Fowler et al.: Distribution and abundance of tuna larvae in near-reef waters of the Coral Sea 
409 
highest abundances found within 5.6 km of the outer 
reefs on most cruises with sufficient numbers of lar- 
vae for statistical analysis. Thunnus spp. larvae were 
more abundant in block C than in either the lagoon 
or block E on the late November cruise (Tukey’s test, 
P<0.01, Fig. 2) (blocks A and B being intermediate), 
and more abundant in blocks A and B than in the three 
other blocks, which did not differ, on the early Febru- 
ary cruise (Tukey’s test, P<0.03, Fig. 2). Thunnus spp. 
larvae showed a similar inshore distribution on the late 
February cruise; however the only significant difference 
was a greater abundance of larvae in block B than 
in the lagoon (Tukey’s Test, P<0.03, Fig. 2). Thunnus 
alalunga larvae were more abundant in blocks B and 
C than in the lagoon on the early November cruise 
(Tukey’s test, P<0.02, Fig. 3) (the the other blocks be- 
ing intermediate) and more abundant in block A than 
in either the lagoon or block E on the early February 
cruise (Tukey’s test, P<0.04, Fig. 3). A similar pat- 
tern of abundance of T. alalunga larvae occurred on 
the late November cruise; however differences among 
blocks were not quite significant (Tukey’s test, P=0.051, 
Fig. 3). Thunnus albacares larvae were most abundant 
in block A on the early February cruise; however there 
were no significant differences among blocks (ANOVA, 
P=0.06, Fig. 4). 
Distributions of E. affinis larvae and Auxis-Euthynnus 
larvae were similar to that of T. alalunga, and appeared 
to be most abundant within 5.6 km of the outer reefs. 
Differences in larval abundance among blocks were not, 
however, significant for the early November (ANOVA, 
P=0.14, Fig. 5) and early February (ANOVA P=0.11, 
Fig. 5) cruises analyzed for E. affinis, or the early Feb- 
ruary (ANOVA, P=0.06, Fig. 5) cruise analyzed for 
Auxis-Euthynnus . 
In contrast to other tuna taxa, the abundance of K. 
pelamis larvae increased in the offshore direction. De- 
spite a significant interaction among blocks and cruises 
(ANOVA, P= 0.004), K. pelamis larvae were more abun- 
dant in block E than in blocks A, B, and the lagoon on 
the early November cruise (Tukey’s test, P<0.02, Fig. 6), 
more abundant in blocks C and E than in the lagoon on 
the early February cruise (Tukey’s test, P<0.002, Fig. 
6), and more abundant in block E than the lagoon on 
the late February cruise (Tukey’s test, P<0.05, Fig. 6). 
The statistical interaction among blocks and cruises 
was most likely caused by a relatively great abundance 
(mean 12.1 larvae/100 m 2 ) of K. pelamis larvae in the 
lagoon on the late November cruise, compared with 
abundance in the lagoon on the early November, early 
February, and late February cruises (means 0.6, 0.0, 
and 3.5 larvae/100 m 2 , respectively, Fig. 6). Apart from 
K. pelamis and T. alalunga larvae on the late November 
cruise, few larvae of any tuna taxon were found in the 
lagoon. 
Size-frequency distribution 
Tuna larvae ranged in size from 1.7 to 15 mm SL; 
however most taxa had a strong size mode at 2-4 mm 
100 
10 
_ 1 
+ 100 
E 
o 
o 
0 ) 
5 10 
03 
0 ) 
O 
c 
05 
TD 
§ 1 
< 100 
10 
1 
0 4 8 12 16 20 
Distance from outer reefs (km) 
Figure 2 
Mean abundance (larvae/100 m 2 +l [± standard 
error]) of Thunnus spp. larvae with distance 
from the outer reefs of the Great Barrier Reef 
during the late November, early February, and 
late February cruises in the Coral Sea. Data 
points indicate the midpoint of sampling blocks 
(A-E) by distance, except for the Great Barrier 
Reef Lagoon (L on the x axis), the display of 
which is categorical and does not reflect the 
true distance from the other blocks. They axis 
is log 10 scale. The x axis shows the width of 
each sampling block (km). The hatched area 
on the x axis indicates the position of the outer 
reef area of the Great Barrier Reef. Within a 
cruise, if data points share a lowercase letter, 
they were not significantly different from each 
other according to Tukey’s post hoc test. Abun- 
dance data was not obtained for block D. 
SL. For all species, larvae were of similar size on each 
cruise, which were at least seven days apart. 
Differences in size-frequency distributions of lar- 
vae between inshore and offshore zones of the Coral 
Sea were taxa-specific, however for those tuna taxa 
where significant differences were detected, there was 
a greater proportion of small larvae in the inshore zone. 
A greater proportion of small (2-3.5 mm SL) K. pela- 
mis larvae was found in the inshore zone, compared 
with the offshore zone, on both the early February 
