204 
Fishery Bulletin 119(4) 
S666 SS 
60°Nj Chilkat River 
British Columbia 
Pacific Ocean 
138°W137°WsCsd136°Ws«185°W 
Stikine River 
ee A 
134°W SS - 133°W 132°W 131°W Ss 130°W 
Figure 1 
Map of the Chilkat and Stikine Rivers in Southeast Alaska and in British Columbia, Canada. The 
influence of environmental and biological factors on marine survival, freshwater overwinter sur- 
vival, and smolt production of Chinook salmon (Oncorhynchus tshawytscha) from these rivers was 
examined. Chinook salmon sampled from the Chilkat River were from the brood years 1999-2009 
and those sampled from the Stikine River were from the brood years 1998-2009. The stars indicate 
the 3 locations where sea-surface temperatures were collected monthly from May through August 
during 1997-2015: Auke Bay Monitor (ABM), Upper Chatam Strait (UCS), and Icy Strait (IS). 
River (Chapell®). The tagging of juveniles occurred from 
mid-September through October for parr and from April 
through May for smolts. The fall sampling period began in 
September at upriver locations and moved downstream as 
the season progressed, ending at the lower portion of the 
main stem of the Chilkat River. Spring sampling started 
in April and was conducted entirely on the lower portion of 
the main stem of the Chilkat River. In both sampling peri- 
ods, juvenile Chinook salmon were captured each day by 
using 100 Gee minnow traps (Cuba Specialty Manufactur- 
ing’, Fillmore, NY) baited with disinfected salmon roe 
8 Mention of trade names or commercial companies is for identi- 
fication purposes only and does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
(Chapell®). The ADFG fit a statistical model to CWT data 
from both sampling events to estimate parr abundance, 
smolt abundance, and overwinter survival (Elliott and 
Peterson”). Estimates of total annual abundance of smolts 
were used to represent freshwater smolt production. 
Data from the spring sampling of the CWT program 
in the Chilkat River were used to create indices of smolt 
migration timing. The number of minnow traps and 
catches of Chinook salmon were used to calculate the daily 
catch per unit of effort over the spring sampling period 
(early April-late May) for each reach of the river (Elliott 
and Peterson”). The daily catch per unit of effort in the 
lower Chilkat River was used as a proxy for the total num- 
ber of fish migrating to the ocean each day. To capture 
differences in annual migration timing, the ordinal date 
