On Wednesday this week (28 September 2011) a young Sei Whale, 10 m long, was reported stranded in a salt marsh on the north side of the Humber Estuary (erroneously reported as a 'field' in some newspapers), near the village of Skeffling. It apparently became trapped while feeding close to the shore during a high equinox tide, then rolled onto its side as the waters retreated, covering its blowhole and dying of asphyxiation.
The stranded Sei Whale.
Sei Whales (Balaenoptera borealis) can reach 20 m long and weigh up to 28 tonnes. They are baleen whales feeding largely on copepods and other small crustaceans. They are fast swimming whales at home in the open water and usually avoid enclosed areas. This means that strandings are rare but when they do become trapped they have little chance of survival. This is the third Sei Whale stranded in UK water in the last 20 years, and 14th in the last one hundred. Following large scale hunting in the nineteenth and twentieth centuries they were driven close to extinction, but numbers have started to recover and the global population is currently thought to be about 80 000; they are still classified as endangered. Experts view individual strandings as sad, but as an indication of recovering stocks, not altogether a bad thing (more strandings will occur when there are more whales).
A Sei Whale as it appears when alive.
According to the Yorkshire Wildlife Trust whale strandings are becoming increasingly common on the Humber Estuary and Northeast English Coast. Whales seem to be particularly vulnerable in the estuary due to its extreme tidal range (7 m).
On 6 September this year a young Fin Whale (Balaenoptera physalus) became stranded in mud on the Lincolnshire side of the estuary, near Immingham Docks. This was dug out and refloated (with some difficulty) by volunteers from the Sea Watch Foundation, Cleethorpes RNLI, Humber Rescue, Lincolnshire Fire and Rescue, the RSPCA, the Coastguard and British Divers Marine Life Rescue, but unfortunately re-stranded and died near Cleethorpes two days later. Like Sei Whales, Fin Whales are a large (up to 27 m), fast swimming, deepwater species that where formerly heavily hunted. Strandings are rare, but again considered a sign of recovering populations. The global Fin Whale population is currently thought to be somewhere between 100 000 and 119 000 individuals.
Volunteers digging out the stranded Fin Whale, earlier this month.
In November 2007 a dead whale was seen floating in the Humber near Alexander Dock, but washed out to sea before experts could determine what species it was. In 2006 a Humpback (Megaptera novaeangliae) became trapped in a ferry port on the river and died and a Sperm Whale (Physeter macrocephalus) was found dead at Spurn Point on the estuary.
A Humpback Whale was stranded and died at Gravesend on the Themes Estuary in 2009. In 2007 a Humpback was stranded at Carnoustie in Angus, Scotland. This was refloated but a day later a whale tangled in fishnets was recovered at Arbroath, which is thought to have been the same animal. In 2006 a Humpback whale was found dead at Lombardsijde in Belgium, having apparently been hit on the head by a ship's propellor.
The Gravesend Humpback.
A Sperm Whale was also stranded on a beach near Redcar in Cleveland in June this year, and died despite attempts to refloat it. In 2006 two Sperm Whales, a male and a female, were stranded at Skegness, to the south of the Humber Estuary. The female was found dead, but volunteers managed to refloat the male. Unfortunately the male was washed up dead the next morning. In 2004 a Sperm Whale became stranded on a sandbank at Sutton Bridge in the Wash and died despite efforts to refloat it. Another dead Sperm Whale was found at Thornham in Norfolk in 2004. This was washed out to sea, and came ashore at Koksijde in Belgium. later Sperm whales were also reported stranded in Holland in 1995, Belgium in 1994 and Denmark in 1991.
In September 2009 a Fin Whale was found dead in Antwerp Harbour in Belgium, apparently having been hit by a ship.
In March 2008 a Cuvier's Beaked Whale (Ziphius cavirostris)was found dead in the Moray Firth in Scotland; this species has been recorded stranded in Ireland and on the Atlantic Coast of Scotland, but this was the first recorded instance of one in the North Sea.
In January 2006 a female Northern Bottlenose Whale (Hyperoodon ampullatus) became trapped in the River Thames, and died despite attempts to rescue it.
The Bottlenose Whale passes the Houses of Parliament in London.
The commonest whale in the North Sea is the Minke (Balaenoptera acutorostrata) but these are seldom stranded, being well adapted to inshore conditions and shallow, tidal waters. Strandings of whales are often blamed on both Naval Sonar and the activities of North Sea oil drillers, but if this is the case it is difficult to explain the apparent immunity of Minke Whales to these disturbances.
Whale strandings in the UK can be reported on the Natural History Museum's website here.
Whale sightings can be reported to the Sea Watch Foundation here.
See also Mammals on Sciency Thoughts YouTube.