CHINOOK SALMON MARKING, COLUMBIA RIVER 247 



were reported during the first week of the commercial fishing season. Only 14 of the 

 75 recoveries were made after the middle of May. 



One of the 6-year-olds, which was caught on September 23, represents an excep- 

 tion to this rule. As only one other exception was found, this record has been 

 checked carefully to determine if it is authentic. The scars were found to be typical 

 of those produced by marking, and no reason for questioning any part of the data 

 presented itself. The nuclei of the scales from this fish do not agree exactly with 

 those of the other fish recovered from this experiment; but the record could not be 

 invalidated on this score, because the nuclei in the collection show a wide range of 

 variation, one extreme of which might be represented by the scale in question. The 

 age indicated by the scales is correct. 



Three possible explanations for the irregularity of this record might be sug- 

 gested : 1 . It may be an authentic exception to the rule that the progeny of the spring 

 run return in the spring. 2. The fingerling from which this fish developed may have 

 been one from the fall run of chinooks that by accident became mixed with the 

 spring chinooks at the hatchery. 3. The fish may have lost the fins by some other 

 means. As there is no evidence that the second or third possibility is true, the first 

 must be accepted tentatively. 



One of the .5-year-olds returned to Tanner Creek and was recovered in the 

 spillway from the hatchery ponds in which it was reared as a fingerling. This is the 

 fourth of the marked spring chinooks that has returned to the tributary in which 

 it was liberated. 



The nuclei of the scales of the adult fish in this collection are more variable than 

 those of any other marked spring chinooks. Most of the variations may be grouped 

 into a single general type, however. In this general type the nucleus consists pre- 

 dominately of stream growth surrounded by a narrow band of intermediates. (See 

 Table 24.) The presence of the band of intermediates at the end of the first year 

 typically results in a gradual transition in the nature of the rings and obscures the 

 points of demarcation, both between the stream and intermediate growth and 

 between the intermediate and ocean growth. The scale shown in Figure 63 is a good 

 example of this condition. A scale with the three types of growth more clearly 

 differentiated is illustrated in Figure 64. In some cases the intermediates are dis- 

 tinctly differentiated from the ocean growth but closely resemble the rings of stream 

 growth. A scale of this nature is illustrated in Figure 65. Without a series of 

 scales with which to compare it, this nucleus might be considered as a pure stream 

 type. 



The band of intermediates varies in width from a maximum of 12 rings, as shown 

 in Figure 66, to none, as shown in Figure 67. Figures 63 and 64 show more average 

 widths. The apparent absence of intermediates in some cases may be due to a lack 

 of contrast between them and the rings of stream or ocean growth. It is especially 

 difficult to distinguish the intermediates when they are only 1, 2, or 3 in number. 

 An extremely wide band of intermediates combined with a slight contrast between the 

 stream and intermediate growths gives the nucleus in Figure 66 the appearance of an 

 ocean type, and it is possible that the outer rings of this nucleus actually were formed 

 in the ocean. If this be the case, the nucleus should be classed as a composite type. 



