FISH LADDER AT WAITAKI DAM

Press, Volume LXXIV, Issue 22432, 20 June 1938, Page 10

FISH LADDER AT WAITAKI DAM

PRACTICABILITY NOT PROVED INSTALLATION OF MORE TURBINES FAVOURABLE EFFECT HOPED FOR The efficacy of the “fish ladder” built into the wing on the Otago side of the Waitaki hydro-electric dam to provide a waterway for quinnat salmon to reach their old spawning grounds in the upper reaches and tributaries of the river will not be proved until the two additional turbines, for which tenders have been received by the Government, are in operation. Water has been running down the “ladder” for four seasons, and there is no evidence that the salmon have used it. The bulk of evidence from actual observations is that so far the “ladder” has not fulfilled its purpose. With only two turbines in operation in the powerhouse, the discharged water makes a current towards the Canterbury bank of the Waitaki and, in seasons in which the water has been clear when the salmon have been running, the fish have been seen making futile attempts to ascend the lofty dam, the crest of which is 70 feet above the river, on that side. It is believed that when the additional two turbines are installed the current will spread more to the Otago bank and that the quinnat will once again make their way upstream. Fish have been seen in the ladder, but whether they were going up-stream or down-stream has not been definitely determined. One trout was caught, the markings on which proved that it had been released in the Waitaki

miles beyond the dam; but this solitary piece of evidence was too slight to suggest that trout were moving downstream. Big Quinnat Caught The “fish ladder” is constantly observed by fishermen in the district and by workers at the powerhouse, and its practicability has not been proved since the original two turbines, installed at the northern end of the powerhouse, started continuous operation on January 1, 1935. In the last season, quinnat salmon were running strongly on the Wailaki and many made their way up the Hakataramea river, near the mouth of which 600,000 eggs were taken from trapped quinnat by employees of the hatchery on the banks of the Hakataramea, a little more than a mile beyond the junction with the Waitaki- This tributary runs clear, but the Waitaki was unusually dirty for the angling season, and it was not till the last 10 days that the fishing conditions were at all good. The usual “fishermen’s tales” have been told of catches of quinnat on the Waitaki, rnd a fish weighing more than 40 pounds was reported to have been caught, at the dam. There is, however, full verification of the landing of two salmon, the male weighing 33 pounds and the female 32 pounds. The “fish ladder” was designed by the Public Works Department in collaboration with Mr A. E. Hefford, Chief Inspector of Fisheries, much useful information being obtained from the United States, where, as also in England, efforts to carry fish over obstacles had been successful. The “ladder” has not yet advanced beyond the experimental stage at Waitaki and the real test of its practicability will not be made until the third and fourth turbines are in operation—and at least 12 months will elapse, before they are installed. Ingenious Pool System The scheme of the “ladder” was to form a small stream by by-passing water through the sluice gates in the wing-dam on the Otago end of the dam along which salmon were expected to find their way up to the lakes above the dam. The “ladder” starts with steps moulded on to the retaining wall at the exit to the draught tube of the turbine nearest to me Otago bank, and it zig-zags up the hillside in a tunnel until it terminates with a second series of steps formed on the wing-dam. Through the wingdam, there are water passages at various intervals. The steps over which the salmon were expected to jump are made by compartmeTjCs, each eight feet long, four feet wide, and two feet deep, arranged above each other in two-feet steps. The pools formed by the down which regulated amounts o( water flow, were considered tc be of sufficient length to enable the fish to gain sufficient speed to jump into the pool above. At intervals the steps are elongated with the intention of providing resting places. Concrete was used for the construction of the “ladder.” for the erection of which the Public Works Department w 7 as under no legal obligation. In some of the states of America, the provision of fishways is a legal requirement designed to protect the important salmon fishing industry and a “ladder” costing 15,000,000 dollars —a larger sum than was expended on the whole of the Waitaki dam construction and the powerhouse equipment—was recently built at one of the major dams. Study of Habits

Whether or not the salmon will use the ladder when the water is carried over to the Otago side is an interesting conjecture, and future observations are likely to give further illustrations of the habits of these fish. Salmon have been found in other countries to battle against the draught tubes of turbines, after finding their way blocked, until they die of exhaustion, in preference to finding another spawning Dead fish have been seen in the "Waitakij but there is no evidence to support the contention that they Have been battering themselves to death against the concrete wall. Quinnat salmon were first liberated in the Hakataramea river in 1901, and some fish were caught in the Waitaki in 1905. From 1910 onwards, mature fish returning to the Hakataramea river and other tributaries of the Waitaki have been trapped for hatchery purposes, and the ova used for the introduction of the species to other rivers. By natural migration, the quinnat have spread to all the large rivers of Canterbury and to some of the smaller rivers, such as the Opihi and Orari.