Parasitic copepods from pelagic sharks in Western Australia

This first attempt to elucidate elasmobranch-copepod associations from Western Australian waters revealed 17 species of commensal copepod from four species of pelagic shark (Galeocerdo cuvier, Caucharhinus obscurus, Carcharhinus plumbeus, and Carcharhinus amblyrhynchos). The copepods represented the families Pandaridae, Euphoridae, Eudactylinidae, Kroyeridae and Caligidae. Praniza stage gnathiids were also common and other symbionts comprised species of Hirudinea, an ostracod and a sphaeromatid isopod. A predominance of tiger sharks (G. cuvier) were caught throughout the study area, which extended from the Montebello Islands to Shark Bay. There was a bias toward female tiger and sandbar (C. plumbeus) sharks caught, and a difference in the infection of tiger sharks in the north and southern regions of the study area. Several hypotheses are suggested: population differentiation of the tiger sharks, population differentiation of the copepods or ecophysiological differences in the two regions. Two major patterns were identified in the distribution of the copepods on hosts: those which occur generally on the body surface of their hosts and had a geographical distribution throughout the entire study area, and those which have a specific body location and a more restricted geographic distribution. Nemesis robusta is the one exception to this rule, as it has a wide geographic distribution, yet is restricted in site of attachment.