Pomacentrus moluccensis
A yellow damselfish from Western Pacific reefs, occasionally in aquariums.
The lemon damselfish, *Pomacentrus moluccensis*, is a bony fish from the Western Pacific that belongs to the family Pomacentridae. It sometimes enters the aquarium trade. This species reaches a maximum length of about 9 cm (4 in).
Its body is deep and compressed from side to side. The head is a bit longer than it is tall, with a large eye and a slanted mouth. Two rows of rounded-tip teeth line the jaws. The dorsal fin contains 13 spines and 13 to 14 soft rays, while the anal fin has 2 spines and 14 soft rays—the first anal spine being half the length of the second. The first ray of the pelvic fins is notably elongated, exceeding the head in length. The pectoral fins are relatively short, and the tail fin is shallowly forked with rounded lobes. The fish is a solid yellow, and except for individuals from the Philippines, a small orange spot sits at the base of the pectoral fin.
This damselfish lives in the tropical western Pacific, roughly between 32°N and 32°S latitude and 92°E to 173°W longitude. It inhabits clear-water lagoons and reefs with branching corals, which offer hiding spots, down to about 14 m (46 ft).
*Pomacentrus moluccensis* stays in small groups around coral reefs. Its diet mainly consists of algae, but it also eats planktonic invertebrates. During breeding season, pairs form; the female deposits eggs on the substrate, and the male guards and fans them to keep them oxygenated. Predators include fish like *Cephalopholis boenak* and *Pseudochromis fuscus*. The damselfish evades them better in high-shelter environments, such as those provided by *Pocillopora damicornis*, than in low-shelter ones like *Acropora nobilis*. As a coral-associated species, its numbers drop sharply after coral bleaching events.
In a crowded aquarium, it may chase peaceful fish. However, if it is the only *Pomacentrus moluccensis* in the tank and faces a more aggressive fish, it typically turns and swims away immediately.
Quick Facts
- Taxon
- Pomacentrus moluccensis
Facts from the source article.
Lore & Background
Pomacentrus moluccensis is a deep-bodied, laterally-compressed fish with a head slightly longer than it is high, a large eye, and an oblique mouth. Its teeth are in two series with rounded tips. The dorsal fin has 13 spines and 13 to 14 soft rays; the anal fin has 2 spines and 14 soft rays, with the first anal spine half the size of the second. The first ray of the pelvic fins is much elongated and longer than the head, while the pectoral fins are rather shorter, and the caudal fin is shallowly forked with rounded lobes. The fish is uniformly yellow, with a small orange spot at the base of the pectoral fin, except in fish from the Philippines.
This species is native to clear-water lagoons and reefs with branching corals, found down to about 14 meters. It lives in small groups and feeds mostly on algae, though planktonic invertebrates are also eaten. During breeding season, pairs form; the female lays eggs on the substrate, and the male guards and fans them. It is preyed on by Cephalopholis boenak and Pseudochromis fuscus, and survives better in high shelter environments like Pocillopora damicornis than low shelter ones like Acropora nobilis. The species declines dramatically following coral bleaching.
Reader's Guide
Pomacentrus moluccensis is a coral-associated species whose significance is tied to its role in reef ecosystems and its occasional presence in the aquarium trade. The article notes that it is preyed on by predatory fish such as Cephalopholis boenak and Pseudochromis fuscus, and its survival is enhanced in high shelter environments like those provided by Pocillopora damicornis compared to low shelter ones like Acropora nobilis. This highlights its dependence on specific coral structures for refuge. Additionally, the species has been shown to decline dramatically following coral bleaching, underscoring its vulnerability to environmental changes affecting coral health. In aquarium settings, the article describes that if the environment is crowded, it may continue to pursue peaceful fishes; when faced with more aggressive fish and it is the only one in the tank, it usually turns around and swims away immediately. These behaviors, along with its uniform yellow coloration and the orange spot at the pectoral fin base (absent in Philippine specimens), contribute to its identity as a distinct damselfish in both wild and captive contexts.
Did You Know?
- Pomacentrus moluccensis grows to a size of 9 cm (4 in) in length.
- This fish declines dramatically following coral bleaching.
More in Clownfish and Damselfish, Part 2 1-24
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