The fishes of Lake Kununurra, a highly regulated section of the Ord River in northern Western Australia

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – The Ord River, situated in the east Kimberley region of Western Australia, is regulated by two dams that supply irrigation water for tropical agriculture. The regulation of water in the 55 km span of river between these dams has resulted in this section now resembling a lacustrine rather than riverine environment that is reflected in its name, Lake Kununurra. Utilising various sampling techniques we captured/observed 4157 fish from 19 species in 13 families, whilst the presence of a further three species was confirmed by reliable sources. Nematalosa erebi, Craterocephalus stramineus and Melanotaenia australis were the three most widespread and abundant species, being encountered throughout the lake and representing -66% of all fish recorded. Ambassis sp., Arius midgleyi, A. graeffei, Glossamia aprion, Amniataba percoides, Hephaestus jenkinsi, Glossogobius giurus and Toxotes chatareus were found throughout the lake but generally at fewer sites and in smaller numbers (-30% of all fish) than the three dominant species. The remaining species Neosilurus ater, Strongylura krefftii, Leiopotherapon unicolor, Syncomistes butleri, Lates calcarifer, Mogurnda mogurnda, Oxyeleotris lineolatus and Ambassis macleayi were generally found at few sites and in low numbers, and accounted for less than 4% of the overall catch. The regulation of the Ord River has apparently altered the species composition and abundances in Lake Kununurra. For example, marine/estuarine species, commonly encountered in the freshwaters of large northern Australian Rivers, are largely absent, while species such as L. unicolor, which is one of the most abundant species in nearby rivers and tropical Australian rivers in general, contributed to <1%) of the total catch.