The yellowtail damselfish (scientific name: Microspathodon chrysurus) is a member of the damselfish family (Family Pomacentridae) that lives on coral reefs in the Western Atlantic Ocean and the Caribbean Sea.

Yellowtail damselfish. Source: Florent Charpin/www.reefguide.org     Juvenile yellowtail damselfish. Source: Kathy Hoyt/www.quiescence.com

Scientific Classification Kingdom: Animalia (Animals) Phylum:--- Chordata Class:------ Osteichthyes (Bony Fishes) Order:-------- Perciformes Family:-------- Pomacentridaedae (Damselfishes) Genus:----------Microspathodon Species:----------- Microspathodon chrysurus (Cuvier, 1830)

Physical Description

Adult yellowtail damselfish are small fish (10  to 21 centimeters in length) with an oval shape.Adults have a dark body with a bright yellow tail.  Juveniles are dark blue in color and are covered by a number of bright light-blue dots. The iridescence juveniles are sometimes called jewelfish.

Distribution

They are found in the subtropical (32°N - 5°S) Western Atlantic from Florida, through the Caribbean Sea, as far south as Brazil.  They are also  found in the Gulf of Mexico. and the Caribbean Sea.

Habitat

Yellowtail damselfish live on coral reefs at depths from zero to 120 meters.  Females tend to establish territories near the reef crest while males live in deeper zones in areas of elkhorn coral rubble. 

Feeding Behavior

Yellowtail damselfish are primarily herbivores that graze on algae.  In addition, they occasionally feed on fire coral polyps and other invertebrate animals.  Juveniles occasionally pick parasites from other species of fishes.

Behavior

Both male and female yellowtail damselfish defend territories that often include the smaller territories of threespot damselfish or dusky damselfish.  Unlike many of the other damselfishes, yellowtail damselfish are not particularly aggressive while defending their territories and they appear to rely on the smaller damselfish living in their territories to aggressively defend their algal food source.  Small individuals who are unable to defend their own territory become wanderers who are forced to attempt to feed in territories defended by larger individuals.

Reproduction

The peak reproduction periods are in February/March and July/August. Large territorial males prepare nests in seven to eleven meters of water by scraping algae and other organisms off of the substrate.  Males attempt to attract mates to their territories by swimming in figure eight patterns ,and may even attempt to herd females to their territories by butting them. Females deposit eggs in nests where they are fertilized by the male. Females may spawn once every three days and males may care for up to five clutches of eggs. Males aggressively defend eggs from potential predators by grunting and chasing.  After three to our days, the eggs hatch and the larvae enter the pelagic stage which lasts for 21 to 27 days.  Larvae settle on shallow patch reefs and the juveniles tend to live near blades of Fire coral.

Conservation Status

Yellowtail damselfish are deemed to be a species that is not at risk.

References and Further Reading 

• Microspathodon chrysurus (Cuvier, 1830)
• Humann, P. and N. Deloach (Editor), 1994. Reef Fish Identification: Florida, Caribbean, Bahamas. New World Publications, Inc. Jacksonville, FL. ISBN: 1878348078
• Deloach, N. 1999. Reef Fish Behavior, Florida, Caribbean, Bahamas. New World Publications, Inc. Jacksonville, FL. ISBN: 1878348280