Abstract
The effects of four different salinities (SW, 50% SW, 100% SW and 150% SW) on specific growth rate, weight gain, food intake and survival of goldfish and crucian carp were investigated for 20 days. Both species were respectively adapted to water source, which has salinity of 8 ppt in the experimental unit for one month and then transferred to SW (8 ppt), 50% SW (12 ppt), 100% SW (16 ppt) and 150% SW (20 ppt) experimental treatments. Four goldfish fish and three crucian carp fish were placed in each aquarium. They were fed with commercial feed (Tetra Pond) to satiation twice a day and individually weighed at weekly interval. The final weight of the goldfish reared in the SW (938 ± 486 mg) and 50% SW (723 ± 269 mg) was significantly larger than that of fish reared in the 100% SW (475 ± 114 mg) and 150% SW (106 ± 318 mg). The specific growth rate was the highest in the SW (SGR: 0.53 ± 0.270% day-1) and the lowest in the 150% SW (SGR: 0.06 ± 0.195% day-1). Food intake was higher in the first three treatment groups (10.33 ± 0.572; 10.86 ± 0.917; 10.17 ± 0.767 g, respectively) than in the 150% SW (7.75 ± 1.612 g). Survival was not significantly different in the four salinity treatments (81.20 ± 23.94 ton 100.00 ± 0.00%). The final weight of the crucian carp breeding in the SW (860 ± 220 mg) and 50% SW (848 ± 394 mg) were significantly higher than the other two treatment groups. It was the worst in the 150% SW (-15 ± 903 mg). Specific growth rate was higher in the SW (SGR: 0.22 ± 0.040% day-1) and 50% SW (SGR: 0.30 ± 0.103% day-1) than the other two treatment groups. It was the lowest in the 150% SW (-0.06 ± 0.300% day-1). Food intake was higher in the first three treatment groups (8.70 ± 1.352; 7.25 ± 0.540; 7.06 ± 0.647 g, respectively) than in the 150% SW (5.60 ± 1.875 g). Survival was significantly influenced in the 150% SW (83.33 ± 19.24%). In conclusion, both species can be transferred to brackish water having not more than 8 ppt salinity. The maximum salinity tolerances of goldfish and crucian carp were 20 ppt. These findings are important in aquarium fish industry. Key words: Goldfish, crucian carp, salinity, growth, survival.
Highlights
Growth is controlled by environmental factors such as temperature, photoperiod and salinity in fish (Fry, 1971)
Specific growth rates were 0.53, 0.34 and 0.27% day-1 in the salinities of SW, 50% SW and 100% SW, respectively
Fish growth was strongly influenced in the 150% SW as seen in Specific growth rate (SGR) (0.06% day-1) and Weight gain (WG) (Figure 1)
Summary
Growth is controlled by environmental factors such as temperature, photoperiod and salinity in fish (Fry, 1971). If salinity is too high or too low in the external environment than fish body fluid (depending on fresh water or marine fish), fish spends more energy to regulate osmotic balance. Less energy remains for growth in these environments because of the use of too much energy for active ion transport. Four hormones (gonadothropin hormone, cortisol, insulin-like growth factor 1 and thyroid hormones) take a role in osmotic regulation (McCormick, 2001).Salinity is defined as the total concentrations of all ions in water. It is not just the concentration of sodium chloride in water
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