C.P. Hominick and J. Duston
Abstract:
Larval striped bass (Morone saxatilis), River Stewiacke Nova Scotia stock, fed Artemia without enrichment exhibited similar good survival and growth to bass fed Artemia enriched with highly unsaturated fatty acids (HUFA). In contrast, other studies found larvae of US stocks of striped bass, similar to marine finfish, suffered high mortality if fed Artemia with no enrichment, since this live feed contains very little HUFA and the fish larvae cannot synthesize sufficient quantities of HUFA. Docosahexaenoic acid (DHA) is believed particularly important for larval development. The contrast between Bay of Fundy and US stocks of striped bass in their ability to utilise Artemia as a food source may be related to differences in life-history patterns and genotype.
On July 4, n=135 striped bass larvae were allocated at random to each of six glass aquaria with static water, temperature 20 C. Three experimental treatments, each replicated: 1) Control; Artemia incubated with corn-oil containing no HUFA; 2) Artemia enriched with commercial HUFA booster (MB30, Microfeast Ltd.); 3) Artemia enriched with purified DHA (Martek Biosciences Corp). Artemia, 30 h post-hatch, were enriched for 16 h by adding fat emulsions to the incubation flasks, then washed and fed to the fish larvae. Treatment duration = 15 days (July 7-21 inclusive). On July 22, n = 10 fish were sampled from each tank, frozen, then fatty acids were analysed by gas chromatography.
Survival of larvae in all treatments was high and almost identical, 91-92%. Mean (SE) body weight of larvae between the three treatments was not significantly different, although the control was lower at 0.141 (0.005) g versus 0.157 (0.006) g for both enriched treatments. HUFA were detected in relatively high levels in larvae in all treatments. DHA was highest in larvae fed Artemia enriched with DHA, range 4.98-6.51% total fatty acids. In the control and MB30 treatments, DHA levels were 2.22-2.42% and 2.86-2.87% of total fatty acids, respectively. Swimbladder inflation was >98% in all treatments.
(Dept. Animal Science, Nova Scotia Agricultural College, P.O. Box 550, Truro, NS B2N 5E3, Canada)