Growth of the rabbitfish Siganus randalli Woodland - University of ...

for the larvae. Twelve to fourteen days after the siganids hatched, newly hatched Arlemianauplii were added to the larval rearing tanks at densities of 1 to 2 mi" and later at 3 to 5mr'. After metamorphosis, commercial salmon mash was added to the diet. Similar methodsof rearing larval siganids have been used by other investigators (Bryan and Madraisau, 1977;Tawada, 1991; Duray and Kohno, 1988; Soletchnik, 1984; May et aI., 1974)Newly hatched larvae are small (1.4 to 1.8 mm in length) and lack pigmented eyesand a functional mouth (Fig. 2). Approximately 24 hours post-hatching, the eyes becomepigmented and the mouth becomes functional (Fig. 3). Soon after the mouth becomesfunctional the larvae can feed on S-type rotifers. Table I provides a generalized summary ofthe development of S. randalli larvae and the associated feeding regime.Although we were able to rear larvae of S. randalli successfully to the juvenile stage,hatchery production was limited and highly variable. A particularly critical period, one inwhich most of the larval mortalities occurred, is the transition from the yolk-sac stage to firstfeeding. Work in our laboratory is currently focusing on this transitional stage. Larvalmortality during this stage must be reduced in order to achieve the production levels requiredto support commercial aquaculture.4