KARLTJK RIVER RED-SALMON INVESTIGATION 



smaller proportion remains at sea for one additional year, returning in their sixth 

 year. (Fig. 30.) Group 3 gives rise, therefore, to four age groups, which we will 

 designate as the 3 S , 4 3 , 5 3 , and 6 3 groups, the first figure in each designation giving 

 the age at maturity and the second figure the numher of years' residence in fresh 

 water. 



Group 4 is the second in point of abundance among the migrating fingerlings 

 and furnishes correspondingly abundant classes in the mature run. Here, again, 

 as in Group 3, a certain small proportion matures precociously and the fish are 

 undersized and of little or no value, to which the name grilse is applied. Two age 

 groups are present among these grilse, corresponding to the two described above 

 in Group 3. The first of these matures during the first season in the sea and the 

 members of it are exclusively male fish under 40 centimeters in length and wholly 

 valueless, although in the fourth year of their age. (Fig. 26.) The second group 

 is one year older, as the fish mature during their second season in the sea, when in 

 their fifth year. In this group, also, the males greatly outnumber the females, but 

 in less degree than in the corresponding class of grilse in Group 3. The most valuable 

 contribution that Group 4 makes to the mature run is the fish that return in their 

 third year of sea life, at the age of 6. (Fig. 29.) Although much less numerous than 

 the 5 3 's, they form a material part of the commercial run. Relatively few members 

 of Group 4 remain at sea an additional year and return as 7-year fish, and we have 

 encountered but one individual captured in the fifth year of sea feeding at the age 

 of 8. Group 4 gives rise to five age groups, which we designate as the 4 4 , 5 4 , 6 4 , 7 4 , 

 and 8 4 groups. Only the 6 4 's have any considerable value. 



Group 5 is the least numerous of all and is encountered only rarely among 

 fingorling migrants or in the adult runs. Their greater age on reaching the sea 

 seems to predetermine them to earlier maturing after a shorter period of sea feeding. 

 A few diminutive male grilse that return after a few months in the ocean have come 

 to our attention. (Fig. 27.) These were exclusively males, as in the corresponding 

 classes of grilse in Groups 3 and 4. We have also encountered a few others (also 

 males) that matured in their second sea year at the age of 6, and a small number 

 of full-sized fish in their third sea year, at the age of 7. The 12 individuals of the 

 7-year group comprised 3 males and 9 females. If further experience with this group 

 shall demonstrate an equally high percentage of females, this will furnish an 

 interesting commentary on the high percentage of the males in Group 5 that mature 

 precociously. This group gives rise to but three age groups, which we here designate 

 the 5 5 , 6 5 , and 7 5 groups, all of which are without commercial importance. 



From the above sketch it is apparent that while the length of the period that 

 the young spend in fresh water has a certain influence on the age at which maturity 

 is attained, the most important factor governing growth is the length of time spent 

 in the sea. Full-sized adults, with females as numerously represented as the males, 

 are produced in the Karluk race not before the third year of sea feeding, whatever 

 the age or size of the fingerlings at the time of the seaward migration. Many 

 individuals mature and return to spawn and die having had less than three seasons 

 in the sea, but these are always markedly undersized, conspicuously deficient in 

 color of flesh and amount of oil, and they develop in minor degree the secondary 

 sexual characters that mark the species They are largely male fish and are known 

 as grilse. 



68335—27 3 



