Studying Beaked Whales entangled in Tuna nets in the northwest Indian Ocean.

Beaked Whales, Ziphiidae, spend the majority of their time in deep oceanic waters, spending most of their lives beyond the continental shelves, and little at the surface. This makes them one of the least well-understood groups of Cetaceans, or Mammals of any kind. Some species have few, if any, sitings ar sea, being known almost exclusively from bodies washed ashore in varying states of decomposition. Because of this, the taxonomy of Beaked Whales is less well-established than is the case for most Mammal groups, with new species and nomenclature revisions being published every few years. 

Studying Whales caught as bycatch offers a cost-effective way to study poorly understood Cetacean populations, providing insights into populations which can help shape conservation policies. Such data collection is often accomplished by training fishermen themselves as citizen scientists. Drift gillnets are widely used many parts of the world to target Tuna, but are also noted for the large amount of large-Vertebrate bycatch they produce. In the northwest Indian Ocean drift gillnets are widely used by the fishing fleets of Iran and Pakistan, presenting a threat to Whales in this area, but also presenting an opportunity for scientists to gather data on these Animals.

In a paper published in the journal Zoology in the Middle East on 13 February 2025, Muhammad Shoaib Kiani of the Institute of Marine Science at the University of Karachi, Mohsen Rezaie-Atagholipour of the Qeshm Environmental Conservation Institute, Rab Nawaz and Muhammad Moazzam of the World Wide Fund for Nature - Pakistan, Bushra Shafiq also of the  Institute of Marine Science at the University of Karachi, Haleh Ali Abed of the Midaf Nature Conservation Society, and Koen Van Waerebeek, also of the Qeshm Environmental Conservation Institute and of the Centro Peruano de Estudios Cetológicos, present the results of a long-term study of Beaked Whale entanglements in Tuna gillnets in Iranian and Pakistani waters.

A citizen science program was established in Pakistan in 2012, in which fishermen on pelagic gillnet Tuna vessels were trained to collect data on Cetacean bycatch. In Iran reviews of mass media at local and national levels, looking for Cetacean-related stories, have been carried out since 2018, and a series of interviews of fishermen was carried out in 2022.

Kiani et al. discovered eight incidents in which entangled Cetaceans could be identified as Beaked Whales in the waters of the Gulf of Oman and Arabian Sea, two in Iranian territory, five in Pakistani territory, and one in international waters.

The first recorded incident happened on 10 February 2015, when fishermen on board the Pakistani vessel Al-Azaan discovered a live Beaked Whale caught in a gillnet they had deployed 95 km to the west of the Swatch (the undersea canyon formed where the Indus River enters the ocean) and 177 km off the coast of Sindh, an area where the seafloor is about 1.5 km deep. 

Based upon video evidence, this Whale was estimated to be 5-6 m long, and slender with a slightly protrudent melon (mass of adipose tissue on the forehead), and a long snout without protruding teeth. This Animal lacked the scars associated with tooth-raking typically seen in male Beaked Whales, and is therefore assumed to have been a female.

The Whale had a brownish-grey dorsal surface, slightly paler on the head, and had a large, Dolphin-like fin about two thirds of the way along its body. This is, along with its location in the tropical Indian Ocean, is considered to be consistent with a Longman’s Beaked Whale, Indopacetus pacificus. This species was first described in 1928 from the skull of a Whale found in Queensland Australia in 1882, with a second skull being found on the shore of Somalia, East Africa, in 1955. For a long time, these two specimens were all that was known of this species, however, recent studies have established that Whales washed up on the shores of the Philippines, Maui (Hawaii), Taiwan, Myanmar, the Andaman Islands, South Africa, and Japan, previously identified as Southern Bottlenose Whales, Hyperoodon planifrons, were in fact Longman’s Beaked Whales, and based upon this data, 65 sightings of live Whales in the  Indian and Pacific oceans have been assigned to the species.

The Whale encountered by the Al-Azaan became entangled in a net as it was being retrieved, allowing the crew to release it without apparent harm by cutting away part of the net. This process took about 30 minutes, and while the Whale is thought to have been unharmed, one of the fishermen received minor injuries.

(a)-(h). Successive steps in gillnet disentanglement operation of a Longman’s Beaked Whale, Indopacetus pacificus, in Pakistani waters. Note the head with moderately bulbous melon (e), (h), long rostrum (f), (g), (h) tubular in dorsal view (h), limited linear scarring (e) and large falcate dorsal fin (f, g). Selected frames were taken from a video. Kiani et al. (2025).

The second recorded incident happened on 31 March 2017, when an un-named Pakistani vessel encountered a 4 m long Whale 383 km off the coast of Pakistan, again in the Swatch area, an area where the sea slightly more than 3 km deep. 

This Whale had a distinct, but non-bulbous melon, a long slender snout, and a low, sub-triangular dorsal fin. The skin of the Whale was a uniform grey, slightly darker towards the tail, and it had no visible scarring of any type. It was not possible to identify this Whale to species level, but it was probably a member of the genus Mesoplodon, possibly Deraniyagala’s Beaked Whale, Mesoplodon hotaula, or Ginkgo-toothed Beaked Whale, Mesoplodon ginkgodens, although this species has never been recorded in the Indian Ocean, or even Ramari’s Beaked Whale, Mesoplodon eueu, although this species tends  to lighten towards the tail, and is a cold-water species, never previously recorded in the western Indian Ocean north of Mozambique. 

The third incident was recorded in August 2017, when a fisherman from Bandar-e-Konarak on the coast of Sistan and Baluchestan Province, Iran, sent a video to the Iranian National News Agency, IRIB News, showing a Whale entangled in a gill net. This incident is thought to have happened in the waters of Iran’s Exclusive Economic Zone, and probably close to Bandar-e-Konarak. 

The Whale could be seen to blow, suggesting that it was alive and breathing. It appears to be a Beaked Whale with no visible teeth. The bulbosity of the melon cannot be determined from the video. The fluke (tail) of the Whale can be seen, and from comparison to the arm of a fisherman, is estimated to be between about 140 cm wide, which would equate to a Whale 4.7-4.9 m in length. The fluke also lacks a median notch, confirming that the Animal is a Ziphiid.

An unidentified middle-sized Beaked Whale, with a melon of unclear bulbosity, net-entangled within Iran’s Exclusive Economic Zone waters off Sistan and Baluchistan Province, northern Gulf of Oman, in August 2017. (a), (b) Flukes without central notch and tailstock; (c) the only registered blow and vague view of the head. Both Mesoplodon sp. and Indopacetus pacificus would be possible. Kiani et al. (2025).

The fourth incident occurred on 18 January 2018, when a small-to-medium sized Beaked Whale was recorded trapped in gillnet 474 km from the coast of Pakistan, an area where the sea is slightly under 3.2 km deep. This Whale was 3.5-4.5 m long, with a medium length snout and a non-bulbous melon and no central notch on its fluke; its colour and/or markings could not be determined due to poor light. This is consistent with it being a member of the genus Mesoplodon. The Pakistani fishermen who encountered this Whale were able to disentangle it from their nets, and report if swam away in good condition. 

The fifth incident occurred on 19 March 2019, when two Beaked Whales, interpreted as a mother and calf, became entangled in the same gillnet off Churna Island, 96 km from the coast of the Pakistani Mainland. The waters here are shallow, at 295 m.

The calf was described as the size of an adult Common Bottlenose Dolphin, making it 3.0-3.5 m in length, while it was not possible to estimate the size of the larger Whale. The smaller Whale had a dark grey upper surface,  and a whitish underside. It had a short snout, and no sign of a bulbous melon, its dorsal fin hooked, no notch could be seen in the tail. These Whale are also interpreted as belonging to the genus Mesoplodon. The fishermen reported successfully disentangling both Whales.

The sixth recorded incident happened in February 2022, when Iranian fishermen reported encountering a Whale caught in a drift gillnet 1300 km off the coast of Bandar-e-Beris in eastern Sistan and Baluchestan Province. Video footage of the incident shows a medium-sized Beaked Whale with a medium-length Dolphin-like beak, and a non-steeply sloping melon, consistent with a member of the genus Mesoplodon. The video also shows that the Whale has two apical or slightly sub-apical mandibular teeth, indicating that it was male, as well as a dark eye-patch, an almost straight mouth, and a small, slightly hooked tail. The length of the Whale is uncertain, but it appears to be about 4.5-5.5 m.

An unidentified Mesoplodon sp. bycaught in far offshore waters of the northern Arabian Sea, 1300 km from Bandar-e-Beris at the eastern side of Iran’s Sistan and Baluchestan Province, in February 2022. (a), (c) Two erupted (sub)apical mandibular teeth indicate an adult male. (b) Dolphin-like, medium-length rostrum, gently sloping melon and smallish dorsal fin. Kiani et al. (2025).

The final incident happened in early June 2023, when a large Beaked Whale became entangled in a drift gillnet in the coastal Iranian Gulf of Oman, about 37 km from the port of Chabahar in eastern Sistan and Baluchestan Province. This Animal was clearly an adult male, with numerous took-rake scars and erupted apical teeth. It was estimated to have been 5.8-6.0 m in length, with an erect, Dolphin-like dorsal fin, and way brownish grey in colour with a lighter head. This is interpreted as being consistent with either a Longman’s Beaked Whale, Indopacetus pacificus, or a Cuvier’s Beaked Whale, Ziphius cavirostris. 

An adult male Beaked Whale being liberated after accidental entanglement in Tuna gillnet in coastal waters of the Gulf of Oman, some 37 km from Chabahar, Iran, in early June  2023. (a) Large body size with two erupted teeth at the apex of the mandibula; (b) a tall, erect, falcate, Dolphin-like dorsal fin, a moderately long and well-defined rostrum; (c) with numerous tooth rakes on anterior body; and (d) some degree of bulbosity in the melon. The morphology of the Beaked Whale is congruent with Indopacetus pacificus, but Ziphius cavirostris cannot be excluded. Kiani et al. (2025).

The first of these incidents is regarded as the first record of Longman’s Beaked Whale, Indopacetus pacificus, in Pakistani waters, with incidents five and seven representing potential additional sightings. A beached individual assigned to the species was recorded in Gujarat State, India, in 2014, making the Pakistan entanglement the second record of the species in the northwest Indian Ocean. Previously a skull has been recorded from the coast of Somalia in 1955, a member of the species was sighted from Socotra Island, Yemen in 1971, and another in the waters of the southern Bay of Bengal in 2009. Five Longman’s Beaked Whales have been recorded as bycatch from Sri Lanka, although these have been disputed, and fourteen sightings and a stranding recorded from the Maldives. 

Incidents two, four, six, and possibly five represent the first records of Mesoplodon sp. in Iranian and Pakistani waters, although none of these specimens could be confidently identified to species level. 

Drift gillnets are considered to be one of the most significant anthropogenic threats to Whales, although evidence to support this is absent in many areas. Kiani et al.'s study shows entanglement is a clear threat to Beaked Whales in the northwestern Indian Ocean, as while all of the reported Whales were freed, it is likely that a greater number of Whales were not released safely, and therefore not reported.

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Whale dies after stranding on Edinburgh beach.

A Whale has died after stranding on a beach in Edinburgh, Scotland. The Whale, identified as a young Sowerby’s Beaked Whale, Mesoplodon bidens, was found on a beach near the mouth of Brunstane Burn on the afternoon of Tuesday 13 October 2020, while still alive, but died shortly thereafter, despite attempts by volunteers from the Scottish Society for the Protection of Animals and British Divers Marine Life Rescue to refloat it. 

 

A Young Sowerby’s Beaked Whale, Mesoplodon bidens, stranded on an Edinburgh beach on 13 October 2020. Lyn Murray/Daily Record.

Sowerby's Beaked Whales are found throughout the North Atlantic and North Sea, although they are reclusive Animals which tend to avoid boats and other Human objects, making them rarely seen. As such their population structure is not really known, and they are classified as Data Deficient under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species. This is the third stranding of a member of the species recorded in the UK this year, with British Divers Marine Life Rescue recording two strandings in August, one in Suffolk and one in Hampshire, which implies a reasonably healthy population in UK waters (although individual strandings are sad, the fact that strandings are occurring implies that Whales are present. Sowerby's Beaked Whales are protected by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas, the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area, and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Historically the species was sometimes targeted by Norwegian Whalers, but this has not been the case in recent history; though these Whales are thought to be at risk from entanglement in fishing gear.

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Berardius minimus: A new species of Beaked Whale from the North Pacific.

Beaked Whales, Ziphiidae, are the second largest group of Toothed Whales in terms of number of species, with 22 species in six genera. Despite this speciousness the group is not well studied, due to their preference for deep water environments and long dive times, which makes them rather hard to study. The genus Berardius currently contains two species, Baird’s Beaked Whale, Berardius bairdii, found in the North Pacific, and Arnoux’s Beaked Whale Berardius arnuxii, found in the Southern Ocean. However, Whalers from Hokkaido, the northernmost of Japan's four main islands, have long recognised two forms of Beaked Whale in the North Pacific, a larger grey form that corresponds to the official description of Baird’s Beaked Whale, and a smaller black form, which might potentially represent a different species.

In a paper published in the journal Scientific Reports on 30 August 2019, Tadasu Yamada of the Department of Zoology at the National Museum of Nature and Science, Shino Kitamura of the Sanriku Fisheries Research Centre, and the Faculty of Fisheries Sciences at Hokkaido University, Syuiti Abe, also of the Faculty of Fisheries Sciences at Hokkaido University, Yuko Tajima, also of the Department of Zoology at the National Museum of Nature and Science, Ayaka Matsuda, again of the Faculty of Fisheries Sciences at Hokkaido University, James Mead of the Division of Mammals at the Smithsonian Institution, and Takashi Matsuishi, once again of the Department of Zoology at the National Museum of Nature and Science, and of the Global Institution for Collaborative Research and Education at Hokkaido University, formally describe the smaller North Pacific Beaked Whalea as a new species of Berardius.

The new species is named Berardius minimus in reference to its smaller size, and is described on  the basis of six specimens found dead either washed up on beaches or floating close to shore around the island of Hokkaido. The species is notably smaller than both other species of Berardius, with the largest specimen observed being only 6.9 m in length, as well as having a shorter, straighter and narrower beak, being darker in colour, almost black, with prominent white spots, and more prone to bites from Cookie-cutter Sharks. The species was found to be genetically distinct from Berardius bairdii, and to have somewhat different skeletal proportions.

Illustrations of (A) Berardius minimus, and (B) Berardius bairdii. The black bars show 1 m. In general appearance, Berardius minimus resembles a small Berardius bairdii with a proportionately shorter beak and more spindle-shaped body, Yoshimi Watanabe in Yamada et al. (2019).

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Evidence for feeding on schooling shallow-water Fish by a Miocene Beaked Whale.

Beaked Whales, Ziphiidae, are small-to-medium sized Toothed Whales, Odontoceti, which hunt Fish, Cephalopod Molluscs and Crustaceans using echo-location in a similar way to Dolphins. However unlike Dolphins they are specialized for deep-diving, generally feeding at depths ranging from a few hundred to a few thousand meters. This is apparently a very successful strategy, as the group comprise about 25% of all living Whale species. However while all crown group Beaked Whales (the crown group comprises all living members of a group, their last common ancestor, and everything descended from it) are either living species known to practice deep-water diving or show adaptations to deep-water diving, such as fused vertebrae, reduced flipper sizes, enlarged sinuses and reduced dentition, the feeding habits of stem-group Beaked Whales (the stem group comprises members of a group descended from the last ancestral species not thought to have given rise to any living species outside the crown group, i.e. species more closely related to the crown group than to any other group, but still outside the crown group) is less clear, with the transition between shallow-water feeding and deep-diving thought to have occurred somewhere in this group.

In a paper published in the Proceedings of the Royal Society Series B: Biological Sciences on 9 September 2015, a team of scientists led by Olivier Lambert of Terre et Histoire de la Vie at the Institut royal des Sciences naturelles de Belgique, describe the discovery of a remarkable death-assemblage in the Late Miocene Pisco Formation at Cerro Colorado in southern Peru, comprising a stem-group Beaked Whale and a large number of Clupeiform Fish (Herring), thought to be closely related to the modern Pacific Sardine, Sardinops sagax.

The Pisco Formation comprises two fining-uppward sequences (sequences in which the particle sizes grow smaller upwards) ranging from course conglomerates (sediments containing mixed pebble-sized rocks with an infilling of sand or finer particles, typically associated with beaches, river beds or similar environments) to diatomaceous mudstones (sediments comprising fine clay particles and the shells of planktonic Diatoms, typically formed far from shore in the sea or a wide lake), and separated by an unconformity (missing section in a stratigraphic sequence, typically caused by exposure of the rocks and erosion associated with a drop in sealevel), dated to between 9.9 and 8.9 million years old by the presence of the Late Miocene marine Diatom Lithodesmium reynoldsii. This formation has produced a rich assemblage of vertebrate fossils, including Sperm Whales, Beaked Whales, Dolphins, Baleen Whales, Turtles, Crocodiles, Seabirds, Sharks and Bony Fish.

The specimen described by Lambert et al. comprises a Beaked Whale assigned to the species Messapicetus gregarius, which is well documented from the Pisco Formation with at least ten known specimens, thought likely to have been female and estimated to have been between 4.1 and 4.5 m in length. This specimen was buried in an inverted position (upside down) with between 40 and 60 well-articulated Bony Fish skeletons surrounding the head and apparently within the chest cavity. These Fish average 38.8 cm in length, with very little variation, and are placed within the Pacific Sardine genus, Sardinops, and are thought to have been very similar to the modern Pacific Sardine, Sardinops sagax.

Lambert et al. believe that these fish represent the last meal of the Whale, which has been partially regurgitated following the Whale’s death. They cite a number of lines of evidence to support this theory. Firstly the Whale and Fish skeletons are located within exactly the same stratigraphic layer, and are all well-articulated, suggesting they died within a short time-span of one-another. Secondly the Fish are found only around the head and body cavity of the Whale, positions consistent with a regurgitated meal. Thirdly, despite the rich fossil fauna of the formation, this is the only locality where these Sardines are found, other than a few isolated scales and bones, and the only Bony Fish death assemblage, suggesting that the locality does represent a unique localized event, rather than the fortuitous deposition of a Whale skeleton within a wider Fish bone-bed layer. Fourthly modern Pacific Sardines consume only planktonic Crustaceans, not large vertebrate carrion, making it unlikely that these very similar Miocene Fish were feeding on a dead Whale when they died. Fifthly the size of the Fish closely matches the size of Fish targeted by living toothed Whales of a similar size to the Pisco Formation specimen. Finally the size and number of Fish suggests a total mass of about 25 kg, roughly the same as the masses of Fish produced by stomach content analysis of extant Toothed Whales of similar size.

Fossil remains of the extinct beaked whale Messapicetus gregarious and associated Clupeid Fish Sardinops sp. cf. S. sagax found in Cerro Colorado. (a) Photograph and line drawing of the articulated caudal portion of a skeleton of Sardinops sp. in left lateral view (note the typically Clupeid urostyle supporting the caudal fin complex), with a complete skeleton of the modern sardine S. sagax for comparison. (b) Imbricated large cycloid scales of Sardinops sp. in right lateral view showing tubercular protuberances in their central region and curved radii-like lines in their lateral fields, with a body of S. sagax for comparison reporting the putative collocation of the scale set. (c) Dolomite concretion with the skull and mandibles of M. gregarious in ventral view; occipital region, hamular processes of the pterygoids, posteroventral and apical regions of the mandibles emerge from the concretion. Abbreviations: bv, articulated bivalve shells; mda, apex of mandibles; mdp, posteroventral part of mandibles; ph, hamular processes; wd, fragment of fossilized wood. (d) Line drawing of the skull of M. gregarious inside the concretion with a reconstructed outline of its body. Multiple individuals of Sardinops sp. found around the head and in the chest region are schematically represented. Stippled line marks the outline of the concretion. Lambert et al. (2015).

The cause of death of the Whale is not immediately obvious. The specimen appears to have been relatively healthy at the time of death, not showing any signs of illness or malnutrition, and apparently feeding normally (typically sick Whales have difficulty feeding). It shows no sign of physical injury, which would be expected if it had been the subject of an attack by a predator such as a large Shark or Sperm Whale. Lambert et al. suggest that it may have died as a result of poisoning, due to toxins produced by a bloom of single-celled algae. Such blooms are a known cause of death in modern Whales, who can either consume the toxic algae along with desired prey, or be poisoned by consuming prey that had itself ingested the harmful algae. The Pisco Formation is known to show evidence by testate (shelled) single-celled algae, and while there is no evidence of such a bloom around the Whale find, lethal toxins are more usually associated with algae that lack shells. Such algal blooms do not (and cannot) occur in deep water, as the algae that produce them are reliant on sunlight to grow.

Modern Pacific Sardines form shoals of the same age, and therefore size, remaining with these individuals throughout their lives. All of the Sardines found at the Pisco Formation Whale death site are of approximately the same size, suggesting that these Fish exhibited similar behaviour.

Life reconstruction of three individuals of the extinct Beaked Whale Messapicetus gregarious preying upon a school of aged Sardines Sardinops sp. (average body length 38.8 cm) in the upper part of the water column along the coast of present-day Peru. The front individual is an adult male, whereas the last in the background is a female. Alberto Gennari in Lambert et al. 2015).

Modern crown group Beaked Whales are all deep-water feeders, but the ancient stem group Beaked Whales from which they descend lack the specialist adaptations that enable their descendants to do this, suggesting that they were shallow-water feeders. This theory is supported by the discovery of a Whale from the Miocene of Peru which apparently died shortly after feeding in a shallow-water environment. The last of these stem-group Beaked Whales appear to have lived around the end of the Miocene, after which they disappeared, leaving only the crown group Beaked Whales, which appeared in the Middle Miocene and which feed in deeper waters. This disappearance of the shallow-water Beaked Whales coincides with the appearance of modern Dolphins towards the end of the Miocene, a group which radiated rapidly and spread quickly around the globe. Lambert et al. suggest that these early Dolphins may have competitively excluded Beaked Whales from shallow water environments, leading to the demise of the stem group Beaked Whales.

Phylogenetic tree illustrating the relationships between extant and part of the extinct Ziphiids. The outgroup is the Eurhinodelphinid Xiphiacetus. Red lines indicate stratigraphic ranges. Dotted lines indicate uncertainty for the age of some members of a genus. Separation between epipelagic and deep-diving taxa is based on morphology, platform versus deep-sea deposits for fossil taxa, stomach content analysis for Messapicetus, and optimization of the deep-diving ecology of most extant genera on the phylogenetic tree. Lambert et al. 2015).

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