Chinook Salmon Research Initiative
Kenai River Chinook Salmon
Fish entering the river in May and June spawn predominantly in the tributaries and fish entering in July and August spawn mostly in the mainstem of the Kenai River. For management, these two life history patterns are delineated as the early and late runs. The early run is normally smaller in magnitude than the late run and averages around 13,000 fish per year with a spawning escapement goal of 5,300 to 9,000 fish. The late run averages 58,000 fish per year with an escapement goal of 15,000 to 30,000 fish. Historically, runs are dominated by six year old fish, those having spent four years in the ocean rearing. There are subsistence, personal use, commercial, and sport fisheries that harvest Kenai River Chinook salmon in Cook Inlet and inriver. The Personal use and subsistence fisheries are the smallest harvesters. The commercial fisheries consist of a set gillnet fishery along the beaches of Cook Inlet and a drift gillnet fishery that operates in central Cook Inlet. The sport fishery is typically conducted from boat both inriver and in the marine; however, some shoreline fishing takes place. The majority of the harvest of early run fish is attributed to the sport fishery with a harvest rate of around 38%. Most of the late run fish are caught in the sport and commercial fisheries with the remainder taken in the personal use and subsistence fisheries. Harvest rates on the late run are about 36% on average, similarly to those seen for the early run.
Adult Spawning Abundance
Assessment of run strength of Kenai River Chinook salmon is conducted using a sonar coupled with an inriver test gillnet project that gathers catch rate, species, and age, sex, and length composition information . Mark-recapture estimates of the inriver run are also calculated using genetic and spawning destination information from Chinook salmon sampled and radio-tagged in the test gillnets, and passage data from weirs placed on select spawning tributaries of the Kenai River. Personal use, subsistence and commercial harvests are reported directly and sport harvests are estimated using a survey. Total run is estimated by adding terminal harvests below the sonar with estimates of inriver run at the sonar. Age, sex, and length composition estimates are made using samples from the commercial and sport fisheries and from the inriver test gillnets. A new sonar site located above the traditional site and outside the influence of tides is being tested which in theory will produce more reliable estimates of inriver run over time as it will sample the entire cross-section of the Kenai River. And although nearby marine harvests of all Chinook salmon are known, stock-specific harvests need to be made in order to accurately estimate the proportions of Kenai-origin Chinook salmon.
Historically, attempts have been made to estimate the abundance of juvenile Chinook salmon in the Kenai River but those programs were met with limited success. Currently there is no program in place to estimate juvenile abundance, so estimates of marine survival are not possible at this time. However, the 2013 Chinook Salmon Stock Assessment and Research Plan recommended an annual project to estimate juvenile abundance in the Kenai River by run (early and late). This project would include funding to capture, coded wire tag, and genetically identify juvenile Chinook salmon by early and late run. Subsequent adult returns would then be sampled for fish possessing coded wire tags germane to Kenai River juvenile’s thus allowing estimates of abundance and marine survival.
Adult Harvest, Genetics, and Coded Wire Tags
Adult Chinook salmon returning to the Kenai and Susitna rivers in Southcentral Alaska provide both sport and commercial harvest opportunities in several marine and inriver fisheries. Each year, the Alaska Department of Fish and Game assesses these returns by conducting research to estimate run sizes in both the Kenai and Susitna systems through weirs, sonar, creel surveys, harvest sampling, or mark-recapture techniques. Recent low Chinook salmon runs in both river systems have heightened concerns about stock-specific harvests in mixed-stock marine fisheries. Fortunately, recent advancements in genetic stock identification techniques of Chinook salmon allow for discriminating between discrete Chinook stocks in mixed-stock fishery samples. These advancements led to the development of a genetic baseline database for Cook Inlet Chinook salmon using collections from 42 locations and other stocks in the Gulf coast of Alaska (Olive et al. 2013 - PDF 736 kB).
Two marine sport fisheries harvest Chinook salmon in Cook Inlet; one occurs along the eastern shore of central Cook Inlet from late April through mid-August and another that occurs year round out of Homer. Past attempts at estimating the stock-specific harvests of Chinook salmon in the central Cook Inlet marine sport fishery using coded-wire tags were incomplete due to low precision of estimates and poor or limited tagging of wild Chinook salmon stocks. The stock-specific harvest of sport caught Chinook salmon out of Homer is also poorly described. Since the 1990s both fisheries have been sampled for maturity and age, sex, length composition information and also for coded-wire tag recoveries, but not for genetic stock identification purposes. Recent estimates of the number of Chinook salmon harvested each year in these fisheries averages about 6,587 fish. A project to estimate the stock-specific harvest for the first time using genetic stock identification techniques in these fisheries is set to begin in 2014.
A commercial fishery in Upper Cook Inlet harvests Chinook salmon in late-June through mid-August while targeting more abundant sockeye salmon. In particular, the East Side set gillnet fishery, located along the eastern shore of Upper Cook Inlet between Ninilchik and Boulder Point, (Eskelin et al. 2013 - PDF 1,412 kB) harvests the majority of Chinook salmon caught in the Upper Cook Inlet commercial fishery. Each year, the fishery harvests approximately 9,600 Chinook salmon, although recent harvests have been below average. On average, the East Side set gillnet fishery accounts for about 2 of every 3 Chinook salmon harvested in the Upper Cook Inlet commercial fishery. Harvests of Chinook salmon in the East Side set gillnet fishery have been sampled for age, sex, and length composition information, and since 2010 tissue samples for genetic analysis were added to the collection effort. Alaska Department of Fish and Game biologist will be sampling the East Side set gillnet fishery for age, sex, length composition, genetics, and coded-wire tag information in 2014.
Stock-specific harvest information in these fisheries is needed to improve the understanding of stock productivity, assist in development of brood tables for long-term stock assessment, and for adjusting escapement goals for stocks in both the Kenai and Susitna river drainages. These fisheries, account for the bulk of Chinook salmon harvested in Cook Inlet marine waters. In forthcoming projects, Alaska Department of Fish and Game will be sampling the harvest of Chinook salmon in these fisheries for genetic tissue in order to estimate the stock composition in these fisheries.
Sport fishing for Chinook salmon occurs year-round in Cook Inlet marine waters though most of the harvest occurs during the months of April through August. The majority of this marine harvest is landed in the ports of Homer, Anchor Point and Deep Creek / Ninilchik beaches. Beginning in 2014, Alaska Department of Fish and Game technicians will collect samples at each of the major access points (the Homer Harbor, Anchor Point tractor launch and marine access area, and Deep Creek tractor launch and marine access area) during the summer fishing season (April – September) and while the tractor launches are operating. During the winter fishery (October – March), samples will be collected from fish harvested in the Homer fishing derbies and as weather allows. All available Chinook salmon encountered will be sampled for genetic tissues, coded-wire tags, and age, sex and length information. Technicians will collect samples from as many Chinook salmon as possible while attempting to distribute effort between private and charter fishing vessels.
In the absence of stock-specific harvest information for this fishery and based on harvest and sample sizes available during the summer and winter fisheries, genetic reporting groups chosen for this fishery are “Susitna River” (including the Yentna River, Susitna River, and Western Cook Inlet populations), “Kenai River” (including Kenai River mainstem and tributary populations), “Other Cook Inlet” and “Outside Cook Inlet”. The “Other Cook Inlet” reporting group includes Cook Inlet populations from Turnagain Arm, Knik Arm, Kasilof River, and southern coastal Kenai Peninsula streams (Anchor River, Deep Creek, Ninilchik River and Stariski Creek). Estimates of Chinook salmon stock composition and harvest by reporting group will be stratified geographically by fisheries occurring north and south of Bluff Point in Kachemak Bay (59°40’N), and temporally based on management criteria.
During and after East Side set gillnet fishery openings, Alaska Department of Fish and Game technicians will sample available Chinook salmon for genetic tissue, age, sex, and length composition information, and coded-wire tags at receiving sites for fish processing plants after each tide. Technicians will collect as many Chinook salmon samples as possible, at as many receiving sites as possible, many sites being sampled more than once. Chinook salmon genetic samples were collected over four years (2010–2013) from fish harvested and sold from the East Side set gillnet fishery. A mixed stock analysis was performed on tissue samples collected in 2010, 2011, and 2013; however, an analysis was not performed on tissue samples collected in 2012 due to small sample size. Geographic locations within Cook Inlet were identified to apportion the sampled harvest, which were: “Kenai River mainstem,” “Kenai River tributaries,” “Kasilof River mainstem,” and “Cook Inlet other.” The Cook Inlet other reporting group represented all remaining Cook Inlet Chinook salmon baseline populations not included in the three other reporting groups, which includes populations within the Susitna River. Reporting groups were defined based on one or more of the following criteria: 1) the genetic similarity among populations, 2) the expectation that proportional harvest would be large (>5%), or 3) the applicability to answer fishery management questions.
Results from the mixed stock analysis of harvest samples collected in 2010, 2011, and 2013 revealed that, on average, Kenai River mainstem Chinook salmon composed the majority (69%) of the East Side set gillnet Chinook salmon harvest. These results are published in a Fisheries Data Series Report (Eskelin et al. 2013 - PDF 1,412 kB). Prior to these analyses and lacking stock-specific harvest estimates, the harvests were treated as though all Chinook salmon harvested in the East Side set gillnet fishery were of Kenai River mainstem (late-run) origin even though it was known that other stocks, such as Kasilof River mainstem spawning fish, were harvested. In 2013, with additional funding through the Alaska Statewide Chinook Salmon Research Initiative, sampling was increased to allow for time and geographic stratification of stock-proportion estimates. Sampling of this fishery for mixed stock analysis will continued until Alaska Department of Fish and Game can confidently assess the variation in stock proportions with respect to geographic and timing characteristics of the harvest.
The Alaska Department of Fish and Game, Division of Subsistence, is studying the local and traditional knowledge of Chinook salmon in the Kenai River. Semi-directed interviews with knowledgeable and experienced fishers from all user groups to record local and traditional knowledge about Kenai River Chinook salmon, including variation in location, abundance, size, and overall health will be conducted. With a focus on small scale, place-based observations with the assistance of maps, the interviews will explore catalysts for changes in Kenai River Chinook stock status and trends as well as changes in key Chinook salmon habitat. Historical use patterns will also be documented.