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Posts from the 'Ecology of Glacial Rivers' category

The Ecology of Glacial Rivers–Su River runs of humpback, sockeye, and coho

Sunday, September 3, 2017
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Adult Coho Salmon–photo credit Susitna Salmon Center

 

The seventh in a series from the Susitna Salmon Center. This segment by Jeff Davis deviates from the ecology theme to tell about the runs of the other four species of  salmon in the Susitna River drainage. From tagging studies, Department of Fish and Game biologists have information about when the runs are, where most of the salmon spawn, how long they spend in freshwater habitats, and other details of the spawning season. Chinook salmon were covered in the previous episode.

Until recently, it was commonly believed that glacial rivers, like the Susitna River, served primarily as migration corridors for Pacific Salmon and that they provided little spawning, rearing, or overwintering habitat. Recent studies tracking radio-tagged salmon in the Susitna River showed that a portion of adult salmon spawn within the Susitna River mainstem. (more…)

The Ecology of Glacial Rivers: Chinook salmon runs–what tagging has revealed

Sunday, August 27, 2017
Fishwheel at Curry. Photo by Susitna Salmon Center

Fishwheel at Curry. Photo by Susitna Salmon Center

The sixth in a series from the Susitna Salmon Center. This segment by Jeff Davis deviates from the ecology theme to tell about chinook salmon runs in the Susitna River drainage:  When the run starts, how many king salmon move up several of the main tributaries, and what the radio tagging studies showed that was news to fisheries biologists.

The Susitna River drainage, like most large glacial rivers in Alaska, supports five species of Pacific salmon. Recent radio-tagging studies conducted by the Alaska Department of Fish and Game have provided new information on the abundance and distribution of returning adult salmon within the Susitna River drainage.

Salmon are an anadromous fish species, which means that they spawn in freshwater but spend part of their life cycle in the ocean. Chinook or King salmon are the first adult salmon species to enter the Susitna River drainage in the spring. Chinook salmon from the Susitna River drainage spend one year as juveniles rearing in fresh water, and most spend 3 or 4 years in the ocean.

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The Ecology of Glacial Rivers: The role of beavers

Sunday, August 20, 2017

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The fifth in a series from the Susitna Salmon Center: The Ecology of Glacial Rivers. This segment by Jeff Davis explains how beavers improve habitat for salmon.

Gravel bars that develop as glacial rivers move across the floodplain expose soils allowing for the establishment of wind-blown seeds of cottonwoods and willows. Willow stems transported and deposited on the gravel bars of glacial rivers also can develop roots and continue to grow in these new locations. Cottonwoods and willows along glacial rivers provide a food source for herbivorous beaver (Castor canadensis). While herbivorous, the Alaska Department of Fish and Game has published observations of beaver feeding on salmon carcasses in the Susitna River.

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Ecology of Glacial Rivers: Side Channels

Sunday, August 13, 2017

The fourth in a series from the Susitna Salmon Center: The Ecology of Glacial Rivers. This segment by Jeff Davis tells how side channels and side sloughs provide important salmon spawning and rearing habitat.

The balance between the amount and timing of high flows and sediment transported from glaciers results in a number of different kinds of habitats in glacial rivers. Previously, we compared the fast main channel that contains a large amount of suspended sediment and clear-water upland sloughs that develop in abandoned channels cut off from the mainstem. Other habitat types common in glacial rivers include side channels and side sloughs. These two habitat types differ in the amount of water they receive from the main channel compared to groundwater sources.

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The Ecology of Glacial Rivers: Upland or backwater sloughs

Sunday, July 30, 2017
upland slough, photo credit Susitna Salmon Center

Upland slough, photo credit Susitna Salmon Center

The third of a new series from the Susitna Salmon Center: The Ecology of Glacial Rivers. This segment by Jeff Davis, and voiced by Katie Kierczynski, describes how suspended sediment changes conditions in main channels of glacial rivers, and how fish have adapted to these changes.

Upland sloughs occur along the margins of glacial rivers and have physical conditions that are very different from the main channel. Upland sloughs develop as the main channel moves across the floodplain abandoning the old channel. Over time, the upstream end of the abandoned channel becomes vegetated and the slough becomes isolated from the mainstem. (more…)

The Ecology of Glacial Rivers: How fish have adapted to silty water

Sunday, July 23, 2017
Longnose Sucker, photo by Annie Helmsworth

Longnose Sucker, photo by Annie Helmsworth

The second of a new series from the Susitna Salmon Center: The Ecology of Glacial Rivers. This segment, by Jeff Davis, describes how suspended sediment changes conditions in main channels of glacial rivers, and how fish have adapted to these changes.

The main channels of glacial rivers carry a large amount of fine sediment suspended in the water column during the summer months when runoff from glaciers is at its highest. This sediment gives glacial rivers their brown or turbid appearance. The amount of sediment can be reduced in glacial rivers that contain lakes, as some of sediment is deposited in the lakes.

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The Ecology of Glacial Rivers: Fish diversity

Monday, July 10, 2017

SSC image from facebook

The first of a new series from the Susitna Salmon Center: The Ecology of Glacial Rivers. This segment, by Jeff Davis, is about how habitat diversity in glacial rivers means more species of fish.

It’s surprising for many people to learn that large glacial rivers, like the Susitna River, support over 20 species of fish. This includes all five species of salmon, Chinook (or king), sockeye (or red), coho (also known as silvers), pinks (or humpy), and chum (or dog) salmon. Three of these salmon species (coho, chum, and sockeye) spawn, and three species (Chinook, coho, and sockeye) rear for one to three years within the Susitna River. Other fish that are popular in the sport fishery, rainbow trout, Dolly Varden char, burbot, and grayling are also found in the Susitna and other glacial rivers. Less common resident fish species include longnose suckers, two whitefish species, blackfish, sculpin, stickleback, and lamprey. The Susitna River also supports an isolated southern population of Bering cisco.

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