Climate Change Affecting Southeast Alaska's Waters Salmon Call Home
By LAINE WELCH
October 23, 2016
One third of Alaska’s salmon harvest each year comes from fish produced in the 17,000 miles of streams in the Tongass rainforest. More than 50 species of animals feed on spawning salmon there, and one in 10 jobs is supported by salmon throughout the region.
“Global climate change may become one of the most pressing challenges to Pacific Salmon conservation and management for Southeast Alaska in the 21st Century” begins a report called “Climate Change Sensitivity Index for Pacific Salmon Habitat in Southeast Alaska” by Colin Shanley and David Albert of The Nature Conservancy.
“In general, the global climate models are saying the wetter places in the world are likely to get wetter and the dryer places are going to get dryer,” said Shanley, who works as a conservation planner and GIS analyst in Juneau.
“This is not a doom-and-gloom outlook,” Shanley stressed. “This is really just getting smarter about how climate change may play out and how it might affect resources that are valuable to us.”
Shanley studied nearly a half century’s records of 41 water gauge stations at Southeast watersheds to model future projections on how flow patterns might change. He said watersheds fed by snow packs will likely experience the biggest impacts.
“Some of the watersheds that are super steep and fed by snow driven catchments are going to see some of the biggest changes. They might not all be bad, but those are the ones that showed some of the largest changes in flow,” he said.
On the other hand, glacial fed waters could provide new and better salmon systems.
“In Southeast, South-central and Prince William Sound there are a lot of glacial fed systems that salmon use and some that salmon haven’t colonized yet. As glaciers shrink and melt, there is some opportunity to create new, and in some cases, better habitat,” he explained. “Some of those glacial systems are really big rivers, so there are definitely opportunities for some shifts in productivity.”
Watersheds that are in good shape should be fairly resilient, Shanley said. For waters adjacent to roads and culverts that have changed historically, the Conservancy plans to do restoration projects, such as making sure there is adequate drainages and adding trees and stumps.
“The wood slows down the water so that can help with higher water levels, and it also provides pools and shade and protection from predators,” Shanley said.
More new research by the Oregon-based Wild Salmon Center (WSC) also provides a glimpse of how a flooded future could hurt salmon in Southeast and other Alaska regions.
Salmon spawn in streams in the fall and eggs develop through the winter, so increased winter flooding could potentially scour their eggs from stream beds and harm the next generations of fish, said WSC science director Matthew Sloat.
In collaboration with the U.S. Forest Service, Sloat modeled the possible flood disturbances on coho, chum and pink salmon spawning habitats in over 800 Southeast watersheds.
They found that as much as 16 percent of the spawning habitat for coho salmon could be lost by the 2080s primarily in narrower, steeper streams. The effects were lower for pink and chum salmon, which spawn almost exclusively in low sloping floodplain streams.
Somewhat surprisingly, the study shows that the overall risk of flood impacts to salmon reproduction in Southeast Alaska appears much lower than previously thought. That’s due to the relatively pristine condition of the area's rivers and floodplains, according to Sloat.
"Flood plains act as pressure release valves that can dissipate the energy of large floods," he said. "Our results identify key parts of watersheds that, if protected, will continue to buffer salmon populations from flood disturbance in the future.” Find the WSC report online at GlobalChange Biology.
The popular January Tanner crab fishery has been cancelled for the fourth year in a row at the Westward Region, meaning Kodiak, Chignik and the Alaska Peninsula.
During the last fishery, a fleet of 80 or more small boats took a combined catch of about three million pounds of crab worth several million dollars to the region. But annual surveys showed the numbers of both legal sized males and females don’t meet the minimums to allow for a fishery.
“We don’t seem to be having a problem making small crab. The problem seems to be getting enough of them to a legal size where we can have a fishery,” said Nat Nichols, shellfish manager at the Alaska Dept. of Fish and Game at Kodiak. It takes six to seven years for Tanner crab to reach their mature, two pound size.
Kodiak is seeing slight crab increases, especially at the east and southeast districts, Nichols said, but it’s slow going. At Chignik, Tanner crab abundance estimates were the lowest in the survey time series that dates back to 1988. At the Western Peninsula, the stock remains in decline and the bulk of the crab were heavily localized in just two areas of one bay.
Biologists point to a warming ocean and predation as the likely causes of the crab declines.
“We are seeing increases in skates, small halibut, cod and pollock in near shore, so I think it’s fair to look at increased predation as a reason why we don’t have these small crabs making it to legal size,” Nichols said.
Nichols added that he has confidence in the annual surveys, and for several years biologists have gone beyond the standard survey grid, thanks to funding from the Aleutians East Borough.
“The results of those additional tows indicate that there are small bits of crab everywhere you look,” Nichols said, “but we haven’t found a large portion that indicates we’re missing them wholesale.”
By the way -- Tanner crab is spelled with a capitol T because it is named after discoverer Zera Luther Tanner, commander of the research vessel Albatross which explored Alaska waters in the late 1800s.
Laine Welch ©2016
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