Effects of diet transition regimen on survival, growth and lipid composition of intensively reared Atlantic cod, Gadus morhua, larvae |
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Authors: | RJ Shields S Irwin PL Smith LA McEvoy |
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Institution: | (1) Seafish Aquaculture, Ardtoe, Acharacle, Argyll, PH36 4LD, UK;(2) Present address: The Oceanic Institute, 41-202 Kalanianaole Highway, Waimanalo, HI 96795, USA;(3) Present address: Department of Zoology, University College Cork, Ireland;(4) Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, UK;(5) Present address: North Atlantic Fisheries College, Port Arthur, Scalloway, Shetland, ZE1 0UN, UK |
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Abstract: | Replicated groups of Atlantic cod were rearedfor up to 40 days in 100 l tanks stocked at adensity of 75 eggs l–1. Larvae weretransferred from rotifers, Brachionusplicatilis, to either fresh-hatched orenriched Artemia nauplii on each of days5, 15 and 25 post-hatch (ph). Rotifers wereprogressively withdrawn over a 5 day period.The type of Artemia offered(fresh-hatched, enriched) did not affectsurvival or growth rates at any of the 3transfer ages. Larvae transferred toArtemia from day 5 ph suffered a highincidence of swimbladder over-inflation andhigh mortality during metamorphosis (< 1%survival to day 36 ph). Cod in the day 15 and day25 transfer groups did not differ significantlyin weight-specific growth rate or size on day40 ph (mean standard length 13.8 mm, dry weight3.8 mg). Highest mean survival rates to day 40ph (18.1%) and lowest mortality followingtransfer to nursery tanks were also observed inthe day 25 transfer groups. Fish that receivedArtemia from day 5 ph containedcirca twice as much total lipid per unit bodyweight and had a 30% higher triacylglycerol(TAG) content compared to all other groups.Ratios of the essential fatty acidsdocosahexaenoic acid (DHA), eicosapentaenoicacid (EPA) and arachidonic acid (ARA) alsodiffered according to age-at-transition.DHA:EPA ratio exceeded 1 only in codtransferred to Artemia on day 25 ph.Based on these findings, it is recommended thatintensively reared Atlantic cod should continueto receive rotifers until completion ofmetamorphosis. |
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Keywords: | Artemia Cod larvae Growth Intensive rearing Lipids Rotifers Survival Swimbladder |
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