94 
A. C. SANGER 
Table 3 summarises the results of the analysis 
of the stomach contents of 275 fish taken from 
14 samples spaced at approximately two- 
monthly intervals over the sample period. The 
dietary importance of several groups of benthic 
insect larvae is evident from the table, with 
ephemeropteran, trichopteran and dipteran 
nymphs and pupae predominating in the diet 
assessed by all four methods of analysis. Terres¬ 
trial arthropods and the aquatic groups Plecop- 
tera, Coleoptera, and Amphipoda were also 
important in the diet. The method-dependent 
differences between the scores for each category 
reflect the biases inherent in the methods. For 
example, whereas dipteran larvae occurred 
frequently and were often numerous, they were 
usually small and did not dominate many guts 
volumetrically. Thus, dipteran larvae scored 
higher values in the occurrence and number 
methods than in the dominance and rank 
methods. 
Fish eggs, almost certainly eggs of G. bispino¬ 
sus, were found in the diet of a few fish in 
December 1981 and 1982, supporting the sug¬ 
gestion that spawning had taken place at this 
time. 
The major aquatic groups, i.e. Ephemerop- 
tera, Trichoptera, Diptera, Plecoptera and 
Coleoptera, were relatively important in all 
monthly samples (Table 4). Terrestrial food was 
more important in the spring and summer 
months, perhaps reflecting a greater availability 
during this period. 
DISCUSSION 
Gadopsis bispinosus is the most abundant spe¬ 
cies of fish in the upper reaches of King Parrot 
Creek. Koehn (1987) found that it was also the 
most abundant species of fish in the upper 
reaches of the Ovens River, Victoria, and has 
shown experimentally that an increase in the 
amount of instream cover led to an increase in 
abundance of the species in that stream. It 
appears likely, therefore, that G. bispinosus 
would be abundant in most north-eastern Vic- 
torian streams with abundant instream cover 
(especially accumulations of cobbles and fallen 
timber) and relatively cool, clear water. 
The length-frequency distributions confirm 
that, at least in King Parrot Creek, G. bispinosus 
is a small to medium-sized species (observed 
maximum TL 257 mm). The causes of adult 
mortality are unknown, apart from predation by 
Salmo trutta (Sanger 1984). It has been sug¬ 
gested that there is a correlation between the 
presence of S. trutta and a decline in the abund¬ 
ance and diversity of the native fish fauna in 
Sample date 
n 
Ephemeroptera 
Trichoptera 
Diptera 
Plecoptera 
Coleoptera 
Hemiptera 
Odonata 
Amphipoda 
Decapoda 
Isopoda 
Annelida 
Terrestrial 
Fish eggs 
G. o/idus 
0 
0 
5 
0 
o 
i 
24.5.80 
12 
22.9 
11.1 
21.5 
11.7 
3.9 
_ 
5.6 
13.6 
2.3 
_ 
- 
3.2 
_ 
_ 
4.2 
21.8.80 
18 
16.0 
10.3 
19.0 
9.5 
9.9 
2.7 
1.3 
12.3 
4.2 
0.5 
- 
5.7 
- 
- 
7.1 
24.9.80 
12 
24.2 
9.0 
27.0 
2.6 
6.6 
- 
- 
8.8 
- 
- 
2.8 
15.6 
- 
- 
3.3 
20.10.80 
13 
22.7 
12.5 
21.0 
20.0 
5.2 
- 
- 
- 
- 
- 
4.5 
12.7 
- 
- 
1.4 
22.12.80 
20 
22.8 
15.1 
25.0 
4.8 
7.8 
- 
- 
- 
1.8 
- 
- 
7.5 
5.1 
- 
10.2 
20.2.81 
18 
20.0 
17.4 
27.9 
- 
9.6 
- 
2.1 
- 
- 
- 
- 
19.8 
- 
- 
3.2 
22.4.81 
23 
24.0 
27.6 
19.4 
3.5 
12.1 
- 
- 
- 
1.4 
- 
- 
4.9 
- 
- 
7.1 
19.5.81 
23 
18.9 
22.9 
25.6 
11.9 
2.1 
- 
1.9 
4.9 
1.6 
- 
- 
2.6 
- 
- 
7.7 
21.6.81 
21 
18.4 
13.6 
29.4 
14.0 
5.4 
1.8 
0.6 
1.8 
3.2 
- 
1.8 
7.2 
- 
- 
2.8 
16.9.81 
20 
23.8 
11.8 
28.6 
16.3 
4.5 
1.4 
- 
- 
- 
1.4 
2.1 
4.1 
- 
2.1 
4.1 
24.12.81 
17 
24.9 
16.6 
25.3 
8.1 
9.0 
0.6 
- 
- 
2.3 
- 
3.7 
6.1 
2.3 
- 
u 
22.2.82 
34 
15.1 
10.3 
16.7 
7.3 
8.5 
2.4 
3.8 
8.9 
4.6 
- 
3.4 
15.4 
- 
- 
3.8 
23.3.82 
26 
20.1 
18.2 
32.2 
1.4 
6.0 
2.9 
0.6 
- 
1.8 
1.2 
1.6 
12.5 
- 
- 
2.1 
17.5.82 
18 
27.9 
17.3 
25.3 
10.2 
5.3 
1.8 
1.2 
2.3 
2.3 
1.6 
- 
4.0 
- 
- 
0.8 
Total % rank 
275 
21.6 
15.3 
24.5 
8.7 
6.9 
0.9 
1.2 
3.8 
1.8 
0.3 
1.5 
8.7 
0.5 
0.2 
3.2 
Table 4. Seasonal comparison of the diet of Gadopsis bispinosus from King Parrot Creek, analysed by the 
method. 
