Journal of Environmental Biology

Toxicity of neem pesticides on a fresh water loach, Lepidocephalichthys guntea (Hamilton Buchanan) of Darjeeling district in West Bengal

Debashri Mondal¹, Sudip Barat*¹ and M. K. Mukhopadhyay²

¹Aquaculture and Limnology Laboratory, Department of Zoology

University of North Bengal, Darjeeling–734 013, India.

²Central Inland Fisheries Research Institute, Barrackpore, Kolkata – 700 120, India

(Received: May 27, 2005 ; Revised received: November 10, 2005 ; Accepted: December 17, 2005)

Abstract: Static renewal bioassay tests were conducted to evaluate the acute toxicity of two neem based biopesticides, applied widely on tea plantation namely, Nimbecidine and Neem Gold either separately as well as, in combination to the fingerlings (mean body length- 4.46± 0.15 cm; mean body weight- 0.49± 0.15g) of a fresh water loach, Lepidocephalichthys guntea (Hamilton Buchanan) acclimatized to laboratory conditions prior to experiment. The 96 hours LC₅₀ values for Nimbecidine and Neem Gold and the combination of the two were 0.0135mgl^-1, 0.0525mgl^-1 and 0.0396 mgl^-1, respectively. The regular water quality analysis showed, that with increasing doses of biopesticides, dissolved oxygen level was lower and other parameters like pH, free carbon dioxide, total alkalinity, total hardness, chloride ions of water increased. The fish under toxicity stress suffered several abnormalities such as erratic and rapid movement, body imbalance and surface floating responding proportionately to the increase in concentrations of the toxicant biopesticides. The 96 hours LC₅₀ values proved Nimbecidine more toxic than Neem Gold and the combination of the two biopesticides.

Copyright © 2007 Triveni Enterprises. All rights reserved. No part of the Journal can be reproduced in any form without prior permission. Responsibility regarding the authenticity of the data, and the acceptability of the conclusions enforced or derived, rest completely with the author(s).