Monthly Archives: October 2013

Whitebeaked dolphin stranding at Newbiggin, Northumberland

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Another dead white-beaked dolphin (Lagenorhynchus albirostris) was reported found on the beach by Lynemouth powerstation on Sunday 27 October. Pictures indicated that the animal had likely been on the beach for about 10 days. I went to the site on Wednesday to investigate the dolphin. It was male, 2.65m long, but unfortunately too decomposed for collection and to allow a useful post mortem analysis. However, samples of skin, blubber and muscle were taken for genetic and pollution analyses, and teeth for aging. It had 26 pairs of teeth in each jaw which is consistent with the 22-28 pairs normally found in the species. The animal had significant tooth wear indicating that is was an older animal. By preparing teeth and reading growth layers it is possible to age the animal and a white-beaked dolphin may live for 40-45 years.

Why do cetaceans (porpoises, dolphins and whales) strand? There are different reasons, most likely a combination of factors, and it may differ depending on whether the animal was alive or dead when stranded. Live animals may strand due to navigational errors especially in areas with large tidal range and gently sloping beaches where the water may disappear quickly on the ebbing tide. Stormy weather and possibly magnetic anomalies may also contribute. However, it is more likely that the animal was sick or had been injured after interaction with fishing gear or a boat. If the animal is unwell and weak it may seek shelter in a shallow bay and beach itself to help keep the blow hole above water to allow it to breath. Animals found dead on beaches may have suffocated in fishing gear and then been dumped by the fisher at sea when the gear was hauled. In such cases there is usually evidence in the form of netmarks on the dorsal and/or pectoral fins, tail flukes or the snout. If the animal had been hit by a boat there is usually some form of physical trauma, an impact wound and/or bleeding.

There are also cases of mass strandings when whole groups of up to several hundred dolphins or whales strand together. Again there may be different factors responsible such as those mentioned above and others e.g. biotoxins (toxic algae blooms) that may make a whole group of animals sick and lead to stranding. Military sonar has been linked to strandings and deaths of several beaked whale species where the sonar has affected the whales’ diving behaviour and caused decompression-related problems (similar to the “bends” that can affect human divers) when they return to the surface after deep dives. In some other species e.g. pilot and sperm whales it may also be the social bonds that may contribute where perhaps one sick animal strand and several other come to the aid the sick animal and also strand in the process. In most cases it is likely a combination of factors that are the cause for the stranding.

For information on how to report strandings in England see: http://ukstrandings.org/how-to-report-a-stranding/

Information from the strandings provides a picture of what species are found in UK waters and show geographic and seasonal distribution. The animals that that undergo post-mortem analyses provide information on causes of death, disease, contaminants, reproductive patterns and diet of the cetaceans living around the UK.

We collaborate with the UK Cetaceans Strandings Investigation Programme (http://ukstrandings.org/) and acts as regional contact that can respond to strandings. Depending on the size of the animal and degree of decomposition, the dead animals are either collected, stored in the freezer room at the Dove Marine Laboratory and later post mortem analysed, or post mortem sampled on the beach.

On a more positive note, there was a live stranding of a harbour porpoise (Phocoena phocoena) on Whitley Bay Beach in on Tuesday morning 29 October. This report came from Marcus Jackson, North Tyneside council coastal warden. The stranding was reported to the  British Divers Marine Life Rescue (http://www.bdmlr.org.uk/) who are trained in dealing live stranded cetaceans. When BDMLR came to the beach members of the public had already refloated the animal. This may have had a successful outcome for the animal but unless correct procedures are followed it is possible to cause more harm than help. So unless you have been trained as a marine mammal medic, please call for expert help if you find a live stranded cetacean.

For more information please contact: Dr Per Berggren (per.berggren@ncl.ac.uk)

Many thanks to Martin Kitching (http://www.northernexperiencewildlifetours.co.uk/) for reporting the white-beaked dolphin stranding.

Whitebeaked dolphin stranding by Alnmouth

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On Tuesday morning 22 October we received a message about a dead white-beaked dolphin (Lagenorhynchus albirostris) found on a beach by Alnmouth, Northumberland. The message came from the UK Cetacean Strandings Investigation Programme (http://ukstrandings.org/) that monitors the UK hotline for stranded cetaceans. We participate in this work by responding to strandings that occur locally in Northumberland. After checking the exact location with those that had reported the stranding we (myself, Simon Laing, Dove Marine Lab intern and Paul Dees, Stage 3 Marine Biology student) set off in the school van with a stretcher, wheelbarrow and basic sampling kit with the intention of retrieving the whole animal. The plan was to bring the dolphin and store it in the freezer room at the Dove Marine Laboratory for a full dissection at a later date. We reached the site after an hour drive and found the animal on the beach just below the high tide mark. It was not as fresh as we had hoped and interviews with locals at the nearby caravan park told us that the animal had stranded on Saturday.

The dolphin was a 2.6m female and we soon realised that we would not be able to move her from the beach along the narrow steep access path to the van. In fact the three of us were barely able to move her at all and struggled to drag her up above the high tide mark. We were not able to weigh her but she was likely weighing 200+ kg. The size and tooth wear told us that this was a mature older female. We extracted teeth for aging and cut out skin, blubber and muscle samples for genetic, stable isotope and contaminant analyses. We also photographed the animal including pictures of the dorsal fin that we will use to match against existing catalogues of known white-beaked dolphins in the North Sea. It was by now late afternoon and we decided to leave the animal and return the next day for more comprehensive sampling.

We returned on Wednesday equipped with scalpels, knives, saw and various sampling bags. We took samples from kidney and liver (for heavy metal analysis), blood (for blood chemistry) and we also took uterus and ovaries (for reproductive biology – she was not obviously pregnant) and stomach (for diet analysis). We then took the whole head for studies of the sound production organs and one of the flippers that we will clean and eventually have on display together with the skull.

The white-beaked dolphin is endemic to the Atlantic Ocean and regarded as a continental shelf species with an abundance of about 10,000 in the North Sea. It is one of the larger dolphins (1.1-1.2m at birth growing to around 2.5-3m and 200-300kg). It is characterized by its short thick white coloured beak, white or pale grey markings on the flanks, counter-shading and curved dorsal fin. They become sexually mature around 10 years of age and the lifespan is about 40 years. They feed on fish and cephalopods. There is little information about the species social structure and group size is 1-20. For more information about the abundance and distribution of white-beaked dolphins and other cetaceans in European waters please see the following recent publication: Hammond PS, Macleod K, Berggren P, et al. 2013. Cetacean abundance and distribution in European Atlantic shelf waters to inform conservation and management. Biological Conservation. 164, 107-122. Read abstract and download paper here: http://www.ncl.ac.uk/marine/research/publication/192635

You can also watch white-beaked dolphin swimming underwater filmed by Ben Burville off the Northumberland coast here: http://www.youtube.com/watch?v=wmDC2Cj_ROk

For more information please contact: Dr Per Berggren (per.berggren@ncl.ac.uk)

Greenland shark stranding by Alnwick

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An unusual stranding occurred on Friday morning when a 3m Greenland shark (Somniosus microcephalus) washed up on a beach by Dunstan Steads, outside Alnwick, Northumberland.

It was discovered by James Robertson, a local farmer, who was out surfing. James called in his observation to the local council and to Dr Per Berggren at the School of Marine Science & Technology who coordinated the recovery of the shark. It was a truly collaborative effort involving local efforts to get the animal off the beach in the late afternoon and then transported in the School van by Marine Science Technician John Knowles from The Dove Marine Laboratory. John then got help from Marine Science MPhil students Andrew Temple and Will Jolly, and Dan Gordon (Great North Hancock Museum) to get the shark into the freezer room at the Dove Marine Lab where it is now sharing the space with six porpoises and one hooded seal.

The Greenland shark is a sub-Arctic species with possibly the most northern distribution of any shark and is normally found around Iceland and Greenland. It belongs to the family “sleeper” sharks (Somniosidae) within the order dogfishes (Squaliformes) and is also sometimes called Gurry shark (due to the fact that it sometimes eat offal from fish and mammals). It inhabits inshore zones to continental shelves usually in depths of 0 to 1200 m (has been recorded at 2,200m depth). During winter months in the species occurs in the intertidal zone and at the surface in shallow bays and river mouths, moving into depths of 180 to 550 m during warmer months.

The Greenland shark is fairly barrel shaped with a short, rounded snout, small dorsal and pectoral fins, and small eyes. The gill openings are also very small in relation to the size of the species. The colour range from dark brown to pale grey and is uniform.

It is one of the largest sharks and can grow up to 7m and way 1400kg. The animal that stranded was comparatively small being 3m and about 120kg. There are no reliable estimates of the Greenland shark lifespan but tagged sharks have been recaptured 16 years later. It is thought to grow at very slow rate and may be the longest-lived vertebrate with a potential life span of over 200 years. It has placental ovoviviparous reproduction and the female can carry up to 10 young pups.

Greenland shark is an apex predator that normally feeds on fish, seabirds, seals, invertebrates and large carcasses. It has about 50 teeth in each the upper and lower jaw. The teeth of the upper jaw are thin, pointed, without serrations and act as anchor while the lower jaw does the cutting. The lower teeth are broad, square and interlocking with short cusps pointing outward. Most shark species can be identified from their teeth and for this species it is important to use teeth from both upper and lower jaw for a positive identification.

This shark is listed as Near Threatened on the basis of possible population declines and limiting life history characteristics. The Greenland shark was historically targeted by shark liver fisheries in Norway, Iceland, and Greenland that may have had a significant impact on the species. The commercial fishing of the Greenland shark for liver oil ended in 1960. Currently the species is taken as bycatch in halibut and shrimp trawl fishers and fish traps and gillnets in Greenland. It is also caught by artisanal fisheries in the Arctic.

The flesh of a Greenland shark is poisonous due to the presence of the trimethylamine oxide. However, it can be eaten if it is boiled in several changes of water or dried or fermented for several months to produce Hákarl. Traditionally Hákarl this was produced by burying the shark in the ground, where the shark would go through several cycles of freezing and thawing. It is considered a delicacy in Iceland and Greenland.

What will happen to the shark now? The shark will be kept frozen until a decision has been made of its fate. There is great interest for the shark and the Natural History Museum is interested in preserving the whole animal but before that the animal will be measured and sampled for biological and ecological analyses.

For more information please contact: Dr Per Berggren (per.berggren@ncl.ac.uk)

The pictures of the shark have kindly been provided by Darren Graham, Northumberland and James and Elizabeth Robertson.

Inshore Fisheries and Conservation Authority (IFCA).