The two species ofGyrocotylein the elephant fish,Callorhynchus milii(Bory)

Abstract

Over 100 specimens of Callorhynchus milii (Bory) the elephant fish from Canterbury Bight and Pegasus Bay were examined for infection with Gyrocotyle spp. Monthly samples from the two areas yielded two species; G. rugosa and G. maxima. The total incidence of G. rugosa for the two areas was 83.8 percent and for G. maxima 3.1 percent. In June is the main hatching period for this fish, so that at this time there are large numbers of small unparasitised fish. This results in the occurrence of the lowest percentage (78 percent) of infected fish at that time. The highest percentage infection occurs in April (91.4 percent) when the fish are mostly over 20 cm long, and by this time are mostly parasitised. Two worms is the most commonly encountered level of infection (66 percent). Infections with 3–4 mature worms were all in fish over 50 cm long. In all fish with 5 or more parasites the worms were small and immature. Of the parasitised first-year fish, 53.6 percent had two worm infections, 34.1 percent had one and 12.2 percent more than two. There appears to be a steady increase in size of worm with size and age of fish. Further observations on the adult G. rugosa and larva are recorded.