A Season of Change at Baker Lake, Great Basin National Park

First published in The Midden*, Great Basin National Park's newsletter, Vol. 20, No. 2, Winter 2020. By Leslie Twiner, biological science technician, who worked and camped at the lake from June to October.*

Taking a water-quality profile of Baker Lake from a pack raft. NPS photo by Jonathan Reynolds.

At 10,620 feet, in a spectacular cirque, Baker Lake is a favourite of backpackers and day hikers. Through the 2020 season the park's crew gathered a wide range of data on the lake and its trout.

Why the lake is changing

Baker Lake holds a healthy population of brook trout and Lahontan cutthroat trout — neither native to the park, both stocked before it became a national park. In September the park introduced native Bonneville cutthroat trout (BCT) into neighbouring Johnson Lake, and it hopes to do the same at Baker Lake. Much of the season's work prepared the lake for treatment with the fish poison rotenone in summer 2021, to remove every non-native fish before BCT arrive.

The reason is climate. BCT need cold mountain streams that flow all year to survive and breed, and with more drought and warmer temperatures that habitat is disappearing fast. Two new populations in high lakes that were historically fishless could be refuges able to survive a changing climate.

Hiking gear up to stash at Baker Lake for the summer. NPS photo by Jonathan Reynolds.

The season's work

• Snorkel surveys. Carrying all the gear they could on their backs, the crew put on dry suits and snorkels and watched the fish, looking for signs that Lahontan cutthroat trout were spawning successfully — a good sign that BCT could also form a self-sustaining population. They recorded what they believe is spawning behaviour.
• Water quality. A sonde in the lake measured pH, dissolved oxygen, conductivity and temperature, giving a profile that shows how well rotenone will work and how much will be needed.
• Depth mapping. With a women's crew from the Nevada Conservation Corps, the team surveyed the lake bed on a 5 m × 5 m grid, measuring depth every 5 metres, to learn how deep the lake is and how much water it holds.
• Water levels. The crew measured the distance from several reference points to the water, so that when levels rise the change can be measured and extended to the whole lake.

All of this will help the treatment succeed. Once the non-native fish are gone, BCT will be brought in to start a new population that is, the park hopes, more resilient to the climate of the years ahead.

Sources

• National Park Service, Great Basin National Park, "A Season of Change at Baker Lake," The Midden, Vol. 20, No. 2, Winter 2020. https://www.nps.gov/articles/000/a-season-of-change-at-baker-lake.htm
• A photograph credited to Stephanie Greenwood is not reproduced.
• Rewritten in hubnx's own words.