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Location: The Duckabush Juvenile trap is located at river mile 0.75, near Brinnon. (see map)
History: Multiple species of salmonids spawn and rear in the cold-water rivers draining from the Olympic Mountains into Hood Canal. These species include Hood Canal summer chum, Puget Sound Chinook salmon (listed as “threatened” in 1999) and Puget Sound steelhead (listed as “threatened” in 2007). Other salmonids include fall chum, coho, and pink salmon.
In March of 1999, the National Marine Fisheries Service (NMFS) listed Hood Canal summer chum as threatened under the Endangered Species Act (ESA). In response to the listing, the Summer Chum Conservation Initiative was developed by WDFW and the Point No Point Treat (PNPT) Tribesto serve as a management plan to recover summer chum in the Hood Canal and Strait of Juan de Fuca region. Under the initiative, guidelines were set for hatchery supplementation, harvest management, habitat improvements, stock recovery timelines and evaluation techniques. As part of the summer chum evaluation, WDFW and the PNPT Tribes work with Long Live the Kings (LLTK), a regional salmon recovery organization, to assess natural production of juvenile salmon in both the Duckabush and Hamma Hamma rivers.
In addition, the success of different steelhead supplementation strategies is currently being investigated via the Hood Canal Steelhead Project led by NOAA Fisheries.
The Duckabush study is led by WDFW staff and began in 2008. An 8ft rotary screw trap is operated twenty four hours a day, seven days a week from mid January through July. A mark-recapture study design is used to expand the catch of juvenile fish to an estimate of the total number of juvenile migrants. Beginning in 2011, DNA samples were collected throughout the entire chum outmigration to determine the ratio of summer vs fall chum leaving the system.
WDFW objectives:
- The primary objective for this study is to evaluate the juvenile abundance, survival, and migration timing of summer and fall chum salmon and of Chinook salmon in the Duckabush watershed.
- The secondary for this study are to estimate freshwater production of coho and pink salmon and steelhead in the Duckabush watershed and improve understanding of Puget Sound Chinook life history.
The juvenile screw traps are both operated continuously from January through July. Both traps catch a portion of the juvenile downstream migration during this period. Once a day, juveniles are collected, identified to species, and counted. Each week, fork lengths are measured for a sub sample of the catch. In order to estimate the total migration, the trap is calibrated with a series of efficiency trials. Efficiency trials are conducted at least twice a week. Fish are marked and released upstream of the trap. Marks include a small fin clip or dye that allows technicians to quickly distinguish them from the rest of the catch. Trap efficiency is estimated based on the numbers of marked fish that are recaptured. Most of the marked fish are recaptured within 24 hours. Freshwater survival (egg-to-migrant) is based on the number of juvenile migrants, the number of female spawners, and the number of eggs per female.
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- Freshwater production of Duckabush Summer chum has averaged 319,244 fry migrants between 2011 and 2012.
- Egg-to-migrant survival has ranged between 6 and 15% between 2011 and 2012.
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- Freshwater production of Duckabush fall chum has averaged 37,855 fry migrants between 2011 and 2012.
- Egg-to-migrant survival has ranged between 1% and 5% between 2011 and 2012.
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- Freshwater production of Duckabush odd-year pink salmon has averaged 188,725 migrants between 2008 and 2012.
- Egg-to-migrant survival of Duckabush odd-year pink salmon ranged between 0.5% and 13.9% in 2008 and 2012.
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- Freshwater production of Duckabush Chinook salmon has averaged 2,003 migrants between 2011 and 2012.
- Unable to determine egg-to-migrant survival due to low adult escapement.
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