Influence of Haemobaphes cyclopterina and H. intermedius (Copepoda) on Arctic cod (Boreogadus saida) and tidepool sculpins (Oligocottus maculosus), respectively

Abstract

A study was conducted to determine the prevalence and effects of two species of blood-feeding copepods on their definitive fish hosts, viz. Haemobaphes cyclopterina parasitizing Arctic cod (Boreogadus saida) and H. intermedius infecting tidepool sculpins (Oligocottus maculosus). Infected and uninfected Arctic cod and tidepool sculpins were captured by SCUBA and dip net in the northwest Atlantic and northeast Pacific, respectively. Biological variables such as condition factor, hepatic somatic index, gonadal somatic index, and haematocrit were compared between the two groups of Arctic cod of both sexes, whereas only condition factor was compared in the two groups of sculpins of both sexes. Prevalence of H. cyclopterina (8%) was considerably lower than that of H. intermedius (46%). This difference is probably associated with the hosts' behaviour, as the Arctic cod is pelagic whereas the tidepool sculpin is restricted to the littoral zone, where infections are probably acquired. Infected Arctic cod of both sexes had significantly lower condition factor, hepatic and gonadal somatic indices, and haematocrit than non-parasitized fish. Only females harboured large numbers of the parasite and showed even more dramatic changes than the corresponding groups. The growth period of H. cyclopterina on Arctic cod from the time of infection to the fully developed egg sac stage is probably about 6 months. In tidepool sculpins, condition factor was significantly lower in infected than in uninfected fish. These results, especially for the Arctic cod, parallel those reported for gadoid fish following infection with haematophagous species of Lernaeocera that impair growth and reproduction.