All posts by Christina

Juvenile Chinook Salmon Outmigration at the Yukon River Mouth

Juvenile outmigration is an important life stage for Yukon River Chinook salmon. Recent research suggests that much of the variability in Chinook salmon production may occur prior to the first summer at sea (Howard et al. 2016, Murphy et al. 2017) and that larger fish with higher energy content at the end of their first marine summer had a greater chance of surviving to adulthood (Howard et al. 2016). Outmigration from the river to the marine environment is physiologically stressful. Larger in-river has been linked to both downstream survival (Zabel & Achord 2004) and adult returns (Zabel & Williams 2002, Woodson et al. 2013) in wild Chinook populations, and suggests that early growth in fresh water may be an important indicator of later growth (Ruggerone at al. 2009). This is consistent with an emerging idea that fish need to prepare themselves for life history transitions such as smolting or offshore migrations. This preparation is associated with increased energy reserves, which are maximized by increased size.

The objectives of this project are to quantify outmigration timing from ice out through the end of the August,  examine size (length and weight), growth, diet, energetic condition, and smolting stage of outmigrating juveniles in relation to environmental variables in the freshwater and nearshore marine environment, and to collect genetic samples to assess outmigrant origin.

Developing a Juvenile Stock-Recruitment Relationship for Chinook Salmon

The main goal of this project is to develop a juvenile stock-recruit relationship for Yukon River Chinook salmon. Information about limits to production in the freshwater environment can play a key role in augmenting standard stock-recruit analysis.  Our second goal is to contribute to understanding about the extent that juvenile rearing habitat is limiting productivity at a given stock level which can then form the basis for setting restoration priorities. The objective of the proposed work is to extend an existing 6-year database of juvenile Chinook salmon density for small non-natal streams tributary to the Yukon River near Dawson City. Sampling in 2018 and possibly 2019 will take advantage of recent strong returns to the Canadian basin.  With an additional 2 years of data the relation between spawner abundance and subsequent juvenile density should be well established so that it can contribute to the goals identified above.