Stress correlated factors with water quality under different rearing conditions of the European sea bass (Dicentrarchus labrax) juveniles

A. Sallam, Ghada; A. Aly, Hadir; M. Fayed, Walied; B. Elhefnawy, Wael; E. Khalid, Asmaa; A. Omar, Eglal

doi:10.21608/ejabf.2020.72712

Stress correlated factors with water quality under different rearing conditions of the European sea bass (Dicentrarchus labrax) juveniles

Document Type : Original Article

Authors

10.21608/ejabf.2020.72712

Abstract

Water exchange rates were manipulated to reduce the negative effect of high stocking density adversely affects the rearing condition such as water exchange rates has to be manipulated to elevate stress factors. European sea bass juveniles with an average body weight of 4.5 g fish/m³ were stocked at three densities (50, 100 and 150 fish/m³)in 12 concrete ponds. Two water exchange rates (20% and 30% of total water volume) were applied for 18 weeks to investigate their influence on reducing the negative effect of stocking density and enhancing the water quality. The results indicated that the 30% water exchange rate was better for achieving high growth performance and feed utilization, regardless of stocking density. Water quality (total ammonia nitrogen, un-ionized ammonia, nitrite and nitrate) was enhanced, dissolved oxygen increased and all harmful nitrogen derivatives decreased when the 30% water exchange rate was applied. Additionally, the 30% water exchange rate significantly increased the water temperature (16.33°C) compared to the 20% exchange rate (14.33°C), and the final body weight, weight gain and specific growth rate were significantly increased (P<0.05) with the 30% water exchange rate. The survival rate was 97%, which was significantly the highest at the density of 50 fingerlings/m³ at a water exchange rate of 30%. Although the feed conversion ratio, protein efficiency ratio, and protein productive value significantly improved with the 30% water exchange rate at all densities, the 100 fish/m³ stocking density achieved the best feed conversion ratio. However, the haematological parameters showed a significant increase (P<0.05) in haemoglobin, haematocrit, white blood cells, lymphocytes, monocytes and neutrophils with a low stocking density and a 30% water exchange rate.

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