446
12 Species Case Studies
(TL) (Heemstra and Randall 1993 ) . The species is reported to be ciguatoxic in some
areas (Wong et al . 2005 ; Oshiro et al. 2010 ) .
Age assessments from sectioned sagittal otoliths showed maturity for females
and males at 2 and 3 years, respectively, with both sexes represented in the oldest
age class of 12 years (KLR unpublished data). In the eastern Torres Straits of northern Australia, Williams et al . ( 2008 ) found a maximum age of 14 years old. In the
eastern Torres Strait, total mortality ( Z ) for squaretail coralgrouper was estimated at
0.40 year
−1 and the growth coeffi cient ( K ) was 0.09 year
−1 (Williams et al. 2008 ) .
12.8.2 Reproduction and Aggregation
The sexual pattern of the squaretail coralgrouper is unknown. Size of sexual maturation is approximately 35–40 cm FL and the species spawns in aggregations ranging
in abundance from 10s to 1,000s of individuals. Squaretail coralgrouper aggregations overlap somewhat spatially and temporally with those of camoufl age grouper
( Epinephelus polyphekadion ) and brown-marbled grouper ( Epinephelus fuscoguttatus ) but where depths of greater than 12–15 m are found, they are typically in
shallower areas than the other two species (Sadovy 2005 ) . In many parts of its range,
squaretail coralgrouper spawning aggregations form over 4–6 months (e.g. Johannes
et al. 1999 ; Rhodes and Tupper 2008 ; Williams et al . 2008 ) , while in Papua New
Guinea and parts of Indonesia, aggregations can form monthly (Hamilton et al.
2004 ; Pet et al. 2005 ) (Fig. 12.15 ). In Papua New Guinea, monthly spawning
throughout the year was confi rmed from back-calculation of otoliths (Rick Hamilton,
personal communication). The lunar timing of aggregation formation and spawning
varies regionally, with new moon spawning in Palau (Palau Conservation Society
2010 ) Indonesia (Pet et al. 2005 ) and Melanesia (Hamilton et al. 2005 ), but at full
moon in Pohnpei (Hutchinson and Rhodes 2010 ). Aggregations in Pohnpei coincide
with seasonally low water temperatures (range = 28.2–29.4°C), but occur during
seasonal upper-level temperature extremes in the eastern Torres Strait (29–30
o C)
(Pitcher et al. 2004 ) .
Individuals of both sexes appear to follow migratory corridors to reach aggregation sites, the males moving individually or in small groups, the females in larger
groups (Rhodes and Tupper 2008 ) . At the spawning site, individuals stay approximately 10 days (Rhodes and Tupper 2008 ) . Throughout the aggregation period,
males establish and aggressively defend territories until spawning (Fig. 12.16 ).
When sex ratios are highly male-biased, possibly as a result of overfi shing, females
are relentlessly chased by males (Johannes et al. 1999 ) . Six colour morphs are
known, some sex-specifi c (Johannes et al. 1999 ) . Observations of pair-spawning 1
h prior to early morning high tide were made in Indonesia (Pet et al. 2005 ) . After the
aggregation period individuals return to home range areas that in Pohnpei measured
0.048 ± 0.018 km
2 S.E. (Hutchinson and Rhodes 2010 ) . Acoustic tagging results in
Pohnpei suggested relatively small catchment areas (200–300 km
2 ) for the species
(Rhodes and Tupper 2008 ) .
12 Species Case Studies
(TL) (Heemstra and Randall 1993 ) . The species is reported to be ciguatoxic in some
areas (Wong et al . 2005 ; Oshiro et al. 2010 ) .
Age assessments from sectioned sagittal otoliths showed maturity for females
and males at 2 and 3 years, respectively, with both sexes represented in the oldest
age class of 12 years (KLR unpublished data). In the eastern Torres Straits of northern Australia, Williams et al . ( 2008 ) found a maximum age of 14 years old. In the
eastern Torres Strait, total mortality ( Z ) for squaretail coralgrouper was estimated at
0.40 year
−1 and the growth coeffi cient ( K ) was 0.09 year
−1 (Williams et al. 2008 ) .
12.8.2 Reproduction and Aggregation
The sexual pattern of the squaretail coralgrouper is unknown. Size of sexual maturation is approximately 35–40 cm FL and the species spawns in aggregations ranging
in abundance from 10s to 1,000s of individuals. Squaretail coralgrouper aggregations overlap somewhat spatially and temporally with those of camoufl age grouper
( Epinephelus polyphekadion ) and brown-marbled grouper ( Epinephelus fuscoguttatus ) but where depths of greater than 12–15 m are found, they are typically in
shallower areas than the other two species (Sadovy 2005 ) . In many parts of its range,
squaretail coralgrouper spawning aggregations form over 4–6 months (e.g. Johannes
et al. 1999 ; Rhodes and Tupper 2008 ; Williams et al . 2008 ) , while in Papua New
Guinea and parts of Indonesia, aggregations can form monthly (Hamilton et al.
2004 ; Pet et al. 2005 ) (Fig. 12.15 ). In Papua New Guinea, monthly spawning
throughout the year was confi rmed from back-calculation of otoliths (Rick Hamilton,
personal communication). The lunar timing of aggregation formation and spawning
varies regionally, with new moon spawning in Palau (Palau Conservation Society
2010 ) Indonesia (Pet et al. 2005 ) and Melanesia (Hamilton et al. 2005 ), but at full
moon in Pohnpei (Hutchinson and Rhodes 2010 ). Aggregations in Pohnpei coincide
with seasonally low water temperatures (range = 28.2–29.4°C), but occur during
seasonal upper-level temperature extremes in the eastern Torres Strait (29–30
o C)
(Pitcher et al. 2004 ) .
Individuals of both sexes appear to follow migratory corridors to reach aggregation sites, the males moving individually or in small groups, the females in larger
groups (Rhodes and Tupper 2008 ) . At the spawning site, individuals stay approximately 10 days (Rhodes and Tupper 2008 ) . Throughout the aggregation period,
males establish and aggressively defend territories until spawning (Fig. 12.16 ).
When sex ratios are highly male-biased, possibly as a result of overfi shing, females
are relentlessly chased by males (Johannes et al. 1999 ) . Six colour morphs are
known, some sex-specifi c (Johannes et al. 1999 ) . Observations of pair-spawning 1
h prior to early morning high tide were made in Indonesia (Pet et al. 2005 ) . After the
aggregation period individuals return to home range areas that in Pohnpei measured
0.048 ± 0.018 km
2 S.E. (Hutchinson and Rhodes 2010 ) . Acoustic tagging results in
Pohnpei suggested relatively small catchment areas (200–300 km
2 ) for the species
(Rhodes and Tupper 2008 ) .