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Regulating harvest, protection, and enhancement of fish populations

December, 1954
Oregon Game Commission Bulletin Game Commission Bulletin


Coordinating Biologist Fisheries Division

DEATH to millions of trash fish in September, 1954 &endash; rainbow trout in every creel in 1956. This is the recent past, and the expected future of Diamond Lake which on September 21 of this year attracted nationwide interest as the scene of the largest fish eradication project ever attempted in modern fishery management.

Let's review the history and circumstances leading up to the event and see how the project was successfully accomplished.

Diamond Lake, thought to be originally barren of fish, is located in the eastern part of Douglas County in the Umpqua National Forest. It contains 2,982 surface acres and lies at an elevation of 5,182 feet. The lake is 31/2 miles long and 11/2 miles wide, with a maximum depth of 521/2 feet. Lake Creek, a tributary of the Umpqua River system, is the outlet stream.

Records indicate that the first planting of rainbow trout took place about 1910. Unexcelled trout fishing prevailed during the 1920's and by present-day standards the size and abundance of rainbow trout caught during that period were incredible. Five to ten pound trout were supposedly an everyday occurrence with one reported weighing 27 1/2 pounds. As recently as 1941, a 21 pound trout was taken.

A rainbow trout egg collecting station was established at the lake in 1919. The eggs obtained were used for restocking the lake and for distribution to other hatcheries throughout the state. A take of 19 million trout eggs was recorded for one year of the 33 year period the station was operated.

In 1940, the Klamath Lake roach or "chub" Siphateles bicolor bicolor, a trash fish species, was observed in the lake for the first time. Supposedly, anglers using the chub as live bait in seeking rainbow trout, had introduced it into the lake. This method of fishing is now prohibited. After the appearance of roach, trout angling declined. Poor fishing was especially evident after 1947 when the angling pressure increased. The decline in trout angling led to a preliminary biological investigation in 1946. As time passed, enormous schools of roach appeared in the shallow shoreline waters. In an effort to obtain a greater survival of the trout plantings, rainbows of 6 to 10 inches in length were stocked in preference to fry and fingerlings because the larger fish have a greater capacity for survival under such highly competitive conditions.

In 1946, roach control activities were instituted and carried out annually in an effort to retard the increase of the trash fish. The program was one of partial control and consisted of seining and selective chemical treatment of the roach schools as they appeared in the shallow shore-line waters. Although millions of roach were thus destroyed, their high reproductive rate kept the roach population growing.

In testing to determine the size of the roach population, an experimental type gill net was set in various locations and depths throughout the lake. In 1950, the net yielded a ratio of one trout to 94 roach; in 1951, one trout to 137 roach; in 1952, one trout to 248 roach; and in 1953, no trout to 420 roach. The ratios show the trend of the relative abundance of each species. Trout were present in 1953 although they were not captured in the gill nets. Furthermore, small roach ranging in size from 1 to 4 inches were not taken, as they were able to pass through the meshes of the net. Frequent observations indicated that more than one&endash;half of the roach population consisted of fish of I to 4 inches in length.

Trout food studies have also been carried out since 1946 through systematic sampling of the lake bottom in order to determine the amount of aquatic or&endash;ganisms available to the fish population. These organisms make up the basic necessary fish food. The decline in the quantity of bottom food of the lake from 292 pounds per acre in 1946 to 2.3 pounds in 1951 is shown in Table I.

Pounds per acre
*Sampling was not done in 1947.


Because of its shallow depth, Diamond Lake has 2,082 acres suitable for the production of fish. Obviously, most of the aquatic fish food organisms were producing tons and tons of roach flesh.

Additional evidence that the once famous Diamond Lake sport fishery had steadily deteriorated is revealed by the creel census records obtained since 1946. A comparison of the total trout catch from 1946 through 1953 is shown in Table II.

Recorded Angler Trips
Total Trout Caught
Average Length in Inches

In reviewing Table II, note the catch for the year 1953. Only 8,455 trout were caught by 5,885 anglers. From a lake of almost 3,000 acres, this gives an av of slightly less than three tr surface acre of waten For c purposes, let us analyze the to from two other popular Orego lakes, East and Paulina lakes in the central Oregon area. (See Table III.)

Comparative Catch Statistics for Diamond, East and Paulina lakes for 1953

Size of lake in acres
Recorded angler trips
Total trout caught
Fish caught per surface acre


From a business point of view, Diamond Lake was rapidly becoming a total economic loss to the sport fishing industry of the state of Oregon. The fishermen that formerly sought their recreation at Diamond were going elsewhere and the lake was not contributing its portion to the sport fishing resource. The continued stocking of trout of legal length on a "put and take" ha.Qia~ and the pursuit of a partial roi control program with a total cost.of 15 to 20 thousand dollars annually was not a sound investment in view of the return of a few thousand rainbow trout in the creel.

Following the presentation of the above data, the Game Commission studied the problem thoroughly. A decision was reached that complete chemical, treatment to remove the entire trash fish population, along with the few remaining game fish and subsequent restocking with rainbow trout, appeared to be the only positive approach in restoring this once famous sport fishery.

If total treatment with rotenone was to be successfully accomplished, some means of preventing the flow of toxic water into Lake Creek at the time of treatment had to be devised.

The installation of a dam in the outlet to impound the lake water until it had lost its toxicity was not considered feasible since it would be damaging to the physical properties surrounding the lake, such as the resort, summer homes and Forest Service camp grounds. Lowering the lake level by siphoning, pumping or draining through an excavated canal was proposed.

An engineering study indicated that the most economical solution was one of lowering the lake level approximately eight feet by means of a canal constructed parallel to the outlet. The cost of siphoning or pumping was found to be prohibitive in comparison to that of excavating a canal. In addition, the canal would be a permanent structure available for reuse in the future if ever necessary.

Inasmuch as Diamond Lake is located in the Umpqua National Forest, authorization for the project had to be obtained from the United States Forest Service. This was granted through a special use permit. The Forest Service also enacted special regulations when necessary, such as closing the lake to all public use during the time of treatment.

In the summer of 1953, a contract was issued to a private concern for the excavation of the drainage canal. Work involved the excavation of a canal, 1,000 feet on land and extending 900 feet out into the lake and the installation of a concrete and steel control structure. This phase of the project was finished by November, 1953.

Chemical treatment was scheduled for September 21, 1954. Draining started on July 15. According to previous calculations, lowering the lake the desired eight feet would take 66 days, provided that a full flow in the canal could be maintained at all times. Because of several unforeseen interruptions when the flow was cut off, slightly less than 7-1/2 feet of water was removed.

The draining of the lake prevented toxic water from entering the Umpqua River system and reduced the water volume of the lake. The canal was equipped with permanent head gates which were to be sealed after the drawdown and just prior to the application of rotenone, thus allowing sufficient time for the water to lose its toxicity before flowing again in the natural channel of Lake Creek. By eliminating eight feet of the surface water, the volume of the lake was reduced from 78,000 acre feet to 53,000 acre feet with a reduction in surface acreage from 2,982 to 2,600 acres. This reduced the quantity of rotenone required by about 35 percent.

The amount of rotenone needed was determined to be 100 tons or 200,000 pounds, plus 275 gallons of emulsifiable or liquid rotenone for treatment of the tributary streams and for aerial spraying of the marsh area near the south shore. All of the material was purchased, delivered, and stockpiled at the lake in August.

In an effort to devise some method of expediting the uniform distribution of the 100 tons of rotenone, tests had been conducted with a mechanical type rotenone spreader to determine its adaptability for the Diamond Lake project. Originated by Eldon Vestal of the California Department of Fish and Game, the cubeater, a barge&endash;like apparatus deriving its name from the South American cube' root from which rotenone is an extract, consisted of a metal hopper, corrugated metal tube, and an outboard motor arrangement for mixing and discharging the dry rotenone powder into the water. The equipment was mounted on a barge having a deck surface of 26 by 16 feet and propelled through the water by a 25 h.p. outboard motor. Testing demonstrated the ability of the equipment to disperse the rotenone at a much faster rate than was possible by any former method and as a result, it was decided to use four such cubeaters in the Diamond Lake undertaking.

During the week preceding the poisoning, preparations began in earnest. For supervisory purposes, the lake surface was divided info four general sections. Large orange and white weather balloons were anchored to designated boundaries, and each section was numbered by placing markers on the shore.

Within each section, one "cubeater" area was established in the deep water, with several smaller shallow areas designated for dispersal of rotenone by outboard motor boats. Each cubeater operated over approximately 300 surface acres while the smaller boats covered from 20 to 50 acres. The appropriate quantity of rotenone for the calculated water volume of each area was stockpiled along the shore line.

On September 20, approximately 100 Game Commission employees and 150 volunteer sportsmen assembled at the lake for indoctrination. Crews were assigned to the cubeaters and given operating instructions. Operators of the outboard motor boats were instructed in the proper manner of distributing rotenone by a practice demonstration in towing burlap bags.

At 5:30 a.m. on the morning of the 21st, the operation began. Distressed roach soon started to appear on the surface of the lake. It also became evident that roach were unexpectedly scarce in the shallow waters. By midmorning dead and dying roach were appearing on the surface in deep water in great numbers. By Tuesday evening, dead roach thoroughly dotted the surface of &endash;the lake. It was now apparent that the bulk of the fish were inhabiting the deeper areas owing to a change in surface water temperature resulting from cold weather. From past experience it was known that the rotenone powder would not descend into the deeper depths for several days. For this reason fish continued to perish for at least three days following the Tuesday application.

Many of the several thousand spectators came with the intention of picking up trout, and dip nets of all descriptions were in evidence. They were greatly disappointed for the most part because the trout were scarce. Only a few trout had been recovered by late evening of the first day.

In noting the number of trout seen and recovered, those reported by others, and trout found along the shore line for several weeks after the poisoning, it is estimated that not over 100 rainbow trout were accounted for with the largest weighing an estimated 12 pounds. Some undoubtedly did not rise to the surface.

The total kill of roach has been difficult to estimate accurately, although tremendous rafts of the dead fish were in evidence along the shore line and floating in the lake. Like the trout, unknown numbers decomposed on the bottom. From frequent observations and sample counts, a conservative estimate would be one roach killed for each 4 square feet of water surface. On this basis, it is calculated that 32,000,000 roach were destroyed. Converted to pounds, at the rate of 40 roach to the pound, the total kill amounted to a conservative 400 tons.

Since the chemical treatment, frequent tests have been carried on with the setting of gill nets to determine if a complete kill of all fish was achieved. Nets have been operated in practically all areas of the lake and to the first of November no live fish have been recovered. Observations along the shore and out in the lake have not revealed the survival of any fish.

Testing commenced on September 29 to determine the period of time that the lake water remained in a toxic condition. Live fish lowered to various depths in wire live boxes have beenused for the purpose. The first experiments on September 29 showed the fish to be in distress in 12 minutes with death occurring in 45 minutes. Similar tests have been continued, and it has just now (early November) been found that the rotenone in certain areas, particularly the surface water, has become inactive.

Restocking is planned for the spring of 1955 with 150,000 Canadian rainbow trout as the initial plant. This is to be followed by 500,000 rainbow fry annually until sufficient brood stock is available in the spawning run at Diamond to supply the necessary eggs. The Canadian rainbow or Kamloops trout, a variety not native to Oregon, is the only trout of pure strain available tu us. Eggs for the Diamond Lake stocking are currently being obtained from British Columbia through the courtesy of the British Columbia Game Commission. It is possible that the lake water may be nontoxic soon enough to be stocked in the early winter of 1954. No open fishing season is planned for 1955.

Total cost of the Diamond Lake project will be approximately $140,000. The Dingell-Johnson program of federal aid to the states for fisheries restoration made the project possible. In Dingell-Johnson projects three-fourths of the necessary funds are provided from the federal excise tax on fishing tackle with one&endash;fourth contributed by the respective states.

We should like to pay special tribute here to the United States Forest Service for the excellent cooperation and special efforts rendered in assisting the orderly progress of the project. The United States Fish and Wildlife Service, the administering agency of the Dingell-Johnson fund, actively aided in formulation of the project and gave every assistance in progress of the project. Cooperation and assistance were gratefully received from the Diamond Lake Lodge owners, the summer home owners and the CaliforniaOregon Power Company. Special and enthusiastic appreciation&endash; is expressed to the many sportsmen who furnished real and necessary help during the poisoning phase of the project.

The rehabilitation of Diamond Laxe and the restoration of its once famous trout fishery is another example of the Oregon Game Commission's desire to provide the maximum production of game fish in all of Oregon's trout waters.


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