480
12 Species Case Studies
with body size (Fig. 12.31a ). Since females do not appear to grow bigger than about
100 cm TL, the largest fi sh are males and these have the most developed hump (Liu
and Sadovy de Mitcheson 2011 ) . Smaller fi sh have different colouration and detail
(Figs. 12.31 a, b, and 12.32a ). The species is also known by other English common
names, such as Napoleon fi sh and Maori wrasse. Sadovy et al. ( 2003b ) has a listing
of 24 non-English common names for the species.
12.13.2 Distribution and Feeding
The humphead wrasse occurs throughout much of the tropical Indo-west Pacifi c,
from the Red Sea and east Africa in the west, but is absent from some marginal
areas of the central Pacifi c, such as Hawaii, Rapa and Pitcairn.
Many aspects of its biology were summarized by Sadovy et al. ( 2003b ) . It is
largely a carnivore, searching the reef and often turning over rocks (Fig. 12.32b ),
looking for molluscs and fi shes (Randall et al. 1978 ) . The fi sh has powerful pharyngeal dentition capable of crushing most molluscs and echinoderms. It is sometimes shadowed by other reef predators, probably seeking opportunistic feeding as
the wrasse turns over rocks. It is one of the few predators on the crown-of-thorns
starfi sh, Acanthaster planci , and a decrease in the population of the fi sh may have
been a factor in population explosions of the coral-eating sea star. In unfi shed or
lightly fi shed areas its densities range from 2 to 27, rarely more than 10 fi sh, per
10,000 m
2 . Where fi shed, densities drop tenfold or more to < 1 fi sh per 10,000 m
2
(Sadovy et al. 2003b ) .
12.13.3 Early Life History and Juvenile Life
The planktonic eggs are 0.66–0.67 mm in diameter, spherical with an oil droplet
0.14 mm in diameter and no pigment. This egg size is towards the lower size limit of
labrid eggs, and is similar to other Indo-west Pacifi c labrids that are up to three orders
of magnitude smaller in body weight. This small egg/large fi sh relationship is also
found in the world’s largest scarid, the bumphead parrotfi sh, which has a similarly
small egg (0.65 mm diameter) (Colin and Bell 1991 ) . Humphead wrasse have
spawned in hatcheries, but the larvae have proven diffi cult to rear due mainly to the
small mouth and, therefore, small food requirements. The few larvae that have been
reared to the juvenile stage took about 25 days post hatch to reach 2 cm in length
(Slamet and Hutapea 2005 ) . At 6 months of age, fi sh are only 5–6 cm TL. At present
it appears unlikely that hatchery production is going to provide a ready supply of
young to form the basis of an aquaculture programme or for release into the wild.
Little is understood about settlement or dispersal although the species is known
to spawn in aggregations of up to several hundreds of fi sh. In Palau, current following drifters launched in areas with spawned eggs were transported a short distance
12 Species Case Studies
with body size (Fig. 12.31a ). Since females do not appear to grow bigger than about
100 cm TL, the largest fi sh are males and these have the most developed hump (Liu
and Sadovy de Mitcheson 2011 ) . Smaller fi sh have different colouration and detail
(Figs. 12.31 a, b, and 12.32a ). The species is also known by other English common
names, such as Napoleon fi sh and Maori wrasse. Sadovy et al. ( 2003b ) has a listing
of 24 non-English common names for the species.
12.13.2 Distribution and Feeding
The humphead wrasse occurs throughout much of the tropical Indo-west Pacifi c,
from the Red Sea and east Africa in the west, but is absent from some marginal
areas of the central Pacifi c, such as Hawaii, Rapa and Pitcairn.
Many aspects of its biology were summarized by Sadovy et al. ( 2003b ) . It is
largely a carnivore, searching the reef and often turning over rocks (Fig. 12.32b ),
looking for molluscs and fi shes (Randall et al. 1978 ) . The fi sh has powerful pharyngeal dentition capable of crushing most molluscs and echinoderms. It is sometimes shadowed by other reef predators, probably seeking opportunistic feeding as
the wrasse turns over rocks. It is one of the few predators on the crown-of-thorns
starfi sh, Acanthaster planci , and a decrease in the population of the fi sh may have
been a factor in population explosions of the coral-eating sea star. In unfi shed or
lightly fi shed areas its densities range from 2 to 27, rarely more than 10 fi sh, per
10,000 m
2 . Where fi shed, densities drop tenfold or more to < 1 fi sh per 10,000 m
2
(Sadovy et al. 2003b ) .
12.13.3 Early Life History and Juvenile Life
The planktonic eggs are 0.66–0.67 mm in diameter, spherical with an oil droplet
0.14 mm in diameter and no pigment. This egg size is towards the lower size limit of
labrid eggs, and is similar to other Indo-west Pacifi c labrids that are up to three orders
of magnitude smaller in body weight. This small egg/large fi sh relationship is also
found in the world’s largest scarid, the bumphead parrotfi sh, which has a similarly
small egg (0.65 mm diameter) (Colin and Bell 1991 ) . Humphead wrasse have
spawned in hatcheries, but the larvae have proven diffi cult to rear due mainly to the
small mouth and, therefore, small food requirements. The few larvae that have been
reared to the juvenile stage took about 25 days post hatch to reach 2 cm in length
(Slamet and Hutapea 2005 ) . At 6 months of age, fi sh are only 5–6 cm TL. At present
it appears unlikely that hatchery production is going to provide a ready supply of
young to form the basis of an aquaculture programme or for release into the wild.
Little is understood about settlement or dispersal although the species is known
to spawn in aggregations of up to several hundreds of fi sh. In Palau, current following drifters launched in areas with spawned eggs were transported a short distance