FORTY-FIRST BIENNIAL REPORT 109 



1947 eggs (marked dorsal and adipose) aud spring-spawned fri>ni i;t4s egg?. ( marked 

 adipose). In addition, two 194S summer plants of fingerliug brown trout (4,000) and 

 rainbow trout (4,000) were made for an additional carryover t<'st. During tlie VMS 

 season, 8,384 anglers fished 31,962 hours for a total of 20,379 wild and idaul.'d lisli. 

 Marked hatchery fish contributed 93.6 percent of total catch. Out of the 19,94.") 

 catchable rainbow trout planted, 18,362 (92.1 percent) were cauglit. Only 72 (3.8 

 percent) of the fall-spawned 1947 carryover plant and 17ij (8.8 percent) of the 

 spring-spawned 1947 carryover plant showed in 1948 creels. No 1947 carryover tisli 

 were taken after August 14. Wild fish contributed 6.4 percent of total 194S catch : 

 1,131 (87.6 percent^ were brown trout, 140 (lO.S percent) were rainbow trout, and 

 21 (1.6 percent) were eastern brook. Average angler catch per hour for the season 

 was 0.63. Sixty percent of the right ventral fish were taken in only 20 fisliing days 

 (4-day samplings following the post-planting closures). 



Additional treatment of aquatic plant beds at Twin Lakes, Maniniutli, .MmiK 

 County, California. Submitted December 28, 1948. 6 pp., 1 figure. 



Abstract: An area of 2.8 acres between center and lower Twin liakcs, in the 

 Mammoth Lake Recreation Area, choked by dense growths of chiefly Anavhuris, was 

 treated with 885 pounds of sodium arsenite powder (75 percent arsenious oxide) 

 giving an initial concentration of 21.2 p.p.m. arsenious oxide ; partial collapse and 

 a "burn" of plant growth down to a depth of 6 inches was observed a week later. 

 The high concentration used forms a test of sodium arsenite in a disturbed water 

 situation where wave action, stream flow, and ground seepages might easily nullify 

 caustic action of the poison at lower concentration. Control of plants in the interlake 

 area will restore the area to angling, interlake boat travel, and to recre.itjonal use 

 of hundreds of vacationers using the Twin Lakes camp grounds. 



Creel inventory at Rush Creek Test Stream, Mono County, California, 1949. 

 Submitted December 19, 1949. 13 pp., 2 figures, 4 tables. 



Abstract : The creel inventory was conducted for 179 fishing days. Fntm April 

 29 to August 29, 19,975 rainbow trout averaging 7i inches long (marked VV) were 

 planted at six intervals. Two special summer plants of fingerling browns i:{,(M)3) 

 and rainbow (3,000) were made for a further carryover test. During tlie 1949 sea.snn. 

 10,004 anglers fished 36,417 hours for a total of 18,020 wild and plant. 'd fisli. Marked 

 hatchery fish contributed 90.8 percent of the total. Out of 19,97ri calrliabb- lainb.iw 

 (marked VV) planted, 15,995 (80.0 percent) were taken. Only 54 of the fall-spawned 



1948 carryover plant and 114 of the spring-spawned 1948 carryover plant (2.2 

 percent combined) were taken in 1949 creels. Wild fish contributed 9.2 percent of \hr 



1949 total catch ; 1,373 (83.0 perecent) were brown, 279 (16.7 percent) wererainb..« 

 and 5 (0.3 percent) were eastern brook. Average catch per angler iiour for tlit- 

 season was 0.49 with the catch per angler day at 1.8. 



Chemical treatment of Upper Twin Lake, Robin.son Creek. Mono County, Cali- 

 fornia. Submitted April 15, 1950. 41 pp., including 14 figures, 9 photos, 3 maps, 

 6 tables, 2 graphs. 



Abstract: Upper Twin Luke, Robinson Creek, Mono County, 1-1 mile* .south- 

 west of Bridgeport, was treated September 8, 1949, with 16.s:;.") p.-niids of ml.e. 

 rotenone averaging about 5 percent, to remove a large i)opulation of chubs, .sandbar 

 suckers, shiners, and sculpins. The lake at spill has 265 surface acres with a maxi- 

 mum depth of 112 feet ; maximum temperature is 65° F., and there is unusmilly lugh 

 oxygen deep into the hypolimnion. I'lan of the project is d.-scribed and .-ndiodird in 

 Figure 5, p. 8A. Only 194 trout were reported from tin- lake, while ov.t ""'•"<!<' 

 rough fish were killed. End concentration of cube used was appn.xini.-it.'ly 0.»»H 

 p p m • 15,200 pounds of cube was used in lake treatment and l.(Ji'..> pounds in treaty 

 ment of about 4 miles of tributaries. Spill from the lake was nontoxic to troul an.l 

 whitefish 75 days after treatment. Restocking and proposed nianaKeinent prok'ran. 

 is discussed and recommendations presented. 



Chemical treatment of Tamarack Lake, Mono Counly, CaliforniM, 19 »9. Sub 

 mitted January 26, 1950. 8 pp., 2 figures. ,,.-,«, r ,..„nr 



Abstract: Tamarack Lake, 12.7 acres at an elev:.tion oi .• ,(Ki feet near 

 Bridgeport, Mono County, California, was infested with san.l-l.ar .suckers U o/oWo- 

 mus arenarius), introduced about 1879 by pioneers of the Bridgeport N alley as for- 

 age for trout in the lake. Elindnation of the sucker popu at.on wa.s ncrompli^hed 

 September 21-23, 1949, with .535 poun.is of cube ( rotenone .5.9 per.-ent ' "** " ;7;;;-7;> 

 step in preparation for the proposed chemical treatment of Lower Twin Lnk. an 

 well as for restoration of Tamarack Lake as a trout water. 



