Part of the show Cancer, Cancer Diagnosis and Chemotherapy
A recent spate of piranha attacks on swimmers in South East Brazil could be caused by rivers being dammed. In one town called Santa Cruz of Conceircao, there had been no reported injuries from those toothy fish until 4 years ago when piranha bites started to occur. By 2002 there was a rapid increase in the number of attacks on tourists and locals who like to swim in dammed portions of the stream, with 38 attacks taking place over 5 weekends. The same was happening in other rivers close to dams. The reason is that damming rivers encourages piranha populations to grow, by perhaps as much as 10 times un-dammed levels. Piranhas lay their larvae in submerged or floating waterweeds like water hyacinth, which collect in slow-moving rivers; the conditions created by dams. In un-dammed rivers it’s thought that occasional floods would sweep away this vegetation and hep to control piranha populations. Damming is becoming increasingly common in south east brazil due the growing need for flood protection in the heavily populated region of the country. Over the years, numerous grisly stories of people being attacked and eaten by ferocious schools of piranhas have surfaced, but the authors of the new report claim there is little scientific evidence to support such behavior. They say at least three of the people supposedly killed by schools of piranhas actually died from heart failure or drowning and were only eaten by the fish after they were dead.