PROGRESS IN BIOLOGICAL INQUIRIES, 1935 411 



The first recoveries from a similar set of experiments carried on in 

 1934 at the Samish Riv^er, in the northern region of tlie Sound, were 

 made during the spawning migration of the present season. Six of 

 these fish, returning as grilse from the marking of November 1934, 

 were recovered with a dip net at the Samish rack. One was reported 

 as taken by a sport fisherman below the rack, and several others 

 escaped, being small enough to pass through the rack. No returning 

 grilse were observed from the earlier Samanish experiments, those 

 of May 1934. 



Collections of biological data from both commercial and sport fish- 

 eries Avere made throughout the season. Scale samples and data as to 

 length and sex were taken for over 3.000 fish obtained from the com- 

 mercial fishery between July 22 and November 20, when the fishing 

 season closed. Weights taken from 2,700 of these fish indicated an 

 exceptional growth during the third year of their lives. Scale sam- 

 ples and measurements were also obtained from several hundred fish 

 in their second year taken by sport fishermen. 



The collection of data was continued on individual catches by all 

 types of gear on Puget Sound since the beginning of the fishing 

 industry there. Almost all the material of this nature still in 

 existence has now been obtained from the records of the industry. 

 This is being analyzed to determine changes in abundance, time of 

 runs and the importance of the various fishing areas. 



KARLUK RI\TER RED SALMON 



An investigation of the red salmon runs of the Karluk Eiver, 

 Alaska, was continued by J. T. Barnaby, assisted by L. D. Townsend 

 and J. F. Hart. ^ . 



Another marking experiment was initiated, 49,092 seaward migrants 

 being marked by the amputation of the left ventral and adipose fins. 

 The returns from various marking experiments have ranged from 20 

 to 25 percent of the migrants niarked. Thus the ocean mortality 

 from seaward migrant stage to adult stage is apparently about 75 

 percent. If we assume the return of only two adults for each 

 spawner, the assumption upon which the existing statute limiting the 

 commercial catch to 50 percent of the total run is based, and if we 

 assume that each female produces the known average of 3,500 eggs, 

 the mortality during the fresh water period, or from eggs to seaward 

 migrants may be calculated under these conditions to be 99.54 percent. 



Since the greatest mortality of this species takes place during the 

 fresh-water period of its life history, further studies were made on 

 the environmental factors which influence the success of each year's 

 spawning. Ph^^sical and chemical data were collected throughout 

 the summer. The chemical analysis of the lake and stream waters 

 indicates that phosphorus and silicon are limiting factors in the pro- 

 duction of plankton, at least during the major part of the summer. 

 The water of the streams entering the lake contained on the average 

 2 one-hundredths of a milligram of phosphorus per liter, and over 8 

 milligrams of silicon per liter. The phosi:)horus content of the lake 

 water during June, July, and August remained at zero and the silicon 

 content of the lake water was 1 1/2 milligrams per liter in June, a trace 

 in early July, zero in late July, and a trace in August. Thus the phos- 

 phorus and silicon were being used up as fast as they became available 



151363 — 37 5 



