ASPECTS OF THE LIFE HISTORY OF THE TWO-SPINED BLACKFISH 
GADOPSIS BISPINOSUS IN KING PARROT CREEK, VICTORIA 
Andrew C. Sanger 
Department of Zoology, University of Melbourne, Parkville, Victoria 3052 
Present address: Inland Fisheries Commission, 127 Davey Street, Hobart, Tasmania 7000 
Sanger, A. C., 1990:11:30. Aspects of the life history ofthetwo-spined blackfish, Gadopsis 
bispinosus , in King Parrot Creek, Victoria. Proceedings of the Royal Society of Victoria 
102(2): 89-96. ISSN 0035-9211. 
The population of the two-spined blackfish, Gadopsis bispinosus , in King Parrot Creek, 
Victoria consisted mainly of individuals with total lengths from 30 to 190 mm. Individuals 
longer than 210 mm comprised less than 2 % of the total sample of 1054 fish. Juvenile 
recruitment occurred in summer. Length-weight relationships indicate that females arc 
slightly heavier than males. The spawning season, as inferred from ovarian development, 
was from October to December when water temperatures increased rapidly from the winter 
minimum. The seasonal nature of ovarian development was strongly influenced by total 
length, with larger females developing gravid ovaries earlier in the spawning season. Total 
length and fecundity were linearly related. The diet was dominated by various aquatic 
benthic invertebrate larvae and terrestrial insects. A comparison of the life histories of the 
two described species of Gadopsis shows them to be very similar. 
APART FROM its description (Sanger 1984), a 
discussion on the use of artificial habitat to 
increase population size (Koehn 1987) and 
recent distributional information (Koehn 1990, 
Lintermans & Rutzou 1990). nothing has been 
published on the biology of the two-spined 
blackfish, Gadopsis bispinosus. Jackson (1978a, 
b) reported on several aspects of the biology of 
the related species G. marmoratus Richardson, 
including habitat preference, feeding, spawning 
and early life history. Collection of such infor¬ 
mation, which may be referred to as life history 
analysis, is of increasing importance given the 
recent level of interest in formal lists of the con¬ 
servation status of Australian freshwater fish 
(Cadwalladeret al. 1984, Harris 1987, Koehn & 
Morrison 1990) and in the management of wild 
populations of native fish for conservation pur¬ 
poses. In combination with detailed distribu¬ 
tional data, life history analysis can provide a 
firm biological basis for decisions on both con¬ 
servation status and management. 
The life history of G . bispinosus is of interest 
not only because of the relatively recent dis¬ 
covery of the species, its somewhat restricted 
distribution and apparent abundance in streams 
inhabited by salmonids (Koehn 1990), but also 
because there is the opportunity for a compari¬ 
son with the work of Jackson (1978a, b). Such a 
comparative approach may reveal factors of 
general relevance to management guidelines for 
Gadopsis species. 
In order to examine the life history of G. bis¬ 
pinosus, a population was investigated in the 
upper reaches of King Parrot Creek (a tributary 
of the Goulburn River in the Murray River 
system), approximately 8 km downstream from 
Kinglake West, Victoria (37°52'S, 145°23'E). 
King Parrot Creek is typical of the streams in 
which this species is found: cool and clear with a 
cobble substrate. 
MATERIALS AND METHODS 
Physical data on mean monthly discharge and 
water temperature in King Parrot Creek were 
obtained from Rural Water Commission 
records from the Flowerdale water quality gaug¬ 
ing station, situated about 10 km downstream of 
the study site. Samples of fish were collected 
with a portable DC electroshocker at approxi¬ 
mately monthly intervals over a period of two 
years. They were killed in a solution of benzo- 
caine and preserved in 4% formaldehyde. 
Total length (TL) was measured to the nearest 
mm and total wet weight to the nearest 0.1 g. 
Fish were sexed by macroscopic gonadal exami¬ 
nation. Males had a single, small, nodular, pink¬ 
ish testis; females had a single, anteriorly 
bilobed, whitish to yellow ovary, within which 
developing oocytes could be seen. Juveniles had 
little or no gonadal tissue present; if present it 
was not obviously testicular or ovarian. Ovaries 
were dissected from preserved specimens, blot- 
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