GONADAL IMPAIRMENT IN ROACH RUTILUS-RUTILUS FROM FINNISH COASTAL AREAS OF THE NORTHERN BALTIC SEA

Gonadal impairment in roach Rutilus rutilus from Finnish coastal water s was studied during 1987-1995. The disease was observed in high preva lence (>10%, for roach in length class 25-30 cm) in roach from 4 sites in the Archipelago Sea, from one site influenced by cooling water dis charge from a nuclear power plant in Gulf of Bothnia, and in roach fro m one site close to a metal processing plant in the northern Gulf of B othnia. The sites in the Archipelago Sea were not directly affected by industrial pollution. The disease was most prevalent in large (old) f emale roach, and it was characterized by degeneration of the ovaries r anging from weak tissue changes in one ovary to complete absence or de struction of both ovaries. Oocytes, in affected gonads, were frequentl y infected by a microsporidian parasite Pleistophora mirandellae. In m ales atretic testes were never observed and only small cysts, containi ng Fl mirandellae, were detected. In several affected roach, both male and female reproductive tissues were observed. The observed pathologi cal changes in the ovaries of roach are suggested to be caused by P. m irandellae.