Effect of weaning age and the use of different sized Artemia nauplii as first feed for jade perch Scortum barcoo

The first days of exogenous feeding are crucial for larval recruitment. A correct first prey item and the determination of the optimal weaning age, can reduce labor cost and fish mortality to a great extent. This study was conducted to evaluate the use of small and regular Artemia fransiscana (AF and EG Artemia, Inve, Belgium) as first feed for jade perch Scortum barcoo, and to determine the minimum required duration of this life feed phase before transition to dry feed can occur. Therefore, we compared first feeding of 3 days AF nauplii instar I with 3 days of EG nauplii instar I and evaluated whether the optimal weaning age for jade perch larvae was at 7, 10, 13 or 16 days post-hatching (DPH). The study was performed in 25-L tanks in a recirculating system and lasted for 21 days (4-24 DPH). Growth, survival and tissue fatty acid composition of the larvae in the different treatments were analyzed. Results indicate that, after the start of exogenous feeding at 4 days DPH, jade perch larvae require a minimum of 9 days of live feed until 12 DPH. Co-feeding ideally starts on 10 DPH. Larvae fed AF Artemia for the first 3 days showed a significantly faster growth than larvae fed EG Artemia, although their survival was lower. Gape width of larvae at 3 and 6 DPH was measured, and implications for prey size are discussed