DISTRIBUTION OF FRESHWATER FISH IN THE OTWAY REGION, 
SOUTH-WESTERN VICTORIA 
J. D. Koehn and W. G. O’Connor 
Arthur Rylah Institute for Environmental Research, 
123 Brown Street, Heidelberg, Victoria 3084 
Koehn, J. D. & O’Connor, W. G., 1990:05:31. Distribution of freshwater fish in the Otway 
region, south-western Victoria. Proceedings of the Royal Society of Victoria 102(1): 29- 
39. ISSN 0035-9211. 
The distribution of freshwater fishes in the Otway region of south-western Victoria was 
determined from surveys carried out at 53 sites between 1982 and 1988. Eighteen fish spe¬ 
cies (14 native and 4 introduced) were recorded. The distribution of native fish appears to be 
related to geomorphological conditions that existed during and after the last glaciation 
20,000-5,000 years ago. The short coastal streams east of Cape Otway may have formed 
after the Bass Strait land bridge was submerged, or may have been subjected to desiccation 
during an ensuing drier period. The native fish fauna of these streams consists of species with 
marine phases in their lifecycles and may have originated by recolonization from the sea. 
Although species with entirely freshwater lifecycles are absent from these streams, they arc 
abundant in the Barwon, Aire and Gellibrand river systems, suggesting that these systems 
were less affected by geomorphological conditions due to their much greater size or to their 
location. 
Australian grayling were collected from nine sites in the Otway coastal streams, and valu¬ 
able populations of freshwater blackfish and of several species of Galaxiidae were also 
recorded. The discovery' of a Tasmanian mudfish in Wye River provides a second location 
for this species in Victoria, and whitebait of Australian grayling were recorded from the 
Cumberland River. Brown trout were found to be widespread but other introduced species 
were rare in the coastal streams. The freshwater fish faunas of the Otway region and of 
northern Tasmania arc compared. The importance of the Otway region in the conservation 
of native freshwater fish species is discussed and careful management is recommended. 
THE FISH fauna of the Otway region (Fig. 1) of 
south-western Victoria, which forms part of the 
study area for the south-western regional water 
strategy plan (Natural Resources & Environ¬ 
ment Committee 1984), has not been surveyed 
since the mid-1960s (Renowden 1968). Most of 
the recent faunal surveys conducted in the 
region (Emison et al. 1975, Bennett 1982, 
Pescott 1982, Conole & Baverstock 1983, 1985, 
King 1986, Wallis 1986, Earl & Bennett 1986) 
were primarily concerned with terrestrial verte¬ 
brates and gathered few or no data on fishes. 
Here we report on recent surveys of freshwater 
fishes conducted at 53 sites in the Otway region. 
We compare the freshwater fish fauna of the 
coastal Otway streams with those of the larger 
river systems such as the Barwon and 
Gellibrand, and relate the distribution of the 
species to the geomorphological history of the 
region, to the species’ life cycles and to avail¬ 
ability of habitat. 
The fish faunas of the Gellibrand and Barwon 
Rivers have been recorded by Tunbridge & 
Glenane (1988) and by Hall & Tunbridge (1988) 
respectively. Some information on the estuarine 
fish species of the region has been published by 
McCarraher (1986). 
STUDY AREA 
The Otway region is physiographically divided 
into the Otway Range and the coastal plains. The 
coastal plains, which are used primarily for agri¬ 
culture, extend up to 50 km inland and are 
bounded to the north by volcanic plains. The 
Otway Range extends for almost 100 km from 
Aireys Inlet (38°28'S, 144°06'E) in the east to 
Moonlight Head (38°46'S, 143°14'E) in the west. 
The range is about 500 m high over most of its 
length, with Mount Cowley being the highest 
point at 670 m (Douglas 1975). 
The wettest part of the region lies along the 
main ridge of the Otway Range where the mean 
annual rainfall is more than 1800 mm, and a 
marked rain shadow extends over much of the 
inland plains to the north-east (Lindforth 
1975). 
The two largest waterways in the region are 
the Barwon and Gellibrand Rivers which drain 
the northern slopes of the Otway Ranges and 
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