It is only slightly less severe in Uganda and Kenya. Agricultural pesticides and poisons extracted from plants are the chemicals of choice. Tanzanian fishermen commonly use Thiodan and Diazinon and plant extracts from Euphorbia tirucalli and Tephrosia vojeli . In Kenya, fishermen also use Triatrix. Their plant extracts come from Cassia fallacina , Cassia didymobotra and Albizia gummifera .
Researchers say pesticides only came into significant use in Kenya in the second half of last year.
Of the plant extracts, Cassia fallacina is more poisonous to fish than Albizia gummifera , while the most potent of the pesticides is Thiodan. The chemicals kill within 6 hours of being consumed by human beings. The fish spoils rapidly when stored at ambient temperature or exposed to the sun. With last week's government intervention in the problem, courts are expected to impose stiffer penalties than the Ksh 5000 routinely imposed on fishermen convicted of using poison. A fisheries officer, Mr Sebastian Onyango, is quoted in the latest issue of East African Alternatives, a Nairobi Monthly, as saying that some of the poisons break down quickly after being ingested by fish and are not easily detected when the samples reach Nairobi.