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The unseen benefits of salmon habitat work

From controlling water flow in critical salmon runs to eliminating invasive species, CIAA helps protect vital salmon spawning grounds.

by | November 29, 2023

Former fisheries technician, Natalie Coash
Former fisheries technician, Natalie Coash helps a silver salmon ascend a beaver dam on Shell Creek. On this day in 2021, seven beaver dams were notched in Shell Creek to allow returning silver and sockeye to get to their spawning grounds. CIAA

The Cook Inlet drainage has been blessed with dozens of lake and stream systems capable of supporting diverse biological communities.

Many of these systems provide the physical, chemical and biological habitats that support the early life stages of salmon. Cook Inlet’s commercial, personal use, and sport fisheries have been the focus of salmon enhancement activities in Alaska for over 100 years.  

CIAA’s focus on habitat

The Cook Inlet Aquaculture Association (CIAA) was established in 1976 with the goal of enhancing Cook Inlet’s salmon fisheries. Initial efforts focused on hatchery production and in developing a better understanding of Cook Inlet’s natural lake and stream systems. Based on these early efforts CIAA established several projects to improve fisheries through habitat protection and rehabilitation.  

CIAA’s initial efforts focused on providing salmon access to spawning habitat through three forms: 

  1. Construction of spawning channels (the ones that were constructed required extensive maintenance and CIAA quickly discontinued this endeavor).
  2. Building flow control structures to maintain adequate stream flows.
  3. Temporary modification of beaver dams, which were holding back adult salmon migrating to their spawning grounds. 

Flow control structures

For many years, CIAA has operated and maintained flow control structures at three sites in Upper Cook Inlet—Daniels, Marten, and Packers lakes—and conducted aerial surveys of numerous stream systems with beaver dams known to hinder upstream migration to historical spawning and rearing habitat.  

These efforts may not be necessary every year; however, over time, they have assisted in maximizing the spawning population in historic spawning grounds. 

For example, CIAA reported the operation of the Marten Lake flow control structure from 1991 through 2018 assisted sockeye salmon in reaching their historic spawning grounds in 11 of the 28 years. 

CIAA also estimated that 12,235 to 15,560 adult salmon reached the spawning grounds during these 11 years.  The benefit to the fishery of the sockeye that spawned during these 11 years is unknown.

Pike with a belly full of salmon smolt
One invasive northern pike with a belly full of salmon smolt. The Alaska Department of Fish and Game recently estimated that about 26% of Matanuska-Susitna lakes and ponds listed in the Anadromous Waters Catalog no longer function as important habitat for the spawning, rearing, or migration of anadromous fish (which includes salmon) due to invasive pike predation.  Matt Smukall

The threat of Northern pike

One of the biggest issues now facing salmon production in Upper Cook Inlet is changes to the biological communities of the numerous small salmon-producing lakes in the northern part of the Cook Inlet drainage by the introduction of the invasive northern pike. 

Northern pike prey on young salmon and can thrive in the small, shallow lakes typical of the northern Cook Inlet drainage. Once established, they dramatically alter the natural biological community and may reduce or eliminate salmon production from a lake system. 

It is difficult to assess the impact of lost salmon production due to an invasive species like northern pike because it occurs over time in small systems where adequate monitoring is expensive. However, CIAA has been able to document lost sockeye salmon production from one system potentially impacted by northern pike–Shell Lake. 

Sockeye salmon returns to Shell Lake estimated during beaver dam aerial surveys averaged 5,000 to 6,000 sockeye from 1991 to 2005 and showed a precipitous decline during weir counts from 2006 to 2021

Based on the more accurate weir counts, escapement of sockeye salmon to Shell Lake averaged 21,295 from 2006 to 2010 and dropped to single digits by 2014. Assuming a conservative 40% commercial harvest rate on sockeye salmon returning to Shell Lake, an estimated 14,200 fish have been lost to the commercial harvest annually since 2014.  

At an estimated average weight of 4.5 lbs and an estimated ex-vessel value of $1.40 this is an estimated annual loss of $89,460 to the commercial fishery or $890,000 over the last decade. CIAA is investigating ways to control invasive northern pike in Shell Lake. Even partial control techniques, if they can be applied to other pike infested systems, could enhance commercial sockeye fisheries substantially.

Fisheries enhancement requires many approaches

Hatchery programs are often the means by which salmon fishery enhancement is addressed in Alaska and there have been dramatic improvements in commercial harvests as a result of hatchery programs. But hatchery programs are not the only means for enhancing fisheries. 

Habitat protection and rehabilitation are also important options for sustaining our salmon resource. Let’s not dismiss the benefits of habitat projects because they come in small increments, are hard to assess, or the benefits are not obvious. Collectively they can make a difference.

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