Aquaculture Research. 2019;00:1–8. wileyonlinelibrary.com/journal/are | 1 © 2019 John Wiley & Sons Ltd 1 | INTRODUCTION The sea cucumber Apostichopus japonicus is the most profitable spe‐ cies cultured in China were produced around 10.000 tons dry weight in 2010 (Hu et al., 2010; Zhou et al., 2017). In the mid‐80s, the Chinese government initiated a national industrial breeding program focused on this species, that allowed during the following decades import‐ ant development and improvement of its aquaculture to overcome the different bottlenecks and reach the actual production (Hu et al., 2010; Mou, Li, Liu & Wang, 2000). Holothuria scabra is the second largely produced sea cucumber species in aquaculture with a current production of 130 tons/year (Robinson & Lovatelli, 2015). However, many other sea cucumbers, such as Actinopyga miliaris, A. mauriti‐ ana, Australostichopus mollis, H. fuscogilva, H. mammata, H. spinifera, H. tubulosa, Isostichopus badionotus, I. fuscus, Parastichopus californi‐ cus and Stichopus horrens, are target species for aquaculture devel‐ opment around the world, though most of them are in their early stage (Domínguez‐Godino & González‐Wangüemert, 2018a; Purcell, Hair & Mills, 2012; Rakaj et al., 2018; Zacarías‐Soto, Olvera‐Novoa, Pensamiento‐Villarauz & Sánchez‐Tapia, 2013). Hatchery culture techniques of larvae and juveniles are the main bottlenecks of sea cucumber aquaculture. Species‐specific Received: 18 December 2018 | Revised: 14 June 2019 | Accepted: 9 July 2019 DOI: 10.1111/are.14267 ORIGINAL ARTICLE Improving the fitness of Holothuria arguinensis larvae through different microalgae diets Jorge A. Domínguez‐Godino | Mercedes González‐Wangüemert Centro de Ciências do Mar (CCMAR), MARESMA Team, Universidade do Algarve Gambelas, Faro, Portugal Correspondence Jorge A. Domínguez‐Godino, Centro de Ciências do Mar (CCMAR), MARESMA Team, Universidade do Algarve Gambelas, 8005‐139 Faro, Portugal. Email: jorge.adg86@gmail.com Funding information Sayanes Mar S.L.; Fundação para a Ciência e a Tecnologia, Grant/Award Number: CCMAR/BI/0007/2015 and IF/00998/2014; CUMARSUR, Grant/Award Number: PTDC/ MAR‐BIO/5948/2014 Abstract Development and design of adequate feeding protocols on sea cucumber larvae are necessary for improvements on larvae growth, survival and production of competent juveniles. This work assessed the Holothuria arguinensis larvae growth and survival, fed with three different single microalgae diets of Chaetoceros calcitrans, Isochrysis galbana and Tetraselmis chui, and two microalgae diets based on a combination of C. calcitrans and T. chuii (C:T; 1:1) and C. calcitrans, T. chuii and I. galbana (C:T:I; 1:1:1) during 2 months. Holothuria arguinensis larvae fed with T:C:I, showed higher survival and larger larval and stomach sizes than the ones fed with the other diets. Comparing the results obtained from the single diets, H. arguinensis larvae fed with I. galbana grew and survived better during the first 5 days. However, higher growth was ob‐ tained on the larvae fed with C. calcitrans from day 5 to day 12; since this day, larvae fed with T. chuii showed the largest size. These results could be related to the dif‐ ferent microalgae size and morphology, in addition to the nutritional value of the different microalgae used. However, no competent larvae that metamorphosed into doliolaria were obtained during this experiment. The tanks used were transparent, which could be causing light stress to the larvae, since competent larvae were ob‐ tained in opaque production tanks in our aquaculture installations during the same time period. The combined diet of C. calcitrans, T. chuii and I. galbana (C:T:I) could improve the growth and larvae competency of H. arguinensis. KEYWORDS growth, Holothuria arguinensis, larvae, microalgae, sea cucumber, survival