Abstract

Sustainable aquaculture and restocking of the sea urchin Loxechinus albus will demand a reliable source of highquality juveniles. Culture techniques for L. albus must be refined on several levels to scale up to commercial production. In this study, the effects of different natural foods (six algal foods and one animal food) and the feeding frequency (three regimes: one continuous and two intermittent) on the growth and feeding of L. albus juveniles with a test diameter of ca. 5 mmbelonging to a single 5-month-old cohort were investigated. Juveniles fed with Rhodophyta: Porphyra sp. and Gracilaria chilensis grew significantly faster (wet body weight and test diameter) than those fed other foods, although these food items are not frequently observed in the gut contents ofwild populations. Juveniles fed with Macrocystis pyrifera showed the lowest growth rates. Differences in ingestion rates and the food conversion ratio (FCR) were principally associated with organic matter and protein content in foods. Although L. albus have been described as generalist herbivores, in this study, they ingested an animal food (marine sponge) and were able to grow significantly better than juveniles fed with M. pyrifera. Juveniles did not show evidence of a compensatory mechanism with a decrease in the frequency of food availability. The growth, ingestion rates and FCR in early juveniles were positively related with feeding frequency, suggesting that continuous feeding is the best and most efficient dietary treatment in terms of growth. Porphyra sp. and G. chilensis, as single species diets, are promising alternatives for the development of cultures of L. albus juveniles; however, further studies are required to compare the efficient use of algae as food (e.g., versus artificial feeds).