Beached bachelors: An extensive study on the largest recorded sperm whale Physeter macrocephalus mortality event in the North Sea

Physical Measures of Welfare in Fin (Balaenoptera physalus) and Humpback Whales (Megaptera novangliae) Found in an Anthropized Environment: Validation of a First Animal-Based Indicator in Mysticetes

Anthropogenic activities impacting marine environments are internationally recognized as welfare issues for wild cetaceans. This study validates a first evidence-based physical indicator for the welfare assessment protocol of humpback (n = 50) and fin whales (n = 50) living in a highly anthropized environment. Visual assessments of body condition, skin health, prevalence of injuries and parasite/epibiont loads were performed using a species-specific multi-scale measuring tool. A total of 6403 images were analyzed (fin, n = 3152; humpback, n = 3251) and results were validated through reliability and positive discrimination statistical tests. Based on physical measures, welfare assessment results showed that 60% of humpback whales were considered in a good welfare state compared to only 46% of fin whales. Significant relationships were observed in both species, between environmental parameters like dissolved oxygen levels, and prevalence of cutaneous lesions like pale skin patch syndrome. Furthermore, animals with injuries due to anthropogenic activities were more likely to be in poorer body condition, suggesting chronic stress affecting welfare.

Female, juvenile, and calf sperm whale Physeter macrocephalus (Linnaeus 1758) records from Ireland

Sperm whales spatially segregate by sex and social behavior as they mature. In the North Atlantic, male whales move to higher latitudes as far as Svalbard at 80° N, while females and young whales typically remain around lower latitudes below 40-45° N. The Azores, Madeira, and the Canary Islands constitute important nursery grounds for female and young sperm whales. Irish waters represent a midpoint for this species' spatial segregation in the Northeast Atlantic, where the species occurs along the submarine canyon systems to the west of the country. Historically, just male whales were thought to be found in this region between 51 and 55° N, but one adult female was caught by commercial whalers in 1910, and a 5.49 m calf was found stranded in 1916. Between 1995 and 2023, 10 female sperm whales have been stranded around the coast of Ireland. Eight of these whales have been stranded since 2013, and there has been at least one stranding per year between 2019 and 2023. Four of these strandings have occurred in Donegal in the northwest of Ireland, indicating the presence of female whales along the continental shelf off this region. Two females were stranded within a day of each other and were found in similar states of decomposition in February 2022, indicating that they may have been part of the same group rather than being lone vagrant individuals. Sperm whale calves and juveniles were also sighted in Irish waters in 2001, 2004, and 2010 in the Rockall Trough, along the Porcupine Bank and Goban Spur, where between 1 and 3 individuals were observed on four occasions while one calf live stranded in 2004. These records indicate a historical presence of female and young sperm whales in this region but that an apparent increase in occurrence has taken place over the past decade.

Survey of selected viral agents (herpesvirus, adenovirus and hepatitis E virus) in liver and lung samples of cetaceans, Brazil

Hepatic and pulmonary lesions are common in cetaceans, despite their poorly understood viral etiology. Herpesviruses (HV), adenoviruses (AdV) and hepatitis E virus (HEV) are emerging agents in cetaceans, associated with liver and/or pulmonary damage in mammals. We isolated and molecularly tested DNA for HV and AdV (n = 218 individuals; 187 liver and 108 lung samples) and RNA for HEV (n = 147 animals; 147 liver samples) from six cetacean families. All animals stranded or were bycaught in Brazil between 2001 and 2021. Positive-animals were analyzed by histopathology. Statistical analyses assessed if the prevalence of viral infection could be associated with the variables: species, family, habitat, region, sex, and age group. All samples were negative for AdV and HEV. Overall, 8.7% (19/218) of the cetaceans were HV-positive (4.8% [9/187] liver and 11.1% [12/108] lung), without HV-associated lesions. HV-prevalence was statistically significant higher in Pontoporiidae (19.2%, 10/52) when compared to Delphinidae (4.1%, 5/121), and in southeastern (17.1%, 13/76)-the most industrialized Brazilian region-when compared to the northeastern region (2.4%, 3/126). This study broadens the herpesvirus host range in cetaceans, including its description in pygmy sperm whales (Kogia breviceps) and humpback whales (Megaptera novaeangliae). Further studies must elucidate herpesvirus drivers in cetaceans.

Life History Traits of Sperm Whales Physeter macrocephalus Linnaeus, 1758 Stranded along Italian Coasts (Cetartiodactyla: Physeteridae)

We investigated the relationship between age and body length, and age at sexual maturity of Physeter macrocephalus individuals stranded along the Italian coast. Our molecular analysis shows that all our samples belong to the C.001.002 haplotype, shared between Atlantic and Mediterranean populations. We show that males attain sexual maturity at 10 years, similar to those from other marine areas. However, considering the same body length class, Mediterranean males are older than Atlantic ones. Our finding of a Mediterranean pregnant female of only 6.5 m in length and an assessed age of 24-26 years is particularly noteworthy, considering that females reach sexual maturity at about 9 years and 9 m of total length in other regions. Comparing our results with the literature data, we highlight the positive correlation between lifespan, adult body length and weight of males from the Mediterranean and Atlantic Ocean. Regardless of whether the relatively small size of Mediterranean specimens is a consequence of an inbreeding depression or an adaptation to less favorable trophic conditions, we recommend to closely monitor this population from a conservation perspective. In fact, its low genetic diversity likely corresponds to a relatively limited ability to respond to environmental changes compared with other populations.

Epibiotic fauna of the Antarctic minke whale as a reliable indicator of seasonal movements

Antarctic minke whales, Balaenoptera bonaerensis, breed in tropical and temperate waters of the Southern Hemisphere in winter and feed in Antarctic grounds in the austral summer. These seasonal migrations could be less defined than those of other whale species, but the evidence is scanty. We quantitatively describe the epibiotic fauna of Antarctic minke whales and explore its potential to trace migrations. Seven species were found on 125 out of 333 examined Antarctic minke whales captured during the last Antarctic NEWREP-A expedition in the Southern Ocean: the amphipod Balaenocyamus balaenopterae (prevalence = 22.2%), the copepod Pennella balaenoptera (0.6%); three coronulid, obligate barnacles, Xenobalanus globicipitis (11.1%), Coronula reginae (8.7%), C. diadema (0.9%); and two lepadid, facultative barnacles, Conchoderma auritum (9.0%) and C. virgatum (0.3%). Species with prevalence > 8% exhibited a modest increase in their probability of occurrence with whale body length. Data indicated positive associations between coronulid barnacles and no apparent recruitment in Antarctic waters. All specimens of X. globicipitis were dead, showing progressive degradation throughout the sampling period, and a geographic analysis indicated a marked drop of occurrence where the minimum sea surface temperature is < 12 °C. Thus, field detection -with non-lethal methodologies, such as drones- of coronulid barnacles, especially X. globicipitis, on whales in the Southern Ocean could evince seasonal migration. Future investigations on geographical distribution, growth rate, and degradation (for X. globicipitis) could also assist in timing whales' migration.

Auditory evoked potential in stranded melon-headed whales (Peponocephala electra): With severe hearing loss and possibly caused by anthropogenic noise pollution

Highly concentrated live mass stranding events of dolphins and whales happened in the eastern coast of China between June and October 2021. The current study adopted the non-invasive auditory evoked-potential technique to investigate the hearing threshold of a stranded melon headed whale (Peponocephala electra) at a frequency range of between 9.5 and 181 kHz. It was found that, at the frequency range of from 10 to 100 kHz, hearing thresholds for the animal were between 20 and 65 dB higher than those of its phylogenetically closest species (Pygmy killer whale). The severe hearing loss in the melon headed whale was probably caused by transient intense anthropogenic sonar or chronic shipping noise exposures. The hearing loss could have been the cause for the observed temporal and spatial clustered stranding events. Therefore, there is need for noise mitigation strategies to reduce noise exposure levels for marine mammals in the coastal areas of China.

Cetacean Strandings From Space: Challenges and Opportunities of Very High Resolution Satellites for the Remote Monitoring of Cetacean Mass Strandings

The study of cetacean strandings was globally recognised as a priority topic at the 2019 World Marine Mammal Conference, in recognition of its importance for understanding the threats to cetacean communities and, more broadly, the threats to ecosystem and human health. Rising multifaceted anthropogenic and environmental threats across the globe, as well as whale population recovery from exploitation in some areas, are likely to coincide with an increase in reported strandings. However, the current methods to monitor strandings are inherently biased towards populated coastlines, highlighting the need for additional surveying tools in remote regions. Very High Resolution (VHR) satellite imagery offers the prospect of upscaling monitoring of mass strandings in minimally populated/unpopulated and inaccessible areas, over broad spatial and temporal scales, supporting and informing intervention on the ground, and can be used to retrospectively analyse historical stranding events. Here we (1) compile global strandings information to identify the current data gaps; (2) discuss the opportunities and challenges of using VHR satellite imagery to monitor strandings using the case study of the largest known baleen whale mass stranding event (3) consider where satellites hold the greatest potential for monitoring strandings remotely and; (4) outline a roadmap for satellite monitoring. To utilise this platform to monitor mass strandings over global scales, considerable technical, practical and environmental challenges need to be addressed and there needs to be inclusivity in opportunity from the onset, through knowledge sharing and equality of access to imagery.

Bacteriological and histopathological findings in cetaceans that stranded in the Philippines from 2017 to 2018

The relatively high frequency of marine mammal stranding events in the Philippines provide many research opportunities. A select set of stranders (n = 21) from 2017 to 2018 were sampled for bacteriology and histopathology. Pertinent tissues and bacteria were collected from individuals representing eight cetacean species (i.e. Feresa attenuata, Kogia breviceps, Globicephala macrorhynchus, Grampus griseus, Lagenodelphis hosei, Peponocephala electra, Stenella attenuata and Stenella longirostris) and were subjected to histopathological examination and antibiotic resistance screening, respectively. The antibiotic resistance profiles of 24 bacteria (belonging to genera Escherichia, Enterobacter, Klebsiella, Proteus, and Shigella) that were isolated from four cetaceans were determined using 18 antibiotics. All 24 isolates were resistant to at least one antibiotic class, and 79.17% were classified as multiple antibiotic resistant (MAR). The MAR index values of isolates ranged from 0.06 to 0.39 with all the isolates resistant to erythromycin (100%; n = 24) and susceptible to imipenem, doripenem, ciprofloxacin, chloramphenicol, and gentamicin (100%; n = 24). The resistance profiles of these bacteria show the extent of antimicrobial resistance in the marine environment, and may inform medical management decisions during rehabilitation of stranded cetaceans. Due to inadequate gross descriptions and limited data gathered by the responders during the stranding events, the significance of histopathological lesions in association with disease diagnosis in each cetacean stranding or mortality remained inconclusive; however, these histopathological findings may be indicative or contributory to the resulting debility and stress during their strandings. The findings of the study demonstrate the challenges faced by cetacean species in the wild, such as but not limited to, biological pollution through land-sea movement of effluents, fisheries interactions, and anthropogenic activities.

Trace element analysis reveals bioaccumulation in the squid Gonatus fabricii from polar regions of the Atlantic Ocean

The boreoatlantic gonate squid (Gonatus fabricii) represents important prey for top predators-such as marine mammals, seabirds and fish-and is also an efficient predator of crustaceans and fish. Gonatus fabricii is the most abundant cephalopod in the northern Atlantic and Arctic Ocean but the trace element accumulation of this ecologically important species is unknown. In this study, trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) were analysed from the mantle muscle and the digestive gland tissue of juveniles, adult females, and adult males that were captured south of Disko Island off West-Greenland. To assess the feeding habitat and trophic position of this species, stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) were measured in their muscle tissue. Mercury concentrations were positively correlated with size (mantle length) and trophic position. The Hg/Se ratio was assessed because Se has been suggested to play a protective role against Hg toxicity and showed a molar surplus of Se relative to Hg. Cadmium concentrations in the digestive gland were negatively correlated with size and trophic position (δ¹⁵N), which suggested a dietary shift from Cd-rich crustaceans towards Cd-poor fish during ontogeny. This study provides trace element concentration data for G. fabricii from Greenlandic waters, which represents baseline data for a northern cephalopod species. Within West-Greenland waters, G. fabricii appears to be an important vector for the transfer of Cd in the Arctic pelagic food web.