Biological Opinions - Bureau of Reclamation

(3) Cover or shelter;
(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and
(5) Habitats that are protected from disturbance or are representative of the historical,
geographical, and ecological distributions of a species.
The primary constituent elements (PCEs) of critical habitat are the specific elements of physical
and biological features essential to the conservation of the species. Based on our current
knowledge of the habitat characteristics required to sustain the species’ life-history processes, the
PCEs specific to self-sustaining LRS and SNS populations are:
PCE 1—Water. Areas with sufficient water quantity and depth within lakes, reservoirs,
streams, marshes, springs, groundwater sources, and refugial habitats with minimal
physical, biological, or chemical impediments to connectivity. Water must have varied
depths to accommodate each life stage: Shallow water (up to 3.28 ft [1.0 m]) for larval
life stage, and deeper water (up to 14.8 ft [4.5 m]) for older life stages. The water quality
characteristics should include water temperatures of less than 28.0 °Celsius (82.4 °F); pH
less than 9.75; dissolved oxygen levels greater than 4.0 mg per L; low levels of
microcystin; and un-ionized ammonia (less than 0.5 mg per L). Elements also include
natural flow regimes that provide flows during the appropriate time of year or, if flows
are controlled, minimal flow departure from a natural hydrograph.
PCE 2—Spawning and Rearing Habitat. Streams and shoreline springs with gravel and
cobble substrate at depths typically less than 4.3 ft (1.3 m) with adequate stream velocity
to allow spawning to occur. Areas containing emergent vegetation adjacent to open
water, provides habitat for rearing and facilitates growth and survival of suckers, as well
as protection from predation and protection from currents and turbulence.
PCE 3—Food. Areas that contain abundant forage base, including a broad array of
chironomidae, crustacea, and other aquatic macroinvertebrates.
The need for special management considerations also includes the following:
• Protect and improvement of water quality by reducing sediment and nutrient loading
• Manage water bodies so that there is minimal departure from a natural hydrograph
• Maintain, improve, or reestablish instream flows to improve the quantity of water
available
• Manage groundwater use to ensure it does not affect surface waters
• Address water level fluctuations in reservoirs
• Maintain appropriate depths in water quality refuge areas for access and maintaining
buffers around refuge areas
• Maintain habitat in reservoirs, the timing and volume of water diverted needs to be
addressed
• Improve access to spawning and rearing habitats
• Manage exotic fishes by restoring habitats for native fishes.
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