DRUCKER: COHO SALMON OF KARLUK RIVER SYSTEM 



from 4.91 to 6.87 mm (mean 6.11 mm); fecun- 

 dity ranged from 2,855 to 6,906 (mean 4,766) . 

 No relation was found: eggs from a female with 

 low fecundity were not necessarily large, nor 

 were those from a female with high fecundity 

 necessarily small. Allen (1958) reported similar 

 findings. 



Unlike the general relation that exists between 

 fecundity and length (i.e., larger fish are more 

 fecund), the size or fecundity of the females I 

 sampled apparently had no relation to the size 

 of the eggs. Large, fecund females had a wide 

 range of egg sizes (Figure 5) . Thus, the larger 

 number of eggs in large females may be due to 

 a larger body cavity that allows more eggs to 

 develop rather than to the fish having smaller 

 eggs. 



COHO SALMON SMOLTS 



Smolts of coho salmon, like those of other 

 salmon that live for a while in fresh water be- 

 fore migrating to sea, migrate seaward at a par- 

 ticular season and under particular light inten- 

 sities. This migration and the associated envi- 

 ronmental factors and information on age and 

 size of migrating smolts are discussed in this 

 section. 



SEASONAL MIGRATION 



Coho salmon juveniles reside in Karluk Lake 

 for 1 to 4 years before they migrate to sea as 

 smolts. From 1961 to 1967 the migration began 

 in mid-May and was usually over by early July 

 (Figure 7). 



Although most coho salmon migrate in the 

 spring (Hamilton and Andrew, 1954; Taft, 

 1934; Gharrett and Hodges, 1950; Semko, 1954) , 

 several exceptions do exist. In the Paratunka 

 River, Kamchatka Peninsula, the migration ex- 

 tends from the end of May to the end of August 

 (Gribanov, 1948) ; in several streams in Oregon 

 it extends from late winter to May (Chapman, 

 1961); in some streams in western Washington 

 it runs from early winter to late spring ( Smoker, 

 1953) ; and at Waddell Creek, Calif., small num- 

 bers of atypical migrants migrate in the fall and 

 early winter (Shapovalov and Taft, 1954) . The 



100 



-| 1 1 T — I 1 1 1 1 rr 



15 20 25 30 4 9 14 19 24 29! 4 9 14 19 

 MAY ' JUNE ' JULY 



Figure 7. — Cumulative seasonal migration of coho salm- 

 on smolts from Karluk Lake, 1961-67. 



number of coho salmon smolts involved in the 

 early or late parts of these migrations, however, 

 represents only a small percentage of the total 

 number of smolts in each migration. 



The warming of the water after the ice breaks 

 up is of major importance in initiating the sea- 

 ward migration of smolts. Hartman, Heard, and 

 Drucker (1967) found this to be a major factor 

 in the migration of sockeye salmon in lakes of 

 southwestern Alaska; and Logan (see footnote 

 2, Table 1) found that the coho salmon smolt 

 migration in Bear Lake, Alaska, did not start 

 until the ice cover on the lake was gone and the 

 water temperature had risen to 4.2° C. Ninety 

 percent of the Bear Lake coho salmon smolts 

 had migrated to sea when water temperatures 

 ranged between 5° and 13.3° C. Coho salmon 

 smolts apparently migrate over a greater 



87 



