Pseudorca Crassidens Research Articles

Mitochondrial genetic variation in false killer whale groups (Pseudorca crassidens) from the Mexican Pacific reveal strong regional differentiation

Marine Mammal ScienceEarly View NOTE Mitochondrial genetic variation in false killer whale groups (Pseudorca crassidens) from the Mexican Pacific reveal strong regional differentiation Anidia Blanco-Jarvio, Anidia Blanco-Jarvio Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Contribution: Conceptualization, Data curation, Formal analysis, Funding acquisition, ​Investigation, Methodology, Writing - original draft, Writing - review & editingSearch for more papers by this authorCarolina Galván-Tirado, Carolina Galván-Tirado orcid.org/0000-0003-3973-256X CONACYT - Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Contribution: Conceptualization, Data curation, Formal analysis, Methodology, Writing - original draft, Writing - review & editingSearch for more papers by this authorHaidé Cruz-Villagrán, Haidé Cruz-Villagrán Megafauna Marina y Pesquerías (MMAPE) Contribution: Data curation, Formal analysis, Methodology, Writing - original draftSearch for more papers by this authorClaudia Alicia Silva-Segundo, Claudia Alicia Silva-Segundo Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Contribution: Data curation, Formal analysis, Methodology, Writing - review & editingSearch for more papers by this authorEva Hidalgo-Pla, Eva Hidalgo-Pla Sea Shepherd Conservation Society, Sea Shepherd Scientific Department, Burbank, California Contribution: Funding acquisition, Resources, Writing - review & editingSearch for more papers by this authorJesús Erick Higuera-Rivas, Jesús Erick Higuera-Rivas Protección y Conservación Pelágica A.C., Ciudad de México, CDMX, Mexico Contribution: Resources, Writing - review & editingSearch for more papers by this authorFernando R. Elorriaga-Verplancken, Fernando R. Elorriaga-Verplancken orcid.org/0000-0002-7360-8039 Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja California Sur, Mexico Contribution: Resources, Writing - review & editingSearch for more papers by this authorHiram Rosales-Nanduca, Corresponding Author Hiram Rosales-Nanduca [email protected] orcid.org/0000-0002-5539-3476 Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Correspondence Hiram Rosales-Nanduca, Universidad Autónoma de Baja California Sur, Departamento Académico de Ingeniería en Pesquerías, Carretera al sur km 5.5 S/N, CP 23080, La Paz, Baja California Sur, Mexico. Email: [email protected]Search for more papers by this author Anidia Blanco-Jarvio, Anidia Blanco-Jarvio Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Contribution: Conceptualization, Data curation, Formal analysis, Funding acquisition, ​Investigation, Methodology, Writing - original draft, Writing - review & editingSearch for more papers by this authorCarolina Galván-Tirado, Carolina Galván-Tirado orcid.org/0000-0003-3973-256X CONACYT - Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Contribution: Conceptualization, Data curation, Formal analysis, Methodology, Writing - original draft, Writing - review & editingSearch for more papers by this authorHaidé Cruz-Villagrán, Haidé Cruz-Villagrán Megafauna Marina y Pesquerías (MMAPE) Contribution: Data curation, Formal analysis, Methodology, Writing - original draftSearch for more papers by this authorClaudia Alicia Silva-Segundo, Claudia Alicia Silva-Segundo Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Contribution: Data curation, Formal analysis, Methodology, Writing - review & editingSearch for more papers by this authorEva Hidalgo-Pla, Eva Hidalgo-Pla Sea Shepherd Conservation Society, Sea Shepherd Scientific Department, Burbank, California Contribution: Funding acquisition, Resources, Writing - review & editingSearch for more papers by this authorJesús Erick Higuera-Rivas, Jesús Erick Higuera-Rivas Protección y Conservación Pelágica A.C., Ciudad de México, CDMX, Mexico Contribution: Resources, Writing - review & editingSearch for more papers by this authorFernando R. Elorriaga-Verplancken, Fernando R. Elorriaga-Verplancken orcid.org/0000-0002-7360-8039 Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja California Sur, Mexico Contribution: Resources, Writing - review & editingSearch for more papers by this authorHiram Rosales-Nanduca, Corresponding Author Hiram Rosales-Nanduca [email protected] orcid.org/0000-0002-5539-3476 Departamento Académico de Ingeniería en Pesquerías, Universidad Autónoma de Baja California Sur, Baja California Sur, Mexico Correspondence Hiram Rosales-Nanduca, Universidad Autónoma de Baja California Sur, Departamento Académico de Ingeniería en Pesquerías, Carretera al sur km 5.5 S/N, CP 23080, La Paz, Baja California Sur, Mexico. Email: [email protected]Search for more papers by this author First published: 09 May 2023 https://doi.org/10.1111/mms.13027Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Early ViewOnline Version of Record before inclusion in an issue RelatedInformation

Current knowledge of the cetacean fauna of the Greek Seas

From 1991-2002 data on the presence and distribution of cetaceans in the Greek Seas have been systematically collated in a database (821 sightings and 715 strandings). Data originated from dedicated surveys, stranding reports, opportunistic sightings and published or unpublished photographic and video documents. Twelve cetacean species have been recorded. Seven of them are permanently present and commonly observed in one or more of the Greek Seas: striped dolphin, common bottlenose dolphin, short-beaked common dolphin, Cuvier’s beaked whale, sperm whale, Risso’s dolphin and fin whale. In addition, the harbour porpoise is present locally in the Thracian and northern Aegean Seas. The humpback whale, false killer whale and common minke whale are occasional Mediterranean species that were sighted or stranded infrequently; the Sowerby’s beaked whale is an accidental species that was found floating dead only once. Five other species (white whale, Blainville’s beaked whale, long-finned pilot whale, killer whale, blue whale) have been erroneously included in the Greek cetacean fauna in the past due to wrong assumptions, false identifications or lack of supporting evidence. The occasional occurrence of pilot and killer whales in the Greek Seas should still be regarded as unconfirmed. The distributional range, stranding numbers and sighting frequencies of sperm whales, Cuvier’s beaked whales and short-beaked common dolphins in the Greek Seas indicate that their local ‘sub-populations’ are among the most important in the entire Mediterranean Sea. Harbour porpoises in the Thracian and northern Aegean Seas are important from a conservation perspective since this species does not inhabit any other part of the Mediterranean Sea.

Variation in blubber thickness and histology metrics across the body topography of a false killer whale (Pseudorca crassidens).

Blubber is a multifunctional tissue essential to the survival of cetaceans. Histological assessment of blubber may be useful in determining odontocete nutritional state but a greater understanding of specific variation across the body is needed. We report on morphological variation of the blubber according to girth axes and sampling planes in a sub-adult male, bycaught false killer whale (Pseudorca crassidens) using metrics of blubber thickness (BT), adipocyte area (AA), and adipocyte index (AI). 48 full depth blubber samples were taken along 6 girth axes at 5 equidistant sampling points on both sides of the body. At these sampling locations BT was recorded, and AA and AI were determined for three distinct blubber layers. Linear mixed effect models were used to assess variation of the blubber across layers and body topography. BT was somewhat non-uniform across the body but was generally thicker in the dorsal region and thinner laterally. AA was greater cranially and AI was greater caudally. The middle and inner layer blubber showed significant differences dorsoventrally with larger AA and smaller AI in the ventral region of the body. Variation of the blubber metrics across the body are indicative of variable functions of the blubber within an individual. Due to the variability observed, we expect that AI of the dynamic inner layer blubber is most informative of overall body condition and that biopsy samples of the outer and middle blubber may still be useful in determining the nutritional status of live false killer whales.

Acoustic recording of false killer whale (Pseudorca crassidens) from Mexico (L).

This study collected acoustic information on false killer whales (Pseudorca crassidens) in Mexican waters, close to Roca Partida Island, Revillagigedo Archipelago. In total, 321 whistles were collected after we found a group with at least ten individuals. The high prevalence of ascending contour types [upsweep (type I): 42.99%] contradicted the idea that false killer whales mostly produce constant whistles. Lack of well-established reproducibility criteria for whistle type categorization among studies may have generated results different from those expected for signal modulation. Future acoustic and ecological studies should be conducted to help clarify these findings and expand the limited knowledge about this species.

Observations of cetaceans in the Maldives, 1990-2002

Cetaceans observed in Maldivian waters were recorded during the period August 1990 to June 2002, from both vessels-of-opportunity and dedicated cetacean-watching cruises. A total of 1,829 cetacean sightings were recorded during 535 days at sea (equivalent to 261 standardised days). There were 83 multispecies sightings, plus a further 58 sightings without associated effort data and 129 strandings were recorded by the author and others, making a total of 2,108 cetacean records. In all, 20 different species were positively identified from sightings. Spinner dolphins were the most abundant species seen, accounting for 35% of sightings and 53% of numbers. This species showed a clear diurnal pattern of behaviour, with many schools entering the atolls in the early morning, and leaving in the late afternoon. Spinner dolphins regularly occurred with pantropical spotted dolphins and both species associated with yellowfin tuna. Bryde’s whales also associated with yellowfin tuna and appeared to be most common in Maldivian waters during El Niño Southern Oscillation events. Blue whales were only recorded during November to April. Dwarf sperm whales were especially difficult to locate in rough weather but relatively common, making up one sixth of all sightings in flat-calm conditions. Melon-headed whales were particularly common in the south of the Maldives, but rare in the centre and north. Other species recorded were humpback whale, sperm whale, rough-toothed dolphin, Risso’s dolphin, bottlenose dolphin, striped dolphin, Fraser’s dolphin, pygmy killer whale, false killer whale, killer whale, short-finned pilot whale, Blainville’s beaked whale, Longman’s beaked whale and Cuvier’s beaked whale.

Vocal behavior of false killer whale (Pseudorca crassidens) acoustic subgroups

Understanding the vocal behavior of cetaceans is an important component of many passive acoustic applications. This study quantifies the vocal behavior of acoustic subgroups of false killer whales (Pseudorca crassidens) from the Hawaiian Archipelago. The acoustic subgroups (N = 523) exhibit diverse vocal behavior that varies between encounters. Overall, 29% of acoustic subgroups only echolocate, 16% only whistle, and 55% emit both types of vocalizations. These results contribute important information for developing automated passive acoustic cetacean tracking, localization, and classification techniques, and thus, support future cetacean monitoring and assessment efforts.

Niche Partitioning Among Marine Mammals Inhabiting a Large Estuary as Revealed by Stable Isotopes of C, N, S, and O

Detailed knowledge on habitat use by marine mammals is critical to understand their role in the ecosystem. The stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) have been widely used to study the trophic ecology of marine mammals, but the stable isotope ratios of other elements such as sulfur (δ34S) and oxygen (δ18O) can better inform about habitat use in areas with strong salinity and redox gradients. The Río de la Plata estuary represents the largest freshwater runoff in the south-western Atlantic Ocean and supports a rich community of marine mammals. Here, we analyzed δ34S values in bone from seven marine mammal species inhabiting the estuary and the adjacent Atlantic Ocean, in order to complement previous isotopic data (δ13C, δ15N and δ18O) and compare their resolution as habitat tracers. As expected, δ34S and δ18O offered relevant insights into the characterization of the habitat used by marine mammals and allowed a better delineation of habitat partitioning between them. Bottlenose dolphins, South American sea lions and South American fur seals seem to be frequent users of the less saline areas of the estuary, whereas Burmeister´s porpoises, franciscana dolphins and false killer whales seemed to prefer the saltier marine waters close to the bottom. Fraser´s dolphins were the only inhabitants of true offshore waters. Our findings demonstrate how the integration of different stable isotope ratios can help disentangle fine habitat partitioning between marine mammals living in a complex ecosystem such as Río de la Plata.

Occurrence and distribution of cetaceans off northern Angola, 2004/05

The occurrence and distribution of cetacean species off northern Angola was examined using dedicated survey data and incidental sighting records. Dedicated surveys for cetaceans were carried out during two geophysical seismic surveys off northern Angola between August 2004 and September 2005. A total of 3,268hr of survey effort data were collected, resulting in 779 on-effort cetacean sightings. There were 263 sightings reported off-effort and incidentally from other platforms and sports fishermen. With 21 cetacean species confirmed, the cetacean community off northern Angola is diverse and primarily tropical in characteristic, comprising four species of baleen whale, two sperm whale species, at least two beaked whale species, and 13 species of delphinid. Humpback and sperm whales were the most frequently recorded cetaceans. The occurrence of humpback whales was significantly higher within neritic waters, and during the winter and spring months in association with seasonal occupancy of their West African breeding grounds. Sperm whales were recorded in water depths exceeding 1,000m and demonstrated significant seasonality, with peak occurrence during the summer and autumn. Atlantic spotted dolphins and common dolphins (Delphinus sp.) were the most numerous delphinids recorded, with spotted dolphins showing a significant seasonal peak during the spring and summer, and common dolphins in the winter. Other species recorded included fin whale, sei whale, Bryde’s whale, dwarf sperm whale, Cuvier’s and Mesoplodon beaked whales, killer whale, short-finned pilot whale, false killer whale, melon-headed whale, Atlantic humpback dolphin, rough-toothed dolphin, Risso’s dolphin, bottlenose dolphin, Pantropical spotted dolphin, spinner dolphin, Clymene dolphin and striped dolphin. Further research is required to document the cetacean community in Angola, particularly given the unknown threat from fishery bycatch and the increasing level of oil and gas exploration in the region.

Diversity, habitat associations and stock structure of odontocete cetaceans in the waters of American Samoa, 2003-06

Little is known about the species composition, distribution, abundance or stock structure of odontocetes in the central and western tropical Pacific Ocean, including those inhabiting the US Exclusive Economic Zone (EEZ) waters of American Samoa. While some information on species presence in this region has been gleaned from anecdotal sightings and whaling and stranding records, odontocete diversity in the waters of American Samoa has never been formally investigated. This lack of information precludes efforts to determine the sustainability of cetacean populations within US EEZ waters. This paper reports on the first dedicated surveys to document the presence and distribution of odontocete cetaceans in the waters of American Samoa. A series of small-boat photo-identification and biopsy surveys for cetaceans were conducted in the nearshore waters of Tutuila during 2003-06. In addition, ship-based visual surveys were conducted in the waters surrounding the Manu‘a Islands, Rose Atoll and Swains Island in summer 2006. A total of 58 groups of odontocete cetaceans were encountered during both small-boat and ship-based surveys: spinner dolphins (Stenella longirostris, n=34), rough-toothed dolphins (Steno bredanensis, n=10), sperm whales (Physeter macrocephalus, n=3), false killer whales (Pseudorca crassidens, n=5), bottlenose dolphins (Tursiops truncatus., n=1), dwarf sperm whales (Kogia sima, n=1), short-finned pilot whales (Globicephala macrorhynchus, n=1), and three groups of unidentified odontocetes. Photographs were analysed for quality and individuals with distinctive markings were selected for entry into a photo-identification catalogue. The resultant catalogue included 46 spinner dolphins, 41 rough-toothed dolphins, 2 bottlenose dolphins, 5 false killer whales, 4 pilot whales, 1 dwarf sperm whale and 4 sperm whales. Thirteen spinner dolphins and 14 rough-toothed dolphins were sighted in multiple years. To investigate stock structure, spinner dolphin genetic data were used to compare mitochondrial control region genetic diversity and allele frequencies between American Samoa and the Hawaiian Islands. American Samoa had a higher genetic diversity, and populations at the two locations were genetically distinct (FST = 0.21). The high diversity at American Samoa indicates that spinner dolphins at this location are not reproductively isolated, but the data do not rule out the possibility that these dolphins may be demographically isolated on ecological timescales.

Marine mammal records from Iran

Iran has 1,700km of coastline that borders the Persian Gulf and the Arabian Sea in the northwest Indian Ocean. Apart from a handful of records, almost nothing is known about which marine mammal species occur in Iranian waters. This review was conducted to fill this information gap. A total of 127 marine mammal records of 14 species were compiled from Iranian coastal waters. Ninety-nine were from the Persian Gulf, 26 from the Gulf of Oman and 2 were of unknown location. Records of finless porpoise (Neophocaena phocaenoides) (25), Indo-Pacific humpback dolphin (Sousa chinensis) (24) and Indo-Pacific bottlenose dolphin (Tursiops aduncus) (22) were by far the most numerous, a probable reflection of their inshore distribution and local abundance. Other species recorded were long-beaked common dolphin (Delphinus capensis tropicalis), roughtoothed dolphin (Steno bredanensis), striped dolphin (Stenella coeruleoalba), spinner dolphin (Stenella longirostris), Risso’s dolphin (Grampus griseus), false killer whale (Pseudorca crassidens), sperm whale (Physeter macrocephalus) and dugong (Dugong dugon). Records of 26 mysticetes were compiled, 10 of which were tentatively identified as Bryde’s whales (Balaenoptera edeni), 1 possible fin whale (Balaenoptera physalus), 3 humpback whales (Megaptera novaeangliae) and the remainder were not identified to species. The largest threat to small cetaceans in Iran is likely to be incidental capture in fishing gear. Nine finless porpoises were recorded as bycatch and this and other coastal species may be declining due to unsustainable mortality rates. Some of the world’s busiest shipping lanes pass through Iranian waters and ship strikes are likely to be the largest threat to mysticetes in the area.

Odontocetes of the Southern Ocean Sanctuary

Twenty-eight odontocete species were identified as occupying sub-Antarctic and Antarctic habitat covered by the 1994 IWC-established Southern Ocean Sanctuary. Toothed whales evidently play an important part in the Antarctic polar ecosystem. Twenty-two species are autochthonous in showing a regular, apparently year-round, presence in the Sanctuary: Physeter macrocephalus, Kogia breviceps, Orcinus orca, Globicephala melas edwardii, Pseudorca crassidens, Lagenorhynchus cruciger, Lagenorhynchus obscurus, Lissodelphis peronii, Cephalorhynchus commersonii, Cephalorhynchus hectori, Tursiops truncatus, Delphinus delphis, Phocoena dioptrica, Hyperoodon planifrons, Berardius arnuxii, Ziphius cavirostris, Tasmacetus shepherdi, Mesoplodon layardii, Mesoplodon traversii, Mesoplodon grayi, Mesoplodon bowdoini and Mesoplodon hectori. Six species are considered vagrants into the Sanctuary: Kogia sima, Grampus griseus, Steno bredanensis, Mesoplodon peruvianus, Mesoplodon densirostris and Mesoplodon mirus. However, vagrant status of these three mesoplodonts is only provisionally assigned, considering that improved knowledge of diagnostic features of beaked whales should, as in recent years, continue to facilitate at-sea identification. Two species are considered as having a ‘contiguous’ range (records less than 2° north of Sanctuary boundaries): Mesoplodon ginkgodens (at 39°S) and Mesoplodon mirus (at 38°24’S). The habitual southern range of at least four odontocetes extends significantly farther poleward than expected. G. melas edwardii is regularly encountered south of the Antarctic Polar Front, much like M. grayi which is known to reach the Ross Sea ice edge (ca. 67°S). Z. cavirostris and L. obscurus cross the Polar Front occasionally. The distribution of M. peruvianus and M. traversii and their relation to SST are unclear. Their southernmost records, 42°31’S and 44°17’S respectively, may either be extralimital or, more likely, reflect ordinary austral range. Temporally non-aligned distribution patterns of Hyperoodon planifrons in Antarctic and South African waters may suggest stock segregation.

Cetacean distribution in the coastal waters of the Sultanate of Oman

Small boat surveys were conducted between 2000 and 2003 in three main regions of Oman’s coastal waters: Muscat, the Gulf of Masirah and Dhofar. Survey data were analysed to calculate relative abundances of the seven most frequently encountered species in these areas. These include (in order of frequency) bottlenose dolphins (Tursiops sp.), long-beaked common dolphins (Delphinus capensis), humpback whales (Megaptera novaeangliae), spinner dolphins (Stenella longirostris), Indo-Pacific humpback dolphins (Sousa chinensis), Bryde’s whales (Balaenoptera sp.) and Risso’s dolphins (Grampus griseus). Other species observed include false killer whales (Pseudorca crassidens), blue whales (Balaenoptera musculus), rough-toothed dolphins (Steno bredanensis) and unidentified beaked whales. Encounter rates per distance searched were plotted by 0.1 x 0.1 degree grid cell, giving an indication of relative abundances and key areas of habitat used by each of the seven most frequently encountered species. These plots demonstrate that the nearshore areas of the Gulf of Masirah, as well as the coastal waters of Dhofar, are areas of concentration for the Arabian Sea’s recently designated Endangered subpopulation of humpback whales, as well as Indo-Pacific humpback dolphins, which are considered Near Threatened on the IUCN Red List of Threatened Species.1 The results presented here provide valuable baseline data for future research and help to inform conservation management efforts that are required to address the highly vulnerable status of the humpback whale and Indo-Pacific humpback dolphin populations in question.

A note on observations of cetaceans in the Indian Ocean Sanctuary, Australia to Israel, April 1995

A forty-day voyage from Hobart (Australia) to Haifa (Israel) included a visual and acoustic census for cetaceans in the Indian Ocean Sanctuary. One hundred and sixty-three sightings were made, 156 occurring within the Sanctuary. Twelve species were identified. Sperm whales (Physeter macrocephalus) were encountered most frequently (51% of identified encounters), whilst spinner dolphins (Stenella longirostris) were numerically dominant. Other species identified included bottlenose dolphins (Tursiops spp.), short-beaked common dolphin (Delphinus delphis), pan-tropical spotted dolphin (Stenella attenuata), rough-toothed dolphin (Steno bredanensis), Risso’s dolphin (Grampus griseus), killer whale (Orcinus orca), short-finned pilot whale (Globicephala macrorhynchus), false killer whale (Pseudorca crassidens), Bryde’s whale (Balaenoptera edeni) and Cuvier’s beaked whale (Ziphius cavirostris). The most sightings occurred WNW of the Seychelles, east of Somalia, and in the Gulf of Aden and Red Sea. Half of the sperm whale sightings were to the east of Ras Hafun (Somalia), and included adults, subadults and at least one calf. Thirteen hours were spent listening for cetaceans using a towed array whilst the ship was underway. Cetaceans were detected at 78% of the listening stations, with a possible four species recorded (sperm whale, spinner dolphin, pilot whale, bottlenose dolphin). The survey shows the value of platforms of opportunity for studying the pelagic communities of cetaceans in the Indian Ocean Sanctuary. It highlights the need for further research in the northwestern sector where anthropogenic threats are varied and increasing.

A note on cetaceans off Kiribati and Tuvalu from a research cruise in October 2010

This paper summarises the results of a sighting survey conducted around the Gilbert Islands (Kiribati) and Tuvalu Islands (Tuvalu) in the central Pacific Ocean between 3 and 17 October 2010. This was the first systematic collection of cetacean sighting data in this region. The main objective of the survey was to investigate the occurrence and distribution of cetaceans around Kiribati and Tuvalu. In addition biopsy samples were obtained to investigate the species identity of Bryde’s-whale-like baleen whales through genetic analyses and to assess feeding ecology of cetaceans in the survey area through the examination of fatty acids. The survey was carried out using a sighting survey vessel, which covered a total of 1,012 n.miles (≈1,875km). A total of 24 schools (640 individuals) of cetaceans was sighted: three schools (five individuals) of Bryde’s-whale-like baleen whales, one school (nine individuals) of sperm whales (Physeter macrocephalus), one school (six individuals) of killer whales (Orcinus orca), one school (14 individuals) of short finned pilot whales (Globicephala macrorhynchus), one school (two individuals) of false killer whales (Pseudorca crassidens), eight schools (483 individuals) of spinner dolphins (Stenella longirostris), and one school (70 individuals) of striped dolphins (Stenella coeruleoalba). Mitochondrial DNA (mtDNA) analyses based on the biopsy samples identified two of the Bryde’s-whale-like whales sighted, as of the putative species Balaenoptera brydei. Compositions of fatty acids of Bryde’s and killer whales are presented. The survey provided new information on the distribution and fatty-acid composition of cetaceans around Kiribati and Tuvalu.

Cetaceans and mass strandings in Thai waters

A total of 25 species of cetaceans have been recorded in Thai waters from stranding and sighting records. A summary of these, together with details of five mass strandings on the Andaman Sea coast of Thailand, are reported here. The first mass stranding, of nine spinner dolphins (Stenella longirostris) was at Talibong Island, Trang Province, in January 1999; six carcasses were examined and three were lost. The second record comprised five spotted dolphins (Stenella attenuata) stranded at Ban Ko Kho Khao, Phang-nga, in February 1999; two dolphins were released alive. The third stranding was of eight spotted dolphins at Mai Phai Island, Phang-nga, in March 2006; five animals died and three were released alive. The fourth mass stranding was of 30 false killer whales (Pseudorca crassidens) at Racha Yai Island, Phuket, in June 2008; 29 animals were released while one drowned. The fifth record consisted of three rough-toothed dolphins (Steno bredanensis) stranded at Nam Bor Bay, Phuket, in July 2008; all three were returned to the open sea. It was difficult to determine the causes of death of the stranded dolphins. However, it was possible that the first two mass strandings were caused by disease. Some strandings were possibly influenced by the landscape of the stranding locations (narrow bay in one case, wide gently sloping beach in another).

Evidence of resident coastal population(s) of false killer whales (Pseudorca crassidens) in northern Australian waters

To help evaluate the distribution, residency, population size and structuring (and hence conservation status) of the poorly known false killer whalePseudorca crassidensin northern Australian waters, we undertook studies of sightings, movement patterns based on satellite telemetry, and genetics. Sighting data indicates that false killer whales are regular, year-round inhabitants of coastal areas of northern Australia. Satellite-tagged animals spent extended periods of time in shallow coastal waters, with no tagged animals leaving the continental shelf. The lack of spatial overlap in the areas visited by individuals tagged in the Arafura/Timor Seas compared to those tagged in the Gulf of Carpentaria suggests that there may be more than one population in northern Australia coastal waters. All 14 genetic samples collected across 1600 km of coastline possessed the same newly identified mitochondrial control region haplotype, designated haplotype 45. Notably, haplotype 45 is distinct from all previously published false killer whale haplotypes globally and is most similar to the two haplotypes that typify the endangered main Hawaiian Islands insular false killer whale population. Based on these results and evidence from recent movement records of those tagged, false killer whales in northern Australia are apparently demographically independent from the offshore population(s). Further assessment of the population conservation status is now required.

Biologically Important Areas II for cetaceans within U.S. and adjacent waters – Hawaiʻi Region

In this assessment we incorporated published and unpublished information to delineate and score Biologically Important Areas (BIAs) for cetaceans in the Hawaiʻi region following standardized criteria. Twenty-six cetacean species have been documented in Hawaiʻi. Eleven odontocete species have distinct small populations resident to one or more island areas: rough-toothed dolphins, pantropical spotted dolphins, common bottlenose dolphins, spinner dolphins, short-finned pilot whales, false killer whales, pygmy killer whales, melon-headed whales, Blainville’s beaked whales, Cuvier’s beaked whales, and dwarf sperm whales. Eight species of mysticetes have been documented, although their occurrence and behavior are poorly understood, with the exception of breeding humpback whales and, more recently, common minke whales. Thirty-five BIAs were delineated or revised from the initial 2015 effort: 33 for small and resident odontocete populations and two for humpback whale reproductive areas. Hierarchical BIAs reflecting core areas of use or population-specific ranges were delineated for nine species. Reproductive watch list areas were designated for common minke whales in the main Hawaiian Islands (MHI) and humpback whales in the Northwestern Hawaiian Islands (NWHI); these areas did not meet the criteria for a BIA due to limited supporting information. All but three BIAs were in the MHI, reflecting the disparities in research effort between this region and the NWHI. Spatial extents of BIA boundaries ranged from 457 km2to 138,001 km2(median = 8,299 km2). Scores (range: 1-3) for Data Support and Boundary Certainty were moderate to high (mean = 2.40 and 2.43, respectively), while Intensity and Importance scores were slightly lower (mean = 1.94 and 1.89, respectively). Many of the Hawaiʻi species have been extensively studied over several decades; accordingly, this region ranks among the highest in terms of Data Support relative to other regions. BIAs presented here describe known ranges of small resident populations, intensities of use, and uncertainties in important areas for cetaceans in Hawaiʻi based on the best available data, and have also revealed knowledge gaps to guide future research efforts.

Spatial distribution of cetacean strandings in the Falkland Islands to define monitoring opportunities

The waters around the Falkland Islands are used by many species of cetaceans, including endangered and data deficient species, but little is knownabout their populations. The Falkland Islands cetacean stranding database was transformed in a geo-spatial database using the available descriptionsof the locations as no GPS locations were recorded until 2015. It was then used to analyse the spatial distribution of strandings over a periodspanning the 1880s to 2015. A total of 169 stranding events could be given a location and mapped. Twelve stranding hotspots were identified. Thispaper also reports on the first recorded stranding of false killer-whales (Pseudorca crassidens) and Antarctic minke whale (Balaenoptera bonaerensis)in the Falkland Islands, increasing the total species recorded to 26. Spatially-explicit cetacean stranding databases can provide important data tomonitor cetaceans in the light of environmental changes from climate change or industrial development. In the case of the Falkland Islands (remoteand sparsely inhabited), identification of hotspots could be used to design an aerial monitoring programme to increase chances of detecting strandingevents, organise a rescue or necropsy team to gain samples. The results in this paper should enhance local capacity to conduct research (samplecollection for pollutant analyses, genetic studies, etc.) and monitor impacts of human activities on cetacean populations, including from the historicalbaseline of average numbers and distribution of strandings provided.

Large mass strandings of selected odontocete species: statistics, locations, and relation to earth processes

Larger mass strandings of open ocean odontocetes (toothed whales) of 10+ animals are examined with a compilation of 710 worldwide events. Sixspecies form 96% of events (false killer, long-finned pilot, melon-headed, short-finned pilot, sperm and white whales), with beaked, killer, andpygmy killer whales forming 4%. Site type was determined for 630 events – three-quarters (76%) are in bays, 14% in shallow topographicallycomplex areas (estuarine environments, straits, keys, reef and coastal lagoons), 8% on relatively unindented coasts, with ice entrapment (of killerwhales) and miscellaneous categories being 2%. For the 76% of events in bays, sites with headland-bay character make up 42%, spit-bays 20%(even though there are only four of them), indented bays 9% and unspecified bay types 5%. Headland-bays and spit-bays become stranding sitesthrough the properties endowed them by their mechanisms of formation and maintenance, but these mechanisms differ greatly for the two.Breakwaters, groyne series, tides, partial burial, and violent storms also appear as themes. Nearshore slopes are less than 1° for 94 of 105 siteshaving bathymetry information, with only two reaching or exceeding 3°. Some types of potential stranding sites can be identified by simplequantitative specifications for planform, sediment size, and seabed slope, although strandings will not necessarily occur there. There is an indicationthat larger strandings are globally correlated with areas of higher oceanic primary productivity near landmasses and oceanic islands, but quantitativestudies are needed to clarify any such possible relationship. There is also an indication that larger strandings are associated with plate tectonics,with few events being seen on the steeper swell resistant active western margins of South America and South Island (New Zealand) in particular.In contrast several larger events are recorded for the relatively older passive margins of the south-eastern sides of these two landmasses, putativelybecause waves and swell have had time to construct stranding sites on them. Similarly, few larger events are seen for steeper shores adjacent tocoastal highlands, such as those of South Africa and Brazil. These observations indicate previously unsuspected relations between the phenomenonof odontocete mass strandings and global scale earth and ocean processes, but they are essentially hypotheses in need of more quantitativeexamination.

Determining the spatial and temporal variability of false killer whales (Pseudorca crassidens) and short-finned pilot whales (Globicephala macrorhynchus) in the Hawaiian Islands from passive acoustic monitoring

False killer whales (Pseudorca crassidens) and short-finned pilot whales (Globicephala macrorhynchus) are resident, toothed whale species to the Hawaiian archipelago. False killer whales are considered of high concern in Hawai‘i with the insular population listed as endangered. Passive acoustic monitoring (PAM) is an effective technique for studying these highly social odontocete species on large temporal and geographical scales. Moored hydrophones were deployed inside and outside Marine Protected Areas (MPAs) through the SanctSound project, allowing leveraging of long-term datasets to assess the acoustic behavior of these species within and beyond the Hawaiian Islands Humpback Whale National Marine Sanctuary and Papahānaumokuākea Marine National Monument. High Frequency Acoustic Recording Packages (HARPs) (200 kHz SR) and SoundTraps (48 kHz SR), recording on various duty cycles, were deployed between 2018–2022 within MPAs (monument: n = 51 months; sanctuary: n = 76 months) and outside MPAs (n = 60 months). PAMGuard detectors were used to detect whistles, clicks, and burst pulses. Detection features were extracted using the PAMpal package and events classified to species using BANTER. Acoustic monitoring provides key information about the value of MPAs and a better understanding of habitat use and behavior of these species.