Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Feeding the lined seahorse Hippocampus erectus with frozen amphipods Jorge Arturo Vargas-Abúndez a , Nuno Simões b, ⁎ , Maite Mascaró b a Posgrado en Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, 04510 Mexico City, Mexico b Unidad Multidisciplinaria de Docencia e Investigación (UMDI-Sisal), Facultad de Ciencias, Universidad Nacional Autónoma de México, Sisal, Yucatán, Mexico ARTICLE INFO Keywords: Seahorse Frozen food Amphipods Prey size Ingestion rates ABSTRACT Amphipods are a natural and alternative feed in aquaculture but their potential use is limited by lack of knowledge of feeding regimes. The present study provides a feeding regime of frozen amphipods (Elasmopus pectenicrus) for the lined seahorse Hippocampus erectus, the second most traded species worldwide. Ingestion rates of amphipods were measured to establish the optimal amphipod size, duration of feeding and feed ration. Use of large amphipods (8.7 ± 1.1 mm total length) increased the total ingested biomass in fish of 60–110 mm stan- dard length, compared to medium and small amphipods, in accordance with previously suggested relative sizes. The highest feeding activity occurred during the first 12 min. Fish ingested 4.5 ± 2.3% their wet weight, which is similar to the feed ration previously proposed for other seahorse species. The present study supports the potential of amphipods as a feed in aquaculture and will aid their use in culture protocols. 1. Introduction Seahorses are threatened by a global demand for traditional medi- cine, curio and aquarium display (Kumaravel et al., 2012; Lourie et al., 1999; Vincent et al., 2011), notwithstanding they are highly vulnerable to overfishing and habitat degradation, because of their unique life history (Foster and Vincent, 2004). As a consequence, most seahorse species have been included in the IUCN Red list of Threatened Species (IUCN, 2016) and in the Appendix II list of endangered species by CITES (Convention for the International Trade in Endangered Species). Among different conservation strategies, aquaculture is of great interest be- cause it is already a common source for aquarium display and may potentially become important for the medicine and curio markets (Cohen et al., 2017; Koldewey and Martin-Smith, 2010; Olivotto et al., 2017). In seahorse aquaculture, live food is indispensable for the early ju- veniles (Calado et al., 2017; Cohen et al., 2017; Olivotto et al., 2008a). Different live preys such as Artemia, rotifers, harpaticoid copepods and mysid larvae have been used, but Artemia and rotifers are by far the most commonly used preys because of their small size and due to the fact that they can be easily cultured in large quantities at high densities (Olivotto et al., 2008b; Planas et al., 2017b). However, their culture is expensive, time consuming and their nutritional profile do not always meet the nutritional requirements of seahorses, despite the nutritional profile of Artemia and rotifers can be enhanced by enrichment proce- dures. For these reasons, identifying suitable live preys for the early rearing of seahorses is a major challenge in aquaculture (Calado et al., 2017). For later stages, frozen foods can ensure constant supply and reduce costs (Olivotto et al., 2010; Woods and Valentino, 2003). Indeed, ani- mals adapted to eat frozen food in captivity may be more valuable for consumers (mainly hobbyists), since non-dependency on live food can simplify rearing and improve survival, thereby reducing requirements when seahorses need to be replaced (Lin et al., 2009b; Payne, 2003). The optimal time for weaning from live to frozen foods has been de- termined for several seahorse species (Lin et al., 2009a; Payne, 2003; Thuong and Hoang, 2015; Woods, 2003; Woods and Valentino, 2003). Unfortunately, commonly used frozen foods (e.g. Artemia, Mysis and rotifers) do not always have the proper nutrient content for all seahorse species, and frequently do not stimulate their feeding behavior, re- sulting in poor growth and fish survival (Thuong and Hoang, 2015). The natural diet of most seahorses species consists of amphipods and copepods (Gurkan et al., 2011; Kitsos et al., 2008; Koldewey and Martin-Smith, 2010; Storero and Gonzalez, 2009; Teixeira and Musick, 2001; Valladares et al., 2017), and amphipods have been attracting interest as an alternative natural food in aquaculture (Baeza-Rojano et al., 2013a, 2010; Woods, 2009) mainly because their culture may be easier and cheaper than commonly used foods. Most amphipod species are detritivores, and despite their low fecundity, they have high re- production and growth rates due to relative large embryos and parental care and reproductive strategies that are generalized throughout the group (Woods, 2009). Furthermore, they can be cultured at high den- sities using artificial substrate and can tolerate wide fluctuations in temperature and salinity (Baeza-Rojano et al., 2013a, 2013b, 2011; https://doi.org/10.1016/j.aquaculture.2018.02.043 Received 1 January 2018; Received in revised form 21 February 2018; Accepted 25 February 2018 ⁎ Corresponding author. E-mail address: ns@ciencias.unam.mx (N. Simões). Aquaculture 491 (2018) 82–85 Available online 09 March 2018 0044-8486/ © 2018 Elsevier B.V. All rights reserved. T