Pedder galaxias - Galaxias pedderensis
By Jean Jackson
Threatened Fish Profile – In Newsletter 29_2, December 1999
(Drawing by Carol Kroger from “Tasmanian Freshwater Fishes” by Wayne Fulton)
Endangered (ASFB, Tasmania, Commonwealth), Critically Endangered (IUCN).
Probably the most endangered freshwater fish species in Australia. The Pedder galaxias is a native freshwater fish that grows to a maximum length of about 160 mm. They have a slender elongate body and dorsally flattened head. The back and sides are light yellow-brown in colour with gold iridescent flecks and irregular blackish-brown blotches (Hamr, 1995).
Pedder galaxias are confined to freshwater and spawn in spring (mid-October) as water temperatures begin to rise. In an artificial stream, captive fish laid their eggs under flat rocks, aquatic vegetation and woody debris. As in other entirely freshwater galaxias in Tasmania, a relatively small number of large eggs is produced, ranging from about 150-1200 depending on the size of the female. Size at maturity is ~95 mm fork length in females and ~75 mm fork length in males (Hamr, 1992).
Distribution and Habitat:
The Pedder galaxias is endemic to Tasmania and naturally occurred only in the original Lake Pedder and tributary streams. It is apparently now extinct in what remains of its natural habitat (tributaries of the Lake Pedder impoundment) as no individuals have been found since 1996 despite intensive searches each summer. The species now survives only as a translocated population in the Western Arthur Range south-west of Lake Pedder. The last fish to be found in the natural habitat lived in the lower meandering sections of two tributary streams, preferring areas where the streams are heavily shaded, sandy-bottomed and highly convoluted with deep pools and instream cover. The diet of the Pedder galaxias consists mainly of aquatic insect larvae, aquatic beetles, small crayfish and copepods (Hamr, 1992).
Most of the original lake and slow-flowing habitat of the species was destroyed with the inundation of Lake Pedder and surrounding areas for hydro-electricity in 1972. Brown trout Salmo trutta were introduced to the new impoundment and the native climbing galaxias Galaxias brevipinnis increased in abundance and distribution within the impoundment and tributaries. There is evidence of predation upon G. pedderensis by brown trout and climbing galaxias and it also likely that these species competed for habitat and food.
It was clear by 1990 that future survival of the species depended on establishing populations in secure habitats free of predatory and competing fish species. In 1991-92, fish from the wild were transferred to a highland lake in the Western Arthur Range. Attempts at captive breeding and artificial fertilisation had limited success, with only 11 juveniles raised. In 1998, Pedder galaxias were found to have bred successfully in the new lake. The species is currently included in a recovery plan (Crook and Sanger, 1997) being implemented by the Inland Fisheries Commission, Tasmania. Every year the fish are counted and samples of invertebrate fauna and plankton are taken to monitor any effect of the fish introduction. If numbers become sufficient, fish will be taken to establish another translocated population. Searches for wild fish in the natural habitat continue every summer, with any fish found to be moved to the translocation site.
Crook, D.A. and Sanger, A.C. 1997. Recovery Plan for the Pedder, Swan, Clarence, swamp and saddled galaxias. Inland Fisheries Commission, Hobart.
Hamr, P. 1992. Conservation of Galaxias pedderensis. Inland Fisheries Commission Occasional Report 92-01. Inland Fisheries Commission, Hobart.
Hamr, P. 1995. Threatened fishes of the world: Galaxias pedderensis Frankenberg, 1968 (Galaxiidae). Env Biol. Fish. 43, 406.
Dr Jean Jackson, Inland Fisheries Commission,
PO Box 288, Moonah, Tas 7009.
Ph (03) 62334140
Fax (03) 6233 4141