Rhodes and Tupper: The vulnerability of Plectropomus areolatus to fishing 
197 
Table 1 
Summary table of sex-specific catch of squaretail coralgrouper (Plectropomus areolatus) at the aggregation site during tagging in 
2005. N = total number of individuals collected during the reproductive season; n=monthly sample size; FDC = first day of catch 
before the full moon; na = data not available. 
Month 
Sex 
n 
January 
February 
March 
Apri 
i 
May 
FDC 
n 
FDC 
n 
FDC 
n 
FDC 
n 
FDC 
N 
Male 
71 
4 
125 
4 
96 
6 
130 
9 
89 
8 
511 
Female 
0 
na 
32 
3 
38 
5 
37 
5 
22 
5 
129 
Unknown 
4 
3 
0 
na 
0 
na 
0 
na 
3 
8 
7 
Total 
75 
157 
134 
167 
114 
647 
(Fig. 1). All receivers were tethered above the barrier 
reef at 10-25 m depth at seaward-facing promontories 
to maximize detection range. All receivers were removed 
after 17 months that covered two full consecutive spawn- 
ing seasons. Prior range testing in Palau under similar 
physical and oceanographic conditions was performed for 
13 receivers along four cardinal directions with a line- 
attached transmitter. The transmitter was towed behind 
the boat and away from the receivers, and times and 
distances from the receiver were recorded by GPS. Dis- 
tance and times were later matched to receiver-logged 
transmissions to determine minimum and maximum 
detection distances. Testing confirmed an average maxi- 
mum detection distance of 442 m along the reef parallel 
to the barrier reef crest and 975 m from the receiver 
seaward. Within the channel (here, Ulong Channel), the 
receiver detected tags at an average of 746 m parallel to 
the channel, while distance perpendicular to the channel 
was constrained by the channel width, similar to the 
constraints for detection distances from the receiver to 
the reef crest (perpendicular to the barrier reef). 
To enhance the potential for tag recovery, a reward 
scheme (US$5 plus fish market value) was broadcast 
island-wide on local AM radio and by flyer postings. Re- 
cords for catch location and gear type were taken from 
local fishermen at the time of reward. Recaptured fish 
were reweighed and measured, and gonads and otoliths 
were extracted for subsequent life history analyses. 
Analysis of catch probability 
A separate creel survey was conducted in 2006 to deter- 
mine the distribution of fishing effort within Pohnpei’s 
small-scale commercial coral reef fishery (Rhodes et 
al., 2007). The 2006 effort data were used to estimate 
the number of likely recaptures for P. areolatus under a 
random distribution (postspawning dispersal) scenario 
(chi-square analysis, after a square-root transformation) 
for each municipality. For this analysis, those fish cap- 
tured by researchers inside the KMS were excluded, as 
were an additional five individuals for which there was 
no recorded recapture location. 
Results 
Initial capture numbers, CPUE, and size distribution of fish 
Between January and May 2005, 647 P. areolatus were 
captured and tagged at the Kehpara Marine Sanctu- 
ary over 33 fishing days and 170 fishing hours, with an 
estimated CPUE of 3.8 fish per hour per fisherman, to 
highlight the vulnerability of reproductive P. areolatus 
to hook-and-line fishing at the aggregation site. Catch 
included 511 males, 129 females, and 7 individuals that 
could not be identified to sex with macroscopic methods. 
Males typically preceded females in catch by 1-4 days, 
except in January when no females were taken (Table 
1). The average sex ratio for catch (February-May) 
was 3.4 males: 1 female, indicating either an absence of 
females within the January FSA or highly variable sex- 
specific differences in catch between January and other 
months. Late-stage vitellogenic oocytes were observed 
in all cannulated females, and no females were captured 
with hydrated oocytes (to indicate imminent spawn- 
ing), although subsequent histological examination of 
gonads from recaptured individuals confirmed evidence 
of spawning activity. All males were ripe at the time of 
capture during all months of tagging. 
Males captured at the FSA were, on average, larg- 
er than females. The size frequency range was 
378-542 mm TL for mature females (mean ±standard 
error [SE] = 458.0 ±2.8 mm TL], and 450-660 mm TL 
for mature males (mean=541.4 ±1.3 mm TL) (Fig. 2). 
Only males were present in size classes above 550 mm 
TL, and only females were observed in size classes 
below 440 mm TL. Individuals of undetermined sex 
ranged from 480 to 575 mm TL (mean=523.3 ±14.6 mm 
TL) and thus overlapped in size with mature males. The 
mean size of captured males declined slightly during 
the survey, while captured female mean size increased. 
During tagging, similar behavior, including courtship 
and territorial displays, was observed between tagged 
and untagged fish to indicate minimal or no effects 
from tagging on at least some behavior commonly as- 
sociated with reproduction. 
