408
12 Species Case Studies
The estimates of size and age at 50% sexual maturity in females during the spawning
season (November to January on the GBR) are 57 cm total length and about 9 years.
Large females attain 40+ years of age and make important reproductive contributions due to disproportionately high numbers of eggs. Males are restricted to size
classes over about 70 cm FL (Johannes et al. 1999 ; Pears et al. 2006 ) .
12.2.2 Reproductive Biology
Noteworthy aspects of the reproductive ecology of the species include late maturity,
limited sexual activity among smaller mature-sized females during the spawning
period, and the likelihood that some females do not undergo sex change. The sexual
pattern for brown-marbled grouper appears to be monandric protogynous hermaphroditism in which juveniles mature and function as adult females before changing
sex, although confi rmation of sex change is still required.
The reported annual spawning periods for brown-marbled grouper are relatively
narrow (e.g. 3–4 months), with seasonal timing and lunar periodicity varying
widely across the Indo-Pacifi c (Johannes et al. 1999 ; Robinson et al. 2004 ; Pet
et al. 2005 ; Pears et al. 2007 ; Robinson et al. 2008a, b , Fig. 8.3). Brown-marbled
grouper has been reported to aggregate in relatively large numbers to spawn, with
over 350 individuals being counted at spawning aggregation sites in Palau (Johannes
et al. 1999 ) and a peak aggregation abundance of 1,050 individuals estimated in
the Seychelles (Robinson et al. 2008 b ) . Spawning aggregations are known
from Australia, British Indian Ocean Territory, Federated States of Micronesia,
Fiji, Indonesia, Kenya, Malaysia, New Caledonia, Palau, Seychelles and Solomon
Islands (Cornish 2004 ; Hamilton et al. 2005 ; Pears et al. 2007 ; Robinson et al. 2008a, b ;
0
200
400
600
800
1000
0
5
10
15
20
25
30
35
40
45
Fork length (mm)
Age (years)
Fig. 12.2 Growth curve for brown-marbled grouper from the Great Barrier Reef: closed squares –
males; open circles – females (Pears et al. ( 2006 ) . With permission MEPS 1 February 2011)
12 Species Case Studies
The estimates of size and age at 50% sexual maturity in females during the spawning
season (November to January on the GBR) are 57 cm total length and about 9 years.
Large females attain 40+ years of age and make important reproductive contributions due to disproportionately high numbers of eggs. Males are restricted to size
classes over about 70 cm FL (Johannes et al. 1999 ; Pears et al. 2006 ) .
12.2.2 Reproductive Biology
Noteworthy aspects of the reproductive ecology of the species include late maturity,
limited sexual activity among smaller mature-sized females during the spawning
period, and the likelihood that some females do not undergo sex change. The sexual
pattern for brown-marbled grouper appears to be monandric protogynous hermaphroditism in which juveniles mature and function as adult females before changing
sex, although confi rmation of sex change is still required.
The reported annual spawning periods for brown-marbled grouper are relatively
narrow (e.g. 3–4 months), with seasonal timing and lunar periodicity varying
widely across the Indo-Pacifi c (Johannes et al. 1999 ; Robinson et al. 2004 ; Pet
et al. 2005 ; Pears et al. 2007 ; Robinson et al. 2008a, b , Fig. 8.3). Brown-marbled
grouper has been reported to aggregate in relatively large numbers to spawn, with
over 350 individuals being counted at spawning aggregation sites in Palau (Johannes
et al. 1999 ) and a peak aggregation abundance of 1,050 individuals estimated in
the Seychelles (Robinson et al. 2008 b ) . Spawning aggregations are known
from Australia, British Indian Ocean Territory, Federated States of Micronesia,
Fiji, Indonesia, Kenya, Malaysia, New Caledonia, Palau, Seychelles and Solomon
Islands (Cornish 2004 ; Hamilton et al. 2005 ; Pears et al. 2007 ; Robinson et al. 2008a, b ;
0
200
400
600
800
1000
0
5
10
15
20
25
30
35
40
45
Fork length (mm)
Age (years)
Fig. 12.2 Growth curve for brown-marbled grouper from the Great Barrier Reef: closed squares –
males; open circles – females (Pears et al. ( 2006 ) . With permission MEPS 1 February 2011)