BODY CONDITION AND REPRODUCTIVE STATUS IN STICKLEBACKS EXPOSED TO A SINGLE WAVE OF SCHISTOCEPHALUS-SOLIDUS INFECTION

This paper describes the results of a study of the effects of Schistoc ephalus solidus on one of its intermediate hosts, the stickleback Gast erosteus aculeatus, in an annual population in which infection is know n to occur in one major wave in autumn. Weight, as a function of lengt h, was lower in infected sticklebacks compared with uninfected fish du ring autumn and spring; in winter and summer, both categories of fish were in equally poor condition. In early autumn, the hepatosomatic ind ices of newly infected fish were higher than those of uninfected fish, perhaps due to a pathological response. Thereafter, relative liver si ze of uninfected and infected sticklebacks was comparable until spring , when it increased sharply in uninfected sticklebacks but remained st able at a low level in infected sticklebacks. Few infected fish reache d maturity. The only males to attain maturity whilst sustaining an inf ection of S. solidus were in particularly good condition. Nuptial colo ration, kidney hypertrophy and testes size were unimpaired in these ma ture infected males, but whether they were capable of successful repro duction remains debatable. (C) 1996 The Fisheries Society of the Briti sh Isles