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Fisheries Management
Fisheries management at Henry's Lake has run the gamut through history from few restrictions with year round fishing to a June through October season open daily from 5 AM to 9 PM with a possession limit of two fish. Recently the fishing season was extended to the end of November and fishing is allowed without any hour restrictions on the lake. The latest change is intended to bring Henry's Lake on line with other reservoir seasons, except that other reservoirs are open year round.
Cutthroat trout have been stocked into the lake since the construction of the Henry's Lake Dam in 1922. Good records have not been kept until the late 1960's, but enough fish have been stocked to sustain the fishery even through the worst periods of habitat degradation, drought, and high winter mortality. By the late 70's it had become clear that fishing was seriously declining and not enough was being done to restore the natural production capacity of the lake. Anglers became concerned when the Idaho Department of Fish and Game eliminating supplemental stocking of rainbow and cutthroat trout hybrids in the early to mid '70s. Hybrid trout have always been very popular with anglers. This was not acceptable to anglers. Dissent culminated with the formation of the Henry's Lake Foundation to improve fisheries habitat and make Fish and Game aware of the popularity of the variety of fish in Henry's Lake. This began a partnership between the Henry's Lake Foundation and Idaho Fish and Game to increase the priority of managing hybrids or cutbows as well as wild trout to enhance the suffering fishery and to institute regulations that would enhance and protect the fishery.
Since that time riparian fences have been built along private reaches of tributaries to arrest the destruction of vegetation by excessive grazing and poor recreation management and to reverse the increasing stream bank erosion that was impacting spawning and rearing habitat. Additionally irrigation ditches were screened to prevent the loss of fish to ditches and ultimately pastures. Fish ladders were installed to allow fish to access the remaining high quality spawning habitat. Fish and Game developed the Henry's Lake Management Plan that outlines species and size composition and catch rate targets for the fishery.
In 1991 a winterkill occurred on the lake making it painfully clear that the troubles with water quality had not been adequately addressed with the other fisheries issues. A Clean Lakes Study was undertaken by the Idaho Department of Environmental Quality with funding from the Environmental Protection Agency and cooperation from Idaho Fish and Game and the Henry's Lake Foundation. Contractors and consultants were hired to develop a nutrient budget for the lake to determine what could be done to address the issues related to nutrient pollution in the lake. By 1996 the report was finalized that showed that the largest volume of nutrients available to the lake was tied up in lake sediments that had accumulated over many years. The largest sources of phosphorus within the watershed were naturally occurring in the upper elevations where sea bed origin sedimentary rock high in phosphorus was exposed to fragmentation, erosion and transport to the lake through surface runoff in tributaries during snowmelt and thunder storms. This made the human related nutrient sources very important as the primary source that could be reduced. Even more important were the wetlands around the lake that could tie up nutrients before they entered the lake where they fertilize lake water and contribute to the excess algae and aquatic plants that were using up oxygen under the ice cover of winter.
There is no complete solution to the nutrient problem. This lake will always have the potential to be choked with plants and algae. The key to extending the life of Henry's Lake is found in riparian and wetland management. Riparian zones function to shade the flowing water in tributaries to reduce warming. Riparian and wetland plants tie up nutrients before they make it to the lake. To improve riparian management additional fences were constructed to enhance streamside and wetland vegetation to create a buffer zone to decrease nutrient loading into tributaries. Conciensious home owners improved antequated septic systems, and grazing management improved through the 90's to have what we see today as a lake with much improved water quality. A permanent aeration system was installed into the lake with funds from the Federal Bureau of Reclaimation that includes 2 3/4 miles of 2 inch pipe and 12 helixers to aerate the lake when oxygen drops to critical levels during some years. Portable aeration equipment was also purchased with this funding and $30,000 of Fish and Game funding to aerate particular trouble spots around the lake as they develop.
Fishing
The opening of fishing season in 2007 will be May 26th. Opening day fishing depends on weather and when the ice thaws from the lake. In 2006 the ice went out on May 10th and opening weekend weather was cold, wet and windy. When the ice thaws fish seek the warmer temperatures near shore. After a couple weeks fish that will spawn in tributaries gather near the mouth of the tributary they were hatched in and as flow from snowmelt increases the spawning fish ascend the stream. Fish that have returned to the lake after spawning distribute throughout the lake. By the end of June most fish that survive spawning have returned to the lake and can be found just about anywhere until the water temperature warms above about 65 degrees F, when they seek the cooler water of areas around the confluence of tributaries and the few springs and seeps that enter the lake.
In the fall, when water temperatures begin to cool, fishing success improves and fish move to shallow water again, seeking warmer water. During this period fishing stays productive until temperatures drop to 38 degrees F or less. At these lower temperatures fishes metabolism slows and feeding reduces and the preference is for smaller food items.