High-M alginate immunostimulation of Atlantic halibut ( Hippoglossus hippoglossus L.) larvae using Artemia for delivery, increases resistance against vibriosis

Abstract

A strategy for microbial management in marine juvenile production should include nonspecific immunostimulation to reduce losses caused by infectious diseases. Halibut ( Hippoglossus hippoglossus L.) larvae (250 day degrees) were distributed into first-feeding tanks of 10.000 l, at a Norwegian halibut juvenile farm. Immunomodulatory high-M alginate was bioencapsulated in Artemia by use of alginate microbeads (2–30 μm), and administered to halibut larvae at three stages during the first feeding period (days 7–9, 20–22 and 41–43). A fourth treatment was run after weaning, 5–3 days prior to a challenge test with two different doses of Vibrio anguillarum O2 that was started at day 90 after first feeding. After 15 days, the mortality at the highest dose was 45±1% in the control and 28±8% in the stimulated group, corresponding to 38% reduction in mortality, whereas no significant differences were measured at the low dose. It is concluded that feeding immunostimulants to halibut larvae for four short periods during 3 months enhanced resistance against vibriosis, and that high-M alginates are suitable as immunostimulants for marine larvae during first feeding and weaning.