Incidence and effects of parasitism by the rhizocephalan barnacle, Briarosaccus callosus Boschma, in the golden king crab, Lithodes aequispina Benedict, from deep fjords in northern British Columbia, Canada

Abstract

In the extremities of a deep northern British Columbia fjord system 40.5% of 3045 golden king crabs Lithodes aequispina Benedict were parasitized by the rhizocephalan barnacle Briarosaccus callosus Boschma. Parasitized Lithodes behave like unparasitized brooding females which migrate to deep water to spawn. The deep release of both host and parasite larvae may promote confinement and heavy self-infection of the host population in the most oceanographically isolated fjords such as Alice and Hastings Arms within the Portland Inlet system. In Observatory Inlet, where more water exchange occurs, both host population and parasitism level were much lower. Parasitism did not inhibit moulting in host crabs nor influence body size in females. Male body size and a secondary sexual characteristic of right cheliped allometry were decreased in parasitized crabs. Multiple parasitism occurred in 12.6% of the parasitized crabs to a maximum of five Briarosaccus callosus per host. Its cause is attributed to infection by different B. callosus larvae. Multiple-parasitized crabs were smaller than single-parasitized crabs. Special concerns for harvesting a heavily rhizocephalan-infected crab stock, such as retaining all parasitized crabs regardless of sex or size, are discussed.