726 
Fishery Bulletin 95(4), 1997 
was abundant only in the diet of the 4. 0-4. 9 and 5.0- 
5.9 mm length classes (Fig. 1). 
Frey width and larval mouth width 
Urocampus carinirostris had the smallest mouth, 
P tasmanianus and A. suppositus the widest mouths 
(Fig. 2, A, D, E). The shapes of the mouths were most 
similar in the case of P. olorum and F. lateralis (Fig. 
2, B and C). Although mouth width of U. carinirostris 
increased linearly with body length (Fig. 2A), such 
an increase in the other four species was best de- 
scribed by a polynomial function (Fig. 2, B-E: Table 
3). Mouth width of U. carinirostris increased slowly 
from 0.19 mm at 8 mm BL to 0.28 mm at 19 mm BL 
(Fig. 2A). The rate at which mouth width increased 
with body length was greater for the other 
four species (Fig. 2, B-E). In A. supposi- 
tus, mouth width increased from 0.33 mm 
at 3.5 mm BL to 0.68 mm at 6.0 mm BL 
(Fig. 2E). The smallest larvae of P olorum, 
F. lateralis, and P tasmanianus had nar- 
rower mouths (<0.15 mm) than both A. 
suppositus and U. carinirostris, owing to 
their smaller size upon arrival in the 
plankton (Fig. 2, A-E). However, mouth 
widths of the first three of these species 
exceeded the maximum recorded for U. 
carinirostris (0.28 mm) by the time each 
had attained 5 mm BL and approached 
0.60 mm in larger larvae. 
The slope describing the relation be- 
tween prey width and larval length for 
each species was less than 0.03. The ex- 
tent to which prey width increased with 
length was thus very small for each spe- 
cies. Minimum prey width for each spe- 
cies was about 0.04 mm (Fig. 2, A-E). The 
large numbers of prey of each species with 
widths of 0.04-0.08 mm were predomi- 
nantly attributable to copepod nauplii. 
Prey widths of between 0.04 and 0. 18 mm 
predominated in U. carinirostris, P. 
olorum, and F. lateralis (Fig. 2, A— C). 
Parablennius tasmanianus ate mainly 
prey 0.04-0. 13 mm wide, but with a maxi- 
mum width of only 0.18 mm (Fig. 2D). 
Afurcagobius suppositus consumed the 
largest prey items, i.e. postnaupliar 
stages of G. imparipes and A. simplex, 
with widths of 0.12-0.30 mm and 0.10- 
0.16 mm respectively. As with the other 
species, A. suppositus also ate smaller 
items (0.04-0.10 mm) (Fig. 2E). 
As U. carinirostris, P. olorum, F. 
lateralis, and P. tasmanianus grew, they 
continued to eat many prey <0.10 mm 
wide, even though the smaller larvae of 
each were capable of eating prey >0.10 
mm (Fig. 2, A-D). Prey width was about 
0.10 mm narrower than mouth width for 
most of the length range of U. carini- 
rostris (Fig. 2 A). The widths of the larger 
Pseudogobius olorum 
371 395 145 183 
2 . 0 - 2. 9 3 . 0 - 3. 9 4 0 - 4.9 5 . 0-7 9 
Favonigobius lateralis 
^ 77 18 10 
^ 100r 
(3 
C 
O 
C 
o 
Q, 
O 
B Others 
PH Synchaeta cf. baltica 
H Bivalve larvae 
B Polychaete larvae 
I"] Harpacticoids 
fl Calanoid copepodites 
■ Acartia simplex 
IH Gladioferens imparipes 
ED Oithona simplex 
EH Copepod nauplii 
Parablennius tasmanianus 
20 163 90 25 
2 . 0-2 9 3 . 0-3 9 6 0-7 9 
2 . 0-2 9 3 . 0 - 3. 9 4 0-4 9 5 0-7 9 
Afurcagobius suppositus 
21 129 38 15 
3 . 0 - 3.9 4 . 0-4 9 5 0 - 5.9 6 0 - 6.9 
Urocampus carinirostris 
21 137 85 25 
60 - 9.9 13 . 0 - 15.9 
10 . 0 - 12.9 16.0 9.9 
Length class (mm) 
Figure 1 
Proportional utilization (p t , %) for length classes of larvae of five species 
of fish caught at four sites in Wilson Inlet between October 1988 and 
April 1989. The numbers of larvae that contained food in each size class 
are shown above the bars. 
