Project

Hypoxia in coastal rivers

Goal: We are using water quality and salmon count data from two streams in southeastern Alaska to assess the extent to which high spawning salmon density and decreasing river discharge can lead to bouts of hypoxia. In addition to summarizing field measurements, we have employed a simulation model coupling salmon respiration and oxygen reaeration to illuminate mechanisms leading to hypoxia.

Methods: Water Quality Monitoring, Bioenergetics, Streamflow monitoring

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Project log

Christopher J. Sergeant
added a research item
Widespread mortality of Pacific salmon Oncorhynchus spp. returning to spawn in Alaska coincided with record-breaking air temperatures and prolonged drought in summer 2019. Extreme environmental conditions are expected to happen more frequently with rapid climate change and challenge the notion that Alaska could indefinitely provide abundant, cool freshwater habitat for Pacific salmon. A total of 110 geographically widespread opportunistic observations of premature mortality (carcasses) were collected from a variety of sources. Premature mortalities were documented for Pink Salmon Oncorhynchus gorbuscha, Sockeye Salmon O. nerka, Chum Salmon O. keta, Chinook Salmon O. tshawytscha, and Coho Salmon O. kisutch. Additionally, observations of Pink Salmon returning to spawn in Prince William Sound streams in 2019, obtained from systematic aerial surveys conducted annually, revealed low migration success in 87% of rain-driven streams (n = 30), 52% of snow-driven streams (n = 65), and only 18% of glacier-driven streams (n = 11). Salmon mortality observations were consistent with death due to heat stress resulting from high water temperatures or drought caused hypoxia and stranding. Developing a better understanding of how broad-scale climate patterns manifest at the stream scale can help us determine whether a major shift in Pacific salmon productivity is underway and inform fisheries management plans to better mitigate future risks.
Christopher J. Sergeant
added a research item
In this article, I describe some recent salmon research in Southeast Alaska and touch on future issues of concern in the region’s three national parks: Glacier Bay National Park and Preserve, Klondike Gold Rush National Historical Park, and Sitka National Historical Park.
Christopher J. Sergeant
added an update
The US Forest Service's Pacific Northwest Research Station has created a nice science story and video of our hypoxia research at this link:
 
Christopher J. Sergeant
added an update
Presented our hypoxia research at a local watershed stakeholders' meeting and handed out the attached one-page brief:
 
Christopher J. Sergeant
added an update
In revision with journal
 
Christopher J. Sergeant
added an update
Manuscript submitted.
 
Christopher J. Sergeant
added an update
Cool paper just out in Fisheries Research using a similar approach to our work. We will be integrating results from this into our intro and discussion. This paper has some excellent and fairly rare data on rates and types of pre-spawn mortality of salmon that can be attributed in part to low stream oxygen.
 
Christopher J. Sergeant
added a project goal
We are using water quality and salmon count data from two streams in southeastern Alaska to assess the extent to which high spawning salmon density and decreasing river discharge can lead to bouts of hypoxia. In addition to summarizing field measurements, we have employed a simulation model coupling salmon respiration and oxygen reaeration to illuminate mechanisms leading to hypoxia.