12 



BULLETIN OP THE BUREAU OF FISHERIES. 



The smaller size of these fish as compared with those from below the mouth of the 

 Willamette River is distinctly shown and is in accord with our explanation of the 

 excessive proportion of small fish in the collections from the lower river; that is, that 

 smaller fish are constantly being added to those in the estuary as a result of migration 

 from above. 



Eight specimens were preserved at the Clackamash atchery, May 27, 1916. These 

 average 56 mm. in length. All have well developed scales. The average number of 

 rings on the scales is 7.5, and the average length of the anterior radius of the scales is 

 28.5. There are four males averaging 53 mm. in length and four females averaging 

 59 mm. 



A good collection of fry was made near Astoria, in the lower part of the estuary 

 June 12 and 13, 1916. (See Tables 8 and 9.) In all, 132 specimens were taken, and it 

 is worthy of note that none were yearlings. Yearlings do not appear in any subsequent 

 collection from the lower part of the river, and it may be concluded from this that the 

 yearling migrants quit the river for salt water about the first of June, if not earlier. 

 This point is given more detailed consideration later. 



Thirty-six of these fry were taken just within the mouth of a small creek near Point 

 EUice. They differ so distinctly from the remainder of the collection that they are 

 considered separately. (See Table 8.) The average length is but 47.7 mm., with the 

 mode at 38 mm. All of the individuals have formed scales, and in all but one, rings 

 are present on the scales. The average number of rings is 4.1, and the average length 

 of the anterior radius is 20.5. Nineteen of these specimens are males averaging 47.5 

 mm. in length. Seventeen females average 48 mm. 



T.\BLE 8. — Fry from within Mouth of Small Creek near Point Eluce, Columbia River, June 13, 



1916. 



Length. 



Number of speci- 

 meas with — 



Plate- 

 lets. 



Scales 

 with 

 rings. 



Scale record. 



Average 



number of 



rings. 



Average 

 length ol 

 anterior 

 radius. 



66 to 70 mm. 

 6r to 6s mm. 

 56 to 60 mm. 

 51 to 55 mm. 



46 to 50 mm. 

 41 to 45 mm. 

 36 to 40 mm. 



Total 



Av. 47.7 mm. 



8.0 

 7.0 

 7.0 

 S-3 

 ■)-3 

 3-4 



33-0 

 28.0 

 39.3 

 25.0 

 20. s 

 iS.o 

 13- o 



The remaining 96 specimens collected in the estuary at this time are distinctly 

 larger, averaging 76.5 mm. in length. In these specimens it is found for the first time 

 that the scales of some of the fish have developed the wider marginal rings which have 

 been designated "intermediate rings." This marginal band of wider rings is usually 

 sharply differentiated from the central part of the scale and begins abruptly — not by a 

 gradual increase in the space between rings. It may even be preceded by a slight 

 narrowing, especially in the older fish. Gilbert (1913) has found similar intermediate 



