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> / bonytail are npt well known, the limited data suggests that in addition to the rivers themselves, flooded, ponded, or even inundated riverine habitats may be suitable for adults, especially in the absence of competing nonnative fishes (USFWS 1990a). DETERMINATION OF CRITICAL HABITAT General--Detailed area descriptions and the biological basis for constituent elements of critical habitat were presented in the Biological Support Document. In determining areas for designation as critical habitat for a species, the Service considers those physical and biological features (i.e., constituent elements) that are essential for its conservation. In addition, areas containing these elements may require special management considerations or protection. As stated at 50 CFR 424.12, such physical and biological features include but are not limited to, the following items: (1) Space for individual and population growth, and for normal behavior; (2) Food, water, air, light, minerals, or other nutritional or physiological requirements; (3) Cover or shelter; (4) Sites for breeding, reproduction, rearing of offspring, germination, or seed dispersal; and generally; (5) Habitats that are protected from disturbance or are representative of the historical geographical and ecological distributions of a species. In considering the biological basis for proposing critical habitat, the Service focused on the primary physical and biological elements that were essential to the conservation of each species. The primary constituent elements determined necessary to the survival and recovery of the four Colorado River endangered fishes include: Water--A quantity of water of sufficient' quality (i.e., temperature, dissolved oxygen, contaminants, nutrients, turbidity, etc.) that is delivered to a specific location in accordance with a hydrologic regime that is required for the particular life stage for each species. Physical Habitat--Areas of the Colorado River system that are inhabited or potentially habitable for use in spawning, nursery, feeding and rearing, or corridors between these areas. In addition to river channels, these areas also include bottomlands, side channels, secondary channels, oxbows, backwaters, and other areas in the loo-year floodplain, which when inundated provide spawning, nursery, feeding and rearing habitats, or access to these habitats. Biological Environment--Food supply, predation, and competition are important elements of the biological environment and were considered components of this constituent 17