Resistance of perch eggs to attack by aquatic fungi

In the distinctive gelatinous Perca fluviatilis egg mass, limited fungal gr owth by Aphanomyces and Saprolegnia spp, especially S. diclina occurred wit hin dead eggs but did not spread to adjacent live eggs. Perch eggs exposed to parasitic challenge by Saprolegnia parasitica, S dieclina(type III) and S. ferax, under fluctuating temperature regimes replicating spring water te mperatures. did not have significantly greater mortality than did unchallen ged controls. The observations suggest that perch eggs have some anti-funga l properties which usually prevent the spread of fungus throughout the egg mass and that under normal spring temperatures there should be negligible e cological consequences of fungal infection in perch egg masses. (C) 2000 Th e Fisheries Society of the British Isles.