Glacier Bay Fish

A bigmouth sculpin takes a rest on a red coral in Glacier Bay

NOAA Office of Ocean Exploration and Research

 

Glacier Bay National Park and Preserve protects million acres of rugged mountains, temperate rainforest, bountiful coastline, deep fjords, open ocean, rich estuaries, wild rivers, lakes, streams and ponds, and a plethora of fish! This complex and dynamic, temperate ecosystem has nearly 1200 miles of coastline, including 950 square miles of ocean habitat and greater than 1000 freshwater systems of available fish habitat for over 200 fish species. From the smallest forage fish like Pacific herring and sandlance to deepwater giants such as 500 pound Pacific halibut and 14-foot sleeper sharks, fish play critical roles in Glacier Bay's rich ecosystems.

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Pacific sandlance (top), Pacific herring (middle), capelin (bottom)

M. Arimitsu

Small but Mighty Important

Small schooling forage fishes include capelin, sand lance, herring, juvenile walleye pollock, juvenile salmonids and myctophids (lanternfish). Though individually small, these fishes are unbelievably numerous, often swimming in large, dense schools. As a key food source, they serve as a critical link between marine primary and secondary producers (phytoplankton and zooplankton) and are prey for fishes, birds, harbor seals, Steller sea lions and even humpback whales.

Numerous studies have documented capelin as important forage species for many sea birds and marine mammals in the Gulf of Alaska. Capelin were extremely abundant and wide spread in the Gulf of Alaska until the late 1970’s when they became almost absent. Increased water temperature and predation are implicated in the mass decline of this important species. Recent research in Glacier Bay suggests that glacial fjords may serve as critical refuges for capelin during warmer temperature cycles in the Gulf of Alaska. Research suggests that these important fish are strongly associated with the tidewater glacier ecosystem in Glacier Bay and could help to replenish the Gulf of Alaska if water temperatures again decrease.

 

East Alsek sockeye salmon in full spawning color.

NPS / C. Murdoch

Rich in Salmon

Adult salmon are unparalleled contributors to Glacier Bay National Park’s ecosystems. Much like small schooling fishes, salmon feed a diversity of other animals and are particularly unique because they link marine, freshwater and terrestrial habitats. Salmon are anadromous, which means they migrate upriver from the sea to spawn in their birth streams after spending 1 to 5 years maturing in the marine environment. Some salmon increase their body weight 1000 times at sea. When they return to their natal stream to spawn and die, salmon bring all the marine derived nutrients they consumed in the ocean back to their freshwater streams. These nutrients feed and fertilize aquatic plants, insects, and other organisms, and ultimately provide food for their own offspring. Salmon fertilize the forest too. Bears, otters, mink, eagles, and other forest animals feast on adult salmon, often leaving their carcasses half eaten and decomposing...bathing the forest with ocean nutrients.

Glacier Bay National Park was expressly established for the study the successional ecological processes following rapid deglaciation. Researcher Dr. Sandy Milner is doing just that with his 35 year study of stream succession and fish colonization in Glacier Bay. His research is not only the longest running study in the park but also the longest continuous study of primary succession in streams anywhere. Dr. Milner’s important work has elucidated the incredible changes that streams undergo after they are born from retreating glaciers. One of many important findings is that Dolly Varden and straying pink salmon may colonize a new stream in just 10 years!

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