Chinook Salmon Research Initiative
Stikine River Chinook Salmon
The Stikine River is a glacially-fed river system located near Wrangell and Petersburg, Alaska in central Southeast Alaska. Over the past couple of decades this river has supported runs of Chinook salmon averaging about 40,000 large (28” and greater in length) fish. After leaving the freshwater as smolts, these fish rear in the Gulf of Alaska and Bering Sea. In general, Stikine River Chinook salmon suffer relatively low harvest rates of around 15-20% having moderate terminal marine harvests in sport and commercial fisheries. Stikine River Chinook salmon are also incidentally harvested inriver by the Canadian commercial fleet, and in very small numbers in an inriver subsistence and recreational fishery. However, in some years the run is large enough to support directed Chinook salmon fisheries and harvest rates can be as high as 50% during some of the larger runs. Being a large transboundary river that originates in Canada, fisheries management on the Stikine River falls under the purview of the Pacific Salmon Treaty. Directed fisheries were closed from 1976-2004 and reopened during years having large runs beginning in 2005. Data from adult and smolt projects combine to estimate full parent year production estimates including details on harvest rate and marine survival.
Spawning abundance is relevant to estimates of large spawning Chinook salmon using a mark-recapture study that has been conducted annually since 1996 by the Alaska Department of Fish and Game, Division of Sport Fish, Department of Fisheries and Oceans, Canada, and Tahltan First Nation. Prior to 1996, aerial survey counts were conducted on the Little Tahltan River from 1975 through 2009 and a weir has been operated on the Little Tahltan River since 1985. For a time these were the primary means of information gathering but were replaced with the more accurate mark-recapture experiment as the main estimation and management tool in 1996.
Radio telemetry studies conducted in 1997 and 2005 found that Chinook spawning in the Stikine River occurs largely in 3 general locations: the Tahltan and Little Tahltan Rivers and the far upper reaches of the Stikine River.
In 1999 a biological spawning escapement goal range was recommended by Bernard et al (2000 - PDF 661 kB) at 14,000 to 28,000 large fish and was estimated using historical run performance constructed from former weir and aerial survey counts. This goal range was reviewed and adopted by Alaska Department of Fish and Game in 1999 and subsequently reviewed and accepted by the Chinook Technical Committee of the Pacific Salmon Commission and the Center for Science Advice - Pacific in 2000.
Available information on this stock suggests the stock is healthy and annual escapements over the past 20 years have been within or above the escapement goal range in all years except 2009. This stock, like others in Alaska, has recently experienced a decline in productivity yet, with one exception, through this time the spawning escapement goal has been achieved. Stikine River salmon research provides fishery managers the tools necessary to manage under the sustained yield principle.
Adult Spawning Abundance
The Alaska Department of Fish and Game, Division of Sport Fish, has conducted mark-recapture studies in the Stikine River drainage since 1996. The ongoing Chinook salmon research on the Stikine River is conducted cooperatively between Alaska Department of Fish and Game, the Department of Fisheries and Oceans Canada, and the Tahtan River First Nation. Since 1975, spawning abundance has ranged from 5,723 to 63,523 and averaged around 25,500 large Chinook salmon. From May to early July, marks are applied to Chinook salmon in the lower Stikine River at Kakwan Point and constitute the first event of the mark-recapture experiment. Fish are captured using drift gillnets. When a fish is caught in the net it is immediately pulled in, the fish is gently cut out of the net and then marked with an individually numbered spaghetti tag and sampled for age, sex, and length information and released alive. To detect potential tag loss, a secondary mark is applied that is easily detected in the event the original tag is lost. Tagged Chinook salmon are then potentially recaptured at three locations making up the second event of the mark-recapture experiment. The first is in the Canadian commercial fishery, and then from June to early September, fish are inspected for marks at the Little Tahltan Weir as well as concentrated sampling for spawning fish on the Verrett River in August which is a large spawning tributary for Chinook salmon in the Stikine drainage. Chinook salmon encountered at all capture locations are inspected for missing adipose fins that may indicate that they were marked as juveniles with a coded wire tag (see Stikine River coded wire tag research).
Since coded wire tags are implanted in the nose of juvenile Chinook, the heads are removed from all encountered fish that are missing their adipose fins and sent to the Alaska Department of Fish and Game Mark Tag and Age Lab for detection of the tag and consequent identification via numbering on the tag of the fish’s origin and age. To learn more about how the department conducts this research, project operational plans that outline project methods, results and data analyses are available online beginning with the most recent plan, which covers the 2013 mark-recapture project (PDF 1,533 kB).
Information gathered during the adult and juvenile work is combined to estimate the total number of Chinook salmon produced by each parent year. Return data is also closely analyzed to improve forecasting methods for the Stikine River stock of Chinook salmon. These data are published in the Alaska Department of Fish and Game Fishery Data Series and are complete for parent years. (see project summary page)
The Alaska Department of Fish and Game, Division of Sport Fish, has conducted studies to estimate the abundance of juvenile Chinook salmon in the Stikine River drainage since 2000. Juvenile Chinook salmon from the same parent year are marked with adipose fin clips and tagged with coded wire tags in the spring (April and May) as smolt before they outmigrate to sea. Due to the large size of the Stikine River drainage, tagging in the spring is the most effective method as compared to fall tagging of fry in other rivers as the smolt are concentrated and it helps ensure that a mixture of the different stocks are equally likely to be tagged.
Since coded wire tag operations on the Stikine River have targeted outmigrating smolt, beach seining on large gravel bars with multiple crews is the most effective capture technique found after more than ten years of operations but baited minnow traps are also used at times. After capture and transport back to camp, they are anesthetized, marked, tagged, and held for 24 hours to assess retention of coded wire tags and to make sure they are healthy prior to release. The spring work starts in mid-April and ends in early June.
Stikine River Chinook salmon rear at sea from one to five years and information accumulates annually on these parent year releases as returning adults are encountered in different fisheries and sampled. The fraction of fish marked with adipose fin clips in these fisheries is used in combination with adult sampling information to estimate smolt abundance. In addition, the fraction of these fish possessing valid coded wire tag released in the Stikine River is used to estimate adult harvests in the various marine commercial and sport fisheries. The estimated harvest of a particular parent year is coupled with estimates of the parent year spawning abundance to reconstruct the complete return. Finally, capture rates of Stikine coded wire tags in the marine fisheries facilitates management and are used as inseason predictors of run strength and harvest rates. An average of 29,438 and up to 48,500 smolt have been tagged each spring in the Stikine River and smolt abundance has ranged from 1.6 million to 4.5 million since 2000.
Data collected from coded wire tag recoveries, when combined with adult spawning abundance estimates, allows for complete parent year production, including marine harvests, smolt abundance, and marine survival of Stikine River Chinook salmon. To learn more about how the department conducts this research, project operational plans that outline project methods, results and data analyses are available online beginning with the most recent plan, which covers the 2013 field season (PDF 883 kB).
Through semi-directed key respondent interviews, local and traditional knowledge will be collected and analyzed to augment current biological information regarding Stikine River Chinook salmon migration, behavior, health, predation, abundance, and habitat. A sample of subsistence fishers, commercial fishers, and sport anglers in Petersburg and Wrangell will be interviewed.
Fishers and anglers will be asked to describe their observations on Chinook behavior, size, abundance, predations and habitat including how their fishing practices have changed to accommodate changes in Chinook abundance. They will also be queried for perceived reasons for the Chinook decline and opinions best management strategies for the Stikine River Chinook stock. These adaptations and observations will be compared to biological data. If changes to production of other marine and freshwater species are occurring, they will be discussed and correlated with the Chinook salmon decline. The project will also compile historical information about Stikine River Chinook salmon.