Northern Kenai Peninsula Management Area
Fishing Research

Fishing Research

 

Kenai River King Salmon Stock Assessment

Kenai River king (Chinook) salmon stock assessment is complex. In total, there are 24 stock parameters used to assess Kenai River king salmon. The comprehensive stock assessment program uses creel surveys, harvest sampling, inriver gillnetting, genetics and estimation of inriver run size using sonar, weirs and radio telemetry to drive the implementation of management plans for these stocks. Objectives of the stock assessment program are to: (1) model inriver run and fishery mortality to manage the fisheries inseason, and (2) develop brood tables for long-term stock assessment and escapement goal analyses.

Cook Inlet marine recreational harvested king salmon
Cook Inlet marine recreational harvested king salmon

Commercial Harvest Sampling

King salmon harvested in the eastside set gillnet (ESSN) commercial fishery in Upper Cook Inlet are sampled by technicians for genetic analysis by clipping off the axillary process beneath the pelvic fin of the fish. Samples are taken throughout the entire commercial fishing season and from all fishing districts. Age, sex, and length composition data are also collected. The goals of this project are to estimate the proportion of king salmon harvested by reporting groups (Kenai River mainstem, Kasilof River mainstem, Kenai River tributaries, or Cook Inlet other), and to estimate the age composition of king salmon harvested in the ESSN fishery. Data collected from the ESSN commercial harvest aid in reconstructing the run of Kenai River late-run king salmon.

Commercially harvested king salmon from the eastside set gillnet fishery are sampled by a technician
Commercially harvested king salmon from the eastside set gillnet fishery are sampled by a technician

Inriver Gillnetting Program

Standardized gillnetting occurs daily at river mile 8.6 in the estuary area of the Kenai River. Sampling occurs daily from May 16 through August 10 and is scheduled around the tides. 60 ft gillnets are drifted downstream with the current to capture upstream migrating salmon. Gillnets of two different mesh sizes (5.0 inch and 7.5 inch stretched mesh) are used to reduce size and species selectivity. Captured king salmon are untangled and placed in a padded cradle, sampled for biological data, then released. In addition, some king salmon are tagged with a radio transmitter (see section on radio telemetry below). Goals of this project are to estimate the age, sex, and length compositions of returning king salmon for each run, to estimate the daily species composition (king salmon vs other salmon species) and daily catch rates or CPUE (catch per unit of effort) of king salmon. Data collected from the inriver gillnetting program are critical for effective inseason management of Kenai River king salmon.

Netting often occurs during crowded conditions. Please yield to and give a wide berth to the ADF&G gillnet and boat
Netting often occurs during crowded conditions. Please yield to and give a wide berth to the ADF&G gillnet and boat
Technicians remove a king salmon from a gillnet to place in a tail-tie to prevent the fish from escaping so it can remain in the water before sampling
Technicians remove a king salmon from a gillnet to place in a tail-tie to prevent the fish from escaping so it can remain in the water before sampling
A King salmon is loaded into the sampling cradle
A King salmon is loaded into the sampling cradle

King Radio Telemetry

Kenai River king salmon were radio-tagged from 2010 to 2016. Early-run king salmon were tagged from 2010-2016, while late-run king salmon were tagged from 2012-2014. Esophageal implant radio transmitters were deployed in king salmon captured at the river mile 8.6 inriver gillnetting project and released to continue their migration. Radiotagged fish were monitored both passively, using a network of stationary radio receiving stations, and actively, by foot, boat, or aerial surveys. Stationary receiving stations allowed 24-hour monitoring of radiotagged Chinook salmon at key points along their migration routes whereas active tracking was used to determine times at specific locations. This system provided multiple, redundant locations for each tagged fish with resolution sufficient to detect noteworthy behavior patterns.

Spawning locations were determined by analyzing all available data. Spawning destinations for tributary spawners were determined via aerial surveys whereas spawning destinations for mainstem spawners were better via boat surveys. Killey River and Benjamin Creek fish were the predominate stocks entering in May and from early to mid-June .studies. Funny River fish primarily entered the river in June. Nearly all fish radiotagged in July in this study were mainstem spawners, although there were low numbers of tributary spawners present in the in first two weeks of July.

Radiotagged Chinook salmon with a spawning destination in the Killey River drainage (including Benjamin Creek) were the largest component of the early run in all datasets. Mainstem spawners were consistently the second largest contributor and Funny River spawners was the third largest contributor. The spawning contribution of all other tributary spawners was minor. Mainstem spawners made up 15% (SE 5%) to 28% (SE 5%) and averaged 21% (SE 3%) of the early run. For mainstem spawners, the area downstream of the Soldotna Bridge had the greatest number and density of mainstem spawners every year (38%), followed by the area between Moose River confluence and Skilak Lake outlet (average 28%), Soldotna Bridge to Moose River confluence (average 21%), and lastly Skilak Lake inlet to Kenai Lake outlet (average 12%).

The proportional composition of Chinook salmon exposed to sport fisheries within the Kenai River was analyzed to estimate fish availablity for harvest relative to entry timing and spawning destination. However, because sport-caught Chinook salmon may be released based on size, sex, coloration, maturity, regulations, or other factors, the estimated composition of fish available for harvest may differ from the composition of the actual harvest because of harvest decisions made by individual anglers.

An esophageal radio tag is handled before it is placed into an applicator and inserted down the throat of a king salmon
An esophageal radio tag is handled before it is placed into an applicator and inserted down the throat of a king salmon
A king salmon with an esophageal radio tag (see antenna sticking out of fishes mouth) is released after sampling
A king salmon with an esophageal radio tag (see antenna sticking out of fishes mouth) is released after sampling
A fisheries biologist tracks radio-tagged king salmon in the Kenai River using a receiver and antenna in a boat
A fisheries biologist tracks radio-tagged king salmon in the Kenai River using a receiver and antenna in a boat

Kenai King Sonar

Adaptive Resolution Imaging Sonar (ARIS) is used at river 13.7 on the Lower Kenai River to estimate passage of king salmon 75cm (~34in.) or longer in length entering the river. The sonar site was chosen for its bathymetric qualities which allow the sonar technology to cover the entire span of the river, and is located just above tidal influence which allows more complete coverage and ensures fish are migrating upstream. Software allows biologists and technicians to measure fish in the ensonified zone to estimate the number of fish 75cm or longer. By only estimating large fish, the esitimates are less likely to be corrupted by presence of other species such as red and pink salmon. The goal of this project is to produce daily estimates of net upstream passage of fish 75cm or longer for both early- and late-runs. Data collected from the sonar are critical for effective inseason management of Kenai River king salmon.

One of the five sonar transducers at the river mile 13.7 sonar site is placed in the channel behind the island
One of the five sonar transducers at the river mile 13.7 sonar site is placed in the channel behind the island
A technician uses computer software to track, count, and measure fish passing the river mile 13.7 sonar site
A technician uses computer software to track, count, and measure fish passing the river mile 13.7 sonar site

More about the Kenai River Sonar

Sportfish Creel Survey

An onsite creel survey has been conducted on the lower Kenai River during king season since 1977. The primary goals of the creel survey are to estimate the number of king salmon both caught and those retained by the sport fishery downstream of the Soldotna Bridge. Periodic counts of anglers sport fishing for king salmon are conducted between the Soldotna and Warren Ames Bridges. Anglers are also interviewed for catch and harvest rate information as they exit the fishery. Harvested king salmon are sampled for biological data including age, sex, length, and genetic tissue. Data collected from the creel survey are critical for effective inseason management of Kenai River king salmon.

An ADF&G technician counts anglers sport fishing for king salmon
An ADF&G technician counts anglers sport fishing for king salmon

Genetic sampling

Recent technological advances in genetics and the development of a king salmon genetics baseline database now provide a tool to differentiate different stocks of king salmon that enter the Kenai River. Sampling king salmon for genetic tissue in the inriver gillnetting program provides information on the return timing of tributary and mainstem spawning fish. King salmon harvested in the sport fishery are sampled for genetic information as well to determine stock-specific harvest estimates and refine fishing regulations. Recently, it has also become possible to incorporate genetic stock information data into comprehensive abundance and run-timing models and obtain stock-specific estimates of annual abundance.

ADF&G technicians sample sport harvested king salmon for biological data and genetic tissue
ADF&G technicians sample sport harvested king salmon for biological data and genetic tissue

For up-to-date Kenai River king salmon counts, please visit: http://www.adfg.alaska.gov/sf/FishCounts/index.cfm?ADFG=main.kenaiChinook


For more information, see the Publications by Eskelin, Perschbacher, Miller, Key, Reimer, Fleischman, and McKinley.


 

Kasilof River Early-run King Salmon Assessment/Enhancement

Crooked Creek is a tributary to the Lower Kasilof River and is where early-run Kasilof River king salmon are assessed and enhanced at the old Crooked Creek hatchery facility. This project has 3 components:

  1. King salmon escapement monitoring and biological sampling,
  2. Smolt stocking and imprinting and,
  3. Adult brood stock collection and egg takes.

Project goals are to census the spawning escapement and total run of naturally- and hatchery-produced King salmon that pass the Crooked Creek weir and to estimate the age and sex composition of the run. Naturally-produced King salmon are born and reared in natural conditions but have experienced some degree of artificial selection in their ancestry. Hatchery-produced king salmon are born artificially by the department and reared in the William Jack Hernandez hatchery in Anchorage and have experienced a high degree of artificial selection in their ancestry. Information collected by this project monitors population dynamics of Crooked Creek King salmon and is used to determine appropriate spawning escapements to ensure a sustainable sport fishery.

King salmon holding in Crooked Creek
King salmon holding in Crooked Creek

King Salmon Escapement Monitoring and Biological Sampling

Escapement monitoring for both naturally-produced and hatchery-produced king salmon occurs daily through the use of a digital video recording (DVR) system, an underwater camera, and a passage chute. Fish are either allowed unobstructed passage upstream through the facility or collected for use as brood stock (see below). From recorded video footage, each fish is observed for marking status (presence or absence of an adipose finclip), and counted. Twice weekly, fish are trapped and sampled for marking status, sex, length, and a scale sample is collected for determining the age of the fish. Genetic samples are also routinely collected.

An ADF&G technician and a biologist sample king salmon for biological data from fish twice weekly
An ADF&G technician and a biologist sample king salmon for biological data from fish twice weekly

Smolt Stocking and Imprinting

Concerns about Crooked Creek king salmon straying to other freshwater streams have resulted in decreased stocking levels. Approximately 145,000 king salmon smolt are stocked into Crooked Creek annually. These fish are reared at the William Jack Hernandez Sport Fish Hatchery located in Anchorage, and delivered to the Crooked Creek Facility the first week of June where they are held in raceways for imprinting, usually for a minimum of 7 days.

Crooked Creek king salmon smolt are stocked into a raceway for imprinting prior to release
Crooked Creek king salmon smolt are stocked into a raceway for imprinting prior to release

Brood Stock Collection and Egg Takes

On sampling days or brood stock collection days, king salmon are trapped and checked for sexual maturity. If fish are thought to be sexually mature, they are passed to a concrete raceway where they are held and later, artificially spawned during an “egg take” when many fish are artificially spawned on the same day to simplify logisitics. Fish that are not mature enough or are too mature are passed upstream through the underwater video system and counted. Gametes (eggs) collected during the egg take are transported to the William Jack Hernandez Sport Fish Hatchery where they are incubated and reared. Only progeny from naturally-produced king salmon are then stocked back into Crooked Creek the following year.

Ovarian fluid from a king salmon is collected during an egg take to test for disease
Ovarian fluid from a king salmon is collected during an egg take to test for disease
King salmon eggs collected during an egg take are prepared for transportation to the William Jack Hernandez Sport Fish Hatchery where they will be fertilized and incubated
King salmon eggs collected during an egg take are prepared for transportation to the William Jack Hernandez Sport Fish Hatchery where they will be fertilized and incubated

Up-to-date Crooked Creek Weir fish counts.

More information about ADF&G Division of Sport Fish hatcheries and stocking programs.


For more information, see the Publications by Gates, Cope, Reimer, Pawluk, and Begich.

 

Russian River Red Salmon Escapement Study

The Russian River originates in the Kenai Mountains on the Kenai Peninsula and drains into the Upper Kenai River between Kenai and Skilak lakes. The Russian River red (sockeye) salmon escapement study is the most long-standing research program in this area. A counting tower was first established in 1963. A weir has been operated at the outlet of Lower Russian Lake annually since 1969. The weir is used to census the spawning escapements of red salmon and count other salmon (silvers and kings) that utilize the upper reaches of the drainage to spawn. Clear water and low water depth in the Russian River make it easy to identify salmon species as they pass through the weir. Biological samples (age, sex, and length) of red salmon are also collected at the weir. In addition, weir personnel collect climatological and river discharge data, operate the Russian River fish pass when necessary, and conduct stream surveys to enumerate spawning downstream of the weir.

The escapement study provides information necessary for in-season management and refinement of escapement objectives. Two runs of red salmon (early and late) return to the Russian River. Escapement goals are established for both runs. The early run has a biological escapement goal of 22,000 - 44,000 fish and the late-run sustainable escapement goal of 30,000 - 110,000 fish as counted through the Russian River weir.

Up-to-date Russian River Weir red salmon passage counts

The Russian River weir near the outlet of Lower Russian Lake
The Russian River weir near the outlet of Lower Russian Lake
ADF&G technicians count sockeye salmon as they pass upstream through the fish trap at the Russian River weir
ADF&G technicians count sockeye salmon as they pass upstream through the fish trap at the Russian River weir

For more information, see the Publications by Simons, Pawluk, and Berkhahn.

 

Invasive Northern Pike

The Kenai Peninsula invasive northern pike control and eradication program has been ongoing for nearly 20 years. Northern pike are an invasive species on the Kenai Peninsula and cause harm to native fish populations such as juvenile salmon, and resident species. Initially control efforts such as gillnetting were used in peninsula lakes to assess northern pike distribution and reduce their abundance systems. By 2008, chemical eradication methods were adopted which uses a natural plant-derived piscicide called rotenone to kill northern pike. The first of these rotenone treatments began with Arc Lake in 2008 and have since included Scout Lake, Stormy Lake, most of the Soldotna Creek drainage and Loon Lake.

The goal of this program is to eliminate northern pike from the Kenai Peninsula. Of the 24 Kenai Peninsula waterbodies known to support invasive northern pike populations, only eight are believed to still contain northern pike. Currently, plans are being developed to remove these last remaining northern pike form a cluster of lakes south of Soldotna. Ongoing monitoring efforts and public education about invasive northern pike will continued into the future. New genetic technology being implemented enables the detection of trace amounts of pike DNA in water samples, and when used in conjunction with netting, helps to define where northern pike are present.

ADF&G biologists apply the fish piscicide rotenone to Stormy Lake during the lake’s treatment in fall 2012
ADF&G biologists apply the fish piscicide rotenone to Stormy Lake during the lake’s treatment in fall 2012
Eradicated northern pike from the 2012 Stormy Lake treatment
Eradicated northern pike from the 2012 Stormy Lake treatment

Learn more about Invasive Pike

For more information, see the Publications by Massengill, Dunker, McKinley, and Begich.

 

Kenai River Rainbow trout

Kenai River rainbow trout have been studied periodically to assess population status, migratory behavior, and spawning locations and timing. A multiple event mark–recapture study was conducted on rainbow trout (Oncorhynchus mykiss) in the upper Kenai River in 2009. The objectives of this study were to estimate the abundance and fork length (FL) composition of rainbow trout in the most heavily fished section of the upper Kenai River (river miles 69.6–73.2), and to compare these estimates to those from previous surveys conducted in 1986, 1987, 1995, and 2001 on the same stretch of river. Overall, it appears that the upper Kenai River rainbow trout population remains above levels seen in the mid- to late 1980s and the number of larger sized (>450 mm FL) fish, capable of spawning in 2009, was comparable to estimates from the 1995 and 2001 surveys. During 2010 radio tags were surgically implanted into large rainbow trout captured in the lower Kenai River during the summer. Movements of radio-tagged fish were monitored from the time of tagging in summer thru the fall, winter and spring to identify the timing of inriver movements to and locations of overwintering and spawning areas of rainbow trout in the Kenai River downstream of Skilak Lake. Recently, in 2017, a multiple event mark-recapture study was conducted on rainbow trout (Oncorhynchus mykiss) in the middle Kenai River, just downstream of Skilak Lake. Preliminary data from the study suggests the population of trout in this section of the river is healthy.

A Kenai River rainbow trout recovers after surgery to implant a radio tag into the abdominal cavity of the fish. Note the radio tag antennae protruding from the incision made in the side of the fish.  The antenna transmits a pulse code sent from the radio tag inside the fish to data receivers.  The data receivers are located along the Kenai River shoreline and in boats operated by department biologists.  Information gathered by the receivers is downloaded to a computer allowing biologists to determine the location of the fish in the river for each day the tag sent a pulse code.
A Kenai River rainbow trout recovers after surgery to implant a radio tag into the abdominal cavity of the fish. Note the radio tag antennae protruding from the incision made in the side of the fish. The antenna transmits a pulse code sent from the radio tag inside the fish to data receivers. The data receivers are located along the Kenai River shoreline and in boats operated by department biologists. Information gathered by the receivers is downloaded to a computer allowing biologists to determine the location of the fish in the river for each day the tag sent a pulse code.
A rainbow trout is measured in a cradle
A rainbow trout is measured in a cradle
An ADF&G technician applies a numbered green floy-tag to a rainbow trout
An ADF&G technician applies a numbered green floy-tag to a rainbow trout
A successfully floy-tagged rainbow trout (see green floy-tag just aft of the dorsal fin) before it is released into the Kenai River in 2017
A successfully floy-tagged rainbow trout (see green floy-tag just aft of the dorsal fin) before it is released into the Kenai River in 2017

For more information, see the Publications by Eskelin, Pawluk, and Begich.