CobiaRachycentron canadumL. reared in low-salinity water: does dietary sodium chloride affect growth and osmoregulation?

Abstract

The effects of NaCl supplementation (0.0%, 2.5%, 5.0%, 7.5% and 10.0% dry weight of a basal diet) on growth, gill histological alterations and osmoregulation of juvenile cobia reared in low‐salinity water (5 g L−1) were assessed. At the end of the experiment, gills were sampled for Na+, K+‐ATPase activity determination and histological evaluation. In all treatments, no mortality was observed. Results showed that dietary NaCl supplementation did not alter growth. At the highest supplementations (7.5% and 10.0%), juvenile cobia showed higher feed intake and feed conversion ratio. Na+, K+‐ATPase activity was higher in fish fed the diet without salt supplementation than in those fed with NaCl‐supplemented diets. The number of chloride cells significantly increased with increasing dietary salt level, being 2.5‐fold higher in fish fed with 10.0% NaCl supplementation (41 cells mm−2) than in those from the non‐supplemented fed group (16 cells mm−2). These findings indicate that dietary salt supplementation stimulated chloride cell proliferation paralleled with a reduction in the gill Na+, K+‐ATPase activity, suggesting a possible decrease in energy consumption associated with osmoregulation. However, the suggested energy sparing did not have a significant impact on juvenile cobia growth.

Effects of Azomite‐ and Sea Salt‐Supplemented Diets on Growth, Feed Conversion Efficiency, Survival, and Resistance against Edwardsiella ictaluri in Channel Catfish Fingerlings

“…Contrary to the positive results obtained in freshwater, under saltwater rearing conditions dietary salt supplementation had no effect on growth or FCR in Barramundi Perch (Harpaz et al 2005). In Cobia Rachycentron canadum and Atlantic Salmon Salmo salar, salt supplementation did not affect feed intake, growth, or feed efficiency (Shaw et al 1975;Santos et al 2014). Dietary salt levels up to 10% had no effects on growth and feed utilization in Black Sea Bass Centropristis striata (Atwood et al 2001).…”

“…; Santos et al. ). Dietary salt levels up to 10% had no effects on growth and feed utilization in Black Sea Bass Centropristis striata (Atwood et al.…”

Fortification of an Aquafeed with Potassium Chloride Does Not Improve Survival of Juvenile Australian Snapper Pagrus auratus Reared in Potassium Deficient Saline Groundwater

“…In contrast, gilthead seabream Sparus aurata reared in low-salinity brackish waters responded positively to high additions of NaCl as evidenced by better survival and growth rate [41]. Cobia Rachycentron canadum reared at low salinity recorded an increase in feed intake and worsening FCR in response to feeds supplemented with increasing levels of NaCl [42]. The effects on cobia were attributed to lower energetic cost of osmoregulation at intermediate levels of NaCl supplementation due to increased proliferation of gill chloride cells and reduction in gill Na + -K + ATPase activity [42].…”

“…Cobia Rachycentron canadum reared at low salinity recorded an increase in feed intake and worsening FCR in response to feeds supplemented with increasing levels of NaCl [42]. The effects on cobia were attributed to lower energetic cost of osmoregulation at intermediate levels of NaCl supplementation due to increased proliferation of gill chloride cells and reduction in gill Na + -K + ATPase activity [42]. Dietary supplementation of NaCl was effective in improving FCR and weight gain of the euryhaline red drum Sciaenops ocellatus when the fish were reared in fresh or brackish-water, but not when the fish were reared in seawater [43].…”

Effects of salinity on growth characteristics and osmoregulation of juvenile cobia, Rachycentron canadum (Linnaeus 1766), reared in potassium‐amended inland saline groundwater

“…Cobia, Rachycentron canadum (Linnaeus, 1766), is a large migratory pelagic fish widely distributed in tropical, subtropical, and warm temperate seas around the world, except the Mediterranean Sea and the central and eastern Pacific Ocean (Hassler & Rainville, 1975; Shaffer & Nakamura, 1989). Cobia are an important species for cage and other intensive aquaculture production systems because of their large size (Denson, Stuart, Smith, Weirlch, & Segars, 2003), excellent meat quality (Chen, 2001), high market value (Liao et al, 2004), fast growth rate (Chou, Su, & Chen, 2001; Franks, Warren, & Buchanan, 1999), adaptability to production systems (Santos et al, 2012), ease of captive reproduction (Liao, Su, & Chang, 2001), and high demand for fillets and sashimi (Chou et al, 2001; Gopakumar et al, 2010). Salinity is an important environmental variable affecting the growth, survival, and feed intake of fishes (Arunachalam & Reddy, 1979; Boeuf & Payan, 2001; Lambert, Dutil, & Munro, 1994).…”