Counting Salmon In Rakaia

Press, Volume CIV, Issue 30939, 21 December 1965, Page 28

Counting Salmon In Rakaia

Officers of the Marine Department have constructed a large fish trap to catch salmon in the Glenariffe stream, a tributary of the Rakaia river. They have prefabricated the 110 ft long trap at the department’s laboratory in Kyle street, Riccarton, and plan to dismantle It and then reassemble Lt to span the stream early next month. Its purpose is to count quinnat salmon so that the department will be able to predict for salmon fishermen whether particular years ahead will be good salmon years or not Made of hardwood and thick treated pine, the trap is designed to sit on the bed of the stream so that the water runs through an adjustable gate and across a screen. Adult salmon swimming upstream to spawn will be channelled into a pen to be counted, weighed and measured. and small fish coming down will be delayed in a trough at the bottom. The Army may help trans-

port the trap to the aite and erect it across the stream. Once in position, it will be manned continuously and the salmon will be counted three times a day. The newly-born fish coming downstream are expected to pass through the trap by the million, and they, too, will have to be counted and possibly fin-clipped for later identification. The department’s scientific officer (Mr M. Flain) said yesterday that he wanted to know how long the salmon stayed out at sea before returning to the river to spawn. At present it was thought that they stayed away be tween three and five years. When this was known, accurate predictions of future salmon season prospects would be possible. If an unusually small number of young salmon came down the stream in a particular season, the department would be able to say that the season of their return a certain number of years ahead would be a poor one.

Mr Flain said his department was considering the possibility of installing an electronic machine to count the fish passing through the trap. A pilot trap was built in

the same place last year to determine hOw valuable the full-scale trap would be. It was used during last year's spawning run. and 2200 salmon were counted going upstream.