Weaning captive bred forktail blenny, Meiacanthus atrodorsalis, to a commercial formulated diet: Optimizing timing, feeding frequency and ration

This study aimed to establish a benchmark regime for weaning the forktail blenny, Meiacanthus atrodorsalis, a popular marine ornamental fish, to a commercial marine fish hatchery diet. Three experiments were conducted to investigate the best age for weaning, and the optimal feeding frequency and ration for this species. Weaning M. atrodorsalis from live prey to the formulated diet was successful at all ages tested between 16 and 30 days post-hatch (DPH), with survival ranging from 71 to 95% on 40 DPH. However, fish weaned starting 19 DPH and beyond showed 35-54% greater standard length, 28-56% greater body depth and 121-291% greater dry weight, as well as a 30-49% reduction in deformity relative to those weaned starting 16 DPH. The greatest standard length, body depth and dry weight of 17.9 ± 0.2 mm, 5.0 ± 0.1 mm and 30.9 ± 1.2 mg respectively, and the lowest rate of deformity of 6 ± 3% was recorded in fish weaned latest, starting 30 DPH. Of the feeding frequencies tested (from 1 feed every 3 days to 4 feeds per day) high survival on 49 DPH of between 94 and 97% was achieved when M. atrodorsalis were fed once every 2 days or more frequently from 32 DPH. However, fish fed once per day or more achieved 10-26% greater standard length, 8-29% greater body depth and 54-300% greater dry weight relative to those fed once every 2 days and once every 3 days. Within the feeding rations tested (2-15% body weight per day), survival was the highest when fish were fed a ration of 5-15% body weight per day, ranging between 86 and 93% on 49 DPH. However, there was a clear growth advantage of 18-29% greater standard length, 9-20% greater body depth and 41-160% greater dry weight when M. atrodorsalis were fed a ration of 8% body weight per day or more, relative to a ration of 2 and 5%. Above an 8% daily ration, growth gains were negligible. Based on our findings, we recommend that weaning M. atrodorsalis onto a commercial hatchery diet commence between 22 and 25 DPH, followed by feeding at least once daily at a ration of 8% body weight per day.