetaceans that died of natural causes showed viral, bacterial, and parasitic infections. The primary pathogens detected were Cetacean Morbillivirus (CeMV, 65.2%, n = 30/46), Toxoplasma gondii (10.9%, n = 5/46), and Brucella ceti (8.7%, n = 4/46). The animals showed typical lesions of the isolated pathogens, such as systemic infection, meningoencephalitis, and pneumonia. Moreover, even with a lower frequency, other relevant pathogens like Photobacterium damselae, Salmonella enteritidis, Erysipelothrix rhusiopathiae, and Chlamydia abortus were isolated. These data were useful to understand the spread and circulation of these pathogens, some zoonotic, in the coastal marine waters of the Campania region. Full article

The feeding characteristics of the chub mackerel, Scomber japonicus from Jeju Island waters and the Yellow Sea were compared by analyzing the stomach contents. Large and small purse seines were used to collect 1437 individuals from Jeju Island waters and 1066 individuals from the Yellow Sea. The fork length of S. japonicus ranged from 21.0 to 43.6 cm for individuals from Jeju Island waters and 19.6 to 41.5 cm for those from the Yellow Sea. Based on the index of relative importance and variation in stomach contents according to fish size, S. japonicus was identified as a piscivore and a spatiotemporally opportunistic feeder. The proportion of fish in the diet increased as the body sizes of S. japonicus from both Jeju Island waters and the Yellow Sea increased, whereas the proportion of copepods, amphipods, and euphausiids gradually decreased. Differences in stomach content compositions were observed due to interactions between size and location. Thus, the feeding characteristics of S. japonicus are affected by the abundance and composition of prey in its habitat. Full article

Tongue-nibbling is a rare and previously undocumented affiliative behaviour in free-ranging killer whales (Orcinus orca), until now seen only in individuals under human care. This study presents the first recorded observation of tongue-nibbling between two wild killer whales in the Kvænangen fjords, Norway. The interaction, captured opportunistically by citizen scientists during a snorkelling expedition, lasted nearly two minutes and involved repeated episodes of gentle, face-to-face oral contact. This behaviour closely resembles sequences observed and described in detail in zoological settings, suggesting that it forms part of the species’ natural social repertoire. The observation also supports the interpretation of tongue-nibbling as a socially affiliative behaviour, likely involved in reinforcing social bonds, particularly among juveniles. The prolonged maintenance of this interaction in managed populations originating from geographically distinct Atlantic and Pacific lineages further indicates its behavioural conservation across contexts. This finding underscores the importance of underwater ethological observation in capturing cryptic social behaviours in cetaceans and illustrates the value of integrating citizen science into systematic behavioural documentation. The study also reinforces the relevance of managed populations in ethological research and highlights the ethical need for carefully regulated wildlife interaction protocols in marine tourism. Full article

Aspergillus spp., particularly A. fumigatus, are increasingly reported as emerging pathogens in cetaceans, yet their clinical and ecological relevance remains poorly characterized. This systematic review synthesizes evidence from 34 studies involving 106 animals, identifying respiratory, neurological, and otic infections as the most frequent presentations with potential interspecies tropism. Invasive disease, frequently fatal, was linked to co-infections—especially with morbillivirus—and environmental stressors such as pollution- and climate-related immune suppression. Despite cetaceans’ role as sentinel species, antifungal susceptibility testing and species-level identification were inconsistently performed. Additionally, azole-resistant A. fumigatus strains were isolated from wild porpoises, indicating environmental antifungal exposure and potential public health implications. Aspergillosis remains underdiagnosed in free-ranging populations, particularly in remote or pelagic species. Conservation implications were scarcely addressed, despite evidence suggesting that fungal disease may contribute to morbidity, stranding, and population impact. This review underscores the need for enhanced surveillance, integrative diagnostics, and recognition of fungal pathogens in a One Health framework. The growing intersection of climate change, emerging mycoses, and wildlife conservation positions Aspergillus infections in cetaceans as both a marine mammal health concern and an ecological indicator of broader environmental changes. Full article

Whale signals originating in the vicinity of a triplet of underwater hydrophones, at a 2 km distance from each other, are recorded at the three sensors. They offer the opportunity to test simple models of propagation applied in the immediate neighborhood of the triplet, by comparing the arrival times and amplitudes of direct and reflected paths between the whale and the three hydrophones. Examples of recordings of individual fin whales passing by hydrophone triplets, based on the characteristics of their vocalizations around 20 Hz, are presented. Two types of calls are observed and their source wavelets extracted. Time segments are delimited around each call using a power detector. The time of arrival of the direct wave to the sensor and the Time Differences of Arrivals (TDOA) between sensors are obtained by correlation of the extracted source wavelets within the time segments. In addition to direct arrival, multiple reflections and the delays between the reflection and the direct arrival are automatically picked. A grid-search method of tracking the calls is presented based on the TDOA between three hydrophones and reflection delay times. Estimates of the depth of vocalization of the whale are made assuming a simple straight ray propagation model. The amplitude ratios between two hydrophones follow the spherical amplitude decay law of one over distance when the cetacean is in the immediate vicinity of the triplet, in a circle of radius 1.5 km sharing its center with the triplet’s center. Full article

Emerging RNA viruses pose a critical threat to aquatic animals, leading to significant ecological and economic consequences. Their high mutation rates and genetic adaptability drive rapid evolution, cross-species transmission, and expanding host ranges, complicating disease management. In aquaculture, RNA viruses are responsible for major outbreaks in fish, while DNA viruses predominate in crustaceans. Marine mammals are increasingly affected by morbilliviruses and highly pathogenic avian influenza (HPAI) H5N1, which has caused widespread mortality events in pinniped and cetacean populations, raising concerns about zoonotic spillover. The absence of effective antiviral treatments and the complexity of vaccine development highlight the urgent need for enhanced biosecurity measures. Furthermore, novel vaccine approaches, such as self-assembling protein nanocage platforms, offer promising solutions for RNA virus mitigation. This review provides a comprehensive analysis of the emergence and significance of RNA viruses in aquatic animals over the last two decades, with a particular focus on biosecurity and vaccine development. Full article

Proline-rich antimicrobial peptides (PrAMPs) primarily exert their antimicrobial effects intracellularly, inhibiting protein synthesis. B7-005, a synthetic 16-amino acid PrAMP, has a broader antimicrobial spectrum compared to native counterparts, despite shorter PrAMPs typically exhibiting reduced activity. This study aimed to enhance B7-005’s potency by extending it with 6 or 11 amino acids derived from the C-terminal sequences of cetacean Tur1A and Lip1 PrAMPs, as well as bovine Bac7(1-35). Six chimeric derivatives were evaluated for antimicrobial and bactericidal potency, cytotoxicity, bacterial membrane permeabilization, and in vitro inhibition of protein synthesis. Extending B7-005 with sequences from other PrAMPs increased its activity against most ESKAPE+E pathogens, reducing minimum inhibitory concentration (MIC) values by 2- to 8-fold, with notable differences among bacterial species, without increasing cytotoxicity toward the A549 cell line. All chimeras retained the ability to inhibit protein synthesis in Escherichia coli and to modestly perturb the E. coli membranes like B7-005. These novel chimeric PrAMPs, particularly the 22-mer derivatives, hold promise for developing new antimicrobial agents. The study also highlights variability in bacterial responses to PrAMPs and underscores how minor sequence differences can significantly impact efficacy against specific microorganisms. PrAMPs thus represent a valuable scaffold to rationally design derivatives targeting high-priority pathogens. Full article

The common dolphin, Delphinus delphis, is the most abundant cetacean species along the western Iberian Peninsula and faces many anthropogenic threats, with bycatch being the most impactful. Its preferred prey, sardine (Sardina pilchardus), has shown fluctuating abundance over the past decade, potentially influencing dolphin distribution. This study provides the first insights into common dolphin distribution along the western Iberian coast, using sighting data from vessel research surveys (2005–2020) to identify hotspot areas while accounting for monthly and seasonal distributions overlapping with sardine abundance. Common dolphin hotspots were located along the central–western and southern Portuguese mainland coasts, coinciding with important fishing ports, oceanographic features, and sardine juvenile habitats. Furthermore, during 2013–2016, common dolphins were observed significantly farther from the coast, coinciding with a period of particularly low coastal sardine biomass. However, GAM analysis indicated that the relationship between sardine biomass and the distance of common dolphins was not significant. This study highlights the major common dolphin hotspots and presents the most comprehensive temporal and distribution maps of the common dolphin along the western Iberian coast, particularly in response to sardine availability. These results can be used by managers to inform conservation measures and for the sustainable management of the Portuguese sardine purse seine fishery fleet, which interacts the most with the species. Full article