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<br />low-desert streams, enjoying the widest distribution
<br />of any species in the region. It has remarkable
<br />capability to disperse into new habitats, appearing a
<br />few hours or days after flow re-establishes in
<br />formerly-dry stream channels. The species is also
<br />markedly resistant to drought, persisting in drying
<br />pools of the deepest and most permanent parts of a
<br />channel (which they find in some unknown manner)
<br />even though crowded in habitats that become hot
<br />and deoxygenated. Longfin dace once were recorded
<br />to survive in tiny volumes of water beneath mats of
<br />filamentous algae, then reproduce a few days after
<br />when summer rains rejuvenated the stream. They
<br />spawn at any time during the year, further
<br />enhancing the rapid recolonization of formerly
<br />desiccated habitats.
<br />Spawning in Colorado River longfin dace occurs
<br />when females come to males over relatively soft, sand
<br />bottoms. A swirling spawning act creates
<br />depressions, or "nest pits" in the sand (Fig. 34) that
<br />are used repeatedly by one or more spawning pairs.
<br />Eggs buried in the walls and bottoms of these pits
<br />hatch in a few days. Young live at first in the pits,
<br />then along stream margins before moving to smooth
<br />runs of open sandy areas with the adults. Spawning
<br />"pits" and spawning activities have not been
<br />observed for the Rio Yaqui form.
<br />Reproductive adults are darkened, and males
<br />may develop yellowing of the fin bases and lower
<br />head and body. Males have large, strong tubercles-
<br />horny projections that develop on the fins, head,
<br />and body-which are used to stimulate and hold
<br />the female during spawning, and perhaps in
<br />combat between males. This species is more
<br />omnivorous than most western fishes, feeding
<br />opportunistically on algae or invertebrates, when
<br />available, and on detritus after floods reduce other
<br />food supplies.
<br />Among small minnows in the Rio Yaqui basin,
<br />the beautiful shiner is just that (Fig. 35), an
<br />attractive member of a widespread group mostly
<br />distributed east of the Continental Divide. Males
<br />develop intense orange pigments that overlie an
<br />almost sky-blue base color on the body. The fins are
<br />orange to reddish orange with dark underlying
<br />pigments. Males have tubercles of various sizes on
<br />the head, paired fins, and caudal peduncle. Females
<br />are straw-yellow or bluish. The spawning act has not
<br />been recorded, but presumably consists of spreading
<br />the eggs over aquatic vegetation, brush" or other
<br />cover, or perhaps simply over the bottom. This
<br />species is similar in size and ecology to spikedace,
<br />living in midwater habitats of pools and runs, along
<br />the shorelines in large streams, and tending more to
<br />move onto riffles in smaller streams. It also feeds on
<br />drifting aquatic and terrestrial invertebrates.
<br />
<br />
<br />Figure 34. The scattering of light-colored depressions along
<br />this sand bar in Kirkland Creek, Arizona, are "nests,"
<br />formed by whirling movements of longfin dacelcharalito
<br />a/eta /arga during spawning. Eggs are deposited in the walls
<br />and bottoms of the cones. Photograph by W. G. Kepner.
<br />
<br />
<br />Figure 35. Beautiful shinerlsardinita hermosa, male (above)
<br />and female (below) (50 and 64 mm in total length,
<br />respectively), from the Rio Piedras Verdes, Chihuahua. This
<br />species formerly occurred in the Mimbres River, New
<br />Mexico, and persisted until the late 1960s in San
<br />Bernardino Creek, Arizona. It remains locally abundant in
<br />Mexico, but was considered of special concern by the
<br />American Fisheries Society.
<br />
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