Enrichment of live feeds with various oil emulsions: effects on yellowtail flounder larvae, and on rotifers and brine shrimp

Metusalach, 1960- (2002) Enrichment of live feeds with various oil emulsions: effects on yellowtail flounder larvae, and on rotifers and brine shrimp. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The production of live feed for use in the culture of marine finfish larvae is critical. Live feed needs to be of high quality to promote good growth, survival and pigmentation. The effect of live feed enrichment on yellowtail flounder (Limanda ferruginea) larvae was studied. Live feeds were enriched with seal oil, menhaden oil and Algamac (algal-based formulated diet) in one experiment, and with seal oil, seal oil+DHASCO (docosahexaenoic acid-rich single cell oil) and Algamac in a second experiment. The survival of larvae ranged from 5.7 to 20%. The specific growth rate (SGR) of larvae fed Algamac was higher than that of seal oil-fed larvae in the first experiment, but was similar with other treatments in the second experiment. The proportion of fish having complete pigmentation and eye migration was 43-53% and 56-72%, respectively. The n-3 highly unsaturated fatty acid (HUFA), essential fatty acid (EFA) contents and EFA ratios in rotifers correlated with complete eye migration of fish in the first experiment, whereas only arachidonic acid (AA) content was found to correlate with normal pigmentation in the second experiment flounder. -- The fatty acid composition of the total lipid of larvae in each feeding reflected, in general, the fatty acid profile of their respective diets. The EFA contents of larvae fed seal and menhaden oil were similar (p>0.05), whereas those of larvae fed Algamac were higher (p<0.05). The fatty acid composition of normally and abnormally pigmented flounder fed the same diet was generally similar. In all feeding regimes, 16:0, 18:1n-9 and 18:3n-3 were the most abundant fatty acids present. -- Enriched rotifers varied in their total lipid contents among the enrichment concentration and period. While the effect of enrichment concentration was absent in the DHASCO treatment (p=0.15), the effect of enrichment period was observed in all treatments (p≤0.01). The EFA contents in rotifers were influenced by both the enrichment concentration and period (p<0.03). An interaction between the enrichment concentration and period exerted a significant effect on the EFA contents (p<0.03) of rotifers, except on the DHA of the Algamac-fed rotifers (p=0.11). -- The total lipid contents of Artemia generally affected (p<0.001) by both the enrichment concentration and period. Fatty acids 16:0, 18:1n-9 and 18:3n-3 were the primary constituents of Artemia lipids. The content of EFA in Artemia fed with different oil emulsions was affected (p<0.001) by both emulsion concentration and enrichment period. A significant interaction existed between enrichment concentration and period on the total lipid and EFA contents (p<0.01), except on the EPA of the seal oil-fed Artemia (p=0.06). -- This study demonstrates that using seal oil and menhaden oil to enrich live feeds gives comparable results on the general performance of yellowtail flounder larvae to those when using commercial enrichments containing high DHA levels, and that this species does not require high dietary DHA for maximal survival, growth and pigmentation. Results also suggest that the concentration of enrichment medium and length of feeding period affect the total lipid, DHA, EPA and AA contents in live feeds.

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