The BLM manages fish habitats according to laws, regulations, BLM policies, and principles of fisheries management within the BLM multiple-use mandate. State and federal game management agencies oversee aquatic species, to the extent they are directly managed. The WGFD is responsible for regulating the sport and commercial take of all fish in the Planning Area. The USFWS has oversight over federally threatened or endangered species. There are no federally listed fish species in the Bighorn Basin (refer to Section 3.4.8 Special Status Species - Fish for more detailed information). However, the BLM directly manages habitat that supports game and nongame fish species where there is such habitat on BLM-administered lands, and BLM management indirectly affects all aquatic species upstream and downstream of BLM-administered lands. The BLM manages wildlife habitat in the Planning Area according to a number of habitat management plans (HMP) (refer to Section 3.4.6 Fish and Wildlife Resources - Wildlife). Although there are no specific HMPs for fish species, actions in existing HMPs that improve riparian habitat often improve habitat for fish species.

Within the Planning Area, BLM-administered lands contain fisheries resources that include cold-water streams draining the Big Horn Mountains to the east and the Absaroka Range to the west; the tail-water trout fishery at Thermopolis; the cool-water fishery of the lower Bighorn, Shoshone, Greybull, and Nowood rivers; and the warm-water fisheries of several small lakes or ponds. There are no natural lakes or ponds in the Bighorn Basin that support fisheries.

Fisheries in the Bighorn Basin occur in the Bighorn River and Clarks Fork of the Yellowstone watersheds and include several major perennial tributaries - Owl Creek, Cottonwood Creek, Grass Creek, Gooseberry Creek, Greybull River, Wood River, Shoshone River, Kirby Creek, Nowater Creek, Nowood River, Shell Creek, Porcupine Creek, and Dry Creek. Most fish populations occur in the larger rivers and their tributaries, although there are several WGFD-stocked reservoirs and ponds.

Fish are typically classified as game or nongame; cold, cool, or warm water, and as native or nonnative. Species are adapted to a variety of stream habitats, from cold, rapid waters in higher elevations to slow, turbid waters of the high desert. According to the WGFD database, of the approximately 1,170 miles of streams on BLM-administered public lands in the Planning Area, approximately 395 miles support fisheries. The rest of the streams have no fish present or populations too low to adequately sample.

Fishing is an important component to the Bighorn Basin culture. The WGFD manages most cold-water streams for brook, brown, cutthroat, and rainbow trout. In addition, management on some streams is focused on mountain whitefish, Snake River cutthroat trout, and Yellowstone cutthroat trout. Many lower-elevation waters in the Planning Area are managed for cool- and warm-water native game fish, such as sauger and channel catfish, along with the native nongame species, such as numerous minnow and sucker species that provide forage for sport-fish species. There are four nongame species on WGFD list of Species of Greatest Conservation Need in the Planning Area - sturgeon chub, mountain sucker, and plains and western silvery minnow. Habitat for these species is being diminished by anthropogenic factors such as alteration to stream channel morphology, and changes due to dam construction and increased sedimentation in the Shoshone and lower Bighorn River systems. There are approximately 40 fish species in the Planning Area (Table 3–27).

Fishery habitat conditions are closely tied to riparian and watershed conditions and water quality. Riparian vegetation moderates water temperatures, increases bank stability, supports insects used as important food source, filters sediment, provides in stream habitat for fish, and provides organic material for aquatic insects. Indicators of the overall health of fish species include population numbers, water quality, water quantity, bank cover, insect/macroinvertebrate populations, habitat quality, gain or loss of important habitats, rangeland health standards, riparian PFC ratings, disease, and presence of aquatic invasive species including zebra mussels, New Zealand mud snails, Asian clams, Didymo, and Quagga mussels.

Historically, agriculture, vegetation management, fire management, development, surface-disturbing activities, motorized vehicle use, and recreation have influenced fisheries habitat in the Planning Area. With the long-term drought, the total amount of fisheries habitat has declined in some streams. Stream segments that previously had perennial flows have been dewatered for various periods (for example, the upper reaches of Kirby Creek and Nowater Creek). Most of these segments are small streams that supported nongame fish. Some streams that contained trout, such as Grass Creek or Enos Creek, have lost some or all of their trout populations.

Due to the recent drought conditions and increased demands for water in the Planning Area, rivers, streams, and reservoirs have experienced low flows and drawdowns. This directly affects fisheries habitat, spawning success, and survival of fish in both streams and reservoirs. Low streamflows have resulted in the siltation of pools in streams that are needed for fish to survive. Pools that have filled with sediment have not received the spring flushing flows necessary to remove it. These same high flows are also necessary to clean sediment-laden spawning gravels; therefore, fish recruitment rates have decreased. The effects of drought can be quickly reversed in streams with a return to more normal weather patterns, but higher flows will not remedy the continued siltation of reservoirs. If the drought continues and in turn causes an increase in plant mortality or wildfires, the present sedimentation rate of the reservoirs could increase.

Some activities in the Planning Area are improving fisheries habitat. The Conservation Districts in the Planning Area have had some success in improving water quality through programs encouraging sprinkler irrigation systems over ditch irrigation systems, relocating corrals and feedlots away from rivers, and replacing septic systems. The net result has been a decrease in sediment from irrigation return flows and coliform bacteria contamination.

Management Challenges

Management challenges for fishery habitats include water depletion, drought, sedimentation, and isolated populations. Water depletions, through consumptive uses and evaporative loss, are expected to continue to increase and could affect water quality and availability for fish, resulting in decreased population densities and a reduction in recreational fishing opportunities. Habitat improvements and enhancements could offset some of the decline in fisheries habitat, but such opportunities on BLM-administered lands are somewhat limited due to irregular land ownership patterns and an inability to influence water diversions and in-streamflows. The state of Wyoming is administratively responsible for issuing water rights and the maintenance and enforcement of water quality standards in the Planning Area (see Section 3.1.4 Water).

Both climate change and short-term variation in weather patterns can contribute to changes in stream systems such as flow, temperature, and turbidity. Aquatic systems are never static, but constantly change in response to environmental variations such as summer heat and winter ice, droughts and floods, and longer-term climatic changes. Lotic systems depend on high-water events to create fish habitat such as scour pools for winter or low-water habitat, large woody debris and undercut banks to create overhead cover, and to clean sediment out of spawning gravels. Living in a dynamic environment, fish tolerate and even need such periodic disruptions to their stream habitats. Such disruptions, if they are too extreme or occur too frequently, can adversely affect fish habitat and can permanently reduce or eliminate fish populations from some stream reaches or stream systems. Many climate-change predictions include increased duration and frequency of droughts and an increase in extreme precipitation events (see Section 3.1.1 Air Quality).

In the Planning Area, many of the lotic fish populations survive in isolated systems. Such systems have limited or no ability to be repopulated from other systems if the present population is extirpated. These populations have survived many periodic droughts, but if climate change in the Planning Area results in droughts that are longer and more severe than historic patterns, fish populations and species numbers could be adversely affected.