Discussion

The Indo-west Pacific encompasses approximately half of the world’s oceans, stretching from the east coast of Africa to Hawaii and French Polynesia. This vast region boasts a fauna of thousands of species of fishes, which harbour a fauna of trematodes that may be as rich or even richer. Over 2,500 trematode species are known for the region so far, but the fauna is far from completely understood. We understand the fauna in outline &hypen; i.e. what kinds of trematodes are likely to be found in most groups of fishes &hypen; but the knowledge gaps in the specifics of the fauna are daunting. There remain hundreds, perhaps thousands, of undescribed species, and currently we are unable to predict total richness for this fauna. The geographical distribution of work on the fauna has been patchy; a few areas are reasonably well-known, but most are not. This patchiness translates into weak understanding of biogeography. Biogeographical understanding is further undermined by limited confidence of parasite identification over range. We cannot envisage that this system will be comprehensively characterised within the foreseeable future. The imperative, therefore, is to pursue the most informative work.