How to Identify a Longfin Damselfish

Video Transcript

"The marine organism we are going to identify now, is the longfin damselfish. One of the most aggressive fish on the coral reef is the damselfish. The longfin damselfish is one of the less common damselfish species. A relatively large damselfish, usually three to four inches long, although they can reach a maximum size of five inches. The longfin damselfish will defend its territory very aggressively. Their territory generally only covers a small area, for example a small coral head in the sand, but they will attack anything that gets too close to it, including fish much larger than itself. Longfin damselfish are somewhat challenging to identify since they can be easily confused with the dusky damselfish. What distinguishes the two species are the shape and length of their dorsal and anal fins. Longfin damselfish have dorsal and anal fins that extend well beyond the base of the tail and usually are more pointed than rounded. Where as the dusky damselfish fins and just add or just passed the base of the tail and are rounded. The colorization of the longfin damselfish is a dark brown to black over its entire body and fins. Although the pectoral fins may appeared to be clear. Juvenile longfin damselfish are very different looking. They have bright yellow bodies with bright little lines that start at the nose and run along the back, often breaking into spots instead of a continuous line. They are distinguished from their other similarly colored damselfish juveniles by a dark spot ringed in blue on their dorsal fin. Longfin damselfish can be found throughout the Caribbean and the Florida Keys. But are less common than other species of damselfish such as the bicolor damselfish. They can be found in depths ranging from a few feet to depths well beyond safe diving limits for recreational scuba divers. Although they are most commonly found in depths of less than eighty feet. They have a relatively small territory that they patrol, and rarely rise more than a few inches above the safety of their patch reef or coral head. If they feel threatened, they will quickly duck into a hole in the reef, but will fairly quickly re-emerged. Longfin damselfish, like all damselfish, feed primarily on algae, and they tend to maintain their own personal algae patch in their territory. Longfin damselfish also reportedly feed on various worms, hydroids, zoo plankton, and tunicates. Longfin damselfish exists as separate male and female specimens. Although the color and patterns do not differ. Eggs are laid by the female on the bottom of the reef, and then the male swims over them to fertilize them. Once fertilized, the male longfin damselfish guards the eggs until they hatch and will be more aggressive than normal in protecting the area around the eggs. Once hatched, the friar are on their own. That's the longfin damselfish."