Growth and survival of juvenile abalone Haliotis diversicolor fed on brown macroalgal gametophytes, a potential alternative initial diet

To elucidate the dietary value of macroalgal gametophytes for post-larval and juvenile abalone Haliotis diversicolor, growth and survival rates of five different size groups of the abalone [1.4–3.4, 2.8–4.6, 4.4–6.0, 5.7–8.3 and 7.6–12.0 mm in shell length (SL)] fed on gametophytes of three brown macroalgae (Eisenia bicyclis, Ecklonia cava and Undaria pinnatifida; Laminariales, Phaeophyta) were examined, and compared with those fed a benthic diatom Nitzschia sp. Most abalone actively fed on all algal diets, but large variations in the growth rate were observed among the diets and abalone growth stages. Mean growth rates of abalone fed Nitzschia sp. were similar or higher than those fed the macroalgal gametophytes in 1.4–4.6 mm SL, but lower in 4.4–8.3 mm SL. For all of the three macroalgal gametophytes, growth rates of the abalone increased linearly from 2–3 mm SL and were highest at around 6 mm SL. However, mean growth rates of larger individuals (7.6–12.0 mm SL) dropped to less than 45 μm day− 1 in all treatments with the macroalgal or diatom diets. These results indicate that gametophytes of the three brown algae are favorable diets for juvenile H. diversicolor of 3–8 mm SL. Introduction of the brown algal gametophytes as diets for juvenile H. diversicolor is considered to be an alternative innovative method to improve the efficiency and stability of the abalone culture.