TROUT MORTALITY

Dominion, Volume 24, Issue 143, 13 March 1931, Page 6

TROUT MORTALITY

Green Beetles Blamed FEEDERS ON TUTU Green beetles feeding on a poisonous plant are suspected of being responsible -for killing fish, during November and December, in the ' Ruamahanga River, Wairarapa, according to a report by Professor Percjval, presented at the meeting ■of the Wellington Acclimatisation So- ° Professor Percival said the conditions appeared similar to those of which he was informed during his journey in Taranaki and Hawke’* Bay. It appeared* that the green beetle fed on the plant known-a» tutu. This plant produced a poison which was bad for stock. The properties of the poison, tutin, had been investigated. A dose of 0.004 minigrammes per kilogramme of body weight was fatal to trout of liin and to Inanga. Also, blowflies and maggots, among other animals, were poisoned. The poison acted on the nervous system and the muscles. The fish found dead and “dopy* during November and December, in conditions where no obvious ■ signs of ■ pollution exist, were usually taken in streams bordered with growths of tutu, and they had commonly many green beetles in their stomachs. It had been pointed out that' the beetles feed on the plant, and he had been told that the beetles taken from tutu were often rather lethargic. The inference was that they dropped off and were eaten, the poison in their stomachs acting bn the fish. _ The clear procedure was the collection of such stomach contents and the chemical examination with the object of determining the presence or absence of the substance, and any quantity which might be there. ... •It was stated by the chairman that acclimatisation societies had been circularised to advertise the need to collect some of the beetles.. ’ ' ,