Threadsail filefish (Stephanolepis cirrhifer) is a saltwater species recorded in Hong Kong, Taiwan.
Scientific name: Stephanolepis cirrhifer · Water: Saltwater
Size: up to 30 cm
The threadsail filefish is a monacanthid - a filefish, and not a tetrodotoxin carrier. Its juveniles associate with drifting seaweed, and it is commercially cultured in Japan. Maximum about 30 cm total length, with a fishing vulnerability of 32 out of 100 and medium population recovery. Low priced.
The first dorsal fin is a single strong spine that can be folded backwards and retracted, while the second dorsal and the anal fins are soft. The pectoral fins are comparatively small and the tail is truncated and fan-shaped; the dorsal and anal fins are colourless, and the second dorsal, anal and caudal fins are rounded. In males one to three of the soft dorsal rays are extended into filaments, the first with a particularly long thread — which is where the name "thread-sail" comes from. There is also a small spike on the belly. The colour runs from light brown through grey to a light greenish-beige, patterned with irregular, broken stripes ranging from medium brown to blackish. Adults usually stay near the seabed at around 10 m, and the species is oceanodromous, migrating between its feeding and spawning grounds over distances that can exceed 100 km; spawning runs from May to August. Juveniles under 5 cm stay in shallow water and feed on small crustaceans, molluscs and algae, while adults are mostly solitary and live among coral and seaweeds. It is also the host of the parasitic copepod Peniculus minuticaudae.
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