Year-round spawning and seed production of the rabbitfish, Siganus guttatus

Abstract

A series of experiments on the spawning and larval rearing of Siganus guttatus was conducted during a 14-month period in 1984–1985. Spawning occurred every month throughout the year, without hormonal treatment, between the first quarter and the full moon. Fertilization rates and hatching rates were high, with means of 84.2% (n=38) and 89.6% (n=34), respectively. Females that had been fed diets rich in cod liver oil or in a cod liver oil/soybean oil/soybean lecithin mixture spawned repeatedly for at least 4 consecutive months. Larvae reared in 20, 26, and 32‰ salinities showed no significant differences in survival rates at day 21. Survival was higher for larvae fed during days 2–4 with rotifers strained through an 80-μm-mesh plankton net than for those fed unstrained rotifers. Larvae readily accepted Artemia nauplii and artificial diets when these were first introduced on day 15 and day 23, respectively. Higher larval survival was obtained in large tanks (≥5 m3) than in small tanks (500 l). Survival rates of 3.5–16.6% (x=7.5%) at day 45 were obtained in six trials of mass larval rearing and 5500–50100 (x=27 700) juveniles per female were produced at day 45, ready for stocking in grow-out farms.