Abstract
Perch, ruffe, brown trout and ten-spined stickleback from Hanningfield Reservoir, Essex were found to be infected withBunodera luciopercaein 1968–1969. Only perch were heavily infected.B. luciopercaeshowed an annual cycle of occurrence and maturation in perch. Mean intensity of infection with B.luciopercaeincreased to a maximum in perch 15–19.9 cms in length but decreased in larger and older fish. There was a significant positive association between the presence ofB. luciopercaeand that of the cestodeProteocephalus percaein perch, with both parasites occurring together more often than expected from chance alone.