Can Atlantic cod (Gadus morhua) larvae be weaned faster onto dry feed at higher temperatures?

Live feed production is costly, labour intensive, and comprises a large proportion of the hatchery production cost. The cost of live food production required to culture marine finfish larvae such as Atlantic cod (Gadus morhua) can be reduced by a shorter and more efficient weaning period. In this study, hatchery reared cod larvae were exposed to different temperatures while being weaned from Artemia (brine shrimp) to dry food from 45 days post-hatch (dph). In the first experiment, two temperatures were used: 11.5 and 7.5 °C. During weaning, the amount of Artemia fed to the larvae was gradually decreased while the dry feed was increased. Larval foraging behaviour and mortality were monitored. The growth rate and mortality of the larvae were not significantly different between the two treatments. However, the larvae in the 11.5 °C treatment showed a significant increase in the intake of dry feed. Thus, a second experiment was conducted at 11.5 and 14.5 °C to examine if weaning could be further improved. Results showed that the growth rate of larvae between the two temperatures did not differ significantly, however, mortality rate in 14.5 °C treatment was significantly higher than 11.5 °C treatment. Larval orientation towards and ingestion of dry feed were not significantly different in experiment two. Results of our experiments suggest that a possible optimal weaning temperature for larval cod between is 11.5 and 14.5 °C.