Hidden Falls Hatchery, Kasnyku Bay

Hidden Falls Hatchery, Kasnyku Bay

by | May 13, 2022

The Hidden Falls Fish Hatchery is located in Tongass National Forest on the northeast coast of Baranof Island, at the head of Kasnyku Bay off Chatham Strait, about 22 miles (35 km) south-southeast of Angoon and 21 miles (34 km) northeast of Sitka, Alaska. Hidden Falls is the outlet to Hidden Falls Lake located adjacent to and above the hatchery at an elevation of 210 feet (64 m) and measures about 1.3 miles (2 km) long by 0.4 miles (0.6 km) wide and is fed by several alpine lakes and cirque glaciers. The descriptive name was given in 1923 by the U.S. Forest Service because the falls cannot be seen by boat until the upper end of the small lagoon at the head of Kasnyku Bay is reached. Baranof Island is in the northern Alexander Archipelago of Southeast Alaska and was named in 1805 by Captain Yuri Lysianskyi after Alexander A. Baranov, the governor of Russian America and chief administrator of the Russian-American Company. Baranof Island is part of an accretionary block that includes Chichagof Island to the north and is bounded to the west by the Fairweather Fault that separates these islands from volcanic rocks of the Pacific oceanic plate. The block is bounded to the east by the Chatham Strait Fault and to the northeast by the Peril Strait Fault. The Chatham Strait and Peril Strait Faults separate the Baranof-Chichagof block from rocks of Southeast Alaska that have entirely different stratigraphic sequences and intrusive rocks. The northeast coast of Baranof Island is comprised of rocks assigned to the Chugach terrane that consists of sedimentary and volcanic rocks derived from a subducting oceanic plate. The bedrock surrounding Kasnyku Bay is an igneous intrusive called tonalite that developed between the Late Paleocene and Oligocene periods on the geological time scale, or 43 to 23 million years ago, and is mainly represented by the Kasnyku Lake pluton that underlies about 64,000 acres (25,900 ha) of Baranof Island and an additional area of unknown extent under Chatham Strait.

The State of Alaska constructed a salmon hatchery at Kasnyku Bay in 1978, and in the process, exposed at Hidden Falls what would turn out to be one of the major archaeological discoveries in Southeast Alaska. Archaeologists found 13 distinct layers of cultural material while excavating and from these identified three components representing major episodes of human occupation. The deepest and oldest component dates to about 9,500 years ago and yielded a variety of chipped stone tools. The hallmark tool of this earliest occupation, called Component I, are small blades of obsidian that were often fastened to bone or wood tools to create a cutting edge. Examination of these microblades revealed the obsidian was obtained from Suemez Island about 150 miles (241 km) south-southeast of Hidden Falls, and from Mount Edziza about 100 miles (161 km) up the Stikine River. The archaeological record indicates people abandoned the site at Hidden Falls, perhaps due to advancing glaciers, and did not reoccupy the site until about 4,600 years ago. By the time people returned to Hidden Falls their tools were made of ground stone and bone. Microblades were absent and other chipped stone tools were not well represented in the excavations. The people from this period, called Component II, subsisted on a diet of cod and other bottom fish, sea mammals, deer, and birds for their diet. They developed methods to catch large volumes of salmon using fish weirs as indicated by a weir found in Cosmos Cove about 2 miles (3.2 km) north of Kasnyku Bay. They used the Hidden Falls site as a seasonal camp for roughly 1,400 years. The most recent culture to inhabit the site is called Component III and dates from about 3,000 to 1,300 years ago. These pre-historical people continued to use ground and chipped stone tools, but there was a greater emphasis on ground bone tools, such as harpoon points for sea mammal hunting. Other recovered artifacts reflect a traditional Northwest Coast cultural adaptation, with stone adzes, axes, mauls, and other woodworking tools. This layer also yielded large volumes of shellfish, including butter clams, littleneck clams, and mussels. Subsistence activities at Hidden Falls over its entire human prehistory focused on resources found close to shore, similar to other peoples that occupied the mainland and inner islands to the south. Their maritime adaptation differed considerably from the Aleut, Alutiiq, Haida, and Nuuchanulth who specialized in offshore hunting and fishing, and possibly suggests a stronger reliance on terrestrial resources made possible by the rich abundance of food at salmon streams and cedar trees for building canoes and houses.

Salmon enhancement in Alaska started in response to rapidly declining salmon populations. The average annual number of salmon caught in Alaska from 1945 to 1975 was 83 million fish, however, for the last 15 years of that period, the average annual catch was just 45 million fish, and between 1973 and 1975 the catch was only 23 million fish annually. In 1969, Alaska received $900 million from North Slope oil and gas leases, and the state legislature decided to invest public funds from oil and gas into the development of salmon hatcheries to provide a long-term source of em­ployment and economic activity. The legislature’s goal was to supplement wild salmon stocks with hatchery fish until a total catch of 100 million fish per year was reached. In 1971, the Division of Fisheries Rehabilitation, Enhancement and Development was created within the Alaska Department of Fish and Game to manage the state-owned fish hatcheries and promote private hatcheries. Currently, there are 30 production hatcheries and one research hatchery operating in Alaska. The salmon hatchery at Hidden Falls was operated by the State of Alaska from 1979 to 1988 when the facility was transferred to the Northern Southeast Regional Aquaculture Association. The hatchery releases about 600,000 Chinook smolts, 3 million coho smolts, and about 84 million chum salmon fry each year. Returning coho and Chinook are caught primarily by trollers and seiners. Trollers catch Hidden Falls Chinook from late May through early July. Seiners catch Chinook later in June and in early July when they target the chum salmon return. The combination of large chum, Chinook, and coho returns makes this hatchery the most economically important salmon augmentation program in Southeast Alaska. In most years, Hidden Falls Hatchery produces a larger chum return for common property harvest than any other facility in North America with returns averaging 1.7 million between 2001 and 2010, with a record return in 1996 of over 4 million fish. The run has attracted up to 240 seine boats during openings and provided fishermen with significantly greater fishing opportunities in the early portion of the fishing seasons. In 2011, several small cruise ships received U.S. Forest Service authorization to take passengers to the hatchery for interpretative tours. These ships range in capacity from 22 to 86 passengers. Hidden Falls Fish Hatchery staff show visitors around the site to educate them on salmon fishery enhancement and aquaculture practices. In 2014, the number of visitors increased to 839, mostly attributed to new cruise ship operators seeking opportunities for their passengers to experience the wild and remote character of the Tongass National Forest. Read more here and here. Explore more of Hidden Falls Hatchery here:

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About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2021 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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