Galaxias fuscus.  A THREAT TO TROUT FISHING?

 

There has been considerable controversy surrounding the Department of Conservation and Natural Resources actions to protect populations of Galaxias fuscus (barred or brown galaxias), a small native fish endemic to Victoria, (The Sunday Herald Sun, 10/4/94, Poison Used in Bid to Save Rare Fish).  This action includes electrofishing and rotenoning streams to remove trout which are identified as the primary cause for the decline of G. fuscus.

 

Is G. fuscus a distinct species to G. olidus?

G. fuscus was first described in 1936 from the Rubicon River.  It was then designated a subspecies of G. olidus (mountain galaxias) by Frankenberg (1969).  McDowell and Frankenberg (1981) then made it junior synonym of G. olidus, (eg, they considered it to be the same species).  However, these decisions were based on the two original specimens it was described from that had since shrivelled up.  Around 1980 it was "rediscovered".  Since then its taxanomic status has been controversial.  Recent evidence shows G. fuscus is morphologically different to G. olidus, there are ecological differences, and it grows larger.  This all adds together supporting the establishment of G. fuscus as a distinct species.

 

Distribution

G. fuscus occurs as nine isolated populations in the upper Goulburn River.  Thirteen populations once existed, (as far as we know, undoubtedly there were more).  Three populations currently remain trout free, (but for how long?).  Over the years, the remaining six populations have been steadily declining as trout slowly expand their range.  G. fuscus is now on the brink of extinction.

 

Threats

There are some headwater creeks which trout have not migrated to yet, either because of waterfalls or distance.  It must be noted that we are not talking about major creeks and streams but tiny little creeks, most are less than 1.5 m across and 0.5 m deep in inaccessible high altitude areas of Victoria's central highlands.  Thus, all populations of G. fuscus (and some other galaxiids) occur in areas where trout are still migrating upstream and have not yet reached their upstream limit which, incidentally, is the same limit G. fuscus has in terms of how far downstream they also exist.  Over time this situation is changing to the detriment of G. fuscus.  Trout predation is the problem.  Trout especially enjoy eating other smaller fish.  Due to their territorial nature, trout that are too small to eat G. fuscus bash them up instead, killing them just the same.  Many galaxiid populations have been lost when trout are illegally introduced above waterfalls.  A well known example is Snob's Creek near Eildon.  A large galaxiid population existed above Snob's Creek Falls for thousands of years before someone illegally dropped trout in above them.  There are no galaxiids present in Snob's Creek today.  Introducing trout was largely pointless as it did virtually nothing to enhance local trout angling opportunities because;

          it is not a creek where people go angling, (albeit very few people would)  Snob's Creek above the falls only has small trout, this makes it unattractive to most anglers.

 

Conclusions

The removal of trout from about half a dozen streams is critical to ensure longterm survival of G. fuscus.  If trout removal does not occur G. fuscus will become extinct.  Trout removal will not impact angling opportunities because;

          most creeks are too small and overgrown to be fished, eg, 0.5 to 1.5 m wide and 0.5 m deep;

          trout present are too small eg, a 20 cm trout is a trophy specimen from these waters, eg, equivalent to a 15lb trout from Lake Purrumbete today;

          there is evidence that these trout stocks do not migrate very much thus they make little, if any contribution to trout numbers in angling areas much further downstream;

          most creeks are too remote and rugged for all but the fittest people to get to;

          despite the fact that many accessible creeks do hold similar stocks of small trout, these are not utilized, eg, no one fishes them.

 

References

Frankenberg, R. S.  1969.  Studies on the evolution of galaxiid fishes with particular reference to the Australian fauna.  Ph.D. thesis, University of Melbourne.  185pp.

McDowell, R. M. & Frankenberg, R. S.  1981.  The galaxiid fishes of Australia.  Records of the Australian Museum.  33(10): 443-605.

 

Reprinted with minor modifications from Local Content Issue 48, the journal of Native Fish Australia Victorian Branch.