ASIAN report
male breeder (defined by having no common grandparents) waited for single-pair mating. As soon as the female breeders had successfully mated a male breeder (i.e. fertilized eggs were observed in their mouths), they were replaced with other female to produce paternal half-sib groups. For the production of full-sib families in the base population, the female breeders incubate fertilized eggs in their mouths and full-sib families were collected daily from the breeding hapas as swim-up fry. However, to better synchronize breeding and reduce chances that the increasingly larger female breeders would swallow their eggs, it was decided to collect full-sib families in later generations (G1–G6) twice per week as fertilized eggs or newly hatched yolksac larvae for artificial incubation in jars and trays. The collected full-sib families remained in the hatchery until they became swim-up fry, at which stage they were transferred to nursing hapas. In total 787 full-sib families were produced in the G0–G6 generations representing 334 paternal and 7 maternal half-sib groups. Swim-up fry from the full-sib families produced in each generation (G0–G6) were stocked into nursing hapas during a period of 46–73 days. Random samples of about 250 swimup fry from each full-sib family in the base population were stocked into separate nursing hapas (1.3 m x 1.0 m x 0.9 m), while two random samples of about 200 swim-up fry from each full-sib family in later generations (G1-G6) were stocked into hapas located in the same freshwater earthen pond. After 1–2 months, the samples of full-sib families in the base population were transferred to hapas with larger mesh size (B-net cages) at a stocking rate of about 150 fry per cage (1.5 m x 2.0 m x 0.9 m) to optimize further growth until tagging. The rearing period in the nursing hapas was standardized for all full-sib families in later generations, first to three weeks (G1–G2) and then to 15 days (G3–G6). Although the B-net 44 »
Aquaculture Magazine
Recording of harvest weight.
cages were smaller (1.0 m x 1.0 m x 0.8 m), the stocking density of about 150 fry per cage was maintained when producing full-sib families in later generations (G1–G6). The full-sib families remained in separate rearing units (nursing hapas and later B-net cages) until the youngest families reached a body weight suitable for physical tagging. All fullsib families within the first three generations (G0-G2) were pooled after tagging and tested in the same growout environments. In later generations, however, full-sib families were
grouped according to their age into two (G3–G5) or three consecutive batches (G6) that were tagged, pooled and stocked for grow-out testing in separate test units at different times, but at about the same mean age to reduce the overall mean age at tagging and age differences between fish tested in the same grow-out environment. As a result, the mean family rearing time was reduced from 92 days (G1) to 54 days (G6) before tagging (Table 1). Breeding candidates (11–36 males and 14–52 females per generation) FEBRUARY/MARCH 2014