SEAWARD MIGRATION OP CHINOOK SALMON. 



35 



A collection of 44 specimens was made at Tisdale Wier, June 24 to 26, 191 1. (See 

 Table 34.) The average length is 78.8 mm. The average number of rings on the scales 

 is 10.3, and the length of the anterior radius is 33.1. Twenty-one males average 78 mm. 

 and 23 females 79.6 mm. in length. 



Table 34.— Data for 44 Fry from Tisdalb Wier, June 24 to 26, 191 1. 



Length. 



xoi to los mm. 

 96 to 100 mm.. 



91 to 95 mm 



86 to 90111m — 



81 to 85 mm 



76 to 80 mm 



71 to 75 mm — 



66 to 70 mm 



61 to 6s mm 



56 to 60 mm ... 



Av. 78.8 mm. 



Number. 



Scale record. 



Average 



number of 



rings. 



Average 

 length of 

 anterior 

 radius. 



33- O 

 35- S 

 34-6 

 29.9 

 31- S 

 39.0 

 27-3 

 as- 9 

 23.0 

 23.0 



33-1 



This completes the description of the young fry taken in the lower Sacramento 

 River. The skewing of the curve of length toward the smaller sizes, which was noted 

 in the collections from the Columbia River, is not apparent in this material. It is only 

 slightly noticeable in Tables 30 and 33. This is, at least in part, due to the fact that 

 there are few collections of any size which contain specimens of the smallest fish. The 

 fact that these specimens from the Sacramento were not collected in the estuary, as 

 were most of the Columbia River fry, would doubtless also have some such efifect. In the 

 estuary the fish hesitate for a time in the brackish water before completing the migration 

 to the ocean. This gives an opportunity for the smaller fish from above to come in and 

 form an abnormally large proportion of the collection. 



The collections from the McCloud River include two made in July and September, 

 1909, and a series made during the fall and winter of 1911-12. A constant feature of 

 the collections made from July to December is the presence of precociously matured 

 males. These also have been noted among the fish from the Columbia River basin 

 (p. 18). Such precociously mature males will not be included in the tables with the 

 immature fish. None of these specimens show a well-defined primary check, as was 

 met with in the Columbia River collections. 



Thirty-eight specimens were taken July 24 and 25, 1909. Nine of these are 

 mature males and average 124 mm. in length. The scales of the mature fish have an 

 average of 1S.5 rings, and the average length of the anterior radius is 63.9. Fourteen 

 of the immature specimens are males averaging 85.5 mm. in length and fifteen are 

 females averaging 91.5 mm. The data for the immature specimens, 29 in number, are 

 given in the following table (35) . 



