Fish parasite responds to climate change!

Fishermen will often have noticed parasites dangling, with their trail of eggs, in the eyes or gills of their catches. These are copepods, a group to which the well-known Cyclops belongs but it is only in the past few years that we could expect one of the isopods or 'sea- slaters' on a fish. One such species was found a few years ago on the Lesser Weever at Whitsand Bay (east Cornwall), Whitsand Bay (west Cornwall) and Perranporth. An account by specialist Tammy Horton appeared in the Journal of the Marine Biological Association in 2000. Earlier this year whilst collecting sand eels at Hayle, Treve Opie found two specimens blocking the mouth of a Lesser Weever - some species actually replace the tongue of the fish. Additionally he found them crawling over the bodies of the sand eels, having not yet settled down to an easy life of parasitism. Until these records Ceratothoa strandachneri, was found only on fish in the more southly parts of their range.

From the Isles of Scilly Martin Goodey and Ren Hathway have sent digital pictures and specimens of slaters discovered on two other fish species - a Garfish and a mackerel. They were sent to Tammy Horton who has identified them as two different species, both known in the N. E. Atlantic but both seemingly to be new to the Cornish coast. So do please collect any specimens - or isopods (and indeed copepods) send them to the Environmental Records Centre for Cornwall and the Isles of Scilly, Allet, Truro TR4 9DJ.

Stella M Turk

Extract from HVMCA newsletter No.27 Autumn 2003