Effect of Macroalgal Diet on Growth Rate and Nutrition of the Pinto Abalone, Haliotis kamtschatkana

Developing methods for the cultivation of the pinto abalone, Haliotis kamtschatkana, has seen increased attention, both by groups using restoration aquaculture to reestablish endangered populations in Washington and British Columbia, and in the State of Alaska, where pinto abalone are viewed as a promising new species for commercial mariculture. To enhance the viability of cultivating H. kamtschatkana for commercial and restoration purposes, more information is needed on the optimal macroalgal diet that maximizes abalone growth and nutrition. This study compares the suitability of two commonly cultivated species of macroalgae as feed: Saccharina latissima (sugar kelp), a kelp with relatively low protein content, and Devaleraea mollis (Pacific dulse), a rhodophyte with comparatively high protein content. Fifty H. kamtschatkana specimens, with a mean shell length of 45.25 ± 4.26 mm, were collected from the wild and fed either S. latissima, D. mollis, or an alternating diet of the two for 28 wk. Feed consumption was measured weekly, whereas shell length and weight change were recorded every 2 mo. Despite consuming significantly more S. latissima than D. mollis (P < 0.001, H. kamtschatkana showed no significant difference in specific growth rate (SGR) (P = 0.775) or linear growth rate (LGR) (P = 0.746) among the diets. Feed conversion efficiency (FCE) was significantly higher for D. mollis than S. latissima (P < 0.001), although there was no significant difference in protein efficiency ratio (PER) (P = 0.129). Proximate composition analyses of abalone tissue showed no significant difference in protein, lipid, carbohydrate, or caloric content across macroalgae diets. Additionally, sexual dimorphism was observed, with females exhibiting significantly higher daily feed consumption (DFC) (P = 0.001), SGR (P = 0.003), and LGR (P = 0.001) than males. These results indicate that whereas both macroalgae species are suitable as feeds for H. kamtschatkana cultivation, the benefits of a D. mollis diet are less pronounced compared with other commercially cultivated abalone species. This study provides actionable insights for those interested in cultivating H. kamtschatkana for commercial or restoration purposes and adds to our understanding of an environmentally and culturally important species in the Northeast Pacific Ocean.