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A PLAN FOR AN ARTIFICIAL SPAWNING CHANNEL FOR PINK SALMON AT SETON CREEK THIS REPORT HAS BEEN PREPARED BY THE TECHNICAL STAFFS OF THE INTERNATIONAL PACIFIC SALMON FISHERIES COMMISSION AND THE DEPARTMENT OF FISHERIES, CANADA. VANCOUVER, B. C. AUGUST, 1959 A PLAN FOR AN ARTIFICIAL SPAWNING CHANNEL FOR PINK SAIMON AT SETON CREEK • This report has been prepared by the technical staffs of the International Pacific Salmon Fisheries Commission and The Department of Fisheries, Canada. VANCOUVER, B.C. AUGUST, 1959 TABLE OF CONTENTS Page Introduction 1 The Size and Distribution of the Pink Salmon Runs 1 The Artificial Spawning Channel 6 Water and Property Requirements 8 Relationship of the Spawning Channel to the Seton Creek Hydroelectric Development 10 A. Seton Creek 11 B. Cayoosh Creek 13 Conclusions 16 .. FIGURES 1. Area Map of Seton and Cayoosh Creeks. 2. Proposed Artificial Spawning Channel - Seton Creek. Introduction The Seton Creek system, tributary to the Fraser River at Lillooet, supported a substantial run of pink salmon prior to the Hells Gate blockade in 1913. After 1913, the run disappear­ ed, but in recent years, following completion of the Hells Gate Fishwaya in 1946, it reappeared and the size of the population has been increasing steadily since that time. On July 3, 1957, the Pink Salmon Protocol was ratified as an amendment to the Sockeye Salmon Fisheries Convention, making the International Pacific Salmon Fisheries Commission responsible for the protec­ tion and extension of the Fraser River pink salmon in addition to the sockeye salmon. Pursuant to its new obligations to the signatory governments, the Commission has in 1957 and 1958 conducted extensive studies on the pink salmon run to the Seton Creek system, and in collaboration with the Department of Fisheries has reviewed the historical record and recent data and considered the future possibilities with respect to carrying out the provisions of the tr.eaty. This brief report summarizes the results of these studies, and recommends the construction of an artificial.. spawning channJ:~l to preserve and extend the pink salmon runs. The Size and Distribution of the Pink Salmon Runs The earliest recorda of the pink salmon (Oncorhynchus gorbuacha) runs to the Seton Creek system are contained in the reports of the Superintendent of the Provincie.l Fisheries Department hatchery on Seton Creek. This hatchery, located one- - 2 - half mile downstream from Seton Lake, was placed in operation in 1903, and for a period of years lar.ge numbers of eggs were taken from salmon in Seton Creek for the purpose of artificial­ ly rearing salmon fry. The fish from which the eggs were taken were held in Seton Creek by means of a weir at the outlet of Seton Lake, and the numbers of fish were readily observed. At first the hatchery utilized sockeye eggs only and the presence of pink salmon was merely noted. Thus in 1905 it was reported(l) that many thousands of humpbacks (pink salmon) entered the retaining pond at the Seton Lake weir. In 1907 a total of 25 million eggs was taken from pink salmon in Seton Creek for .. rearing in the hatchery. This means that at least 25,000 pink salmon reached the outlet of Seton ' Lake and there is no indica- tion that the supply of eggs was limited by the number of fish present. No pink salmon eggs were taken in 1909 but 30,033,000 pink salmon eggs were taken in 1911 at the outlet of Seton Lake 2 and Mr. Ledgerwood reported( ) that "we would have had no trouble in taking 60,000,000 humpback eggs had we a hatching house large enough to accommodate them." This potential egg­ take figure indicates that at least 60,000 pink salmon reached the area at the outlet of Seton Lake. On October 28 he remark- ed that "the creek is full of dead humpback and the smell of rotten fish is quite bad at times. It is worse down in Cayoosh Creek than it is here on Lake (Seton) Creek." (At that time Cayoosh Creek was considered to extend down to the Fraser River and Seton Creek was considered to be a tributary of Cayoosh - 3 - Creek. Seton Creek is now considered to be the principal stream and Cayoosh Creek its tributary {Figure 1), and this terminology is u s ed throughout this report.) In 1913, the pink salmon runs to areas above Hope were obstructed by the blockade at Hells Gate and no pink salmon were reported in Seton Creek. The runs also failed to appear in significant numbers in any of the subsequent cycles up to 1945. The fishways at Hells Gate were completed in 1946, and in 1947 a run of one to two thousand pink salmon was observed in Seton Creek. A run of similar size was reported in 1949. In 1951 a run of ten to twenty thousand pink salmon was reported, princi­ pally in the side channels below the junction of Seton and Cayoosh Creeks. None of these fish were observed to have entered Seton Lake. In 1953 the pink salmon escapement increas­ ed to over 50,000 fish(3), and for the first time since 1913, spawning was noted in a heavy concentration immediately below the lake outlet. In 1955 the population was estimated to be between 75,000 and 100,000 fish{3). Counts showed that 8805 of these pink salmon passed" through the fishway over the Setori Dam, which had been constructed between 1953 and 1955, but the actual number that spawned above the dam is not accurately known since an undetermined number drifted downstream over the dam. Five hundred of these fish passed through Seton Lake to spawn in Por tage Creek. A few fish {approximately 500) also spawned in Cayoosh Creek. Concentrated spawning was observed in the area ... \ ' \ ' ! S ETON - LAKE >> ,.u "-->\', ....;:---~( ~ ~~~ "Tt <0 c I ' ..... (1) SCALE I Inch ~ 2000 Feet AREA MAP OF SETON AND CAYOOSH CREEKS - 4 - just downstream from the Seton Creek Dam and in portions of Seton Creek below its confluence with. Cayoosh Creek. No numeri cal evaluation of the distribution by areas is available. In 1957, the escapement of pink salmon was determined to be 58,810 with an additional 1867 in Portage Creek(4). It is estimated from tagging and dead fish recovery that only about 1100 fish spawned in Seton Creek above the dam and that 1500 fish spawned in Cayoosh Creek below the diversion dam. It was observed that the spawning fish selected first the 1000 foot section of Seton Creek immediately dolmstream from Seton Dam and that the other portions of the available spawning area became occupied only after this upper area was filled to capacity. Such selection of the best spawning area first is character­ istic of both sockeye and pink salmon spawning in the Fraser River system. Not only was this area below the dam selected first, but the density of spawners was much greater than in other parts of the spawning ground. On the basis of dead fish recovery, at least 30 per cent of the population, or about 18,000 fi~~~ spawned in the 11,300 square yards in this area. This represents a density of about 1.6 fish per square yard, whereas in the other 134,700 square yards of spawning area, the density of spawners averaged 0.3 fish per square yard. From the observations of distribution of pink salmon in 1953, 1955 and 1957 and the conservative estimate of the pink salmon that entered the upper portion of Seton Creek in 1911, it is believed that prior to 1913 the total cyclic spawning - 5 - escapement to Seton and Cayoosh Creeks was 200,000 pink salmon. The 1957 escapement of 58,810 fish is .considered to be optimum for the present spawning area, and any additional escapement to these streams will require additional spawning area if a maximum level of abundance is to be reached and maintained. In the short span of five cycles the escapement increased from a few thousand to the present level, and the available evidence indicates there should be a further increase in abundance if sufficient additional spawning area can be provided. The pink salmon populations in the Fraser River system consist of two groups which have been classified as early and late, both as to time of migration and time of spawning(4). Individual populations within these groups cannot be distin­ guished in the fishery, so that regulations designed to permit increased escapement of Thompson River fish in the early group will also permit increased escapement of Seton Creek fish. The Thomp son River system comprises the largest historically record­ ed spawning area for pink salmon in the Fraser River system. The pink salmon runs to this area, as to Seton and Cayoosh Creeks, were almost completely destroyed by the block at Hells Gate in 1913 and subsequent cycles, but, following the comple­ tion of the Hells Gate fishways in 1946, are now being rehabili­ tated. Regulation of the fishery to ensure adequate escapement of pink salmon to the Thomps on River system for continuation of this rehabilitation will unavoidably result in increased escape­ ment to the Seton-Cayoosh system. Historical records of the - 6 - size of the pink salmon escapement to this system, as already discussed, clearly indicate that the size of the pink salmon escapement was in the order of 200,000 fish. The size of the escapement in light of present scientific knowledge was probably too large and could have caused overcrowded conditions on the spawning grounds. Since the pres ent spawning grounds are fully utilized, it becomes necessary to determine practical means of supplementing the existing spawning grounds.

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