Fisheries, Subsistence, and Habitat
Publications Searchable Database
Search Again| Division: | Sport Fish |
| Title: | A qualitative evaluation of parameters used to assess Kenai River king salmon, 1986-2010 |
| Author: | Eskelin, T, and J. D. Miller |
| Year: | 2010 |
| Report ID: | Alaska Department of Fish and Game, Special Publication No. 10-18, Anchorage |
| Abstract: | Two populations of king salmon return to the Kenai River to spawn. The first population, composed of king salmon bound for tributaries of the Kenai River (tributary spawners), enter the river from late April through early July. The second population, composed of king salmon that spawn in the Kenai River itself (mainstem spawners), enter the river from late June through mid August. Kenai River king salmon are managed as two stocks (early run and late run). A comprehensive stock assessment program using multiple assessment parameters drives the implementation of management plans for both stocks. Each of the stock assessment parameters has error associated with it. In total, there are 24 stock parameters used to assess Kenai River king salmon, all of which are used to assess the late run and only 14 of which are used to assess the early run. Ten parameters are estimated directly by active sampling, reported harvest, or from the Statewide Harvest Survey (SWHS). The remaining 14 parameters are estimated indirectly by using information from parameters that were estimated directly. The assessment of inriver run size contributes considerably more error for both runs than any other parameter used for assessing Kenai River king salmon stocks. Inriver run size estimates are produced with split-beam sonar, which does not accurately differentiate king salmon from more numerous sockeye salmon. Other sources of error associated with Kenai River king salmon stock assessment that are important and need to be addressed are 1) actual harvest of Kenai River king salmon in the Cook Inlet commercial Eastside setnet (ESSN) fishery is unknown, and 2) the timing and overlap between the tributary and mainstem spawning populations are not consistent with a management cutoff date of July 1 to delineate the early and late run stocks, thereby introducing multiple sources of error in accounting for each population. Current studies are being conducted to address the largest sources of error associated with Kenai River king salmon assessment including 1) the testing of DIDSON (dual frequency identification sonar) for assessing inriver run size, and 2) the use of genetic stock identification (GSI) techniques as a tool for improving assessment of stock-specific harvest estimates, and run timing and productivity of tributary and mainstem spawning fish. DIDSON has been tested on the Kenai River at the current sonar location and can differentiate king salmon from other species more accurately than split beam sonar. Future transition from the current split-beam sonar to DIDSON should reduce the amount of error associated with inriver run-size estimates. Collection of GSI information will improve understanding of the overlap in run timing and harvest of Kenai River tributary and mainstem populations, and harvest estimates in mixed-stock fisheries such as the ESSN fishery. In addition, GSI information collected inriver may provide estimates of annual abundance that are independent of sonar estimates and can be used to evaluate biases that may exist in the sonar estimates. |
| Keywords: | Kenai River, king salmon, Chinook salmon, stock assessment, Oncorhynchus tshawytscha, split-beam sonar, genetic stock identification, Eastside set net, total run, inriver run size, spawning escapement, brood tables, escapement goal analysis. |