Gaughan and Potter: Analysis of diet and feeding strategies within an assemblage of estuarine larval fish 
725 
ton samples. Mean monthly concentrations of zoop- 
lankton in Wilson Inlet were similar from October 
1988 to April 1989; only January had a significantly 
(P<0.05) higher concentration (Gaughan and Potter, 
1995). 
All copepods, irrespective of stage, contributed 
74.7% of the total mean concentration of zooplank- 
ton (Table 1). The cyclopoid Oithona simplex , the 
calanoids Gladioferens imparipes and Acartia sim- 
plex, and several species of harpacticoids were the 
only copepods that were common in Wilson Inlet 
(Gaughan and Potter, 1995). Considering just the 
copepods, adults of A. simplex and G. imparipes, 
which represented the largest prey types consumed 
by fish larvae in Wilson Inlet, contributed only 2.9% 
of the total mean concentration of this taxonomic 
group. The smaller species and developmental stages 
of copepods were thus approximately 33 times more 
abundant than the adults of A. simplex and G. 
imparipes collectively. The mean concentrations and 
relative contributions of other zooplankton taxa that 
were eaten by larval fish during this study are shown 
in Table 1. 
Numbers of prey items consumed 
and dietary composition of fish larvae 
The total number of larvae of each species examined 
during this study are shown in Table 2, and the num- 
bers of larvae in size classes of each species which 
contained food are shown in Figure 1. 
The mean number of prey items found in each larva 
was less than five for A. suppositus and F. lateralis. 
Table 1 
Mean monthly concentrations and relative contributions 
of zooplankton in Wilson Inlet between October 1988 and 
April 1989. 
Mean 
Relative 
concentration 
contribution 
Taxa 
no. organisms/m 3 ) 
(%) 
Copepod nauplii 
164,827 
48.1 
Calanoid copepodites 
33,755 
9.8 
Oithona simplex 
44,629 
13.0 
Acartia simplex 
6,771 
2.0 
Gladioferens imparipes 
719 
0.2 
Harpacticoids 
5,523 
1.6 
Polychaete larvae 
34,997 
10.2 
Bivalve larvae 
18,435 
5.4 
Synchaeta cf. baltica 
9,787 
2.9 
Other taxa 
23,303 
6.8 
Total 
342,746 
between five and ten for P. olorum and 17. carini- 
rostris and 28.7 for P tasmanianus (Table 2). Like- 
wise, the maximum numbers of prey consumed were 
much lower for the first four species than for P 
tasmanianus (Table 2). The number of prey ingested 
by larvae increased with body size only in the case of 
U. carinirostris. 
Various developmental stages of copepods domi- 
nated the diets of larval fish in Wilson Inlet; the ro- 
tifer Synchaeta cf. baltica and the larvae of bivalves 
and polychaetes were also occasionally important 
(Fig. 1). Only the postnaupliar stages of copepods in 
the diets were identified to species. Each of the com- 
mon types of copepod contributed to the diets of fish 
larvae. 
During the growth of P olorum, F. lateralis, U. 
carinirostris , and P tasmanianus , the contribution 
of copepod nauplii declined while that of postnaupliar 
stages increased (Fig. 1). Oithona simplex was par- 
ticularly important to P. olorum and U. carinirostris, 
representing over 30% of the diet of the three larg- 
est size classes of the former species and over 40% of 
the diet of all size classes of the latter species. By 
contrast, despite the increased contribution by O. 
simplex to larger size classes ofP tasmanianus, cope- 
pod nauplii dominated the diet of all size classes, 
contributing > 40% to each (Fig. 1). The diet of 
F. lateralis <4.0 mm BL consisted mainly of copepod 
nauplii and to a lesser extent of bivalve larvae and 
O. simplex. The main prey types of F. lateralis 
from 6. 0-7. 9 mm BL were harpacticoids (40.9%), 
calanoid copepodites (20.6%), and phytoplankton 
(15.6%). 
Polychaete larvae, copepod nauplii, and harp- 
acticoids each contributed over 25.0% of the diets of 
the smallest size class of A. suppositus, whereas 
harpacticoids alone contributed 60.0% to larvae >6.0 
mm BL (Fig. 1). Harpacticoids also contributed 15.3 
and 27.0% of the diet in the 4. 0-4. 9 and 5. 0-5. 9 mm 
length classes, respectively. Gladioferens imparipes 
Table 2 
Mean and maximum numbers of prey per larva for five 
teleost species in Wilson inlet, n = the total number of lar- 
vae of each species examined. 
Species 
n 
Mean 
prey/larva 
Maximum 
prey/larva 
Pseudogobius olorum 
1,946 
7.7 
30 
Favonigobius lateralis 
451 
4.0 
15 
Afurcagobius suppositus 
485 
2.5 
19 
Parablennius tasmanianus 
469 
28.7 
103 
Urocampus carinirostris 
434 
9.7 
23 
