Growth of the fish parasite Ichthyophonus hoferi under food relevant conditions

The physical and chemical limits for growth of the internal fish parasite, Ichthyophonus hoferi, have been studied to understand better the ecology of I. hoferi both as a possible food contaminant and a fish pathogen. The effect of temperature (0 degrees-30 degrees C), pH (3-7) and NaCl (0%-10%w/v) on growth were tested in a multi-factorial experiment. Growth was observed at all pH-values, from 0 degrees to 25 degrees C and from 0% to 6% NaCl. No significant differences (P > 0.05) were detected in the growth ability in the temperature range 0 degrees-25 degrees C and from pH 3 to 7. However, increasing the concentration of NaCl significantly decreased the growth of I. hoferi and it is therefore unlikely that I. hoferi will develop and spoil processed products (pickled or salted herring) by continued growth. Hyphal growth could be initiated by incubating spores under CO2, and this may be a potential problem in gas packed fish products.