THE EFFECT OF DIETARY
ARACHIDONIC ACID CONCENTRATION ON ATLANTIC HALIBUT (Hippoglossus
hippoglossus) BROODSTOCK PERFORMANCE. ASSESSMENT OF EGG, MILT AND LARVAL
QUALITY
E. Alorend, G. Bell, N. Bromage,
D. Paterson, A. Barge, P. Morris, G. Rosenlund.
In order to evaluate the impact
of four different diets on halibut broodstock, eight tanks were set
up. Each tank contains 15 females and 5 males. The four broodstock diet
formulations contained 0.4% ARA, (0.4g ARA/100g dry feed), 0.6% ARA, a
control feed not supplemented with ARA and a control feed in which a
proportion of the fish meal was replaced with squid meal, to
improve palatability. The experimental diets have now been fed for
a period of 3 years. The spawning period is regulated by photoperiod. Four
tanks spawn in May and the four others spawn in August. A pit tag
identifies each fish. This allows individual length and weight data
to be collected every 2 months. During the spawning season,
milt, eggs, at different developmental stages, and yolk sac larvae are
sampled for subsequent biochemical analyses (lipids, fatty acids and PGF2G).
Fish
fed the enriched ARA diets have shown significantly better growth
compared to the other two treatments. During the second spawning season,
fish fed on 0.4% ARA significantly improved their whole production. Fatty
acid analyses on eggs, yolk sac larvae and milt show significant ARA uptake
and deposition relative to the diet.
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To be continued in the next issue