Effects of food type and feeding frequency on the performance of early juveniles of the sea urchin Loxechinus albus (Echinodermata: Echinoidea): Implications for aquaculture and restocking P. Francisco Cárcamo 1 Departamento de Medio Ambiente, Instituto de Fomento Pesquero, Doctor Marín 340, Coquimbo, Chile abstract article info Article history: Received 30 May 2014 Received in revised form 15 October 2014 Accepted 29 October 2014 Available online 15 November 2014 Keywords: Algal foods Food conversion rate Aquaculture Feeding regimes Juvenile sea urchin Loxechinus albus Sustainable aquaculture and restocking of the sea urchin Loxechinus albus will demand a reliable source of high- quality juveniles. Culture techniques for L. albus must be refined on several levels to scale up to commercial pro- duction. 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 mm belonging 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 of wild pop- ulations. 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). © 2014 Elsevier B.V. All rights reserved. 1. Introduction The edible sea urchin, Loxechinus albus (Molina, 1782), is the only commercially valuable sea urchin species in Chile, and its fishery is the largest in the world (Moreno et al., 2007). This species is distributed from the coast of Peru (6° S) to the southern tip of Chile (55° S) and from the intertidal zone down to 106 m in depth (Larraín, 1975; Moreno and Molinet, 2013). Along the Chilean coast, it is harvested ex- clusively by artisanal fishermen and is a species of great economic and social importance (Moreno et al., 2007). Landings have decreased from 60,000 tons in 2002 to 29,000 tons in 2012. 2 The depletion of tra- ditional fishing grounds has encouraged the migration of fishermen to distant parts of southern Chile in search of new natural beds to exploit (Moreno et al., 2007, 2011; Stotz, 2004). The overexploitation of this sea urchin under the present management strategies makes its sustain- ability uncertain over the long term (Moreno et al., 2007; Stotz, 2004). However, Chilean fishermen have recently shown a great interest in the implementation of sea urchin restocking programs (Cárcamo, 2004b). For instance, pilot experiments in which hatchery-reared juvenile sea urchins are experimentally seeded have been conducted independently in management areas for benthic resources; however, the outcomes have been uncertain (Jerez and Figueroa, 2007). Several studies have attempted to develop techniques for L. albus culture, including larval and juvenile production (Bustos et al., 1991; Cárcamo, 2004b; Cárcamo et al., 2005; González et al., 1987; Zamora and Stotz, 1994) and enhancement of gonad quality (Cárcamo, 2004a; Lawrence et al., 1997; Olave et al., 2001). However, one bottleneck to develop- ment of the urchin culture that has been identified in a number of coun- tries is the long period required to rear urchins to market size (Bustos et al., 1991; Lawrence et al., 2001). The quantity and quality of food (Fernandez and Boudouresque, 2000; Frantzis and Grémare, 1993; Lowe and Lawrence, 1976), and the feeding frequency (Lawrence et al., 2003) can influence the physiol- ogy and growth of sea urchins. L. albus is one of the most important ben- thic herbivores in intertidal and shallow subtidal rocky environments along the Chilean coast (Vásquez, 2007). Some studies have investigated feeding and nutritional ecology in adults of L. albus (Bückle et al., 1980; Contreras and Castilla, 1987; González et al., 2008; Vásquez et al., 1984) and in juveniles greater than 20 mm in test diameter (González Aquaculture 436 (2015) 172–178 E-mail address: francisco.carcamo@ifop.cl. 1 Tel.: +56 51 2544730; fax: +56 51 2544313. 2 Review of landings according to official information provided by the Chilean National Fisheries Service (www.sernapesca.cl). http://dx.doi.org/10.1016/j.aquaculture.2014.10.045 0044-8486/© 2014 Elsevier B.V. All rights reserved. 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