Influence of size and nutritional value of Artemia franciscana on growth and quality of halibut larvae ( Hippoglossus hippoglossus) during the live feed period

Abstract

In a first feeding experiment, halibut larvae were offered either short term enriched (ST) 1-day old Artemia franciscana or A. franciscana of successively increasing size (ST, 2-, 3- and 4-day old juveniles), from day 0 to day 60. No differences, either in growth (approximately 6.5% daily weight increase, DWI) or in survival (ca. 25%) between the two treatments were observed, but both were satisfactory. However, feeding increasing sizes of A. franciscana increased the number of completely pigmented and metamorphosed larvae from 4 to 20%. Protein/lipid ratio in the feed seems to be important for pigmentation and metamorphosis, provided the levels of essential fatty acids (esp. DHA) are sufficient. Juvenile A. franciscana may therefore be a better live feed than ST A. franciscana for halibut larvae. The fact that a relatively high load of bacteria was introduced by 4-day old A. franciscana, may have had a negative influence on the growth of the larvae. Tests indicated that a great part of the bacteria exhibited hemolytic activity, and many of the bacteria were apparently Vibrios. Strict microbial control in the production of live feed is very likely just as important as control of the nutritional composition of the larval feed. This is a challenge for further work.