Appropriate food of suitable nutritional value is crucial for first-feeding stages of the larvae of cobia Rachycentron canadum, a very fast growing marine fish species. Best survival and growth results in cobia larviculture have been reported with a starter diet of HUFA-enriched rotifers and -as mouth size permits - followed by freshly-hatched and eventually HUFA-enriched Artemia nauplii. Using the smaller-sized Vietnam Artemia franciscana (AF) strain instead of the Great Salt Lake A. franciscana strain, it has been shown that the rotifer-feeding period could be shortened with 3 days, resulting in significant improvements in larval survival and growth. This study verified the possibility to feed umbrella-stage Artemia for further shortening and eventually completely substituting rotifer start feeding. The experiment was conducted in 200-L tanks and lasted 18 days. AF umbrella Artemia was used as sole feed during the whole rotifer feeding period (UAF), compared to the use of enriched rotifers for the first 2 days followed by AF-umbrella (ER + UAF) and the use of enriched rotifers as control (ER). The feeding incidence of UAF treatments was significantly lower (P < 0.05) in the 1st feeding day, however, the ingestion and digestion of AF were evident. Growth and survival as well as deformities at day 18 post-hatching were not significantly different for all treatments (P > 0.05). The viability of cobia larvae after exposure to high salinity stress was lower in the ER treatment at day 8 post-hatching, but higher at day 18 post-hatching (P < 0.05). The ability of cobia larvae to ingest and digest AF umbrella at first feeding as well as the nutritional suitability of AF umbrella is discussed. The possibility to use umbrella-stage Artemia opens an opportunity to simplify the rearing protocol and to reduce production costs of cobia larviculture. |
