The effects of dieldrin on various life stages of the African catfish Clarias gariepinus (Burchell)

Early life stages (ELS) of Clarias gariepinus were found to be less sensitive to acute dieldrin toxicity than ELS of Nile tilapia, Oreochromis niloticus; 96 h LC50 for 37 day old fry were 11.7 and 4.95pg/l, respectively. Growth of O. niloticus fry was significantly reduced in 22.4 pg/l dieldrin whereas growth of C. gariepinus fry was unaffected. Adult C. gariepinus rapidly absorbed dieldrin from aquaeous solution and accumulated it in their tissues, especially in the liver where after 30 days in 4.0 pg/l bioconcentration was close to 1000 fold. Chronic exposure of C. gariepinus to dieldrin had no effect on blood haematocrit and haemoglobin, but appeared to slow the growth of catfish, and had a clear negative effect on the reproductive potential of mature females