Henrys Lake Quarterly Newsletter - January 2022

First off we would like to thank everyone who commented through both the e-mail and online surveys, called, stopped by the office, and e-mailed us their thoughts on the proposed Henrys Lake Regulation change. Your feedback was essential to the regulation changing process and in November 2021, the Idaho Department of Fish and Game commission voted YES to a season change on Henrys Lake.

The current Henrys Lake regulations which came into effect on January 1, 2022 are as follows:

Section: Those portions of the lake within the posted boundaries of Staley Springs and within 100 yards of Hatchery Creek
• Closed to fishing

Remainder of Henrys Lake:
• February 15 through Friday before Memorial Day Weekend - trout limit is 0, catch-and-release
• Saturday of Memorial Day Weekend through February 14 - trout limit is 2, Brook Trout counted in the trout limit
• Fishing must cease after the 2-trout daily bag limit has been retained

                                          A changing of the guard

Throughout the month of December our staff were out on the ice angling for trout just like many of you. We were conducting a study to better understand angling mortality to trout during the ice fishery on Henrys Lake. Fish and Game employees were angling just out from the hatchery grounds from November 30th to December 17th, 2021. Trout were caught on a 1/8-ounce jig head with a 1-inch long by 1/4-inch-wide piece of sucker meat via jigging or using a dead stick.

Trout caught were tagged with an orange T-Bar tag to identify each individual fish and held in our spawning shed at the Henrys Lake Hatchery for at least two weeks. Trout were then measured for length and weight; and released back into Henrys Lake. We also recorded hook placement (lip, mouth, gut, or external), gear used (jigging or dead stick), whether the trout bled or not on the ice, water temperature and air temperature.

Figure 1. A Yellowstone Cutthroat Trout caught during the study which was hooked in the lip.

Figure 2. A Yellowstone Cutthroat Trout caught during the study which was hooked in the mouth.

In total, 49 trout were caught and tagged this winter which included 41 Yellowstone Cutthroat Trout, 6 Brook Trout, and 2 Hybrid (Yellowstone Cutthroat x Rainbow Trout) Trout. Of the 49 fish captured, there were no mortalities throughout the study. The majority of trout were caught by jigging (69%) while 31% were caught on dead sticks. The most common locations trout were hooked was the mouth (63%) and lip (33%). The lip being described as the outer edge of the mouth (Figure 1) and the mouth being described as anywhere from the lip back to the first gill raker (Figure 2). The remaining trout were either hooked externally (2%) or the hook location was unknown because the hook removed itself before a location could be determined (2%), and no trout were observed as gut hooked. A gut hook in this study was described as being hooked anywhere from the first gill raker to the esophagus.

The average Yellowstone Cutthroat Trout captured was 445.5 mm (17.5in) and weighed 896 g (just under 2 lbs). The average Hybrid Trout was 464.5 mm (18.3 in) and weighed 1045.5 g (2.3 lbs). The average Brook Trout was 337.5 mm (13.3 in) and weighed 349.2 g (0.77 lb).

Figure 3. Angled trout held in the spawn shed at the Henrys Lake Hatchery.

Figure 4. Henrys Lake Fisheries Technician Andy Johnson holding the largest Brook Trout caught in the study (19.6 inches).

Each captured fish was implanted with an orange T-bar anchor tag at the base of the dorsal fin. Each tag is printed with a unique identification number, phone number, and website address. If you catch a trout with one of these orange tags, please report it to us by phone (1-866-258-0338) or online (http://www.tag.idaho.gov). You will be able to find out all about that specific fish while providing us with valuable information!

We hope to continue this study during the 2022 ice season to further understand mortality of trout during the ice fishery.

The amount of oxygen in water is crucial to the survival and health of trout. When oxygen levels decline, a fish becomes stressed and its body cannot perform to its full potential. As such, the more oxygen there is available in the water column the better trout health and survival can be. Each winter we track oxygen levels under the ice by measuring the amount of dissolved oxygen throughout the water column at multiple locations on the lake. We use this data to make predictions about oxygen levels for the remainder of the winter. This information is also useful in planning and preparing for our spawning operations which typically occur in February.

Unfortunately due to variable ice conditions, we were unable to safely conduct dissolved oxygen monitoring throughout December 2021 and this work was delayed to begin in January 2022. We will continue to monitor oxygen levels throughout the rest of the winter and will provide an update on oxygen levels under the ice in the next edition of this newsletter.

1. Dissolved oxygen monitoring: As stated above, due to variable ice conditions in December we were unable to safely sample the lake for dissolved oxygen as we have in past years. This winter we will conduct our dissolved oxygen surveys throughout January and February 2022.
2. 2022 full season creel: Every three years our staff conduct interviews with anglers and gather information throughout the entire fishing season on Henrys Lake. These interviews provide us with valuable information on the current state of the fishery. Please keep an eye out for our staff around the lake this year, they would love to talk with you about your fishing experience.
3. Spawn: Each year we spawn Yellowstone Cutthroat Trout and Yellowstone Cutthroat x Rainbow Trout Hybrids at Henrys Lake in February and March. We fertilize the eggs and incubate them on site before shipping them to other IDFG hatchery facilities where we raise them to fingerling sizes. These fish are then stocked back into the lake in the spring and fall.
4. Gillnetting: Our annual gillnet survey takes place just after ice-off (April/May). Information gathered from this survey allows us to monitor trends in the abundance, size, age structure, and survival rates of trout and chubs in Henrys Lake.

Our next quarterly newsletter will be sent out in April 2022 so stay tuned!
If you have any questions, thoughts or concerns please contact the Henrys Lake Biologist Nathan Tillotson at nathan.tillotson@idfg.idaho.gov