Biology and Life Cycle of Siganus vermiculatus (Siganidae, Pisces)

Abstract

The herbivorou s fish Siganus vermiculatus (Valenciennes) (Siganidae; Pisces), a mangrove swamp dweller, was studied in the field and in captivity in Fiji. The fish has a lunar spawning cycle, benthic sticky eggs, and pelagic larvae. Metamorphosis occurs between 23 and 27 days after hatching. The fry live in small schools in brackish or fresh water among mangrove roots. The young and adults are found mainly in shallow, murky water of mangrove swamps where they move in and out with the tides . The adults are sometimes seen in clear water near coral reefs or over sandy bottoms. Feeding takes place during the day and at night and consists mainly of grazing on algae and mangrove roots. A tolerance of extreme fluctuations in physicochemical parameters (temperature 19 to 38°C; salinity 2 to 55 ppt; dissolved oxygen 1.2ppm; pH 6.2 to 8.4) permits the species to live in mangrove swamps.