Abnormal development in embryos and hatchlings of the Australian lungfish, Neoceratodus forsteri, from two reservoirs in south-east Queensland

Abstract

Few of the localities currently inhabited by the Australian lungfish, Neoceratodus forsteri, are in pristine condition. Most populations of wild lungfish in south-east Queensland are now isolated in reservoirs. The barriers formed by the building of dams and weirs across natural rivers separate lungfish groups from each other, cut across possible pathways for normal movement in the environment, and have additional and more serious effects. Water levels in reservoirs fluctuate in spring when lungfish are spawning, and do not allow dense stands of submerged aquatic plants to become established. Lungfish need these plants as sites for oviposition, and newly hatched young need them as refuges and sources of food. Potential recruitment of young lungfish in reservoir populations faces another threat, that of anomalous development of the embryos, hatchlings and juveniles, severe enough to kill many embryos within days of oviposition, and destroy the young fish before they are more than a few months old. Similar anomalies are not present in young fish from a river environment raised under identical conditions. Reasons for poor development, which has now been found in two reservoirs, may be related to the diet of the adult lungfish, and possibly to genetic factors.