Goetz and Quinn: Behavioral thermoregulation by adult Oncorhynchus tshawytscha prior to spawning 
261 
Table 1 
Mean length of adult Chinook salmon (Oncorhynchus tshawytscha) captured and tagged in coastal waters near Puget 
Sound in Washington in 2005 and 2008, and associated tagging and recovery data for discrete weekly tagging events. 
Standard deviations of mean lengths are given in parentheses. PIT=passive integrated transponder. 
Tag and release date 
Mean fork 
length (mm) 
No. of 
archival/PIT 
tags 
No. of 
acoustic tags 
No. of PIT 
detections 
No. of 
archival 
recoveries 
No. of archival 
and acoustic 
recoveries 
ll-Aug-05 
780.7 (84.7) 
19 
15 
5 
4 
3 
17-Aug-05 
738.1(117.5) 
57 
7 
11 
9 
1 
24-Aug-Q5 
735.1 (82.0) 
72 
10 
17 
27 
3 
31-Aug-05 
750.1 (105.7) 
50 
10 
7 
19 
4 
Mean or total for 2005 
744.1(99.8) 
198 
42 
40 
59 
11 
9-Aug-06 
795.7 (63.9) 
50 
19 
12 
13 
7 
16-Aug-06 
768.4(96.0) 
32 
11 
3 
8 
4 
23-Aug-06 
820.3 (72.3) 
29 
9 
2 
11 
2 
30-Aug-06 
789.7 (64.5) 
32 
7 
4 
13 
3 
6-Sep-06 
796.7 (64.8) 
21 
5 
0 
6 
1 
13-Sep-06 
842.0(117.3) 
10 
2 
2 
3 
0 
Mean or total for 2006 
794.2 (82.6) 
174 
53 
23 
54 
17 
had PIT tag detectors in a pool immediately upstream of 
the exit, indicating the proportion of fish using the lad¬ 
der. Archival loggers attached externally, just behind the 
dorsal fin, recorded ambient temperatures experienced by 
the salmon. For data loggers, we used model iBCod (Alpha 
Mach, Ste-Julie, Quebec) type Z (high resolution ±0.125°C, 
precision ±1°C, temperature range of -5-26°C, weight of 
12 g in air), a size appropriate for tagging fish 50-100 cm 
in fork length, and attached them to the salmon by using 
nickel pins and vinyl disks. The temperature loggers 
recorded data hourly for 95 d but had to be recovered to 
acquire the data. Moreover, the precise location of the fish 
had to be inferred from the thermal regime or detection of 
a transmitter in the fish (if it had one) when it passed a 
receiver. 
Locations of 95 Chinook salmon were determined by 
using acoustic transmitters weighing <12 g. Vemco (Bed¬ 
ford, Canada) V13-1L (22) and V13P-1L pressure sen¬ 
sors (63) and V9-6L (11) acoustic tags, with 20-60 s and 
30-90 s minimum and maximum pulse rates (or intervals 
between each signal transmission), were inserted into 
stomachs. The detection range of the tags in marine and 
deep areas in fresh water was about 100-400 m for the 
V9 and 200-600 m for the V13 tags. Detection ranges for 
all tags declined to about 10-100 m in shallow areas and 
were affected by proximity to the shoreline, fish depth, 
and other local features. 
Data retrieval from tags and environmental monitors 
Vemco VR2 acoustic receivers (16 in 2005 and 21 in 2006) 
were installed along the migration corridor (Fig. 1; see also 
Goetz, 2016) before the Chinook salmon were tagged and 
before they were retrieved after the spawning season. All 
detections were checked, and erroneous records, incon¬ 
sistencies, and data anomalies were removed. Data from 
other researchers were obtained either through direct con¬ 
tact or from online databases (Hydraphone Data Repos¬ 
itory, available from website; Ocean Tracking Network, 
available from website). Four sets of antennae and PIT 
tag readers were installed in the fish ladder; sequential 
detections indicated the direction of movement. 
To characterize the conditions available to salmon, we 
obtained data on salinity, temperature, and DO concen¬ 
tration from fixed stations and from water-quality data 
collected by various agencies (Table 2), including data in 
the large lock during 1 d each year of the study by mea¬ 
suring temperature and salinity changes over a series of 
lock-filling events. We monitored temperature hourly in 
the large lock during the course of the study by using a 
thermometer at a depth of 10 m (in 2005) and near surface 
(in 2006). 
Data analysis 
Telemetry data indicating time and depth at fixed receivers 
were combined with hourly data from archival tempera¬ 
ture loggers to reveal the thermal experience of individual 
fish along their route. This was done by constructing, for 
each fish, a chronology by merging the logger data (with 
temperature, date, and time) with the receiver data (with 
date, time, and depth, at fixed locations). Salmon were 
excluded from analysis if they apparently died, they were 
not detected upriver of the locks, or the date and location 
of the recovery of their archival tag could not be verified. 
Analyses were designed to describe the behavior and envi¬ 
ronmental experience of fish by recovery location and by 
segment of the migration route. The segments were as 
follows: 1) marine waters of Puget Sound to the locks, 
2) upper estuary above the locks in Salmon Bay, 3) ship 
canal and Lake Union, 4) Lake Washington, including the 
deltas of the Sammamish River and the Cedar River, 5) the 
