Cornwall Mammal Group
fin whale-(Balaenoptera physalus)
Order: Cetacea, Cornish Name: Morvil
Conservation:
Following the loss of perhaps 80% of the population to whaling, recent conservation
efforts have resulted in a gradual recovery, and it now stands at about 119,000 individuals worldwide. Fin whales are still hunted by Japan despite the International
Whaling Commission moratorium banning commercial whaling. Instead, Japan claims an exception from the moratorium to conduct scientific research. In the UK fin whales are protected by the Wildlife and Countryside Act 1981. Fin whales are a
national BAP species. Fin whales are listed as ‘endangered’ on the IUCN Red List of
threatened species.
Recognition:
A 15 m fin whale washed up dead near Sennen in October 2004 and samples were
taken for analysis by volunteers from the Cornwall Wildlife Trust Marine Strandings
Network. In February 2008 a dead fin whale calf, recorded by the Cornwall Wildlife Trust Marine Strandings Network at 6 m, washed up at Porthallow. A 19 m long female fin whale stranded alive at Carlyon Bay in 2012. It was attended by BDMLR but but due to its emaciated state and size was beyond help.
Tissue samples were taken for analysis.
Distribution:
Rarely recorded around Cornwall, fin whales prefer deeper, offshore waters. They are usually found off the north and west of Scotland, western Ireland and southwest England, between July and December. Elsewhere, three distinct populations are thought to exist: North Atlantic (and eastern Mediterranean), North Pacific and southern hemisphere.
Records:
2007-2012: 8
2002-2007: 7
Pre-2001: 24
Total: 39
The fin whale is the second largest animal
on Earth after the blue whale. It can reach
lengths of over 26 m when fully grown, but is just 6 m at birth. Females are generally
larger than males. Like many whales, it is grey on top and white underneath and has a streamlined body with a pointed head, so is
easily confused with similar species such as blue, sei and Bryde’s whales. There is a small, arching, dorsal fin about two-thirds of the way along the back, while the pectoral fins on its sides are relatively small and pointed. The blowhole on the top of its head is divided into two, and a ridge runs from here down the head to the tip of the upper jaw. The throat is pleated and expands hugely when the whale takes a mouthful of prey and water. Instead of teeth, plates of baleen covered in fine bristles hang down from the upper jaw, these filter out the prey from the water when the whale closes its mouth. The easiest way to positively identify a fin whale is from the unique colour pattern on either side of the jaw, as the left side of mouth and
baleen plates are grey, while the right side is white. This is thought to have developed
from it swimming while feeding mainly with its left, grey, side facing upwards and the right, white, side facing downward, helping to camouflage it from threats above and below. Fin whales can be spotted, even at great distances, when they exhale giving off a tall, narrow spray of moisture. In diving, the back of the animal will roll across the surface of the sea until the dorsal fin appears, upon which the whole animal will sink down, rarely showing the tail above the water. They make very loud, low frequency vocalisations that can be heard hundreds of miles away underwater, and these may be used to communicate.
Fin whales occur in all the world’s oceans and also in the eastern Mediterranean,
although they are rare in polar waters and uncommon in the tropics. They migrate
long distances from warmer breeding grounds to colder feeding grounds every year.
Pregnancy lasts about a year and the single calf is weaned after 6 months, in time
for the annual migration. A calf will mature and become sexually active after 6 to 12
years (when they have grown to around 20 m in length) and the females can mate
every second or third winter. Fin whales can live for up to 90 years. Large whales
such as the fin whale usually travel alone except when a mother is with her calf.
However, small groups of 3 to 7 have been observed on many occasions and as many
as 100 individuals can gather in rich feeding grounds.
This species lives mainly in the deep water of the open ocean, and is rarely seen close inshore unless there is deep water nearby. Around Cornwall the area they have been most frequently observed is between Cape Cornwall to Fal Bay.
As filter feeders, they take huge mouthfuls of water to collect plankton, krill, squid and small fish in their baleen plates. They do this by either swimming along slowly at the surface with the mouth open, or by lunging partially out of the water on their front or right side.
Adult fin whales have no natural predators, although pods of killer whales may attempt to separate a young calf from the mother and drown it. Whaling is currently their biggest threat and the population globally has fallen dramatically over the centuries because of this. Fin whales were the most hunted of all whale species in the 20thCentury and 725,000 were killed in the southern hemisphere alone. Entanglement
in fishing nets and ship strikes have also been reported. Sonar may also be a threat
to them, as the loud noises produced by these devices can cause deafness if the
whales are close to the sources, and it can also mask their vocalisations, making it
difficult for them to keep in touch over long distances.
Did you know?:
Fin whales are also know as finbacks, finners, common rorquals, razorbacks and herring whales. Common rorqual and finback are both old English terms and were used in Cornwall.
Survey Methods:
Boat-based surveys carried out from from ships that cross areas of open ocean (e.g
ferries) through programmes such as Organisation Cetacea (ORCA) and Marinelife.
© PGH Evans - Sea Watch Foundation
