Parasites as biological tags for sailfish Istiophorus platypterus from east coast Australian waters

A total of 52 sailfish Istiophorus platypterus from Queensland (Australia) coastal waters were examined for parasites which might provide information on the relationships and movements of fish from different areas. Sailfish from 4 locations between Cape Moreton in southern Queensland and Dunk Island in the north were dissected from 1987 to 1989. Of the 36 parasite taxa which were identified from sailfish, 22 were new host records. Both ordination and classification strategies applied to a combination of 8 long-lived and 8 short-lived parasite taxa indicated different histories of movement for fish from northern and southern locations. The distributions of 2 trypanorhynchs, Callitetrarhynchus gracilis and Otobothrium d~psacum, a copepod, Pennella jnstructa, and a sanguinicolid, Card~cola grandis, were primarily responsible for discriminating these groups of fish. Analyses of the parasite data from adjacent fishing seasons at Cape Moreton (summer) and Cape Bowling Green (winter). which controlled for apparent interannual variability in parasite abundance, produced clear evidence of discreet subpopulations of sailfish from these locations. Sa~lfish from the Whitsunday Islands were all mature and, in instances, in spawning condition, whereas fish from other areas were either immature or non-active. Some of the Whitsunday fish had parasite faunas similar to those from northern fishing grounds while others were more similar to Cape Moreton fish. These combined data suggest that fish from the northern and southern grounds may mix in the reef waters of the Whitsundays when mature The results of analyses undertaken in t h ~ s tudy and a concurrent study (Speare 1994, Aust. J mar. Freshwat. Res. 45: 535-549) indicate the utility of parasites to discriminate between billfishes with different histories of movement.