Diet of marine ﬁsh larvae and juveniles that use rocky intertidal pools at the Portuguese coast By M. Dias 1 , A. Silva 2 , H. N. Cabral 1 and C. Vinagre 1 1 Centro de Oceanograﬁa, Faculdade de Ci^ encias, Universidade de Lisboa, Campo Grande, Lisboa, Portugal; 2 CVRM-Centro de Geosistemas, Departamento Engenharia Civil, Arquitectura e Georecursos, Instituto Superior T ecnico, Universidade de Lisboa, Lisboa, Portugal Summary The use of tidal pools during early ontogeny is likely to enhance growth, condition and survival chances of the tran- sient marine ﬁsh larvae and juveniles that use them. How- ever, the diet of such individuals within tidal pools is poorly known; this knowledge is important to understand why such high numbers of individuals use these environments in spring and summer on the Portuguese coast. Transient marine ﬁshes were sampled monthly over a two-year period in four tidal pools of a rocky reef on the west Portuguese coast. The diet composition in the tidal pools of the most abundant marine ﬁsh larvae/juveniles, Diplodus sargus and Atherina spp., were investigated. Stomach and gut contents of 483 individuals (354 D. sargus ranging in total length from 9 to 87 mm and 134 Atherina spp. ranging in total length from 10 to 31 mm) were analyzed and dietary indices estimated for the diﬀerent developmental stages. The diet of D. sargus composed mainly harpacticoid copepods, chironomid larvae, ostracods, chiron- omid adults and amphipods; whereas the diet of Atherina spp. was mainly harpacticoid copepods, ostracods and gas- tropods. Along the ontogenetic development, the proportions and diversity of food items in the D. sargus diet varied. Importance of the harpacticoid copepods decreased with increasing ﬁsh size, while that of amphipods and isopods increased. Larvae and juvenile D. sargus and Atherina spp. found in rocky reef tidal pools are opportunistic consumers of a wide range of prey and thus take advantage of the high prey availability in these habitats. Introduction Ontogenetic shifts in habitat use are a common pheno- menon in marine ﬁshes (Beck et al., 2001; Gillanders et al., 2003) and occur as an adaptive response to reduce predation, enhance food availability and reduce competition (Clark, 1974; Cushing, 1975; Lenanton, 1982; Boesch and Turner, 1984; Macpherson, 1998). Several species of ﬁsh use nursery grounds in the larval and juvenile stages, moving to subtidal waters as adults (Randall, 1955; Norris, 1963; Major, 1978). The use of tidal pools during early ontogeny is likely to enhance growth, condition and survival chances of the indi- viduals that use them (Thompson and Lehner, 1976; Mor- ing, 1986, 1990; Gibson, 1994; Mahon and Mahon, 1994; Macpherson, 1998; Strydom, 2008). These habitats are highly structured, with many crevices, holes and macroalgae that make them spatially complex. In this way they provide refuge, and have a high biodiversity and abundance of potential prey. During spring and summer, the tidal pools warm during the ebb tide, attaining temperatures more favorable for ﬁsh growth than those of subtidal waters (Beckley, 1985a; Moring, 1986; Amara and Paul, 2003; Cunha et al., 2007). Rapid growth enables young ﬁshes to seek refuge and avoid a major part of the size-selective pre- dation (Pihl and Van der Veer, 1992; Gibson, 1994; Leggett and DeBlois, 1994; Van der Veer et al., 1994). Various coastal habitats are well known to be nurseries for juvenile marine ﬁsh (Clark, 1974; Lenanton, 1982). These include estuaries (Wallace and Van Der Elst, 1975; Day et al., 1981; Wallace et al., 1984; Costa and Bruxelas, 1989; Vinagre et al., 2010), coastal lagoons (Franco et al., 2006; Abecasis et al., 2009; Ribeiro et al., 2012), salt marshes (Vei- ga et al., 2006), coral reefs (Nagelkerken et al., 2000), man- groves (Nagelkerken et al., 2000; Dorenbosch et al., 2004), surf zone reefs (Berry et al., 1982), seagrass beds (Nagelker- ken et al., 2000; Dorenbosch et al., 2004; Verweij et al., 2008) and the sandy beach surf zone (Lasiak, 1981, 1983). Estuarine nurseries are the best documented to date, with numerous studies from as early as the larval phase of numer- ous ﬁsh species (e.g. Miskiewicz, 1986; Roper, 1986; Boehlert and Mundy, 1988; Whitﬁeld, 1994; Harris and Cyrus, 2000). Rocky tidal pools are probably the least studied nurseries for marine ﬁsh, leaving a considerable research void worldwide. Several studies were developed for rocky tidal pools that included transient juvenile ﬁsh. However, newer studies are scarce, which indicates that the scientiﬁc community has not focused on these habitats in recent years. Published works concern transient ﬁsh recruitment in the tidal pools of South Africa (Beckley, 2000) and New Zealand (Willis and Roberts, 1996); species diversity and seasonal changes in Brazil (Bar- reiros et al., 2004), India (Tsering et al., 2012) and California (Moring, 1986); community structure in Colombia (Castell- anos-Galindo et al., 2005), Australia (Griﬃths, 2003a), Azores (Santos et al., 1994), Japan (Murase, 2013), Barbados (Mahon and Mahon, 1994) and Brazil (Cunha et al., 2008); spatial and temporal dynamics in Australia (Griﬃths, 2003b) and Japan (Arakaki and Tokeshi, 2006); spatial and vertical U.S. Copyright Clearance Centre Code Statement: 0175-8659/2014/3005–970$15.00/0 J. Appl. Ichthyol. 30 (2014), 970–977 © 2014 Blackwell Verlag GmbH ISSN 0175–8659 Received: October 23, 2013 Accepted: January 20, 2014 doi: 10.1111/jai.12450 Applied Ichthyology Journal of