Effects of a seaweed feed inclusion on different life stages of the mottled rabbitfish Siganus fuscescens

The dietary effects of the red seaweed Asparagopsis taxiformis on the growth, innate immune response and sexual maturation of captive-bred rabbitfish, Siganus fuscescens, were assessed in two feeding trials. The first investigated different forms of seaweed (whole, methanolic extract and residue of extraction) and dietary inclusion levels (1.5%, 3% and 6% of feed) on the growth rate, feed efficiencies and intestinal microbiome of juvenile fish in a 4-week feeding trial. The second feeding trial assessed the long-term use (3 months) of A. taxiformis supplements on reproduction in S. fuscescens, by measuring the proportion of adult fish with sexual organs, their gonadosomatic index and their innate immune response. The first trial demonstrated the growth potential of dietary A. taxiformis with up to 49% increase in specific growth rate, and up to 31% reduction in feed conversion ratio, for fish receiving the highest extract inclusion compared with those fed the control diet. Additionally, the hindgut microbiome of the fish fed the seaweed diets had lower abundances of potentially pathogenic Tenacibaculum sp. compared with the control fish after 2 weeks. In the second feeding trial, the fish fed the 3% whole seaweed diet had a higher proportion of adult fish and improved innate immune response compared with the control fish but there were no significant effects of seaweed on gonadosomatic index. Overall, the red seaweed A. taxiformis shows potential as a novel functional ingredient for farmed rabbitfish to promote their growth, health and sexual maturation.

Automated summary

The study assessed the dietary effects of red seaweed Asparagopsis taxiformis on the growth, innate immune response, and sexual maturation of captive-bred rabbitfish, Siganus fuscescens. Results showed that feeding the seaweed could increase the growth rate and feed conversion ratio of fish, while reducing potentially pathogenic microbial abundance. Additionally, seaweed diets could improve the proportion of adult fish and their innate immune response.