Formulated algae-based feed with low polyphenol content and its effect on the feeding preference of juvenile blue abalone Haliotis fulgens

This study evaluated the effect of polyphenol reduction in a feed formulated with Eisenia arborea and its effect on the feeding preference of the abalone Haliotis fulgens through multiple selection tests. Two feeds were formulated: one without polyphenol reduction (EA01) and one with polyphenol reduction (EA02). Rehydrated E. arborea (ER03) was used as the control feed. The polyphenol content was quantified in EA01 and EA02, and the stability and hardness of all three feeds were measured at 24 h after immersion. Feed preference was evaluated through attraction and consumption tests on day 1, 6, and 12. The polyphenol concentration was reduced by 41% in EA02 (13.9 mg GAE g −1 ) compared to that of EA01 (33.3 mg GAE g −1 ). Both formulated feeds showed 88% stability and hardness values > 680 g cm −2 , which were greater than those of the control (ER03, 66% and 285 g cm −2 , respectively). Abalone were more attracted to EA02 and ER03 on day 1, 6, and 12 than to EA01 on the same days. A similar trend was observed with consumption. EA02 and ER03 were the most consumed feeds (> 6 g day −1 ) throughout the experiment, and no significant differences in consumption were observed between these feeds. On the other hand, juvenile H. fulgens showed a greater attraction to and consumption of EA02 (reduced polyphenol content) than EA01 (no reduction in polyphenol content). This allows us to conclude that EA02 can replace rehydrated algae as a suitable feed source for juvenile H. fulgens.