CAPE TOWN, South Africa— Anglers, conservationists and scientists are angered by CapeNature's tentative plans to treat four rivers with rotenone to kill bass and trout, both exotic species that were introduced to the nation more than a century ago.
Both largemouth and smallmouth bass are especially popular gamefish in South Africa.
Fishermen also are concerned about what other rivers might be next if the government agency poisons the Krom, Suurvlei and Rondegat rivers in the Cederberg and the Krom in the Eastern Cape.
The poisoning would be a "radical move that could devastate the ecosystem," said Leonard Flemming, a microbiology PhD student, writing in Piscator, the journal of the Cape Piscatorial Society. He wonders why the agency is not focusing on habitat destruction, which he believes is the major cause of diminishing populations of native fish.
"It is a shotgun approach that kills everything in its path, so we need to know beforehand what the implications are and how it will affect the long-term rehabilitation of the rivers," added Bill Bainbridge, chairman of the Federation of Southern African Flyfishers.
Peter Thorpe of Flyfishing Magazine stated: "Rotenone will transform the Krom into an underwater desert, impacting every element of the food chain, possibly permanently exterminating rare dragon and damselfly species."
CapeNature's Dean Impson countered that any underwater desert would last just a few months, "but a year later there would be lots more aquatic invertebrates."
He also asserted that rotenone, a natural poison derived from the roots and stems of several tropical and subtropical plants, has been successfully used in the United States and Spain.
Its use, he added, would allow CapeNature to "turn the clock back," making the rivers once again pristine.
He also said that invasive fish worldwide have "significantly contributed to the decline of most, if not all, indigenous fisheries through competition, predation and hybridization and often are the greatest dangers to their conservation."
If an economic impact assessment supports the move, CapeNature could begin poisoning the rivers this summer.
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