About Stephanolepis cirrhifer (Temminck & Schlegel, 1850)
Stephanolepis cirrhifer, commonly called the thread-sail filefish, reaches a maximum adult length of about 30 centimetres (12 inches). Its first dorsal fin is a strong, retractable spine that can fold backwards, while the second dorsal fin and anal fin are soft. The species has comparatively small pectoral fins and truncated, fan-shaped tail fins. There is a minor inconsistency in the source description that notes the dorsal and anal fins are colorless, also says the second dorsal, anal, and caudal fins are rounded. In males, 1 to 3 soft dorsal fin rays extend as filaments, with the first ray forming a particularly long thread. Thread-sail filefish also have a small abdominal spike. Their base coloration ranges from light brown to grayish to light greenish-beige, with subtle patterning made up of irregular, broken stripes in shades from medium brown to blackish. Juvenile thread-sail filefish typically shelter from predators within clusters of drifting seaweed. Adults usually live near the seabed at depths around 10 metres (33 feet), and are mostly solitary, residing among coral and seaweed. This species is oceanodromous, meaning it migrates entirely within ocean waters between its feeding and spawning grounds, which can be over 100 kilometres (62 miles) apart. Its spawning season runs from May to August. Juveniles under 5 centimetres (2.0 inches) live in shallow water, where they feed on small crustaceans, mollusks, and algae. The thread-sail filefish is an omnivore that eats both plant and animal matter. Its diet includes kelp, and consists mainly of amphipods such as gammarids and skeleton shrimp, as well as the seagrass Zostera marina. It also feeds on smaller organisms including bryozoans and some species of serpulid tube worms. Additional recorded prey items include fish, isopods, cirripeds, polychaetes, pelecypods, seaweeds of the genus Sargassum, and gelatinous plankton such as the moon jellyfish Aurelia sp. and the giant jellyfish Nemopilema nomurai. S. cirrhifer acts as a host for the pennellid copepod parasite Peniculus minuticaudae, which most often infects the fins of female fish. The thread-sail filefish is cultured and sold commercially as food in Asian countries including Korea and Japan. In Korea, it is an ingredient in jwipo. Demand for the fish is very high in Korea, so fisheries often use fish hatcheries to breed additional fish to supplement wild stock. This hatchery breeding has led to genetic differentiation between wild-born and hatchery-born S. cirrhifer; as many as 95 alleles have been found to be unique to one population, from minor genetic variations that occur exclusively in either population.
