Freshwater fish fauna of Tasman Peninsula

Abstract

Of the 25 native freshwater fish species found in Tasmania, nine occur on Tasman Peninsula along with one species of introduced fish, the brown trout Salmo trutta. The spotted galaxias Galaxias truttaceus and the common jollytail G. mandalus were the most widespread and abundant species found and fishes within the family Galaxiidae dominated the fauna. The life cycles of the fish species could be classified into three types largely based on the juvenile and adult habitats. Type 1 species, exemplified by the pouched lamprey Georria australis, breed and the young undergo a period of development in freshwater and there is an extended period spent at sea. Type 2 species, such as the short-finned eel Anguilla australis, breed at sea and, after a marine juvenile stage, mature in freshwater. lype 3a species breed in estuaries, the young spend a period of development at sea and the fish mature in freshwater. The common jollytail is an example of this type. Type 3b species, such as the spolted galaxias, mature and breed in freshwater and, as with Type 3a, have a marine juvenile stage. Most fish were collected in habitats characteristically possessing abundant cover in the form of aquatic vegetation, logs or boulders. The only introduced species, brown trout, was not widespread on the peninsula and its effect on the native fish, although uncertain, appears minimal. Due to the necessity for all species of native freshwater fish found on the peninsula to migrate up and down streams at some stage of their life cycles, caution is expressed regarding any modifications to stream habitat which may prevent this.