Reports of stranded seahorses started appearing on 29 March from Studland, followed by other findings at Worbarrow Bay near Kimmeridge, Greenhill Bay in Weymouth and Chesil Beach at Portland.
The finds include both seahorse species which are native to Britain, the spiny seahorse Hippocampus guttulatus and the short-snouted seahorse Hippocampus hippocampus.
“To have so many seahorses washing up in Dorset in such a short time is unheard of and we are very grateful to the people who found them for publicising their finds,” says Julie Hatcher, marine awareness officer for Dorset Wildlife Trust.
“While there is no obvious reason for the deaths it certainly indicates that Dorset has a good population of seahorses along the coast.”
All the seahorses found were small individuals likely born in the last year and would have matured this to adulthood this summer.
“It may be that they struggled to find enough food early in the year or were caught out by some rough sea conditions and accidentally washed up on the beach,” adds Hatcher.
“We are keen to hear of other records that might give us a clue as to the cause.”
Several sites in Dorset are known to have seahorses, including Studland Bay where both species have been found to breed.
Studland Bay and Worbarrow Bay are currently being considered as a possible Marine Conservation Zone with a decision about the designation expected in the next couple of weeks, this would greatly benefit the seahorses that live there.
There have also been reports of more seahorse strandings along the south coast.
“There have been ten sightings of both species from Poole Bay, Isle of Wight and Southampton since Christmas,” says Neil Garrick-Maidment from The Seahorse Trust.
“An unusually high amount, especially bearing in mind the weather has been relatively mild compared with other years.”
The Seahorse Trust suggests that increased chemical and noise pollution in the area may be to blame, seahorses are highly affected by noise pollution.
“As well as the seahorses, we have also had four dolphins and one seal washed up, a higher than normal number of dead animals,” adds Garrick-Maidment.