Abstract
The acute toxicity of lead nitrate to grass carp (Ctenopharyngodon idella) juveniles was assessed in a static renewal bioassay for 96 h. In addition, an experiment was conducted to determine the growth performance during 60-day sublethal (Pb(NO3)2) exposure. The results indicated that median lethal concentration (LC50) of lead nitrate to Grass carp for 96 h of exposure was 246.455 µ. The chronic exposure to sublethal concentration of lead nitrate to the studied fish showed a significant decrease in final body weight in comparison to control group. The lead nitrate also had significantly decreased effect on body weight in comparison to the control. Also, the food conversion ratio (FCR) was significantly increased in comparison to control (P < 0.05). The lead nitrate also caused a significant decrease in the survival rate (P < 0.05). Key words: Lethal concentration (LC50), lead nitrate, growth, grass carp, Ctenopharyngodon idella.
Highlights
Heavy metals have long been recognized as serious pollutants of the aquatic environment
Acute toxicity of lead showed that mortality is directly proportional to the concentration of the lead nitrate while the percentage of mortality is virtually absent in control (Table 2) showing the relation between the lead concentration and the mortality rate for 96 h of Grass carp
Results according to SPSS18 analysis showed that the median lethal concentration (LC50) of lead nitrate to Grass carp for 96 h of exposure is 246.455 μ (Table 3)
Summary
Heavy metals have long been recognized as serious pollutants of the aquatic environment. The accumulation of metals in the aquatic environment has direct effect on man and aquatic ecosystem. Heavy metal contamination usually causes depletion in food utilization in fish and such disturbance may result in reduced fish metabolic rate and cause reduction in their growth (Javed, 2005a). The present work was design to investigate acute toxicity and toxic effect of lead on the growth performance of Grass carp under chronic sublethal concentrations to evaluate its potential to growth in contaminated water. Metal concentrations in aquatic organisms appear to be of several magnitudes, higher than concentrations present in the ecosystem (Laws,2000) and this is attributed to bioaccumulation whereby metal ions are taken up from the environment by the organism and accumulated in various organs and tissues. Metals are non-biodegradable and considered as major environmental pollutants causing cytotoxic, mutagenic and carcinogenic effects in animals (More et al, 2003)
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