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There did not appear to be a significant difference in selection between the tests when the position of the cells was reversed (Fig. 5). This was of particular concern during the noon observations because the south cell was almost entirely in shadow and the north cell almost entirely in sunlight. The distribution studies in the CD headspring support this finding that the chubs tend to remain in close proximity to the vegetation. The collections indicated that chub densities were greatest in the cove (trap site 2), which had the densest vegetation in the headspring, and decreased farther upstream, where the vegetation beds were less distinct (Table 1). Trap site 6, which was farthest upstream and had the least amount of vegetation, yielded the least number of chubs (Table 1). Discussion These observations and experiments support the assertion that aquatic vegetation is an important habitat component of Owens tui chub and that they tend to remain in close association with it. Other researchers have found this to be true of the tui chub as a species and for other subspecies of tui chub (Moyle 1976; Vicker 1973; Kimsey 1954; Cooper 1978; Williams and Bond 1981). The question remains as to why this relationship exists. Although a detailed study of this relationship was not undertaken, observations made in the laboratory and field during the course of the study indicate that it is due mainly to four factors: spawning, water velocity displacement, predator avoidance, and feeding behavior. These are discussed briefly below. Spawning. The use of aquatic vegetation by tui chubs as a spawning substrate is well documented. Kimsey (1954) found that eggs from Lahontan tui chubs were adhesive and developed only if they were attached to plants or otherwise kept off of the bottom. Cooper (1982) found that Lahontan tui chub eggs from Pyramid Lake, Nevada were adhesive. Cooper (1978) and Vicker (1973) observed that Lahontan and Mohave tui chub, respectively, spawn over aquatic vegetation. Although I did not find eggs attached to the aquatic vegetation in either headspring, I found that newly extruded eggs are similar in description to those of Lahontan and Mohave tui chubs and are quite adhesive. The adhesiveness of Owens tui chub eggs and the preponderance of aquatic plants in their habitat would suggest that they also utilize aquatic vegetation as a spawning substrate. Water Velocity Displacement. Measurements of water velocities were taken in the CD headspring using a Marsh - McBirney velocity meter on several occasions in the fall of 1987. Zero velocities were recorded in vegetation beds which were surrounded by open water that had velocities of 0.15 m/s and higher. Chubs were seen darting across these areas of relatively high velocity, usually to move from one vegetation bed to is