CHINOOK SALMON MARKING, COLUMBIA KIVEK 



221 



For the same reason the mark adopted was not the best. It was felt that the cUp 

 in the gill cover would not prove so tisf actorj^ and that nearly complete regeneration 

 might be expected. The results have shown this to be the case. In order to reduce 

 the possibility of complete regeneration the clip was placed low on the opercle, so as 

 to cut through the branchiostegal rays, the interopercle, and into the preopercle. The 

 line X— — X on the diagram (fig. 4) indicates the approximate extent of this clip. 



A number of specimens were held in a tank at the hatchery for several months 

 and the process of regeneration noted. At the end of about four months the clipped 

 section was regenerated almost completely, so that but a slight indentation of the 

 margin of the gill cover remained. This regenerated tissue seemed to be mainly soft, 

 however, while the bones apparently were regenerated more slowty. 



Fifty specimens were preserved for reference during the course of the marking. 

 These average 134.6 millimeters (5.3 inches) in length. The scales show a more or 

 less well-defined gi'owth of the first year, followed by a band of wider rings repre- 

 senting the second year's growth. Figure 5 illustrates a scale showing a well-defined 

 winter band terminating the first j'ear's growth, and Figure 6 a more typical scale in 

 which the boundary between the fii'st and second years is not shown so definitely. 

 The average number of rings in the first year's growth is 15.2 and in the second 6.6. 



46 5 

 The average length of the anterior radius of the scale is j^^ millimeter to the end 



CO Q 



of the first year and j^^ millimeter to the periphery.^ 

 collection are given in Table 1 . 



The complete data for this 



T.4.BLE ]. — Chinook-salmon yearlings marked at Bonneville hatchery March 2 and 11, 1916 



' In practice the image of the scale, as projected by a camera lucida to the level of the base of the microscope, is measured by 

 means of a millimeter scale. The magnification of this projected image used in making this study is 120 diameters. For the sake 

 of convenience the measurement is given as a fraction, the numerator of which is themeasurement of the image and the denominator 

 the magnification used. 



