Journal of the Royal Society of Western Australia, 90(3), September 2007 
ao 
.SP 
*s 
0 50 100 150 200 250 300 350 400 450 
Total length (mm) 
Figure 3. Length-weight relationships of the Goldfish captured in the Vasse River during December 2003, March 2004, March 2005 and 
May 2006. In the given equation, W = weight (g) and TL = total length (mm) of the fish. 
and connected to the main channel. This wetland has 
only seasonal connectivity to the main channel and thus 
management actions should be undertaken to ensure 
that it does not act as a recruitment source of Goldfish. 
The length-weight relationship for Goldfish in the 
Vasse River is: 
W = 1.168(10'^)(TL^-®’^), where W = the wet weight (g) of 
the fish and TL = the total length (mm) of the fish (Fig. 3). 
The von Bertalanffy growth equation is L = 
374.26[l-e‘‘’“’'''‘’'’'“'], where L, is the approximate length 
at age t (in years), von Bertalanffy variables are: K = 
0.651, t,| = 0.0163 and L<=<> = 374.26. Based on this equation. 
Goldfish at age 1 year in the Vasse River attain 
approximately 177 mm TL, whereas at ages 2, 3, 4, 5 and 
6 they reach ~ 271, 321, 346, 356 and 367 mm TL, 
respectively (Fig. 4). 
The largest fish captured was 411 mm TL and 
weighed approximately 2.2 kg and was in its eighth year 
of life. The higher proportion of larger fish captured 
during 2005 was probably a result of the lower water 
levels encountered due to removal of the slot boards at 
the Old Butter Factory which are usually inserted to 
artificially maintain water levels. 
Many of the larger fish had gonads that had clearly 
spawned and are classed as 'spent'. Examination of some 
of the 0+ cohort (6 month old fish) revealed that gonadal 
development was commencing and that they would have 
spawned at the end of their first year of life. 
Diets and ecological impact of Goldfish in the Vasse 
River 
The stomach contents of 20 Goldfish (28-386 mm TL) 
examined from the Vasse River were dominated by 
detritus that was largely comprised of cyanobacteria 
(blue-green algae), but additionally contained diatoms, 
nematodes, anisopteran larvae, coleopteran larvae, 
dipteran larvae, eastern mosquitofish, green algae and 
some terrestrial insects. 
Community engagement 
An approach identified by Koehn & MacKenzie (2004) 
as important in the management of feral fishes includes 
not only the recognition of pest species by managerial 
and government organisations but it is important to 
engage the scientific and community sectors in all aspects 
of the process. The recognition of feral Goldfish 
populations as a threat to ecosystem health in the Vasse 
River, at least, has been accepted, largely as a re.sult of 
the involvement of managerial organisations such as 
Geocatch, Fisheries WA, the Vasse-Wonnerup LCDC, 
combined with community participation and wide local 
media coverage. 
Discussion 
The age and growth analyses of Goldfish in the Vasse 
River demonstrated substantial growth rates compared 
to populations elsewhere. The only previous age and 
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