Lethal and sub-lethal effects of DDT, carbofuran, trifenmorph and niclosamide on oreochromis niger gunther (1898)
Abstract
Oreochromis niger fry were exposed to various
concentrations of DOT, Carbofuran, Trifenmorph and
Niclosamide to determine the toxicity of these
chemicals to the fish. The concentration lethal to
50% of the fish population in a given time range
24 hrs - 96 hrs, for each of the chemicals, was
determined. The growth and swimming patterns of
these fish in sub - lethal concentrations of the
biocides were also studied.
DOT was found tobe the most poisonous to fish
with a 24 hr LC 50 of 0.042mg/litre. Carbofuran was
the least toxic with an LC 50 of 0.225 mg/litre. The
toxicity of all the four chemicals increased with
concentration and time.
The swimming. activity of the fish decreased with
time in all the experiments except in Niclosamide.
There was a negative linear relationship between fish
activity and time.
The fish increased weight very slowly from the
first to the fifth week. Growth or increase in fish
weight had a positive linear relationship with time
in all the experiments. Increase in weight was however
slower in the treatments than in the control except
in sub - lethal levels of Carbofuran. The experiment
shows that fish cannot be grown in water containing
sub - lethal amounts of DOT, Trifenmorph and
Niclosamide as they are highly toxic. The fish safe
levels would be too low for the control of snails.
Citation
MSc.Publisher
University of Nairobi Faculty of Science