Burbot (Lota lota maculosa) are freshwater cod that have recently been identified as potential candidates to expand intensive freshwater aquaculture. However, burbot larvae require live food for several weeks before they can be weaned onto commercial feeds. To determine if dependance on live feed could be reduced, we evaluated two products, Gemma dry diet and a liquid artemia replacement (EZ Artemia spp.), for their ability to reduce the time of live feeding of burbot larvae. The effect of weaning on growth performance and survival was monitored for 70 days.
In trial 1, larvae were divided into six feeding regimes: a current standard rearing protocol of the Aquaculture Research Institute of University of Idaho fed live feeds (marine rotifers Brachionus plicatilis and Artemia nauplii.) for more than 40days before weaning onto the dry diet; a positive control group exclusively fed live feeds, negative control fed Gemma diet alone, treatment 1 fed Artemia nauplii and no rotifers, treatment 2 fed rotifers and no Artemia nauplii, treatment 3 fed rotifers, Artemia nauplii and EZ Artemia spp. Live feeds were administered from 11 days post hatch (dph) until introduction of Gemma diet at 21 or 40 dph and EZ Artemia spp. at 22dph. The stocking densities were 150 larvae/L and growth was assessed at 15, 25, 35, 42, 49 56, 63, and 70 days after stocking. Larvae in the standard rearing protocol had highest survival (>24%), followed by larvae fed exclusively live feeds (22.17%). Larvae fed rotifers, Artemia nauplii and EZ Artemia spp. resulted in significantly (P < 0.05) reduced survival. Use of EZ Artemia spp. in treatment 3 reduced the period of using live feeds by 17days when compared to the standard rearing protocol.
In Trial 2, additional feeding regimes were tested that aimed at further identifying feeding regimes that could reduce the use of live feeds while maintaining high growth and survival. Burbot larvae were divided into five feeding regimes: a standard rearing protocol fed live feeds for a prolonged period, treatment 1 fed Artemia nauplii and EZ Artemia spp., treatment 2 fed rotifers and EZ Artemia spp., treatment 3 exclusively fed EZ Artemia spp. and treatment 4 fed Artemia nauplii but introduced Gemma diet at 25dph. Live diets were administered at 11dph until when Gemma diet was introduced at 25 or 40dph and EZ Artemia spp. at 20 or 25dph. The stocking densities were 100/L and survival, and total length were assessed at 14, 28, 42, 56 and 70 days after stocking. Larvae fed live feeds for a prolonged period had significantly higher survival (>30%), followed by larvae fed Artemia nauplii and EZ Artemia spp. (20.7%), thirdly, larvae fed rotifers and EZ Artemia spp. had 17.5% survival. Larvae fed Artemia nauplii and Gemma diet had the least survival, but higher total growth.
Use of EZ Artemia in treatments 1 and 2 reduced the time and amount of using live feeds by 19 and 24 days, respectively when compared with the standard rearing protocol. Early use of Gemma diet in treatment 4 also reduced live feeding period by 19 days. The results demonstrate a potential to reduce the time of live feeding through incorporation of EZ Artemia and/or Gemma micro-diet as replacements for live feeds. This study provides a starting point for reducing live feeds in burbot larval culture.