Heavy Infestation by the Parasitic Copepod Lernaeenicus of Sprats in the River Crouch

WHITEBAIT sprats in the estuary of the River Crouch collected in May 1957 were found to be heavily infested with copepod parasites. The fishes were collected by using a 12-ft. beam trawl with shrimp netting, several hauls being made between Burnham-on-Crouch and Holiwell Point, just inside the mouth of the River Crouch in Essex. Of the 140 sprats ( Culpea sprattus ) captured, 43 (31 per cent) were afterwards found to be parasitized by the copepod Lernaeenicus . The two British species of this genus, L. sprattae and L. encrasicola , were both present. It is a general rule that L. sprattae is fixed in the eye of the fish while L. encrasicola has its head buried in the tissues of the body, usually in the back, and the present sample was no exception to this rule. The sprats may be divided into the following categories : 97 sprats with no copepod parasites 32 sprats with one L. sprattae in one eye 2 sprats with two L. sprattae in one eye 7 sprats with one L. encrasicola in the back 1 sprat with two L. encrasicola in the back 1 sprat with one L. sprattae in an eye and one L. encrasicola in the back