SHORT COMMUNICATION: Effects of salinity on growth and survival of common snook Centropomus undecimalis (Bloch, 1792) larvae

Common snook Centropomus undecimalis, herein referred to as ‘snook’, are a stenothermic estuarine ¢sh found in the tropical and subtropical waters of North and South America (Rivas 1986). In Florida, adult snook spawn primarily in the spring and summer months from April through September (Taylor, Grier & Whittington 1998). Spawning events occur at inlets and tidal passes of estuaries and along sandy beaches (Taylor et al. 1998). Eggs and larvae of snook are thought to disperse from spawning areas by tidal and wind-driven currents (Tolley, Dohner & Peebles 1987). In Florida, a small number of pre£exion and post-£exion snook larvae have been collected in nearshore waters, whereas young juveniles recruit to a variety of saltwater, brackish and freshwater shoreline habitats (Gilmore, Donohoe & Cooke 1983; Peters, Matheson & Taylor1998). In Florida, snook play an important role in supporting one of the state’s highly popular recreational ¢sheries, and declining populations in the Gulf of Mexico have led to concern among resource managers (Muller & Taylor 2006). Over the years, increased ¢shing pressure and habitat loss (Bruger & Haddad1986) have spurred a renewed interest in investigating the feasibility of snook stock enhancement (Brennan, Walters & Leber 2008). Although snook have been identi¢ed as a candidate for aquaculture, high mortalities in the early larval stage remains a culture constraint (Wittenrich, Rhody, Turingan & Main 2009). Despite initial successes in arti¢cial propagation and rearing of snook (Lau & Sha£and 1982; Neidig, Skapura, Grier & Dennis 2000), the development of reliable hatchery methods for intensive rearing through larval and juvenile stages is necessary. Salinity can strongly in£uence physiological processes and morphological developments in marine ¢n¢sh (reviews in B uf & Payan 2001;Varsamos, Nebel & Charmantier 2005). The successful establishment of a species in a given habitat depends ‘on the ability of each developmental stage to cope with changes in salinity through osmoregulation’ (Varsamos et al. 2005, p.401). Most marine ¢n¢sh larvae are able to osmoregulate at hatching (Alderdice 1988). Functional capability of osmoregulation improves throughout ontogeny as specialized tissues and organ systems develop, where the primary site for ionic regulation shifts from the skin to the gills (Rombough 2004). Because osmoregulation is an energydemanding process, in some species, energetic cost is thought to be lower at iso-osmotic salinities. Here, gradients between body £uids and the external environment are minimal (Holliday 1969), and more energy is available for growth and/or survival. However, results vary among species, within species and across developmental stages. Studies with gilthead seabream Sparus aurata (Tandler, Anav & Choshniak 1995), fat snook Centropomus parallelus (Araujo, Cerqueira & AlvarezLajonche' re 2000), haddock Melanogrammus aegle¢nus (Opstad 2003) and Brazilian £ounder Paralichthys orbignyanus (Sampaio, Freitas, Okamoto, Louzada, Rodrigues & Robaldo 2007) larvae showed an increase in survival or growth at intermediate salinities ( 15 but 30 g L ). Others found improved growth or survival at higher salinities ( 34 g L ), such as Aquaculture Research, 2010, 41, e357^e360 doi:10.1111/j.1365-2109.2010.02511.x