Segregation in space can be dealt with in 

 two parts. First, there is the possibility 

 of segregation to areas that are unequally 

 distant from the river mouth. This, it will be 

 shown, is equivalent to segregation in time 

 and therefore can be discussed under that 

 heading. Second, there is the possibility 

 of segregation along paths of migration 

 at sea if spawning groups travel to- 

 ward the river independently and merge 

 only when they enter. There may be 

 some tendency for the runs to each of the 

 several rivers to favor certain lines of ap- 

 proach to their home streams, but segrega- 

 tion of whole river populations is far from 

 complete, even at the mouths of these rivers; 

 so it is most unlikely that there is segregation 

 of their components in Kvichak Bay. Segrega- 

 tion of spawning groups in the area of the 

 fishery is therefore considered negligible, and 

 only segregation in time is discussed here. 



Segregation in time might be expected. 

 Though the entry of Kvichak River spawning 

 groups into the streams is completed within a 

 month, these groups spawn at widely different 

 times. During the 3-month period July 25 to 

 October 25 there is always some spawning 

 activity in the system. Peak spawning is in 

 August for some groups, in mid-October for 

 others. 



Spawning groups also spawn in at least 

 three distinct types of locations as indicated 

 by the FRI spawning ground enumerations of 

 1955-59, which accounted for 70 percent of 

 the observed spawners in creeks and rivers, 

 25 percent on lakeshore beaches, and 5 percent 

 in spring-fed ponds. In recent years sub- 

 stantial numbers of spawners have also been 

 observed in deep water (Orrell and Demory, 

 1962). Spawning environments range from 

 coffee-colored tundra streams in the lowlands, 

 through clear, spring-fed waters in the foot- 

 hills to milky, glacier-fed creeks and beaches 

 in the mountainous regions. Spawning groups 

 occupy each of these environments and it is 

 probable that they may be separated genetic- 

 ally. Because timing of the spawning groups 

 on the grounds differs enormously, the groups 

 might have been segregated before their 

 arrival. 



Because it is in the fishery that the selective 

 harvest must be undertaken, spawning groups 

 must be identified there. In the Kvichak-Naknek 

 fishery this identification is complicated by 

 the intermingling of the runs to the several 

 rivers, and at present it is not possible to 

 determine positively to which system individ- 

 ual fish or groups of fish are bound. If identi- 

 fication is not possible by direct inspection 

 in the fishery, the possibility remains of 

 defining groups at some point within the river 

 system and then back-plotting to determine 

 the most probable time of passage of these 

 groups through the area of the fishery. Such 

 an approach is possible only in the event 

 that the escapement and the run reflect a 

 similar degree of segregation in time. For- 

 tunately, available data show this to be true. 

 First, it has been indicated (Bureau of Com- 

 mercial Fisheries, 1958) that 55 percent of 

 Kvichak River fish travel through the area of 

 the fishery in 3 days or less after tagging. 

 Second, when cumulative curves of abundance 

 of salmon are plotted, one for the Kvichak- 

 Naknek catch in Bristol Bay and one for the 

 escapement at Igiugig on the upper Kvichak 

 River, it is apparent that the time lag between 

 modes of abundance in the fishery and modes 

 of abundance at Igiugig is quite uniform. For 

 the years 1955-58, the range was 5.7 to 10.4 

 days, with an average of about 8 days. From 

 these data it appears that the chronological 

 order of arrival of the fish in the fishery is 

 preserved at least during their migration 

 through the Kvichak River. Furthermore, it 

 appears that extent of segregation of spawning 

 groups in the escapement upriver reflects a 

 similar segregation in the fishery. 



The final step is to establish the extent to 

 which recognizable spawning groups are segre- 

 gated as they pass upriver. An experiment 

 designed for this purpose was started in 1957. 



METHODS AND MATERIALS 



The escapement up the Kvichak- River is 

 estimated from counts made from towers lo- 

 cated near the native village of Igiugig (fig. 1) 

 below the outlet of Iliamna Lake. The fish are 

 sampled by seine to determine age, size, and 

 sex ratio as well as frequency of net scars 

 and injuries. Records are complete for 1955-59. 



