Seasonal variations in the body composition and bioaccumulation of heavy metals in Nile tilapia collected from drainage canals in Al-Ahsa, Saudi Arabia

Abstract

The body composition of Nile tilapia (Oreochromis niloticus) collected from drainage canals in Al-Ahsa, Saudi Arabia and the concentration of four heavy metals; zinc (Zn), cadmium (Cd), cobalt (Co) and lead (Pb) in both fish muscles and the water collected from this environment were assessed across the four seasons. The body composition was found to change with the seasons, with the best body composition being recorded in autumn and winter, where higher levels of protein (17.24, 17.65%), and fat (0.58, 0.71%) and lower water content (80.15, 79.86%) respectively were noted. The concentration of heavy metals in both fish muscles and the water body also varied significantly with the seasons. In the fish muscles, the highest content of Zn (0.409 mg/kg dry weight) and Cd (4.140 mg/kg dry weight) was recorded in winter, however, the highest concentration of Co (0.318 mg/kg dry weight) and Pb (1.96 mg/kg dry weight) was observed in spring and summer respectively. On the other hand, the water samples collected in autumn showed the maximum concentration of Cd (1.385 mg/L), Co (0.762 mg/L) and Pb (0.18 mg/L) however, the maximum concentration of Zn (0.0041 mg/L) was recorded in winter. With the exception of Cd, the accumulation of the studied heavy metals in fish muscles was within the safe limits for seafood recommended by various organizations.

Physico-chemical and microbiological changes in commercial tilapia (Oreochromis niloticus) during cold storage

“…The protein content found in this study (19.1%) was higher than the values reported in other studies on tilapia (38). However, the moisture content in this work was lower than those found by Younis et al (2015) (38) and Fonseca et al, (2013) (41), which could explain the differences found in in lipid and protein contents.…”

“…According to these results, tilapia can be classified as a lean fish because its fat content is below 2 g fat/100 g. However, in the present study tilapia showed a lipid content of 2.8% and should, therefore, be classified as low-fat fish (total lipid content from 2% to 4%) (40). The protein content found in this study (19.1%) was higher than the values reported in other studies on tilapia (38). However, the moisture content in this work was lower than those found by Younis et al (2015) (38) and Fonseca et al, (2013) (41), which could explain the differences found in in lipid and protein contents.…”

“…Taking into account this limit, the shelf life of tilapia used in this study would be lower than 7 days. In other studies on tilapia (38,41,44), this limit has been reached after a longer period of time. This is due to that in this work the day 0 of study was not the slaughter day, but the day of purchase in the supermarket.…”

“…Regarding the fat content, Puwasatien et al (1999) (19) reported that tilapia muscle contained 1.8% of fat. Visentainer et al (2005) (39) and Chaijan (2011) (20) reported even lower lipid contents (1.09 and 1.10%, respectively), Younis et al (2015) (38) reported values lower than 1% of fat. According to these results, tilapia can be classified as a lean fish because its fat content is below 2 g fat/100 g. However, in the present study tilapia showed a lipid content of 2.8% and should, therefore, be classified as low-fat fish (total lipid content from 2% to 4%) (40).…”

“…The chemical composition of tilapia is highly affected by: season, environmental conditions, water quality, state of maturity, feeding conditions or sex (37,38). Regarding the fat content, Puwasatien et al (1999) (19) reported that tilapia muscle contained 1.8% of fat.…”