Dec 2007: Understanding the Blue Green Algae Bloom

From Damon Keen – IDFG.

Although I’m not a water quality expert, here are a few observations about the bloom we saw this year.

1)Blue green algae are in fact not true algae at all. They are actually cyanobacteria that photosynthesize, produce oxygen and “feed” on the nutrients in the lake.

2)Blue green blooms can occur in many nutrient rich waters, namely waters high in phosphorous and nitrogen. Blooms can occur anytime, but are often seen in late summer and early fall.

3)As with other plant life, when the blue greens die, the decomposition process uses oxygen. Therefore, if conditions are right (or wrong), low oxygen conditions can occur as the bloom “dies” off. This is not common, but we probably saw a minor event like this at Henrys Lake around Labor day.

4)Henrys Lake is a nutrient rich body of water. Most of the phosphorous is delivered to the lake through runoff that occurs in the system naturally. Many other sources of nutrient delivery occur including: septic systems, lawn fertilizers, grazing practices (animal waste) and others.

5)Other factors can contribute to blue green blooms. Those factors include but are not limited to: High water temperatures, drought conditions, lack of flushing effect (although runoff contributes nutrients to the system, it can also dilute the nutrient load by the flushing effect), early ice out, long periods of sunshine, lack of precipitation and others.

6)Nutrient delivery can be reduced by ‘filtering” the water before it reaches the lake. Important filters or buffers around the lake include: Wetland areas, healthy riparian areas, and shoreline vegetation.

7)Blue green blooms can also be toxic, depending on the species present. Toxic blooms are not common and did not occur on Henrys Lake this year. When toxicity does occur, toxic impact to fish is usually not noted. When fish mortality is noted, it can be related to point

So What Can be Done? 1)Maintain/improve the shoreline buffers and riparian areas around the lake. In recent years, two important areas have been enhanced. The lower Duck creek/Kelly Springs area is no longer grazed and vegetation has been dramatically improved along a large area surrounding those two tributaries and a large shoreline area. Additionally, areas north and south of the county boat dock have been fenced and shoreline filtering improved there. However, maintaining/improving other shoreline buffers is important also. 2)Repair/upgrade and pump septic systems. 3)Monitor your own practices, especially if you’re close to the water body. Are you contributing nutrients to the lake by your unwise practices? Can you reduce personal impact?


March 2007:Telemetry Update – Reported by Damon Keen, Asst Henrys Lake Hatchery Specialist, Idaho Dept of Fish

The radio telemetry project was started this winter, thanks to the partnership with the Henrys Lake Foundation and their financial contribution towards the purchase of radio tags.

We currently have 43 fish tagged and have monitored those fish periodically throughout the winter, via snowmobile. Although it’s far too early to draw any conclusions from these movements, the early indicators are interesting. The best descriptor would be to say the fish are scattered, with some moving great distances quite often and others staying “home.”

Stay tuned as we continue to monitor. Dan Garren, our regional biologist is heading up this interesting project. Dan will have the analysis at the conclusion of the project, forecast to end sometime in late fall or early winter (depending on tag life) 2007.

For two short video segments on Henrys Lake, visit this website by Kris Millgate, a reporter for Tight Line Media: The first segment “Spawning Fish 04/18/07” shows the Henrys Lake spawning effort by Idaho Dept of Fish and Game and volunteers. The second segment “Wired Fish 04/25/07” covers the telemetry project.


2006 Highlights: Radio Telemetry Trout, Fish Planting, Restoration and More

Radio Telemetry Trout in Henrys Lake

October 2006

A one-year project to monitor the movement of trout in Henrys Lake was begun this month by implanting 30 fish with radio transmitters. The Idaho Department of Fish and Game in a joint effort with the Henrys Lake Foundation, radio tagged and released 30 trout into Henrys Lake. Each week the IDFG will monitor the location of each fish and over the course of the year will be able to learn more about how the trout use Henrys Lake and spawning streams through their movements. The final results of the study will be publicly available at the conclusion of the project in early 2008. If available, interim reports will be posted to the Henrys Lake Foundation website.

Completion of Henrys Lake Fish Planting

September 2006

Idaho Department of Fish and Game reported the completion of the fish plant for Henrys Lake this year. The actual counts are: 149,800 Hybrids (sterile cutthroat and rainbow hybrids), 1,124,685 Yellowstone Cutthroat Trout, 107,125 Brook Trout (sterile) and 1,381,610 Total. The plantings went well with little mortality. While the total number of fish was less than planned for the cutthroat and hybrids, the size of the fish was excellent and should result in good survival. The numbers of brook trout exceeded the objective and size again was excellent. It was also noted that statewide IDFG plants 20% of all trout fingerlings (put and grow) at Henrys Lake.

Fry Trap Results on Targhee and Howard Creeks

September 2006

The Idaho Dept of Fish and Game placed traps on the two creeks earlier in the summer to measure the number of fry that move downstream into Henrys Lake. This is one way to determine the success of the natural spawning effort upstream by the cutthroat trout. The department reported a good number of fry moving down Targhee in particular and marked an upswing in natural production. The results were better than anticipated and suggest that the new natural-bottom bridges over Targhee and Howard Creeks were having an immediate positive impact.

Restoration of Duck and Kelly Creeks

August 2006

Duck and Kelly Creeks are important tributaries on the southwest side of Henrys Lake. Over the years the creeks have become silted over and no longer provide meaningful spawning habitat. In order to restore the habitat on Duck and Kelly Creeks a cooperative agreement has been reached with the US Fish and Wildlife Agency, the Henrys Lake Foundation and the owner of the property through which the creeks run. This is a $20,000 project to “improve habitat values for fish and wildlife” through restoration, enhancement, creation and management activities.” The project will begin in the spring of 2007 and will include fencing along the stream banks, re-vegetation, grade and water flow improvements.

Targhee and Howard Creek Cutthroat Trout Spawning Access Restored

June 2006

To mark the completion of the new natural-bottom bridges over Targhee and Howard Creeks, a ribbon cutting ceremony was held on June 3rd at the Targhee Bridge with a reception following at the home of HLF President Ron Slocum. In attendance were Senator Mike Crapo and members of his staff as well as representatives from Idaho Dept of Transportation, the Idaho Department of Fish and Game, US Forest Service, and other organizations that assisted in this collaborative effort to restore access to the historic spawning beds for Yellowstone Cutthroat trout in these two tributaries of Henrys Lake. The replacement of the obstructive culverts on these two creeks now allows unimpeded access to miles of historical spawning habitat that was blocked by the culverts. Many trees and boulders were placed in the streams to form pools and runs thereby returning the creeks to natural grades and flow rates. The stream banks were planted with willows and other native plants to provide shade and cover.