Cornwall's Gentle Giant
PUBLISHED: 17:41 13 August 2010 | UPDATED: 15:59 20 February 2013
In this May issue, Cornwall Life learns about the life of the elusive basking shark and where to spot them around the county
Abigail Crosby from the Cornwall Wildlife Trust looks at the elusive life of the basking shark, which often cruises our Cornish waters
The basking shark is the ultimate gentle giant. Growing up to 12 metres long, weighing up to seven tonnes, and with a lifespan of around 50 years, it is the second-largest shark in the world (after the Indo-Pacific whale shark) and the largest wild animal to regularly visit our British waters. Dark grey or greyish-brown in colour, the basking shark has the typical shape of a shark but with an unusually long snout. Although generally elusive by nature, these magnificent creatures are often seen cruising the waters of our Cornish coasts, usually from May onwards and into the summer months, in search of their food source, zooplankton (tiny, microscopic animals floating in the water). Out of the blue, mouth agape, the basking shark is surely one of the most inspiring sights in the animal kingdom.
Like many sharks, the basking shark has excellent senses. Tiny sensory pit organs on its head detect the electrical discharges given off by the zooplankton movements. These sharks feed over enormous distances by seeking out dense patches of plankton and swimming along with their huge mouth open wide, filtering out seawater through specially adapted gill rakers which line the gills. A 7 metre shark can filter out up to 25kg of plankton in one hour. You will find huge concentrations of plankton in areas such as tidal fronts that develop close to headlands. These fronts can be caused by abrupt differences in temperature, strong tidal flows and sudden variations in seabed depth. The high productivity of these frontal areas is an important element of the coastal food chain, supporting fish, seabirds and marine mammals as well as basking sharks. Recent research has revealed that basking sharks are 60 times more likely to be seen in a frontal area than in a non-frontal area.
It is thought that basking sharks come into our inshore waters not just to feed but to find partners to mate with. Basking sharks become sexually mature at around 20 years old, with females having multiple partners. The courtship of this enormous fish involves two or more sharks swimming parallel to each other, following close behind one another, and occasionally making contact. After a gestation period of 18 months, a litter of five or six pups are born, which are about 1.5 metres long at the time of birth but are rarely seen before reaching at least 3 metres.
Although usually fairly torpid in behaviour, basking sharks have been known to get agitated and even to breach out in the open water, a behaviour which tends to be restricted to large groups of basking sharks. It was previously thought that sharks breached in order to remove parasites, but scientists now believe that it may be related to courtship or that it could even be a mechanism to attract the attention of other sharks and keep groups together.
These sharks were once fished heavily for their fins and liver oil (used in lamps and as a lubricant), and this, combined with late age of maturation and low number of young born, led to this species being officially listed as 'vulnerable'. As a result of over 80,000 animals being slaughtered during the 20th century, numbers are thought to have declined by 95% or more from historic levels. Thankfully though, they are now protected under the Convention for the International Trade in Endangered Species (CITES). Because scientific research showed that they migrate between waters of different countries, they were recently added to the Convention on Migratory Species. Since 1998 the basking shark has been protected within the UK under the Wildlife and Countryside Act. However, many sharks are thought to die as a result of injuries inflicted while feeding at the surface, from collisions with boats. Others become entangled in fishing nets and ropes.
Rare, elusive and difficult to study, it is only in recent years that this giant has begun to give up its secrets. Much remains unknown about these fascinating but enigmatic creatures, which makes their annual visits to our waters all the more interesting and valuable for visitors and researchers alike.
The WiSe Scheme
The WiSe Scheme, launched in February 2003, aims to reduce the number of incidents of disturbance and harassment in UK waters, and to promote the safe observation of marine wildlife. Year-on-year the number of incidents of marine wildlife harassment have increased. Marine conservationists throughout the UK are aware that marine wildlife such as basking sharks may be physically harmed and can show serious signs of stress when approached in an insensitive manner by leisure or commercial pleasure craft who may be unaware of the sensitivity of marine wildlife. The course involves classroom study on all aspects of marine wildlife behaviour and their likely reaction to the approach of vessels. The training is delivered by experts with years of practical experience in field research and ecotourism.
For further information visit www.wisescheme.org
How to help basking sharks
Cornwall Wildlife Trust (CWT) established its first monitoring project on basking sharks in 2008 based on the cliffs at Carn Gloose. The aims of the project are to: provide a deeper understanding of basking shark distribution and behaviour, encourage the reporting of live and dead basking sharks, and provide the findings to enable conservation action including the development of Marine Conservation Zones.
As the first survey of its kind in the region, this project acted as a starting point for CWT in training and maintaining volunteer effort. Cornwall Wildlife Trust's Seaquest Basking Shark Project is calling for volunteers to help collect data on basking sharks from the Cornish coastline during this summer. There will be a watch station at Gwennap Head at Land's End and the project will help the Seawatch SW project survey for basking sharks, as well as other marine wildlife and birds. It also hopes to get some surveys established around other parts of the coastline and will be provide training.
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Where to spot them?
One of the best areas in Cornwall to spot the sharks is at Kennack Bay on The Lizard Peninsula, OS map ref: SW735165. Due to the topography of the area, most of the Cornish sightings of basking sharks occur around the Lizard and Penzance area during the late spring into the summer. This is because warm water from the Atlantic pushes into the coastal waters on the western coasts of Cornwall, providing food for these sharks.
Directions: From the A30 join the A39 (signposted to Falmouth and Helston). Continue on A39 and then take A394 (signposted to Helston and Penzance). Stay on the A394, following signposts to the Lizard.