Host‐parasite relationship: occurrence and effect of C eratothoa parallela ( O tto, 1828) on B oops boops ( L ., 1758) in the S outhern T yrrhenian S ea

Summary The host‐parasite relationship between bogue ( B oops boops ) and C erathotoa parallela ( I sopoda: C ymothoidae) was studied in the S outhern T yrrhenian S ea (overall prevalence of isopods in the area, age‐dependent and sex‐dependent prevalence). Yearly prevalence ranged from 1.0% in M arch to 10.7% in October, with a positive correlation between prevalence and mean sea surface temperatures ( SST ), highest values being related to the period of increasing SST . The first four age‐classes were parasitized, with prevalence decreasing according to the age of the host. The relationship between total length ( TL ) and total weight ( TW ) was examined in infested and non‐infested specimens of the same age whereby slight differences were detected, i.e. at a given length non‐infested specimens weighed more than infested fishes. The parasite occurred throughout the study area with wide fluctuations in prevalence, from 0 to 36.4%, the values being higher in the eastern part of the study area. C . parallela parasitize the bogue B oops boops in a manner that does not constitute a serious threat to the life of the host.