Organochlorines in Chrysichthys nigrodigitatus and Liza grandisquamis from Lagos Lagoon and Agboyi Creek, Nigeria

Abstract

Catfish (Chrysichthys nigrodigitatus) and mullet (Liza grandisquamis) were sampled from Lagos Lagoon and Agboyi Creek and analysed for alpha-BHC, beta-BHC, lindane, delta-BHC, heptachlor, heptachlor-epoxide (B), aldrin, dieldrin, endrin, endrin aldehyde, endrin ketone, cis-chlordane, trans-chlordane, endosulfan 1, endosulfan 11, endosulfan sulphate, methoxychlor, p,p′-DDE, p,p′-DDD and p,p′-DDT. Sampling was conducted four times at the designated sites during the dry season months of December 2008 and February 2009 and the wet season months of May and September 2009. The muscle tissues and organs of the finfishes were subjected to cold extraction with petroleum ether/acetone (1:1 v/v) mixture and clean-up on silica gel adsorbents. A gas chromatograph coupled with electron capture detector (GC-ECD) was used to detect and determine the organochlorines. The residue levels of the fishes were higher in the Lagos Lagoon than in Agboyi Creek while a higher concentration of the residues was observed during the dry season. The female fishes accumulated higher organochlorines than the male fishes. The order of residue accumulation in the organs of the fishes was gills >livers > large intestines > kidneys > muscles. The dietary surveys indicated that the amount of fishes consumed ranged from 20 to 200 g/day, with a mean value of 40 g/day. The estimated daily intakes of the organochlorines were within the acceptable daily intakes while the levels of residues in the fishes were within the permissible residue limits.