513
12 Species Case Studies
12.19 The Moorish Idol – Zanclus cornutus
Patrick L. Colin, Mandy T. Etpison, and Paul Collins
Coral Reef Research Foundation, PO Box 1765 , Koror , Palau 96940
email: crrf@palaunet.com
NECO Marine , Koror , Palau
e-mail: etpison@palaunet.com
Department of Science, University of Glamorgan, Treforest Campus, Pontypridd,
Wales, UK
e-mail: paul@abolutediving.uk
12.19.1 General
The Moorish idol, Zanclus cornutus , (the only member of the monotypic family
Zanclidae) is one of the iconic fi shes of the Indo-Pacifi c, yet its biology and reproduction are poorly known. It has an extremely broad distribution from the east coast of
Africa and the Persian Gulf across the Indian and Pacifi c Oceans to the western shores
of the Americas. It is related to the surgeonfi shes, sharing a somewhat similar larval
type (Johnson and Washington 1987 ) . Its maximum reported total length is about
23 cm, but at least in western Pacifi c areas most fi sh are much smaller. The species is
widespread where there is hard substrate and down to 180 m. It usually occurs in
schools that range from a few fi sh to over 100 animals. It feeds mainly on sponges. It
is a popular aquarium fi sh but is diffi cult to maintain (Myers 1999 ) . Despite the distinctive nature of this species very little work has been conducted on it.
12.19.2 Reproduction and Aggregation
For many years schools of hundreds of Moorish idols have been observed at numerous locations on the western barrier reef of Palau from December to March, with
peaks in January–February (Fig. 12.53 ). These have been reported as probable
spawning aggregations (e.g. Etpison 1997, 2004 ) , but had not previously been verifi ed under SCRFA criteria as spawning aggregations (Chap. 1).
A few reports of pair-spawning by Moorish idol exist. Colin and Bell ( 1991 ) saw
three pair spawnings (no aggregation) on the edge of a tidal channel at Enewetak
Atoll just after high tide near dawn. Sancho et al. ( 2000a, b ) listed 5 spawns (both
pair and group) by Moorish idol at Johnston Atoll without further detail. A few pairspawns, outside of aggregations, have been observed by the senior author on the
Palau barrier reef about 2 h after high tide in mid-day time periods.
In Palau, while knowledge is still imperfect, aggregations of Moorish idols usually occur around the fi rst and last quarter moons with peak numbers of fi sh on the
day before, the day of, and the day after the quarter moon. At Blue Corner and other
sites, several species of surgeonfi shes also form what are believed to be spawning
12 Species Case Studies
12.19 The Moorish Idol – Zanclus cornutus
Patrick L. Colin, Mandy T. Etpison, and Paul Collins
Coral Reef Research Foundation, PO Box 1765 , Koror , Palau 96940
email: crrf@palaunet.com
NECO Marine , Koror , Palau
e-mail: etpison@palaunet.com
Department of Science, University of Glamorgan, Treforest Campus, Pontypridd,
Wales, UK
e-mail: paul@abolutediving.uk
12.19.1 General
The Moorish idol, Zanclus cornutus , (the only member of the monotypic family
Zanclidae) is one of the iconic fi shes of the Indo-Pacifi c, yet its biology and reproduction are poorly known. It has an extremely broad distribution from the east coast of
Africa and the Persian Gulf across the Indian and Pacifi c Oceans to the western shores
of the Americas. It is related to the surgeonfi shes, sharing a somewhat similar larval
type (Johnson and Washington 1987 ) . Its maximum reported total length is about
23 cm, but at least in western Pacifi c areas most fi sh are much smaller. The species is
widespread where there is hard substrate and down to 180 m. It usually occurs in
schools that range from a few fi sh to over 100 animals. It feeds mainly on sponges. It
is a popular aquarium fi sh but is diffi cult to maintain (Myers 1999 ) . Despite the distinctive nature of this species very little work has been conducted on it.
12.19.2 Reproduction and Aggregation
For many years schools of hundreds of Moorish idols have been observed at numerous locations on the western barrier reef of Palau from December to March, with
peaks in January–February (Fig. 12.53 ). These have been reported as probable
spawning aggregations (e.g. Etpison 1997, 2004 ) , but had not previously been verifi ed under SCRFA criteria as spawning aggregations (Chap. 1).
A few reports of pair-spawning by Moorish idol exist. Colin and Bell ( 1991 ) saw
three pair spawnings (no aggregation) on the edge of a tidal channel at Enewetak
Atoll just after high tide near dawn. Sancho et al. ( 2000a, b ) listed 5 spawns (both
pair and group) by Moorish idol at Johnston Atoll without further detail. A few pairspawns, outside of aggregations, have been observed by the senior author on the
Palau barrier reef about 2 h after high tide in mid-day time periods.
In Palau, while knowledge is still imperfect, aggregations of Moorish idols usually occur around the fi rst and last quarter moons with peak numbers of fi sh on the
day before, the day of, and the day after the quarter moon. At Blue Corner and other
sites, several species of surgeonfi shes also form what are believed to be spawning