84 
J. D. KOEHN AND T. A. RAADIK 
Corrick (1981) predicted further loss of wetland 
areas through drainage, clearing, cultivation and 
flood mitigation and irrigation works. His pre¬ 
diction appears fulfilled because calculations 
from recent studies of this area (Corrick unpubl. 
data) show an overall loss of 99% of potential G. 
cleaveri habitat (shallow freshwater marshes 
94%, deep freshwater marshes 99%). 
The loss of such large areas of habitat suitable 
for G. cleaveri must be the greatest threat to this 
species in Victoria in recent times and may ac¬ 
count for its fragmented distribution. Similarily, 
Frankenberg (1974) stated that the range of G. 
cleaveri in Tasmania had undoubtedly been 
fragmented due to the draining and clearing of 
swamps. 
In New Zealand populations of the three 
species of mudfish have declined drastically 
with the loss of habitat due to swamp drainage, 
development and agricultural practices 
(McDowall 1990). Whilst concern has been ex¬ 
pressed for all three species, Skrzynski (1968) 
and Eldon (1979b) have questioned whether 
Neochanna burrowsius can survive, especially 
with continued agricultural modifications. 
Cadwallader (1975) suggested that preservation 
of habitat areas through the establishment of re¬ 
serves should be instigated for this species. A 
population of N. burrowsius established in an 
artificial pond (Eldon 1988) survived for several 
years before dying out as a result of a prolonged 
drought (NZ MAF 1990) 
Other threats to adult G. cleaveri , such as 
interspecific competition and predation by in¬ 
troduced trout, Salmo trutta, Oncorhynchus 
mykiis or redfin, Perea jluvialitis , are unlikely to 
be major, especially in swampy habitats with 
poor water quality unsuitable to these species. G. 
cleaveri whitebait may be subject to predation, 
however, whilst migrating upstream. Habitat 
disturbance and competition from other intro¬ 
duced species such as carp, Cyprinus carpio , 
goldfish, Carassius auratus, and tench, Tinea 
tinea , are possible but difficult to assess. Sedi¬ 
mentation is unlikely to affect G. cleaveri unless 
the habitat areas become completely filled. 
Because G. cleaveri is restricted to a special¬ 
ised aquatic habitat, climatic changes may have 
serious impacts, although the impact of the 
Greenhouse Effect is as difficult to predict as it is 
for other native species (Burchmore 1990). 
Lower winter rainfall may affect spawning and 
particularly access to the sea, and an increase in 
the tidal limit may alter available wetland habi¬ 
tat for mature G. cleaveri. 
In a recent review of the conservation status of 
native fish in Victoria (Koehn & Morison 1990) 
G. cleaveri was listed as vulnerable, a category 
including “taxa not presently endangered but 
which are at risk by having small populations 
and/or by occupying restricted habitats suscep¬ 
tible to rapid environmental change and/or 
populations which are declining at a rate that 
would render them endangered in the near 
future”. Although we have documented ad¬ 
ditional localities for G. cleaveri , our results 
reinforce the rarity of the species. The reduc¬ 
tions in available freshwater wetlands and on¬ 
going threats to such habitats justify the reten¬ 
tion of G. cleaveri in the vulnerable category. 
CONCLUSIONS 
G. cleaveri is more widespread in Victoria than 
previously believed, occupying natural and 
modified habitats along lowland coastal areas, at 
least from Wilsons Promontory to the western 
Otways. There is a need for further surveys to 
determine the range of the species in swampy 
habitats within and outside of this area, particu¬ 
larly on French Island which contains remnant 
tea-tree swamp habitat that once existed 
throughout the Koo-Wee-Rup swamp area and 
the entire Western Port catchment. The dis¬ 
covery of G. cleaveri in this area would 
strengthen arguments that present populations 
are remnants of a once much larger, more uni¬ 
formly distributed population. Collection of 
whitebait as they ascend coastal streams may 
also be a useful method of determining G. clear- 
eri distribution (Koehn & O’Connor 1990a). 
The behaviour and habitat needs of this 
species are similar to those of the New Zealand 
mudfishes. The specific habitat needs of G. 
cleaveri make it particularly susceptible to habi¬ 
tat changes; therefore the massive reductions in 
suitable freshwater wetland habitats have un¬ 
doubtedly been the greatest threat to the species. 
The management and conservation of such wet¬ 
land areas are vital for the preservation of G. 
cleaveri in Victoria. 
ACKNOWLEDGEMENTS 
We thank Bill O’Connor, Damien O’Mahony 
and Mathew Westaway for field assistance, 
David Denney for local information, Andrew 
Corrick for the use of unpublished data and 
Darwin Evans for his comments on the manu¬ 
script. Wordprocessing was completed by Kae 
