Heritability of energy intake and allocation and their correlated responses to selection on growth traits in cultured juvenile and adult red abalone Haliotis rufescens

Abstract

Increasing abalone growth rates and their physiological efficiency in the use of energy through selective breeding could improve abalone production. High potential responses to selection for growth traits have been estimated in several abalone species; however, the genetic bases underlying individual differences in physiological performance are unknown. The aims of this study were to estimate the heritable variation of physiological traits associated with energy intake and allocation for the red abalone Haliotis rufescens; and the potential correlated responses to selection between growth and physiological traits at three developmental stages. Growth traits (shell length and width, and total mass) and physiological traits [energy intake, standard metabolic rate (SMR), and energy losses by ammonia excretion and feces] were measured in individuals belonging to 60 full-sib families in 2-years old juveniles, 3-y old young adults, and 4-y old near-harvest adult (n = 500–380 individuals/age; total n = 1300). Food intake showed significant h2 in juveniles and young adults (0.37 and 0.14, respectively); but near zero h2 in near-harvest adults. Variation in energy required for SMR showed low but significant h2 (0.13) in young and near-harvest adults. Variation in energy lost through ammonia excretion showed significant h2 in juveniles (0.33) and in near-harvest adults (0.14). Heritability for variation in the energy losses through feces was not significant. Heritabilities for growth traits were all moderate to high and significant for young and pre-harvest adults, but were not significant for juveniles. At the young adult stage, food intake was negatively and highly genetically correlated with each of the growth traits (−0.70 to −0.85); and at the near-harvest adult stage both SMR and ammonia excretion showed high-negative genetic correlations with each growth trait (−0.88 to −1.00). Thus, estimated correlated response to selection indicated that if selection was exerted for higher growth (choosing 5% best individuals), we would be indirectly selecting for abalones with lower food intake (correlated responses of −11 to −15%); or lower metabolic demands of (−14 to −24%), if the selection was applied to young or near-harvest adults, respectively. In turn, shell length could be enhanced up to 18% per generation. These results suggest that higher growth in red abalone is genetically associated with a more efficient use of food and a lower metabolic demand. The possibility to reduce food intake or metabolic demands by selecting for faster growing abalones would be a very positive development for the sustainability of this culture.