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Family Pomacentridae - Damselfishes

Pomacentrus wardi- Ward's Damsel

 

An adult Ward's Damsel in the dark colour form.

 

An adult Ward's Damsel in the pale colouration.

 

A large juvenile Ward's Damsel in the pale colouration.

 

Small juvenile Ward's Damsels, with the pale form on the left and the darker form on the right.

 

A small juvenile Ward's Damsel in the dark form.

 

Dark form Ward's damsels, with a juvenile on the left and an adult on the right.

 

Newly settled recruits of Ward's Damsel amongst Sargassum macroalgae.

 

Distinguishing features

A small herbivorous damselfish with a dark brown body. There appear to be two colour morphs around Magnetic Island, the typical dark form which is also found throughout the midshelf reefs of the GBR, and a paler form which seems restricted to the inshore fringing reefs. The small juveniles of the dark form have dark upperparts, a yellow belly, an ocellus on the rear of the dorsal fin, and a series of electric blue lines on the forehead. The pale form juveniles differ in that they lack the dark forehead, the yellow is tinged with orange, the blue lines are less prominant. In both colour morphs the juvenile characteristics are lost with age, and the adult fish greater than 1 year old appear a uniform drab brown. Maximum size about 11cm.

Locations

Found commonly in all bays of the island.

Habitat Preferences

This is the most abundant herbivorous damselfish around Magnetic Island, and is common in all reef habitats except the high intertidal, where it is replaced by P. tripunctatus.

Biology & Ecology

Ward's Damsel is a dominant component of the herbivorous fish fauna at Magnetic Island, feeding on turf algae from a small defended territory. They replace P. tripunctatus about halfway out across the reef flats, and their distribution continues down to the subtidal areas of the reef crest and slope. They like to farm algae on hard substrata, so are most common near areas of coral rubble offering some shelter. The two colour morphs have not been scientifically documented, but preliminary genetic analysis indicates they are the same species. At Magnetic Island (8-15km offshore), the pale form and the dark form are found in roughly equal numbers. At Orpheus Island (25km offshore) the dark form is approximately twice as common as the pale, and at Walker Reef on the midshelf (60km offshore) the pale form is seen only as a rare vagrant.

Papers and articles

Daniela M. Ceccarelli, Geoffrey P. Jones, Laurence J. McCook 2001. TERRITORIAL DAMSELFISHES AS DETERMINANTS OF THE STRUCTURE OF BENTHIC COMMUNITIES ON CORAL REEFS. Oceanography and Marine Biology: an Annual Review. 39: 355-389 .

Daniela M. Ceccarelli, Geoffrey P. Jones, Laurence J. McCook 2005. Effects of territorial damselfish on an algal-dominated coastal coral reef. Oecologia (2005) 24:606 .

Daniela M. Ceccarelli, Terry P. Hughes, Laurence J. McCook 2006. Impacts of simulated overfishing on the territoriality of coral reef damselfish. Mar Ecol Prog Ser 309: 255–262 .

Daniela M. Ceccarelli, Geoffrey P. Jones, Laurence J. McCook 2005. Foragers versus farmers: contrasting effects of two behavioural groups of herbivores on coral reefs. Oecologia (2005) 145: 445–453 .

David J. Booth, Giglia A. Beretta 2002. Changes in a fish assemblage after a coral bleaching event. Mar Ecol Prog Ser. 245: 205–212 .

 


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