Fish surveys of the Upper Yukon and Tanana Rivers 2020–2022

From summer 2020 through fall 2022, Alaska Department of Fish and Game (ADF&G), Division of Sport Fish staff will conduct a rapid, systematic inventory of anadromous and resident fish distribution and associated aquatic and riparian habitat in select drainages of the upper Tanana River and in select drainages of the Fortymile River and adjacent Yukon River drainages.  This proposal is part two of a multi-year inventory effort that began in 2019, when project staff inventoried fish assemblages in Yukon & Tanana river drainages downstream of the 2020 study area.  In 2020 project staff will continue where they left off and continue working upstream in those drainages.  Target streams will be selected to fill gaps in coverage of the State of Alaska's Catalog of Waters Important for the Spawning, Rearing or Migration of Anadromous Fishes (AWC) in freshwater habitats expected to support anadromous fish populations likely to be impacted by human activities.  Each of two crews will sample standardized target stream reaches using electro-fishers, with sufficient effort to collect all species (perhaps with the exception of rare species) of the extant fish community.  At each sampling site, crews will also document standard aquatic and riparian habitat characteristics.  These observations will be recorded in the Alaska Freshwater Fish Inventory database (AFFID) and made publicly available via the AFFID internet mapping service.  For each water body in which anadromous fish are observed, nominations to the AWC will be submitted.

Crews sampled 135 sites from 2020–2022.

Following ADF&G's AFFI protocols (nate.cathcart@alaska.gov for specific protocols), 2 crews, each with 2 members, will use helicopters to simultaneously sample fish communities in selected study stream reaches for approximately 12 days during the summer of 2020. Target survey sites will include wadeable headwater streams sampled with a backpack electrofisher, and un-wadeable streams (including mainstem rivers) sampled with a raft-mounted electrofisher. Two helicopters will provide access to the stream study sites for headwater and un-wadeable sample crews. Sites within the study area that have the highest potential for habitat degradation will be identified through consultation with the ADF&G Division of Habitat and Federal Land managers, and any sites they identify will be given a higher sampling priority. 

The proposed study area for 2020 also has an extensive road system along the Tanana River. In addition to using helicopters to access difficult-to-reach streams, project staff plan to use the road system and a jet outboard-powered 18-foot skiff to sample more easily accessed streams in the study area. This will likely extend the overall number of sites crews are able to sample this year while not requiring the added expense of helicopter charters for the entire project effort.

Study area selection

The long-term goal of the AFFI program is to complete a statewide baseline inventory of fish assemblages and associated aquatic and riparian habitats. At its inception, the AFFI program developed a systematic approach to rank and prioritize Alaska’s 139 subbasin-level hydrologic units.  Subbasins were chosen because they most closely match the scale of the project study area of a typical helicopter-supported, regional baseline fish inventory. A survey priority index (SPI) of the subbasins was then developed based on: amount of past survey effort in the subbasin, removing lands considered to have adequate protection from anthropogenic degradation such as National Parks & Preserves, the ratio of current AWC coverage to the total length of all mapped streams within the subbasin, and a Human Activity Index (HAI) created by The Nature Conservancy (Feirer et al. 2006), assessing 4 types of human activities that could impact Alaska ecosystems. At the time of this proposal, the AFFI program has surveyed 68 of the 139 subbasins that were originally prioritized. This prioritization method has been documented by AFFI staff in an unpublished internal document that is available upon request.

The 74,982 square kilometer study area comprises all or some of the subbasins of the Upper Tanana River (e.g., Chena River, Healy Lake-Tanana River, Nebesna-Chisana River, Salcha River, Tok-Tanana River, and Upper Copper River subbasins) and in select subbasins of the Yukon River (e.g., Fortymile River and Ladue River-White River).  The Upper Yukon region and a few of the more northeasterly subbasins of the Tanana River will be sampled in 2019.  The remaining upper Tanana River subbasins and any other remaining subbasins in the entire upper Yukon and upper Tanana region will be sampled in 2020 and if necessary, 2021.

Target stream selection

The number of headwater streams in the study area will exceed the project’s limited sampling effort capacity; therefore, a subset of mapped streams, comprising the longest stream segments not currently listed in the AWC, will be selected as target streams.  The headwater team will sample approximately six to eight headwater streams per day and the raft team will float and sample one un-wadeable stream per day, including a reach from all mainstem rivers in the study area. 

Based on past AFFI projects, it is estimated that a minimum of 72 headwater target streams will be sampled, and 12 un-wadeable target streams will be rafted and sampled during the course of the 12 field days.  However, project staff are pursuing additional funding opportunities and anticipate being able to complete a full 20-day field survey, which would allow field staff to sample a minimum of 100 headwater target streams and approximately 20 un-wadeable target streams provided there are no other weather or logistical problems preventing sampling all 20 days.

Sampling methods

At selected reaches, the fish community will be sampled with standardized methods and effort, according to AFFI protocols.  Fish will typically be collected by single-pass electrofishing (other non-lethal gear types, such as beach seines, angling or minnow traps, may be deployed if conditions prohibit safe or effective electrofishing).  Electrofishing is the principal fish collection gear because it is recognized as the most comprehensive and effective method for collecting fish in lotic systems. 

At all target streams, a length of stream (referred to as a reach) standardized by stream width (i.e., 40 or 120 wetted-channel-widths in wadeable and un-wadeable target streams, respectively, or in large rivers, the maximum length of stream that can be sampled in 1 day), will be sampled to include all aquatic habitat types within that reach.  Collected fish will be identified to species, tallied, fork length measured, and examined for external abnormalities. Additionally, standard water chemistry, channel morphology, and riparian habitat parameters will be recorded at each sample site.  To enhance data quality and completeness and data entry efficiency, all collected data will be entered each day into an integrated database installed on a notebook computer. 

Read the metadata file for assistance with the dataset.

Data can be visualized here:

https://www.adfg.alaska.gov/sf/SARR/AWC/index.cfm?ADFG=main.interactive

Once in the mapper, the default visual is the Anadromous Waters Catalog. Clicking on the "AFFI" tab along the top banner produces all the site visits by this project.

For more help, click the red 'User Guide' link in the secondary banner above the map.

Any other questions or data needs, please contact the program biologist at nate.cathcart@alaska.gov

Pacific Coastal Salmon Recovery Fund, Award: 53013 (administered by the Alaska Sustainable Salmon Fund)