Estimation of Chinook Salmon Escapement, 

Distribution and Run Timing in the Togiak 

River Watershed Using Radiotelemetry, 

Togiak National Wildlife Refuge, Alaska, 2012 

Alaska Fisheries Data Series Number 2014-11 

U.S. Fish and Wildlife Service

Anchorage Fish and Wildlife Field Office 

Anchorage, Alaska 

October 2014 
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Alaska Fisheries Data Series Number 2014-11, October 2014 

U.S. Fish and Wildlife Service 

Authors: 1U.S. Fish and Wildlife Service (USFWS), Anchorage Fish and Wildlife Field Office, 605 W 4th Avenue, 

Anchorage Alaska 99501, theresa_tanner@fws.gov; 2USFWS, Fisheries and Ecological Services, 1011 E. Tudor 

Rd., Anchorage, AK 99503

Estimation of Chinook Salmon Escapement, Distribution and Run 

Timing in the Togiak River Watershed Using Radiotelemetry, 

Togiak National Wildlife Refuge, Alaska, 2012 

Theresa L. Tanner and Suresh A. Sethi 

Abstract

Radiotelemetry was used to determine distribution and run timing of Chinook 

salmon Oncorhynchus tshawytscha in the Togiak River watershed. Additionally, 

mark-recapture techniques were employed to estimate Chinook salmon 

abundance. In 2012, radio transmitters were implanted into 147 Chinook salmon 

and another 161 fish were marked with spaghetti tags in the lower 5 km of the 

Togiak River for the marking event. A total of 106 radio-tagged fish (72%) were 

successfully tracked to spawning locations. Fifteen radio-tagged fish (10%) had 

an indeterminate fate, 18 (12%) were known harvests, and 8 (5%) were assigned a 

fate of dead/regurgitated. Eighty-four percent (n = 57) of the tracked fish selected 

spawning locations in the mainstem of the Togiak River, and 15% (n = 22) 

selected spawning locations in the tributaries, primarily in Nayorurun River (8%, 

n = 8) and Kemuk and Ongivinuk rivers (5%, n = 5, each). A resistance-board 

weir was installed in Gechiak Creek to serve as the primary recapture event for 

the mark-recapture effort. A total of 283 unmarked and 8 marked Chinook 

salmon were counted through the weir from 26 June through 2 September. A 

second recapture event was conducted in the form of 16 carcass surveys, 

conducted 11 August through 2 September, in which 145 unmarked and 2 marked 

Chinook salmon carcasses were examined. The spawning population estimate for 

Chinook salmon that entered the Togiak River in 2012 is 13,050 fish (95% CI = 

{7,844; 24,762}). Tests to determine differences in run timing between tributary 

and mainstem spawning populations indicate that tributary fish entered the lower 

river earlier than mainstem spawning fish. Movement behavior of spawning 

Chinook salmon, e.g., holding in the lowest mainstem river section for a period of 

days or weeks, prolongs exposure of in-migrating fish to harvest efforts. 

Introduction 

Chinook salmon Oncorhynchus tshawytscha returning to spawn in the Togiak River watershed 

are harvested in subsistence, sport, and commercial fisheries. For the Togiak River watershed, 

the Alaska Department of Fish and Game (ADF&G) established a Sustainable Escapement Goal 

threshold of 9,300 Chinook salmon based on aerial surveys (Baker et al. 2009). Average 

estimated Chinook salmon spawning escapement from 1996 to 2005 was 11,862 fish, and 

average harvest was 11,273 fish, representing a 49% exploitation rate. In 2007, the harvest 

included 9,213 fish harvested in the commercial fishery, 902 harvested in the sport fishery, and 

1,158 harvested in the subsistence fishery (Sands et al. 2008). 

Current monitoring of Chinook salmon escapement into the Togiak River watershed is limited to 

aerial surveys. Total escapement can be estimated by expanding visual counts with assumed 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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correction factors. The accuracy of aerial survey counts is greatly affected by stream life, 

variable run timing, observer efficiency, weather, water conditions, aircraft characteristics (type, 

speed, altitude, and pilot experience), and other factors (Bue et al. 1998). Aerial survey 

estimates within the Togiak River watershed have not been verified or compared with other 

methods, and the accuracy with which the observations index actual abundance is unknown. A 

complete aerial survey focused on Chinook salmon escapement for the Togiak drainage has not 

been completed since 2005 (Salomone et al. 2009). The Office of Subsistence Management 

(OSM), through its strategic planning process, identified a need to obtain reliable escapement 

estimates for Chinook salmon in the Togiak River (OSM 2005). The Bristol Bay Regional 

Advisory Council has voiced support for this need since 2003, and development of a reliable 

estimate of Chinook salmon escapement into the Togiak River was explicitly requested in the 

2008, 2010 and 2012 Request for Proposals for the Fisheries Resource Monitoring Program. 

Improving long-term escapement monitoring of all species of adult Pacific salmon in the Togiak 

River has been a top priority issue with the Togiak National Wildlife Refuge, Togiak Traditional 

Council, and ADF&G. Accurate monitoring of Chinook salmon abundance is needed to ensure 

that adequate escapements are achieved so that healthy Chinook salmon populations are 

sustained and subsistence harvests and other needs are maintained. Subsistence harvest and 

Chinook salmon spawning and rearing habitat in the Togiak River occur within the Federal 

Conservation System boundaries of the Togiak National Wildlife Refuge. Providing a harvest 

priority to subsistence users in these waters is mandated under Title VIII of ANILCA. This is 

the final year of a 3-year radiotelemetry study to estimate Chinook salmon abundance in the 

Togiak River watershed. 

Objectives for the project were to: 

1. estimate the proportion of tagged Chinook salmon migrating past a weir on Gechiak Creek; 

2. estimate the abundance of Chinook salmon escaping into the Togiak River watershed such 

that the estimate will have a 90% probability of being within 25% of the true abundance; 

3. estimate the weekly age and sex composition of spawning Chinook salmon in Gechiak 

Creek, such that simultaneous 90% confidence intervals have a maximum width of 0.20; 

4. estimate the mean length of Chinook salmon by sex and age; 

5. document Chinook salmon spawning locations in the Togiak River watershed; and 

6. evaluate the effectiveness of aerial spawning ground surveys for monitoring Chinook salmon 

abundance in the Togiak River watershed.

Objective 6 was not met in 2010, 2011, or 2012. ADF&G staff obtained only partial aerial 

counts, and abundance estimates from aerial survey data were not possible. 

Study Area

The Togiak River is located in southwest Alaska and lies within the Togiak National Wildlife 

Refuge (Figure 1). The watershed encompasses 5,178 km2, comprises 9 major lakes and 5 major 

tributaries, and is bound on the east by the Wood River Mountains and on the west by the 

Ahklun Mountains. The Togiak River originates at the outlet of Togiak Lake and flows 93 km to 

Togiak Bay. The watershed upstream of the confluence with Pungokepuk Creek is part of a 

congressionally designated Wilderness Area. Detailed descriptions of the lakes and tributaries 

can be found in the Togiak Refuge Fisheries Management Plan (USFWS 1990). 

Five species of Pacific salmon Oncorhynchus spp. are found in the Togiak River watershed 

along with rainbow smelt Osmerus mordax, rainbow trout O. mykiss, Dolly Varden Salvelinus 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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malma, Arctic char S. alpinus, northern pike Esox lucius, Arctic grayling Thymallus arcticus, and 

northern pike Esox lucius (USFWS 1990). 

Figure 1. Map of the Togiak River watershed in Southwest Alaska. 

PUNGOKEPUK 

PUNGOKEPUK 

LAKE

NAGUGUN 

WEST

TOGIAK

LAKE

UPPER TOGIAK

LAKE

HIGH LAKE

TOGIAK

RIVER

TOGIAK NATIONAL WILDLIFE

REFUGE WILDERNESS BOUNDARY

GECHIAK

CREEK

KILOMETERS 

0 2468 10

N

U.S.S.

ARCTIC OCEAN

BERING

SEA

ALASKA

CANADA

ANCHORAGE 

FAIRBANKS

PACIFIC OCEAN

TOGIAK BAY

NAYORURUN

RIVER

ONGIVINUK

ONGIVINUK

LAKE

TOGIAK

LAKE

KEMUK

RIVER

NENEVOK

LAKE

GECHIAK

LAKE

TOGIAK TWIN HILLS

STUDY 

AREA 

RIVER

LAKE

CREEK

(KASHAIAK)
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Methods

A radiotelemetry experiment was conducted to estimate the abundance, distribution, and run 

timing of Chinook salmon in the Togiak River watershed. Fish were captured and marked with 

radio transmitters and spaghetti tags in the lower 5 km of the mainstem. A resistance-board weir 

was installed in Gechiak Creek to enumerate fish passage and to obtain a proportion of marked to 

unmarked Chinook salmon. Movements and final spawning destinations of radio-tagged fish 

were documented using a combination of fixed data logging receiver stations and aerial- and 

ground-based mobile tracking. 

Mark-Recapture Procedures 

Marking event---A three person crew fished a drift gill net (18.3 m long, 4.6 m deep, 20.3 cm 

stretched mesh size), with one crew member piloting the boat and the other two positioned in the 

bow tending the net. The gill net was deployed from the bow of the boat, and the boat motor was 

idled in reverse to keep the net perpendicular to the shore while drifting downstream in the center 

or deepest sections of the river. Each sampling area is less than 1 km in length, and fishing 

continued until the end of the area was reached or a fish became entangled in the net. Drift time 

was monitored and recorded with a stopwatch. All fish except Chinook salmon caught in the net 

were identified to species, counted, and immediately released. Statistical weeks defining 

temporal strata were used for sampling (Table 1). Sampling effort was standardized across 

temporal strata in order to mark Chinook salmon in proportion to abundance, a sampling feature 

that was crucial to obtain unbiased mark-recapture estimates of spawning abundance when using 

a systematic subsample during recapture events (Tanner and Sethi 2012). Gillnet fishing efforts 

were targeted to 2 hours of soak time per day, for an average of 14 hours soak time in each 

temporal stratum. 

Table 1. Allocation schedule for Chinook salmon radio transmitters in the Togiak River, 2012. 

Strata Dates Radio Transmitter Allocation Spaghetti Tag Color 

1 21–30 June 45 Fluorescent Pink 

2 1–10 July 45 Fluorescent Green 

3 11–20 July 45 Fluorescent Yellow 

4 21–30 July 45 International Orange 

5 31 July–9 August 20 White 

6 10–12 August 20 Florescent Pink/Green 

Total: 200 

Chinook salmon longer than 450 mm (mid-eye to fork of tail) were tagged with radio 

transmitters manufactured by Advanced Telemetry Systems, Incorporated® (ATS; Model No. 

F1840B). Transmitters were encapsulated in a biologically inert polypropylene copolymer and 

equipped with a stainless steel nylon coated whip antenna. Transmitters weighed 22 g, which 

never exceeded 2% of the fish’s body weight (Winter 1983). Radio transmitters were implanted 

through the esophagus using a plunger as described by Burger et al. (1985). Two hundred radio 
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tags consisting of 25 unique pulse digital codes dispersed over eight radio frequencies between 

163.3 and 164.0 MHz were used. The combination of codes on each frequency allowed for the 

identification of individual fish. A mortality code was transmitted after 8 hours of inactivity. 

Additionally, 30.5 cm serially numbered spaghetti tags (Floy Tag and Manufacturing, Inc.; 

Model No. FT-4) were applied near the rear base of the dorsal fin between the interneural bones 

using a hollow needle. The tag was secured to the back of the fish with a Nico press sleeve. The 

spaghetti tags, or Floy tags, served as a highly visible mark, and each marking strata was 

represented by a separate color (Table 1). Marking criteria dictated that only healthy, lightly 

stressed Chinook salmon would receive both a radio tag and a Floy tag. If multiple Chinook 

salmon were captured in a single net set, only the first fish was implanted with a radio tag. All 

others were marked solely with a spaghetti tag and released. 

We incorporated hook-and-line sampling to complement our gillnet fishing efforts. Hook-andline sampling entailed letting out line with lead weight and spinner until they ‘tapped’ along the 

substrate while the boat driver maintained a slow downstream troll. Fishing effort was timed and 

standardized to one hour of total line soak time. Chinook salmon captured by hook and line only 

received Floy tags. All of the spinners were single hook and had the barbs pinched down to 

minimize injury. 

Efforts were made to minimize stress to Chinook salmon during capture and handling. Captured 

fish were removed from gill nets as quickly as possible, and gillnet meshes were cut if the fish 

could not be easily removed from the net. Chinook salmon were then placed in a padded tagging 

cradle alongside the boat to allow the fish to be processed without removal from the water. The 

general health and appearance of each fish was recorded and mortally injured fish were not 

marked. Marked Chinook salmon were immediately released into the river after tagging. Total 

handling time for each marked fish was recorded. Handling time was calculated from the time 

the fish was first detected hitting the gill net, i.e., the net floats were disturbed, until the fish was 

sampled and released. 

Recapture events---A resistance board weir (Tobin 1994; Stewart 2002) was installed in Gechiak 

Creek (59.2218ON, 160.25049 OW), approximately 2 rkm upstream from Togiak River. Weir 

panels were constructed of 2.5 cm inside-diameter schedule 40 polyvinyl chloride electrical 

conduit. Resistance boards were attached to each panel to aid floatation. Panel dimensions were 

5.8 m long by 0.9 m wide with 7.62 cm center to center picket spacing. The panels were 

attached to the river bottom by way of a steel substrate rail and a 10 mm cable running from 

bank to bank (Figure 2). A 1.2 m apron of mesh chain link fence served to stabilize the substrate 

and acted as a barrier to fish passage beneath the rail. A fish passage panel designed as a chute 

was positioned near the deepest part of the channel, allowing fish to pass into a live trap to 

facilitate biological sampling and passing adult salmon through the weir. Two panels, not 

maintained with their resistance boards deployed and marked with orange buoys on either side, 

were positioned in the thalweg of the creek to allow for boat passage. 

The weir served to recapture fish marked in the lower river and to enumerate all fish moving up 

the creek. Fish were counted intermittently throughout the daylight hours from roughly 0600 

through 2400 hours. The duration of each counting session varied depending on the number of 

fish arriving at the weir. A contrasting substrate was placed on the stream bottom in front of the 

counting panel to enhance visibility of fish and to facilitate species identification as they were 

passed through the counting panel. When the weir was unmanned, the live trap was closed to 

passage. The weir was cleaned of debris and inspected daily for integrity. Repairs were made as 

needed. 
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Starting in mid-August, we conducted multiple spawning ground surveys. Surveys continued 

through the spawning period and ended in early September. Ground surveys were conducted 

with two or more observers. To prevent bias, surveys were conducted opportunistically and 

independently from telemetry tracking efforts. Surveys covered all areas accessible by boat to 

adult salmon in known spawning areas. Surveyors wore polarized glasses to reduce water 

surface glare. All carcasses were identified to species and Chinook salmon were examined for 

marks. The following data was recorded for each ground survey: date, time, crew, reach name, 

GPS coordinates (NAD83 datum) and waypoint, count of marked and unmarked carcasses of 

Chinook salmon, the color and serial number for each marked fish, count of live Chinook 

salmon, water clarity (excellent, good, or poor), lighting conditions (sun, partial overcast, 

overcast), wind generated surface turbulence (calm, moderate, rough), and any other pertinent 

comments. If a fish could not be positively identified as a Chinook salmon, it was excluded from 

both counts and counted as “unknown”. Once a carcass had been sampled, it was be mutilated 

by cutting off the caudal fin and marking an operculum to avoid double-counting in future 

surveys. 

Figure 2. The resistance-board weir installed in Gechiak Creek (photo taken in 2011). A remote telemetry 

station was co-located with the camp on top of the river left bluff. 
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Biological sampling--- For all Chinook salmon tagged in the marking event, length was 

measured to the nearest mm (mid-eye to fork of tail) and sex was determined from external 

characteristics (Mecklenburg et al. 2002). Three scales from the preferred area on the left side of 

each fish (Jearld 1983) were removed, cleaned, and mounted on gummed scale cards. After the 

field season, scale impressions from the gum cards were made on acetate blanks using a heated 

hydraulic press. Scale impressions were viewed with a microfiche reader and fish age was 

determined using the standards and guidelines of Mosher (1968). Fish ages were reported 

according to the European method described by Jearld (1983) and Mosher (1968), where the 

number of winters the fish spent in fresh water and in the ocean are separated by a decimal. Fish 

with scales that could not be aged were not included in the age analyses. 

Chinook salmon passing through the weir at the recapture event were sampled for age, sex, and 

length (ASL) data using a temporally stratified sampling design (Cochran 1977), with statistical 

weeks defining strata. A weekly sample target of 155 fish was drawn for ASL information. 

Samples were dispersed throughout the week and taken periodically during the day. All fish 

within the trap were included in the sample to avoid potential bias caused by the selection or 

capture of individual fish, even if the target number of fish was exceeded. Non-target fishes 

captured in the live trap were identified to species, enumerated, and released upstream of the 

weir. 

Additionally, genetic tissue samples were collected from the axillary processes of Chinook 

salmon handled for ASL data collection in both the marking and recapture events. These 

samples were archived in individual vials for later genetic analysis. 

Data Analysis

Radiotelemetry tracking methods---Radio-tagged Chinook salmon were tracked throughout the 

Togiak River watershed using a combination of seven fixed monitoring stations (Table 2; Figure 

3) and mobile tracking from boats and fixed-wing aircraft. Six of the fixed monitoring stations 

were located on the mainstem, and one was located on a tributary. One station was co-located at 

the field camp site and weir on Gechiak Creek. The first fixed station on the mainstem was 

placed upstream of the capture and tag deployment site to help delineate all of the radio-tagged 

fish that moved into the study area, which is defined as the bottom of Mainstem A (Figure 4). 

Fixed monitoring stations were used to record up- and downstream movement of individual 

tagged fish. Each fixed station included a single receiver-datalogger (ATS model R4500C or 

R4520C), a single 4-element Yagi antenna, antenna mast, 12-volt deep cycle battery, solar panel, 

voltage regulator, and strongbox. Data from fixed receiver stations were downloaded weekly to 

a notebook computer. 

Aerial surveys were used to identify specific spawning locations in the Togiak River and its 

tributaries. Aerial surveys were conducted from a fixed-wing aircraft equipped with an Hantenna mounted on each wing strut. Aerial surveys were flown at altitudes of approximately 

100–400 m above ground along the Togiak River and its tributaries. A global positioning system 

(GPS) built into the receiver-datalogger (ATS model R4500C or R4520C) was used during aerial 

surveys to record latitude and longitude coordinates and signal strength of each transmitter 

located. Two receivers monitoring four separate frequencies each were used to reduce the scan 

time for aerial surveys. 

Boat surveys were used from the river mouth upstream to Togiak Lake to more precisely locate 

spawning in the mainstem Togiak River. Boat surveys were conducted using a portable receiverdatalogger (ATS model R4500C or R4520C) and a 4-element Yagi antenna. A hand-held GPS 
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was used during boat surveys to record latitude and longitude coordinates for each transmitter 

located. 

Table 2. Name and location (decimal degrees) of fixed telemetry stations in the Togiak River watershed, 

2012. 

Station Name Latitude Longitude 

Entry 59.11696 -160.35397 

Second 59.18352 -160.27887 

Gechiak 59.22189 -160.25049 

Ranger 59.26802 -160.20891 

Nayorurun 59.36012 -160.09184 

Kemuk 59.36882 -159.98930 

Ongivinuk 59.40030 -159.79631 

Figure 3. Remote data logging receiver station locations and tagging areas in the Togiak River, 2012. 

TAGGING AREA

REMOTE STATIONS
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Figure 4. Mainstem river sections corresponding to ADF&G aerial survey delineations and tributary fates 

assigned to radio-tagged Chinook salmon in the Togiak River, 2012. The exception is the Twin Hills Channel, 

which was designated as a possible spawning fate for the first time in 2010.
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Radiotelemetry data interpretation---Each radio-tagged Chinook salmon was assigned one of six 

possible fates based on information collected from mobile and fixed receivers (Table 3). Fish 

whose spawning locations could be identified based on tracking results were assigned a fate of 

either mainstem or tributary spawner. Mainstem spawners were assigned to one of six river 

sections (Figure 4). The boundaries of these (A-F) corresponded with aerial survey segments 

used by ADF&G (Brookover et al. 1996). Tributary spawners were assigned to one of six 

tributaries. In addition to the tributary survey areas designated by ADF&G, in 2010 we added 

the Twin Hills Channel as a possible spawning tributary (Tanner and Sethi 2011). Chinook 

salmon whose spawning location could not be determined with reasonable certainty were placed 

into an unknown category. The unknown category was further divided into two groups: fish that 

were unsuccessfully located post-tagging; and fish that were successfully tracked within the 

system, but disappeared after at least two to three weeks of movement, indicating possible 

harvest and removal of that fish from the system. Fish whose radio tags were detected within the 

local villages or canneries from aerial surveys were also classified as Suspected Harvest. Fish 

assigned a fate of harvested or dead/regurgitated were censored from the sample. 

For fish assigned a spawning fate, the amount of time spent holding in the lower river (defined as 

locations below or within Mainstem A) was estimated from the date the fish was tagged through 

the date the fish was first detected beyond the mouth of Gechiak Creek confluence, which 

defined the upper most portion of Mainstem A (Figure 4). Basic statistics (mean, minimum, and 

maximum number of days) were calculated for 2012, and a one-way ANOVA was conducted 

across the 2010–2012 study years to compare the number of days spent holding in the lower river 

for tributary and mainstem spawners. 

Table 3. Fate of Chinook salmon radio-tagged in the Togiak River, 2012. 

Fate Description 

Spawning Location: 

 Mainstem (1 of 6 river sections) A fish that spawned in Togiak River. 

 Tributary (1 of 6 tributaries) A fish that spawned in a tributary of the Togiak River. 

Unknown Fate:

 Insufficient location information A fish that could not be located by either fixed or 

mobile telemetry tracking. 

 Suspected harvest A fish that was tracked to multiple locations over a 2-4 

week period before disappearing from the system, or a 

radio tag that was detected within a local village or 

cannery during an aerial survey. 

Removed From Study: 

 Harvested A fish that was reported harvested in either the 

commercial, sport, or subsistence fisheries. 

 Dead/Regurgitated A fish that did not complete its spawning migration 

because it either died or regurgitated its radio tag. 
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Spawning abundance estimation---Chinook salmon abundance estimation follows methods 

outlined in Tanner and Sethi (2012); additional details regarding the mark-recapture sampling 

protocol and defense of modeling assumptions are provided therein. Adult Chinook salmon were 

tagged in the lower part of the mainstem Togiak River; however, recapture occurred 

systematically on a single spawning subpopulation at a weir on an upstream tributary (Gechiak 

Creek), and so opportunistic carcass surveys were conducted to supplement the recapture event. 

While tagging and recovery occurred over several weeks, release and recovery data were pooled 

and analyzed with a single release/single recapture closed-population Lincoln-Petersen estimator. 

We implemented a Bayesian version of the Lincoln-Petersen estimator, ܰ

෢஻. In this formulation, 

modeling both tags and unmarked salmon captured in the second sample session as binomial 

processes: 

݉ଶ|݊ଵ	, ݌	~	ܤ݅݊݋݈݉݅ܽሺ݊ଵ	, ݌ሻ 1 

 2 ሻ݌ ,	ܷሺ݈݉݅ܽ݋݅݊ܤ	~	݌ ,	ܷ|ݑ

where p is the probability of detection, or catchability, u is the number of unmarked Chinook 

counted in the recapture event (at the weir), and U is the number of unmarked animals in the 

overall population. Priors were as follows: 

logሺܷሻ ~ܷ݂݊݅ݎ݋݉ሺ0,14ሻ 3 

 4 ሻ1,1ሺܽݐ݁ܤ~݌

Finally, total abundance, ܰ

෢஻, was included as a derived parameter in the model as ݉ଶ ൅ ܷ. The 

Bayesian estimator was implemented in WinBUGS (Spiegelhalter et al. 1999) from R using the 

R2WinBUGS package (Sturtz et al. 2005). We ran five chains of 1,000,000 iterations, with a 

burn-in period of 950,000 iterations, and a thin rate of 100, for a total of 2,500 retained joint 

posterior parameter draws for subsequent inference. The fitted model was monitored for chain 

convergence by visually examining MCMC trace plots and ensuring that all tracked parameters 

had Gelman-Brooks-Rubin statistic <1.10 (Brooks and Gelman 1998; Kery and Schaub 2012). 

Appendix 1 of Sethi and Tanner (2012) provides R code to fit the model. 

Tests for differences in run timing---Run timing information can be used to ascertain whether 

subpopulations within the Togiak River passed the tagging site as a well-mixed group, or 

whether subpopulations entered the river in separate groups. To test for differences in run 

timing, we used tag release dates of successfully fated fish, where fated spawning location 

indicates a subpopulation (e.g., Gechiak, Ongivinuk, or Mainstem A spawner). 

Following Tanner and Sethi (2012), we examined the following questions associated with run 

timing of Chinook subpopulations in the Togiak River during the 2012 season: 

1. Are there differences in the run timing between pooled tributary and pooled mainstem 

populations (H0: There is no difference in run timing between tributary and mainstem 

spawners)? 

2. Are there differences in the run timing amongst the tributary subpopulations (H0: 

There is no difference in run timing between tributary subpopulations)? 

3. Are there differences in the run timing amongst the mainstem subpopulations (H0: 

There is no difference in run timing between mainstem subpopulations)? 

4. Are there differences in the run timing between the Gechiak subpopulation and the 

pooled “rest-of-river” population (H0: There is no difference in run timing between the 

Gechiak tributary subpopulation and the rest-of-river population)? 
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Hypotheses were evaluated using “tests of independence” through use of the Fisher exact test 

implemented in R. 

Results 

Marking event---Gillnet sampling for Chinook salmon was conducted for a total of 96 hours 

between 21 June and 6 August, and a total of 331 Chinook salmon were captured (Figure 5). Of 

the 331 Chinook salmon captured, 147 received radio tags with a secondary spaghetti tag and 

154 Chinook were tagged with only a spaghetti tag, for a total of 301 fish marked in gillnet 

sampling (Table 4). Of the additional 29 fish captured in gill nets, 20 were recaptured marked 

fish, 8 fish escaped the net or the cradle before they could be marked, and one other Chinook 

salmon received mortal gill damage. Other species captured included chum O. keta (n = 163) 

and sockeye O. nerka (n = 87) salmon, rainbow trout (n = 4), and char Salvelinus spp. (n = 10). 

Hook-and-line sampling for Chinook salmon was conducted between 26 June and 7 August for a 

total soak time of 19 hours. Nine Chinook salmon were captured, seven of which received 

spaghetti tags, and the other two escaped from the cradle before being marked. Other species 

captured included char (n = 5) and chum salmon (n = 1). 

All sampling efforts resulted in a total of 308 marked fish: 147 Chinook salmon with both a radio 

tag and a Floy tag and 161 fish with only a spaghetti tag (Table 4). The average handling time, 

from the time the fish was detected hitting the gill net until the fish was sampled, tagged, and 

released was 3.9 minutes for the first Chinook salmon encountered in the net and 6.1 minutes if a 

second Chinook was captured and released in the same set. The most Chinook salmon captured 

in a single drift net set was 5 fish, and the maximum handling time for the fifth Chinook salmon 

was 13 minutes. The average handling time for all fish in all sets was 4.1 minutes (min = 2, max 

= 13, mode = 4). 
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Figure 5. Cumulative total catch of Chinook (n = 331), sockeye (n = 87), and chum (n = 163) salmon caught 

by gill net in the lower Togiak River, 2012. 

Table 4. Radio transmitter and spaghetti tag deployment numbers for determining spawning distribution 

and population estimate of Chinook salmon. A total of 308 Chinook salmon were marked in the lower Togiak 

River, 2012. 

Strata Dates Radio Transmitters 

Deployed 

Floy Spaghetti 

Tags Deployed 

 Gill Net Only Gill Net Hook & Line 

1 21–30 June 10 11 3 

2 1–10 July 52 59 2 

3 11–20 July 29 35 0 

4 21–30 July 40 41 2 

5 31 July–9 August 15 6 0 

6 10–12 August 1 2 0 

Total: 147 154 7 

 

0

50

100

150

200

250

300

350

Cumulative Gillnet Catch

Date

Chinook (n=331)

Chum (n=163)

Sockeye (n=87)
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From the marking event in the lower Togiak River, age data were obtained from 308 Chinook 

salmon, of which 39 fish could not be aged because of illegible or regenerated scales. Seven age 

classes were present in 2012, with ages 1.3 (47%) and 1.4 (20%) comprising 67% of the sample 

(Table 5). Sex was determined for 281 Chinook salmon, with an additional 27 fish sampled who 

could not be sexed using secondary sexual characteristics. Females comprised 59% of Chinook 

salmon sampled (Table 6; Figure 6). Lengths were measured from 307 Chinook salmon, and 

averaged 819 mm (673 min, 988 max) for females and 755 mm for males (355 min, 996 max; 

Table 7). 

Table 5. Age composition of Chinook salmon marked in the lower Togiak River, 2012. 

Age n % SE (%) 

1.2 12 4 1.1 

1.3 145 47 2.8 

1.4 62 20 2.3 

1.5 2 1 0.5 

2.2 4 1 0.6 

2.3 34 11 1.8 

2.4 10 3 1.0 

Totala

 269 100 a

Total does not include fish sampled whose age could not be determined (n = 39). 

Table 6. Sex composition of Chinook salmon radio tagged in the lower Togiak River, 2012. 

Sex n % SE (%) 

Female 167 59 2.9 

Male 114 41 2.9 

Totala

 281 100 a

Total does not include fish sampled whose sex could not be determined (n = 27). 
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Figure 6. Sex composition of Chinook salmon radio tagged in the lower Togiak River, 2012, by strata. Total: 

Female n = 167; Male n = 144; Unknown Sex n = 27. 

Table 7. Mean length from mid-eye to fork of tail (mm), SE, range, and sample size by age of Chinook 

salmon radio tagged in the lower Togiak River, 2012.

Length Age Class 

1.2 1.3 1.4 1.5 2.2 2.3 2.4 

na 12 145 62 2 4 34 10 

Mean 596 786 847 870 700 805 804 

SE 35.8 5.3 7.3 - 14.1 9.6 10.0 

Minimum 355 646 758 834 675 703 750 

Maximum 828 987 996 905 734 911 845 

a

Does not include fish sampled whose length and age could not be determined (n = 39). 

0

10

20

30

40

50

60

70

123456

Count by Sex

Strata

Female

Male
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Recapture events---The resistance-board weir installation in Gechiak Creek was completed on 25 

June and began operating on 26 June. Daily operations began at 0600 hours. Weir operation 

was disrupted due to high water 15–17 July, with partial counts on 29 June, 4 and 14 July, and 2 

September. The weir was operated until rising water hindered safety on 3 September. Water 

levels receded sufficiently for weir removal to be completed 14–15 September. 

In total, 291 Chinook salmon were counted through the weir, with the highest daily count 

occurring on 26 July (Appendix 1). Of the 291 Chinook salmon enumerated, 283 were 

unmarked and 8 were marked with spaghetti tags. Other species captured included Coho O. 

kisutch (n = 4,553), chum (n = 34,308), and sockeye (n = 6,053) salmon (Figure 7), rainbow trout 

(n = 69), char (n = 1,237), and round whitefish Prosopium cylindraceum (n = 1). An additional 

111 fish that were counted through the weir could not be identified to species. 

From the recapture event in Gechiak Creek, age data were obtained from 174 unmarked Chinook 

salmon sampled from the weir, of which 23 fish could not be aged because of illegible or 

regenerated scales. Nine age classes were present in 2012, with ages 1.3 (38%) and 1.4 (19%) 

comprising 57% of the sample (Table 8). Sex was determined for 166 Chinook salmon, with 8 

additional fish who could not be sexed using secondary sexual characteristics. Females 

comprised 38% of Chinook salmon sampled (Table 9; Figure 8). Lengths were measured from 

174 Chinook salmon, and ranged from 605 mm to 924 mm for females and 331 mm to 981 mm 

for males (Table 10). 

In total, 38 carcass surveys were conducted over 16 days from 11 August to 2 September. 

Within the mainstem, 18 surveys were completed in sections A and B, 13 surveys were 

conducted in sections C and D, and 3 surveys done in section E. Carcass surveys accomplished 

within the tributaries included three surveys in the lower Nayorurun and one survey in the lower 

Ongivinuk. A total of 152 Chinook salmon were identified, of which 2 were marked fish (one 

mark each from strata 2 and 4), 145 were unmarked, and 5 were inconclusive regarding marking 

due to scavenger feeding (Appendix 2). 
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Figure 7. Cumulative count of Chinook salmon (n = 291) counted through the Gechiak Creek weir (top) and 

cumulative count of sockeye (n = 6,053), chum (n = 34,308), and coho (n = 4,553) salmon counted through the 

Gechiak Creek weir by species (bottom), 2012. Breaks in data series indicate dates when the weir was 

inoperable due to high water. 

0

50

100

150

200

250

300

350

26‐Jun 3‐Jul 10‐Jul 17‐Jul 24‐Jul 31‐Jul 7‐Aug 14‐Aug 21‐Aug 28‐Aug

Cumulative Chinook Count

Date

Chinook

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

26‐Jun 3‐Jul 10‐Jul 17‐Jul 24‐Jul 31‐Jul 7‐Aug 14‐Aug 21‐Aug 28‐Aug

Cumulative Count by Species

Date

Sockeye

Chum

Coho
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Table 8. Age composition of unmarked Chinook salmon sampled through the Gechiak Creek weir, 2012. 

Age n % SE (%) 

1.1 8 5 1.7 

1.2 23 15 2.7 

1.3 57 38 3.7 

1.4 29 19 3.0 

2.1 1 1 0.6 

2.2 8 5 1.7 

2.3 15 10 2.3 

2.4 9 6 1.8 

3.2 1 1 0.6 

Totala 151 100 a

Total does not include fish whose age could not be determined (n = 23). 

Table 9. Sex composition of unmarked Chinook salmon sampled through the Gechiak Creek weir, 2012. 

Sex n % SE (%) 

Female 63 38 3.8 

Male 103 62 3.8 

Totala 166 100 a

Total does not include fish whose sex could not be determined (n = 8). 
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Figure 8. Weekly sex composition of unmarked Chinook salmon sampled through the Gechiak Creek weir, 

2012. Total: Female n = 63; Male n = 103; Unknown Sex n = 8. Sampling occurred 27 June – 2 September in 

2012. 

Table 10. Mean length from mid-eye to fork of tail (mm), SE, range, and sample size by age of unmarked 

Chinook salmon sampled through the Gechiak Creek weir, 2012. 

Length Age Class 

1.1 1.2 1.3 1.4 2.1 2.2 2.3 2.4 3.2 

na 8 23 57 29 1 8 15 9 1 

Mean 380 565 776 825 331 603 731 853 755

SE 14.3 17.5 10.3 12.8 - 41.7 25.9 22.5 - 

Minimum 331 381 557 669 331 473 508 760 755

Maximum 447 731 910 981 331 853 870 940 755

a

Number sampled does not include fish whose age could not be determined (n = 23). 

0

5

10

15

20

25

123456789

Count at Weir Site

Week

Female

Male
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Radiotelemetry---All seven fixed telemetry stations were operational in time to capture upstream 

movement by radio-tagged Chinook salmon. The Entry and Second fixed stations were installed 

on 20 June, one day before the first radio tag was deployed in the lower river. The fixed station 

co-located with the field camp on Gechiak Creek was installed on 23 June. The Ranger fixed 

station was installed on 26 June. Kemuk, Nayorurun, and Ongivinuk fixed stations were 

installed on 4 July. The first radio-tagged fish moved past Ranger station on 14 July. 

Four aerial searches were conducted between 25 July and 31 August. Thirty-two boat searches 

were conducted from 7 July to 9 September. Boat tracking was systematic, with an emphasis 

placed on locating tagged fish that had not been recorded at fixed stations or were not detected in 

boat or aerial searches in more than a week. 

Radio transmitters were implanted into 147 Chinook salmon between 21 June and 12 August. Of 

the 147 tagged Chinook salmon, 106 fish (72%) were successfully tracked to spawning areas, 15 

(10%) were not successfully tracked to a spawning location, 18 (12%) were harvested, and 8 

(5%) were assigned a fate of dead/regurgitated (Table 11, Appendix 3). Seventy-nine percent (n

= 84) of the fated spawners selected spawning locations in mainstem areas of the Togiak River, 

with 43% (n = 45) in the mainstem between Gechiak Creek and Nayorurun River. Twenty-one 

percent (n = 22) selected spawning locations in tributaries, with only 2% (n = 2) selecting 

locations in Gechiak Creek (Table 12). In 2012, more radio-tagged fish spawned in the 

Nayorurun River than any other tributary, including Gechiak Creek. 

Based on telemetry data, we determined that radio-tagged fish, regardless of their spawning 

destination, spent an appreciable amount of time holding within Mainstem A of the lower river 

before pushing upriver to spawn. This is consistent with the holding behavior previously 

reported in this system (Tanner and Sethi 2011, 2012). For radio-tagged fish that ultimately 

spawned in Mainstem B–F in 2012, an average of 19.6 days were spent holding in the mainstem 

river below the Gechiak Creek confluence (range = 3, 40 days; standard deviation = 8.9). Fish 

that spawned in the tributaries held for fewer days, with an average of 13.2 days holding time 

(range = 4, 25 days; standard deviation = 6.2). 

Though we did not systematically track radio-tagged Chinook salmon downstream of our capture 

site for the marking event, we did collect enough data through incidental boat and aerial tracking 

events to identify fish movement that we refer to as back-out behavior. These were fish radio 

tagged in the lower river and held near the capture site for two to six days, and then dropped 

back into Togiak Bay near the river mouth but beyond the commercial drift fishery boundary of 

2012. One fish held in the bay for more than a week before moving back upriver to spawn in 

Mainstem B (Fish ID 17; Appendix 3). We detected similar movements in three other fish (Fish 

ID 17, 19 and 96; Appendix 3) that were captured in the commercial fishery. Two of the 

harvested fish were reported to us as being in good or excellent condition, and the third was held 

on ice when reported to us, such that we were able to examine the intact fish for tagging damage, 

e.g., damaged/ruptured stomach. In revisiting our harvest data from 2010 and 2011, we were 

able to identify a few radio-tagged fish from each of those years that also exhibited back-out 

movement into Togiak Bay. In 2010, fish detected in the bay after tagging returned to Togiak 

River to spawn (Fish ID 2 in Mainstem F and Fish ID 145 in Pungokepuk Creek), with a third 

radio-tagged fish reported from the commercial fishery as being in good condition (Fish ID 60; 

Tanner and Sethi 2011). In 2011, we did not detect any fish that backed out into the bay, 

returning to the river to spawn; however, three radio-tagged fish located for a week or more 

within the lower river post-tagging were later captured and reported by the commercial fishery 

(Fish ID 20, 47 and 78; Tanner and Sethi 2012). 
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Table 11. Fate of Chinook salmon radio-tagged in the Togiak River, 2012. 

Fate Number Percentage 

Spawning Location: 

 Mainstem (1 of 6 river sections) 84 57 

 Tributary (1 of 6 tributaries) 22 15 

 Total 106 72 

Unknown Fate: 

 Undetermined/insufficient location information 9 6 

 Undetermined/suspected harvest 6 4 

 Total 15 10 

Removed From Study: 

 Harvested 18 12 

 Dead/Regurgitated 8 5 

 Total 26 18 

Total Tagged: 147 100 
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Table 12. Distribution of Chinook salmon by river section within the Togiak River drainage based on radio 

tracking 2008-2012 and ADF&G average aerial survey estimates 1987-2005. 

 Number (Percent) 

River Section 

2008 

Radio 

Tracking 

2009 

Radio 

Tracking 

2010 

Radio 

Tracking 

2011 

Radio 

Tracking 

2012 

Radio 

Tracking 

1987-2005 

Aerial 

Surveysa 

Mainstem

Mainstem A 26 (34) 35 (30) 15 (9) 22 (19) 13 (12) 162 (4) 

Mainstem B 11 (14) 14 (11) 18 (11) 20 (18) 19 (18) 221 (6) 

Mainstem C 17 (22) 22 (19) 26 (16) 23 (20) 26 (25) 547 (15) 

Mainstem D 0 (0) 7 (6) 13 (8) 13 (12) 12 (11) 289 (7) 

Mainstem E 2 (3) 18 (15) 28 (18) 13 (12) 7 (7) 503 (13) 

Mainstem F 1 (1) 8 (7) 28 (18) 8 (7) 7 (7) 957 (24) 

Total 57 (74) 104 (88) 127 (80) 99 (88) 84 (79) 2,679 (69) 

Tributary

Gechiak Creek 10 (13) 6 (5) 9 (6) 4 (4) 2 (2) 392 (10) 

Pungokepuk 

Creek 2 (3) 3 (3) 8 (5) 1 (1) 2 (2) 159 (4) 

Nayorurun 

River 6 (7) 3 (2) 6 (4) 2 (2) 8 (8) 213 (5) 

Kemuk River 2 (3) 2 (2) 4 (3) 1 (1) 5 (5) 274 (7) 

Ongivinuk 

River 0 (0) 0 (0) 3 (2) 6 (5) 5 (5) 202 (5) 

Twin Hills 

Channelb - - 2 (1) 0 (0) 0 (0) - 

Total 20 (26) 14 (12) 32 (20) 14 (12) 22 (21) 1,240 (31) 

Drainage Total 77 118 159 113 106 3,919 

a

ADF&G 1987-2005 average aerial survey estimates from Westing et al. (2007). 

b

Twin Hills Channel not included in surveys prior to 2010. 

‘-’ means no data.

Spawning abundance---The Bayesian implementation of the pooled Lincoln-Petersen estimator 

successfully reached convergence (Figure 9), with Gelman-Brooks-Rubin statistic of all tracked 

parameters <1.002. The abundance estimate was similar to the Chapman point estimate, with a 

posterior median estimate of total run size of ܰ

෢஻ ൌ 13,050 with a 95% credibility interval of 

{7,844; 24,762} (Figure 9). The estimated probability of detection was low with a posterior 

median of 0.037 and a 95% credibility interval of {0.018, 0.057} (Figure 9). Probability of 

detection during the 2012 field season was nearly identical to that from the 2011 field season, 

with a posterior median detection probability of 0.034 and 95% credibility interval {0.017, 

0.058} (see Tanner and Sethi 2012). 
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Figure 9. Marginal posterior distributions (left panels) and trace plots (right panels) for a Bayesian 

implementation of the pooled Lincoln-Petersen estimator of total Togiak River Chinook salmon abundance in 

2012 that escaped past the commercial fishery in Togiak Bay. Distributions are based upon 2,500 posterior 

draws; red lines represent a kernel smoothed density estimate. Trace plots (right panels) display five MCMC 

chains overlaid on each plot. 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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The 2012 run size was approximately 6,000 fish larger than the 2011 run. From the Bayesian 

analysis and the conditional pooled Lincoln-Petersen model, we can state that there is a 99% 

chance that the 2012 run was larger than the 2011 run. 

Run timing---Results from 2012 were consistent with run timing analyses from 2011 and 2010 

(Tanner and Sethi 2011, 2012). Fisher exact tests indicate a significant difference in run timing 

between the pooled group of mainstem spawning fish versus tributary spawning populations (p = 

0.008). Overall, the run transpired slightly earlier in 2012 compared to 2011. In 2012, pooled 

mainstem and tributary groups had the highest tag releases during the 1-10 July release stratum, 

whereas these pooled groups had the highest tag releases during the 10-16 July stratum in 2011 

(Tanner and Sethi 2012). No fish tagged after the 21-30 July stratum spawned in tributary 

locations, whereas 14 fish tagged after the 21-30 July stratum spawned in the mainstem river 

(Table 13), indicating that tributary fish likely entered the river earlier than mainstem spawning 

fish. There was also a difference in run timing identified among tributary populations (p = 

0.041), indicating that Kemuk fish entered later than the other tributary populations in 2012 

(Table 13). No difference in run timing was identified among mainstem populations, or in a test 

between the Gechiak and rest-of-river run, although we caution that these tests likely have low 

power. 

Table 13. Number of radio-tagged Chinook salmon tracked by strata to spawning enclaves in the Togiak 

River drainage (n = 106), 2012. 

 River Section 

Mainstem Tributary 

Strata A B C D E F Gechiak Pungokepuk Nayorurun Kemuk Ongivinuk 

Twin 

Hills 

Channel

1 1 0 0 0 0 1 0 0 2 0 3 0 

2 3 7 7 6 2 3 1 1 5 1 1 0 

3 4 2 6 4 2 0 1 0 0 0 1 0 

4 3 4 7 2 3 3 0 1 1 4 0 0 

5 2 6 5 0 0 0 0 0 0 0 0 0 

6 0 0 0 0 0 1 0 0 0 0 0 0 

Total 13 19 25 12 7 8 2 2 8 5 5 0 
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Discussion 

A sonar project stationed on the Pongokepuk River in 1988 and 1990 estimated the Chinook 

salmon run starts on approximately 25 June (Irving et al. 1995). In 2009, 2011, and 2012, we 

captured one or two Chinook salmon on our first day of fishing effort, which began between 21 

and 25 June (Anderson 2010; Tanner and Sethi 2012). In 2010, we captured eight Chinook 

salmon on the first day of fishing on 22 June (Tanner and Sethi 2011). In 2008, fishing effort 

began on 20 June, but the first Chinook salmon was not captured until 26 June (Anderson 2009). 

We believe that in all years we were able to capture the beginning portion of the Chinook salmon 

run, except perhaps in 2010, when the earliest portion of the run may have been slightly 

underrepresented in the tagged population. 

To promote unbiased mark-recapture estimates of spawning abundance, we ensured that our 

sampling effort was standardized across temporal strata in order to mark Chinook salmon in 

proportion to abundance. Additionally, we conducted opportunistic carcass sampling to 

supplement our recapture effort beyond the weir recapture, in order to increase the precision of 

our spawning abundance estimate. 

Throughout the life of the project, we maintained low rates of tagging-related mortality and radio 

tag regurgitation. The number of dead fish or regurgitated tags/total fish radio tagged was 7/127 

in 2008, 4/154 in 2009, 6/211 in 2010, 6/171 in 2011, and 8/147 in 2012 (Anderson 2009, 2010; 

Tanner and Sethi 2011, 2012). Our low mortality rates were due to a combination of 

concentrated effort to minimize fish stress and handling time, as well as the continuity of our 

crew across years. Our capture methods ensured that fish remained in the water at all times. 

Fish were worked and cut from the net while in the river; were sampled from a cradle attached to 

the exterior of the boat, and had minimal handling from time of capture (i.e., when floats were 

disturbed) to release. From 2009–2012, most of the crew had experience with esophageal 

tagging, primarily on the Togiak project, ensuring the crew maintained familiarity and expertise 

with the study area, fishery, and methods from year to year. 

Both the Gechiak Creek weir and the carcass surveys were valid and attainable recapture 

methods. However, both efforts offered difficulties as well. Throughout weir operations (2010–

2012), high water events rendered the weir unsafe to operate, and was not fish tight for at least a 

few days of each season, leaving gaps in the enumeration of unmarked to marked Chinook 

salmon spawning in Gechiak Creek. Additionally, the proportion of radio-tagged fish attributed 

to the Gechiak varied from year to year, from 2% of the tagged population in 2012 to 13% of the 

tagged population in 2008 (Anderson 2009). The addition of carcass surveys may increase the 

precision of spawning abundance estimates, but access to a large number of carcasses in this 

system was more limited than expected. Though 38 carcass surveys were conducted over a 23 

day period, only 152 Chinook salmon carcasses were available for examination. We observed 

that many carcasses flushed through the system or were found in deeper water, rather than in 

shallows or shorelines, and those carcasses that were readily available in shallows and shorelines 

were highly scavenged by wildlife. By combining the two recapture methods, we were able to 

more precisely estimate spawning abundance. 

Historical aerial surveys (Westing et al. 2007) indicate that most Chinook salmon utilize the 

upper mainstem sections for spawning. However, our telemetry data shows that the lower 

sections in Mainstem A-C had the highest proportion of spawning within the Togiak system. We 

believe the inversion of the mainstem contribution in the old aerial surveys was due to the 

difficulty in conducting accurate aerial surveys in areas where the river is deeper, darker and has 

more channel complexity, such as in Mainstem A. Approximately 80% of spawning occurs in 

the mainstem, primarily in the lower sections that include areas that cannot be accurately 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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surveyed in aerial counts using fixed wing aircraft. There is, however, a considerable amount of 

between-year variability in the use of the spawning enclaves, with shifts between mainstem 

section use and tributary contribution. 

Returning Chinook salmon typically held in the lower reach of the mainstem Togiak River 

upstream of the tagging site (Mainstem A; Figure 1) for two weeks or longer, with some fish 

holding as many as 40 days before moving further upstream for spawning. Differences in 

holding behavior were significant across years for 2010-2012 (one-way ANOVA, F2,319=3.11, p 

= 0.045) and between mainstem versus tributary spawners (t-test, t320=2.60, p = 0.009). 

However, the difference in mean holding days across groups was not great, typically 7 days or 

less, and no clear pattern emerged across time or spawning distribution. 

In addition to holding behavior, we found evidence of fish backing out into salt water after 

moving into lower mainstem reaches through opportunistic aerial surveys which covered the 

lower mainstem and Togiak Bay near the mouth of the Togiak River. The process of radio 

tagging may stress fish and lead to slower progressions toward ultimate spawning fates (Bernard 

et al. 1999; Bromaghin et al. 2007); however, the Togiak system is only 93 rkms long, and we 

found most tags were ultimately fated as spawning. Due to limited aerial tracking in the salt 

water of Togiak Bay, we were only able to confirm 10 radio-tagged fish that backed out into salt 

water after entering Togiak River in 2010-2012. Of these, three fish returned to successfully 

spawn and seven were harvested in the commercial drift gillnet fishery in Togiak Bay. 

From 2008 through 2012, the sex ratios of tagged Chinook salmon in lower river samples had 

greater percentages of females than males: 69% in 2008, 59% in 2009 (Anderson 2009, 2010), 

55% in 2010, 70% in 2011 (Tanner and Sethi 2011, 2012), and 59% in 2012. These findings 

were consistent with the selectivity of the gill net mesh size used, because it favored capture of 

larger-bodied Chinook salmon that tends to be female. In 2010 and 2012, most Chinook salmon 

sampled at the weir were males (55% and 62%, respectively), though in 2011, females 

comprised more than half (55%) of the fish sampled at the weir. 

In all years of this study, the dominate age classes were ages 1.3 and 1.4. The dominate age 

class in 2010 and 2012 was age 1.3 (2010: 74% of marked fish and 55% of fish sampled through 

the weir; 2012: 47% of marked fish and 38% of fish sampled through the weir), which is 

consistent with the 2008 study (Anderson 2009: 54% of marked fish) and with the studies by 

MacDonald (1997) and MacDonald and Lisac (1997). However, in 2009, age 1.4 fish (49%) 

dominated the sample of marked fish (Anderson 2010), which is similar to our results in 2011 

(Tanner and Sethi 2012), with 71% and 49% of the fish sampled from gill nets and the weir, 

respectively. 

Between 2009 and 2012, the average female Chinook salmon captured in the lower river 

marking event measured 850 mm, with annual averages of 880 mm, 830 mm, 876 mm, and 819 

mm, respectively. The males sampled at the marking event averaged 771 mm overall across all 

years, with annual average lengths of 688 mm, 798 mm, 806 mm, and 755 mm, respectively 

(Anderson 2010; Tanner and Sethi 2011, 2012). Comparatively, the average length for females 

captured in the Gechiak Creek weir 2010-2012 measured 840 mm, with annual averages of 815 

mm, 871 mm, and 814 mm, respectively. The Chinook salmon males measured at the weir 

averaged 658 mm over the 3 years, with annual averages of 626 mm, 667 mm, and 668 mm, 

respectively (Tanner and Sethi 2011, 2012). 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Recommendations 

Due to the declines in Chinook salmon numbers state-wide, we recommend that some 

monitoring effort of the Togiak spawning abundance need be pursued. Our results show that 

mark-recapture is a viable approach for estimating Chinook salmon abundance in the Togiak 

River under appropriate sampling protocols. However, this approach is expensive in both time 

and resources, and is not viewed as a method for use in long-term annual monitoring. Therefore, 

we recommend coupling mark-recapture and telemetry sampling studies with aerial surveys to 

allow for an aerial survey catchability coefficient, ݍ, to be estimated, which could be used to 

translate an aerial index, ܫ௔, to an abundance estimate, ܰ: ܰൌܫ௔⁄ݍ. This could help provide a 

lower cost option for estimating abundance in years with only aerial surveys. 

To make inferences about the abundance of a salmon run complex we recommend that study 

designs using systematic sampling on specific subpopulations be carefully analyzed for potential 

induced capture heterogeneity, which can occur when tributary and mainstem-spawning stocks 

exhibit segregated run timing. Sampling protocols which release tags in proportion to abundance 

provide a solution in such cases. Even when tagging in proportion to abundance, study designs 

which use systematic recapture samples on subpopulations within the run complex are limited to 

a maximum recapture sample size equal to the subpopulation size. These designs will lead to 

imprecise abundance estimates if the targeted recapture subpopulation is small relative to the 

overall stock complex run size. In such cases, additional recapture sampling may be necessary to 

improve the precision of abundance estimates. Fortunately, if tagging effort can be administered 

such that tag releases are in proportion to run abundance, a wide range of recapture sampling 

schemes will result in valid data for the Lincoln-Petersen model. For example, we found carcass 

surveys provided additional, low-cost recapture sampling to supplement weir projects. 

Acknowledgements 

The success of this project hinged on the cooperation of all parties involved. We thank the U.S. 

Fish and Wildlife Service technicians and volunteers who assisted with field work: Stephanie 

Meggers, Dan Prince, Mike Polchlopek, Chris Ringlee, Sydney Clark, Peter Ott, Coby Sims, 

Laura Junge, and Casey Balthrop. The staff at Togiak National Wildlife Refuge provided 

logistical support and aerial flights. Pete Abraham proved himself a vital asset in innumerable 

ways. We are grateful to the Togiak Village Council and Togiak Village residents for their 

support of this project. We also thank the many Togiak River sport fish guides and the local 

commercial fisheries entities for their valuable support and assistance. Finally, we remember 

and honor our fellow crew member, Robert McArdle, 12 March 1985–25 March 2013. 

The U.S. Fish and Wildlife Service Office of Subsistence Management provided funding support 

for this project through the Fisheries Resource Monitoring Program; project number FIS 10-402. 

Project FIS-10-402 co-investigators include Pat Walsh (TNWR), Courtenay Gomez (BBNA), 

Jason Dye and Tim Sands (ADF&G).
Alaska Fisheries Data Series Number 2014-11, October 2014 

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28 

References 

Anderson, C.A. 2009. Estimation of Chinook salmon distribution and run timing in the Togiak 

River watershed using radio telemetry, Togiak National Wildlife Refuge, Alaska, 2008. U.S. 

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Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 1. Daily count of Chinook salmon marked with spaghetti tags and unmarked Chinook salmon 

through the Gechiak Creek weir, 2012. 

Date 

No. Untagged 

Counted 

No. Tagged 

Counted 

Total Daily 

Count 

Cumulative Total 

Count 

 

26-Jun 0 0 0 0 

27-Jun 1 0 1 1 

28-Jun 0 0 0 1 

29-Jun* 0 0 0 1 

30-Jun 0 0 0 1 

1-Jul 2 0 2 3 

2-Jul 1 0 1 4 

3-Jul 2 0 2 6 

4-Jul* 2 0 2 8 

5-Jul 2 0 2 10 

6-Jul 1 0 1 11 

7-Jul 3 0 3 14 

8-Jul 4 0 4 18 

9-Jul 2 0 2 20 

10-Jul 5 0 5 25 

11-Jul 6 0 6 31 

12-Jul 8 0 8 39 

13-Jul 6 0 6 45 

14-Jul* 8 0 8 53 

15-Jul - - - - 

16-Jul - - - - 

17-Jul - - - - 

18-Jul 6 0 6 59 

19-Jul 6 0 6 65 

20-Jul 3 0 3 68 

21-Jul 3 0 3 71 

22-Jul 5 1 6 77 

23-Jul 1 0 1 78 

24-Jul 8 0 8 86 

25-Jul 11 0 11 97 

26-Jul 20 1 21 118 

27-Jul 5 0 5 123 

28-Jul 3 1 4 127 

29-Jul 7 0 7 134 

30-Jul 8 0 8 142 

31-Jul 2 0 2 144 

1-Aug 18 1 19 163 

2-Aug 3 0 3 166 

3-Aug 1 0 1 167 

4-Aug 3 0 3 170 

5-Aug 12 0 12 182 

6-Aug 4 1 5 187 

7-Aug 2 0 2 189 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 1. Continued. 

Date 

No. Untagged 

Counted 

No. Tagged 

Counted 

Total Daily 

Count 

Cumulative Total 

Count 

8-Aug 2 0 2 191 

9-Aug 12 0 12 203 

10-Aug 4 0 4 207 

11-Aug 13 0 13 220 

12-Aug 5 0 5 225 

13-Aug 6 0 6 231 

14-Aug 9 1 10 241 

15-Aug 2 0 2 243 

16-Aug 4 0 4 247 

17-Aug 2 0 2 249 

18-Aug 4 0 4 253 

19-Aug 11 1 12 265 

20-Aug 4 0 4 269 

21-Aug 0 0 0 269 

22-Aug 0 0 0 269 

23-Aug 1 0 1 270 

24-Aug 1 0 1 271 

25-Aug 2 0 2 273 

26-Aug 0 0 0 273 

27-Aug 0 1 1 274 

28-Aug 5 0 5 279 

29-Aug 1 0 1 280 

30-Aug* 8 0 8 288 

31-Aug 2 0 2 290 

1-Sep 0 0 0 290 

2-Sep 1 0 1 291 

Total 283 8 291 

‘-’ denotes days the weir was inoperable due to high water. 

* denotes days the weir may not have been fish tight, and the count must be considered a partial 

count. 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 2. Daily and cumulative counts of marked and unmarked Chinook salmon in carcass surveys by 

date and location, 2012. 

Date 

River 

Section 

Surveyed 

Unmarked 

Daily Count 

Unmarked 

Cumulative Count 

Marked 

Daily 

Count 

Marked 

Cumulative 

Count 

11-Aug B 0 0 0 0 

12-Aug A 1 1 0 0 

17-Aug B 1 2 0 0 

17-Aug C 2 4 0 0 

17-Aug Nayorurun 1 5 0 0 

18-Aug A 1 6 0 0 

21-Aug A 3 9 0 0 

21-Aug Nayorurun 1 10 0 0 

22-Aug E 1 11 0 0 

23-Aug B 2 13 0 0 

23-Aug C 4 17 0 0 

23-Aug D 5 22 0 0 

23-Aug Nayorurun 1 23 0 0 

24-Aug A 1 24 0 0 

25-Aug B 13 37 0 0 

25-Aug C 8 45 0 0 

26-Aug A 8 53 0 0 

26-Aug B 8 61 0 0 

26-Aug C 1 62 0 0 

26-Aug E 1 63 0 0 

27-Aug B 13 76 1 1 

28-Aug A 0 76 0 1 

28-Aug B 4 80 1 2 

28-Aug C 4 84 0 2 

28-Aug D 3 87 0 2 

29-Aug A 8 95 0 2 

29-Aug B 5 100 0 2 

31-Aug A 2 102 0 2 

31-Aug B 4 106 0 2 

31-Aug C 14 120 0 2 

31-Aug D 2 122 0 2 

1-Sep C 3 125 0 2 

1-Sep D 2 127 0 2 

1-Sep E 5 132 0 2 

1-Sep Ongivinuk 1 133 0 2 

2-Sep B 2 135 0 2 

2-Sep C 7 142 0 2 

2-Sep D 3 145 0 2 

 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 3. Summary of biological data and tracking history for radio-tagged Chinook salmon in the 

Togiak River, 2012. Lengths are from mid-eye to fork in the tail. 

Tagging Stratum Date Tagged Fish ID Age Sex Length (mm) Fatea 

1 21-Jun 1 - F 831 Ongivinuk 

1 24-Jun 2 1.3 M 646 Ongivinuk 

1 25-Jun 3 1.3 F 720 Nayorurun 

1 26-Jun 4 1.3 M 837 Unknown† 

1 27-Jun 5 1.3 U 709 Unknown 

1 27-Jun 6 1.4 F 850 Harvested 

1 29-Jun 7 1.3 U 812 Harvested 

1 29-Jun 8 - U 805 F 

1 29-Jun 9 1.3 F 762 Harvested 

1 30-Jun 10 1.2 U 592 A 

1 30-Jun 11 1.3 F 831 Ongivinuk 

1 30-Jun 12 1.3 U 734 Nayorurun 

2 2-Jul 13 1.3 M 740 Regurgitared 

2 2-Jul 14 1.3 F 863 A 

2 2-Jul 15 1.3 F 843 Nayorurun 

2 2-Jul 16 1.3 M 729 Unknown† 

2 2-Jul 17 - U 752 B 

2 2-Jul 18 1.2 F 726 Harvested 

2 2-Jul 19 1.4 F 862 Harvested 

2 2-Jul 20 1.4 F 864 C 

2 2-Jul 21 1.4 F 835 Harvested 

2 2-Jul 22 - M 833 Harvested 

2 2-Jul 23 1.3 F 813 C 

2 3-Jul 24 1.3 M 743 B 

2 3-Jul 25 1.3 M 726 Gechiak 

2 3-Jul 26 2.3 F 769 Nayorurun 

2 4-Jul 27 1.4 M 776 C 

2 4-Jul 28 - M 793 E 

2 4-Jul 29 1.4 F 846 Unknown 

2 4-Jul 30 1.3 M 753 C 

2 4-Jul 31 1.3 M 713 Nayorurun 

2 5-Jul 32 1.3 F 798 D 

2 5-Jul 33 1.3 F 829 Harvested 

2 5-Jul 34 1.4 F 900 A 

2 6-Jul 35 1.3 F 777 B 

2 6-Jul 36 1.4 U 958 F 

2 7-Jul 37 1.3 F 810 D 

2 7-Jul 38 - M 718 B 

2 8-Jul 39 2.3 F 715 C 

2 8-Jul 40 1.4 M 843 B 

 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 3. Continued. 

Tagging Stratum Date Tagged Fish ID Age Sex Length (mm) Fatea 

2 8-Jul 41 1.2 M 542 Dead/Regurgitated 

2 8-Jul 42 1.4 F 902 D 

2 8-Jul 43 1.3 F 758 Nayorurun 

2 8-Jul 44 - F 862 B 

2 8-Jul 45 1.3 F 779 Kemuk 

2 8-Jul 46 1.3 M 758 Unknown† 

2 8-Jul 47 1.3 F 833 B 

2 9-Jul 48 1.3 F 775 Nayorurun 

2 9-Jul 49 1.3 F 843 Ongivinuk 

2 9-Jul 50 1.3 U 882 Harvested 

2 9-Jul 51 1.3 F 802 F 

2 9-Jul 52 1.3 M 766 D 

2 9-Jul 53 1.3 M 739 C 

2 9-Jul 54 2.3 F 834 Unknown 

2 9-Jul 55 1.3 M 837 E 

2 9-Jul 56 - F 865 Dead/Regurgitated 

2 10-Jul 57 1.4 F 835 Pungokepuk 

2 10-Jul 58 1.3 U 797 Harvested 

2 10-Jul 59 1.3 U 730 F 

2 10-Jul 60 1.3 U 675 D 

2 10-Jul 61 1.4 F 835 C 

2 10-Jul 62 2.3 F 905 Unknown† 

2 10-Jul 63 1.3 U 735 A 

2 10-Jul 64 1.3 M 760 D 

3 11-Jul 65 1.3 F 797 Dead/Regurgitated 

3 11-Jul 66 1.3 M 802 A 

3 11-Jul 67 1.3 F 745 Dead/Regurgitated 

3 11-Jul 68 1.5 F 905 A 

3 11-Jul 69 1.3 M 746 C 

3 12-Jul 70 - F 777 D 

3 12-Jul 71 - M 729 B 

3 12-Jul 72 1.3 M 788 D 

3 12-Jul 73 - U 765 D 

3 12-Jul 74 2.3 F 856 Harvested 

3 13-Jul 75 1.3 F 855 E 

3 13-Jul 76 1.3 F 790 Dead/Regurgitated 

3 13-Jul 77 1.4 F 895 B 

3 13-Jul 78 1.3 M 737 C 

3 14-Jul 79 1.4 M 996 C 

3 14-Jul 80 1.4 M 899 C 

 

 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 3. Continued. 

Tagging Stratum Date Tagged Fish ID Age Sex Length (mm) Fatea 

3 15-Jul 81 1.3 M 835 D 

3 16-Jul 82 1.3 F 887 Unknown† 

3 16-Jul 83 1.4 F 834 Dead/Regurgitated 

3 17-Jul 84 - F 872 Ongivinuk 

3 17-Jul 85 1.3 M 752 E 

3 18-Jul 86 2.3 M 766 C 

3 18-Jul 87 2.3 F 764 Gechiak 

3 18-Jul 88 1.3 F 987 A 

3 18-Jul 89 1.3 F 909 C 

3 18-Jul 90 1.4 F 852 Harvested 

3 19-Jul 91 1.3 F 858 Unknown 

3 19-Jul 92 1.3 F 840 A 

3 19-Jul 93 1.3 M 875 Harvested 

4 21-Jul 94 1.4 F 777 Unknown 

4 21-Jul 95 2.3 U 778 Unknown 

4 21-Jul 96 1.4 F 822 Harvested 

4 22-Jul 97 1.3 U 845 Kemuk 

4 22-Jul 98 1.3 M 820 Kemuk 

4 22-Jul 99 1.3 F 762 A 

4 22-Jul 100 1.3 F 785 F 

4 22-Jul 101 - F 843 A 

4 22-Jul 102 2.2 F 675 Dead/Regurgitated 

4 22-Jul 103 - F 865 Unknown 

4 22-Jul 104 2.3 F 794 A 

4 23-Jul 105 1.3 M 772 Harvested 

4 23-Jul 106 2.3 M 875 B 

4 23-Jul 107 1.3 M 677 B 

4 23-Jul 108 1.3 F 799 E 

4 23-Jul 109 1.2 M 604 Kemuk 

4 23-Jul 110 1.3 F 879 E 

4 23-Jul 111 1.3 M 742 Kemuk 

4 23-Jul 112 1.3 M 846 Pungokepuk 

4 23-Jul 113 2.3 M 911 Harvested 

4 24-Jul 114 1.3 F 848 E 

4 24-Jul 115 1.3 M 665 Harvested 

4 24-Jul 116 1.3 M 728 C 

4 25-Jul 117 1.3 F 847 F 

4 25-Jul 118 2.3 M 751 C 

4 25-Jul 119 1.4 F 902 C 

4 26-Jul 120 2.3 U 856 D 

 

 
Alaska Fisheries Data Series Number 2014-11, October 2014 

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Appendix 3. Continued. 

Tagging Stratum Date Tagged Fish ID Age Sex Length (mm) Fatea 

4 26-Jul 121 1.3 F 839 C 

4 26-Jul 122 1.3 M 681 Harvested 

4 26-Jul 123 2.2 F 734 C 

4 26-Jul 124 2.3 M 703 C 

4 26-Jul 125 1.3 F 857 Unknown 

4 27-Jul 126 2.3 U 808 D 

4 27-Jul 127 1.4 F 849 C 

4 27-Jul 128 2.4 F 810 Unknown 

4 27-Jul 129 2.3 M 851 B 

4 28-Jul 130 1.3 F 865 Nayorurun 

4 28-Jul 131 1.4 F 823 Unknown† 

4 29-Jul 132 - F 912 B 

4 29-Jul 133 1.3 U 752 F 

5 31-Jul 134 1.4 M 922 B 

5 31-Jul 135 1.4 M 856 C 

5 31-Jul 136 2.3 M 852 C 

5 31-Jul 137 1.4 M 764 C 

5 1-Aug 138 - M 933 B 

5 1-Aug 139 2.3 F 821 B 

5 4-Aug 140 1.2 F 828 C 

5 5-Aug 141 1.3 F 769 C 

5 6-Aug 142 - F 774 B 

5 7-Aug 143 - M 685 A 

5 8-Aug 144 1.3 U 814 B 

5 8-Aug 145 - M 683 A 

5 8-Aug 146 2.3 F 843 B 

6 12-Aug 147 1.4 F 758 C 

†Denotes fish whose fate is unknown but are suspected to have been harvested. 

a

Mainstem spawning fates are as follows: 

A = From the first fixed telemetry station to Gechiak Creek 

B = Gechiak Creek to Pungokepuk Creek 

C = Pungokepuk Creek to Nayorurun (Kashaiak) River 

D = Nayorurun River to Kemuk River 

E = Kemuk River to Ongivinuk River 

F = Ongivinuk River to Togiak Lake