Effects of salinity on growth and metabolism in blue tilapia (Oreochromis aureus)

Abstract

Tilapia were acclimated to the water source which had 8 precipitation (ppt) of salinity in the experimental unit before the experiment started and then, they were transfered to five different saltwater (SW) treatments: SW (8 ppt), 50% SW (12 ppt), 100% SW (16 ppt), 150% SW (20 ppt), and 200% SW (24 ppt). The objectives of this study were; to investigate the effects of five different salinities on specific growth rate (SGR), weight gain (WG), food intake (FI) and survival of tilapia in the long term trial (30 days) and find out how salinity affects muscle water content, hematosomatic index (HSI), and blood chemistry (sodium, chloride, potassium, glucose, total protein and triglycerides) in the short term trial (6 to 12 h). In the long-term trial, six fish were stocked in each aquarium. They were fed with commercial feed (Bagcı trout) to satiation twice a day and individually weighed at ten-days interval. Growth rate was highest in the 50% SW (SGR 0.95 ± 0.18% per day); there was no significant difference among the first three treatments. Growth rate was lowest in 200% SW (SGR 0.23 ± 0.08% per day). Weight gain and food intake showed identical results as SGR. Survival was high in the first three groups (72.2 ±1 9.2 to 100.0 ± 0.0) but it was lowest in the 200% SW treatment (22.2±19.2%). In the short-term trial, six tilapia were placed per aquarium. They were exposed to SW, 50, 100, 150 and 200% SW treatments and the fish were gradually acclimated to salt water. Blood samples were taken to analyse plasma sodium, chloride, potassium, total protein and triglycerides. Liver and muscle samples were collected for HSI and moisture values. Plasma sodium chloride increased in parallel with salinity rise. Total protein and triglycerides significantly reduced as salinity increased. Glucose and potassium were not altered significantly. HSI and muscle water content decreased when salinity concentration was elevated. Blood chemistry demonstrated that isosmotic water concentration was between 8 and 12 ppt. Salinity did not affect HSI and moisture until it reached as much as 16 ppt (100% SW). The results show that the optimum condition for farming blue tilapia, Oreochromis aureus, both with respect to growth rate and metabolic parameters is at salinities lower than 12 ppt. This is an important finding for the tilapia industry.

Can intraspecific variations be exploited to develop salinity tolerance of Oreochromis niloticus?

“…The results of the current research agree with Küçük et al (2013) who reported that O. niloticus acclimated to 8ppt of salinity and transferred to four different salinities (12, 16, 20 and 24ppt) had no significant difference among the first three treatments while decreased growth rate was observed at 24ppt. Similarly, our results agree with Stickney, (1986) who found that O. niloticus survived after direct transferring to 50% seawater (17ppt), but not 75% (26ppt) seawater.…”

“…Metabolic rate in tilapia increased with increasing salinity, accordingly energy requirement increased and feed consumption and utilization were affected (Zikos et al,2014). In different salinities marine or freshwater fish, spend more energy to hold sodium and chloride ions in their bodies or take them off (Küçük et al, 2013).…”

Overview of Length-Weight Relationship, Condition Factor and Size at First Maturity of Nile tilapia Oreochromis niloticus (L.) in Different Water Bodies of Ethiopia: A Review

“…When the water salinity alters, fish faced biological aspect problems (lengthweight, maturity and body condition), and physiological changes (oxygen consumption and energy demand) in their environment in which they live. Because, each fish species has its own optimum salinity ranges for growth and metabolism (Küçük et al, 2013). In summary, the implication of the higher body condition indicates the higher energy content, adequate food availability, reproductive potential and favorable environmental condition as well as good water quality (Pauker and Rogers, 2004) and intensive fish stock assessment as well as watershed management like the vulnerable Lake beseka is critically important.…”

Metabolic cost of acute and chronic exposure of Nile tilapia (Oreochromis niloticus) to different levels of salinity

“…have estimated the overall energetic cost for osmoregulation in fish to be between 25 and 50% of the total cost of metabolism, the accepted hypothesis is that iso-osmotic water reduces energy utilization for osmoregulation as compared to sea water and freshwater (Semra et al, 2013). Thus, freshwater and seawater species have lower MO 2 in brackish water than in their respective natural environments (Maceina et al, 1980;Jordan et al, 1993;Gaumet et al, 1995;Morgan et al, 1997;Ern et al, 2014).…”