The Feistiest of Reef Fish- Damselfish

Of the approximately 5,000 species of fish found along the coral reef, perhaps none are as feisty and territorial as the damselfish. Notoriously aggressive, these fish are known to nip at anything that comes between them and their food source. Likewise, these fish fiercely guard their egg clutches during spawning; quickly attacking anything that comes within close proximity. There are approximately 315 species of damselfish found worldwide, 14 species of which are found in the tropical waters of the Western Atlantic. Of those, the Sergeant Major is one of the better known and abundant species.

Found throughout temperate waters of the world, damselfish are palm-sized fish that rarely exceed six inches in length. They are brightly colored in shades of orange, red, yellow and blue, and are characterized with forked tails and a nostril on each side of the head. Attracted to the reef for protective habitat and food, damselfish feed on algal mats found among the coral, as well as other plant matter and small animals suspended in the water. With a tiny mouth lined with sharp teeth, damselfish are skilled at grinding their teeth on algae, resulting in an audible clicking sound.

It is during feeding time that the aggressive behavior of the damselfish becomes very apparent. Competing with parrotfish and surgeonfish for algae, the tiny, but quick damselfish are known to be formidable challengers, antagonizing their rivals until they leave the area. The Blue tang, however, is one of the few fish that has learned how to avoid the nips of the damselfish by feeding in large swimming groups.

Reef Brief is a weekly column published in the San Pedro Sun
Of all damselfish in the Caribbean, the Sergeant Major is one of the more plentiful and common species. This fish is larger than most damselfish (eight inches) and is named for five black bars on the side of its body that resemble the insignia of a rank in the military. The upper body of the Sergeant Major is yellow, occasionally with shades of blue, and the lower body is white with shades of gray, with a dark spot near the pectoral base. In addition to their aggressive feeding behavior, these fish participate in courtship rituals, in which nests are prepared. At this time, males also change colors and actively pursue females during the morning hours by continually circling and nudging them. Reproduction occurs during a five-month spawning period from April to August, which is linked to the lunar cycle. After approximately 200,000 eggs are laid on coral heads, the male protectively guards them until the eggs mature and hatch, after which time he returns to his normal coloration.

Fortunately, because of the curious and aggressive behavior of the Sergeant Major, and Damselfish in general, scientists continue to focus much attention on these fish. Currently in Belize and throughout the world, damselfish have a healthy population and are not threatened. However, just like all other living creatures in the sea, the damselfish is dependent on many factors, such as a healthy reef environment, for it to continue to thrive.

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