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Toxicity of ammonia and nitrite to silver perch (Bidyanus bidyanus)

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Frances, Jane (1998) Toxicity of ammonia and nitrite to silver perch (Bidyanus bidyanus). Unspecified thesis, University of Tasmania.

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Abstract

Acutely toxic concentrations (LC 50) of ammonia and nitrite were estimated for
juvenile silver perch (Bidyanus bidyanus) during 96h experiments. Additional
experiments were conducted for at least 25 days to determine the growth-limiting
concentrations of ammonia and nitrite for juvenile silver perch. Furthermore, the
effects of exposure to metabolic and reagent ammonia were compared. Gill
histopathology was examined in each experiment to determine if changes in gill
structure correlated with exposure to toxicant, and whether gill histopathology was a
useful indicator of sub-acute intoxication for this species.
The acutely toxic concentration (LC 50) of un-ionised ammonia (UAN) was defined as
the concentration at which silver perch lost the ability to orientate. At this point, fish
were removed from the experiment, as preliminary research had shown that
prolonged exposure beyond this point always led to death. The LC 50 was estimated
to be 1.2 mg L-1 UAN. The acutely toxic concentration (LC 50) of nitrite was
estimated to be 160 mg L-1NO2 -N.
Following a 39 day exposure, growth (wet weight gain) of juvenile silver perch was
reduced at concentrations of ammonia above 0.36 mg L-1 UAN. There was no
significant difference in wet weight gain of control fish or those exposed to 0.02 mg
L-1 metabolic ammonia. Growth of silver perch exposed to nitrite at concentrations
above 1.43 mg L -1N02 -N for 25 days was reduced.
Following acute exposure to ammonia, there was a significant increase in the
percentage of filaments affected by epithelial lifting, but no other significant change
in gill histopathology was observed. Acute exposure to nitrite resulted in no
significant changes in gill histopathology, although macroscopic observation
indicated browning and discolouration of gill tissue at concentrations above 130 mg
L-1NO2 -N.
After 39 days' exposure to ammonia, there was an increase in the occurrence of
epithelial lifting, while no other index of gill histopathology was significantly
different. Exposure to metabolic ammonia also increased the percentage of filaments
affected by epithelial lifting. Following 25 days' exposure to nitrite, there was a
significant difference in the percentage of gill filaments affected by epithelial lifting
and hypertrophy.
These results indicate critical concentrations of ammonia and nitrite which will assist
in the management of nitrogenous wastes in pond or tank culture of silver perch.
Understanding of these concentrations may increase production and reduce the
incidence of critical water quality conditions.

Item Type: Thesis (Unspecified)
Keywords: Nitrites, Ammonia, Bidyanus bidyanus, Toxicity testing
Copyright Holders: The Author
Additional Information:

Thesis ( M.App.Sci )--University of Tasmania, 1998. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:04
Last Modified: 11 Mar 2016 05:55
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