Lake Washington sockeye salmon have been counted each year since 1972 as they enter freshwater at the Hiram M. Chittenden Locks. The Washington Department of Fish and Wildlife (WDFW) counted the sockeye from 1972 through 1992, and currently Muckleshoot Indian Tribe and WDFW staffs conduct the counts cooperatively. Although small numbers of sockeye enter the system in May and early June, the period from the second week of June through the end of July is the standard counting interval used to determine if there are sufficient sockeye to open fishing seasons. Sockeye counts begin on June 12th each year to provide consistent data from year to year. The sockeye are sample counted daily during set time periods as they pass through both the locks and the fishway, and the counts are converted into a daily total number of fish passing upstream. In early July, State and Tribal managers begin to make weekly projections of the expected total run size based on the current total counts. When the co-managers believe that the total run size includes sufficient surplus fish above the escapement goal of 350,000 sockeye, sport and Tribal fishing seasons will be opened.
The pre-season forecast for the 2015 sockeye return is 164,595. The estimate is based primarily upon fry production from the spawners in 2010, 2011, and 2012. Since lake and marine survival rates are highly variable from year to year, the actual return to Lake Washington could be higher or lower than 164,595.
In 2015 a comprehensive biological sampling program will continue gathering critical information for the management of Lake Washington sockeye salmon, including changes in populations, survival rates, genetic identification, changes in size, etc.
The goal is to collect approximately 200 adult sockeye each week as they move from seawater into the Lake Washington Basin. Biologists from the Muckleshoot Indian Tribe will lead the sampling effort, with the collaboration of WDFW staff who will assist in the collection and processing of samples from the adult sockeye. Seattle Public Utilities provides funding for processing and analysis of these biological samples.
- Genetic Samples (DNA)
- Mark Samples (Otoliths and tags)
The following are examples of three important biological data sets.
Age Composition - Sockeye salmon age compositions are a necessary step in measuring survival rates. Insufficient age data have been collected in recent years because of budget constraints and due to the difficulty of collecting a representative sample. Scales from the adult fish will be used to determine ages.
Wild/hatchery proportions - Artificially produced sockeye salmon will be an important component of the return in 2011 and coming years. The hatchery fish are 100% otolith (small bones inside the head) marked for differentiation from wild-origin sockeye. The accurate estimation of the numbers of returning hatchery fish is important to evaluate hatchery performance, and can be used to inform in-season fishery management decisions.
Genetic Diversity - Because genetic (DNA) analysis has only recently become available as an assessment tool, consistent genetic sampling programs have not been a part of the management process. Tissue samples collected from Lake Washington sockeye stocks will be used to make future comparisons between populations based on DNA profiles. This may allow the in-season monitoring of the returns of various wild and hatchery stocks, the crafting of protective measures in fisheries, and may allow the measurement of the influence of hatchery fish on wild sockeye.