386
JAMES E. DEACON AND W. L. MINCKLEY
have disappeared as new ones arose. Some fish species have been dispersed widely, by accident or design. Other, native ones, have been
extirpated, or their stocks were greatly depleted forcing them back into the
most inaccessible parts of their ranges. In this chapter we stress, insofar as
possible, the inland, indigenous fishes of deserts; their habitats in the
pristine state; and their behavioral, morphological, and physiological
adaptations for life.
Fishes as a group are remarkably diversified, reflecting in considerable
detail the rigorous environmental forces under which they operate. Special
environmental features require special adaptations, "adjustments . . . to diverse niches in the environment" (Hubbs, 1941a). Thus, some perpetually torrential streams support highly specialized fishes and other animals
that have evolved sucking discs or hooks. Modifications of their mouths,
fins, or other body parts hold against the constant turbulence and thrust of
current (Hora, 1922). At the other extreme, downstream parts of rivers,
lakes, or quiet springs are lentic in nature, and deep-bodied, slowly moving
fishes may predominate. In open water of quieter places, small, slim,
silvery species occupy pelagic space. Some moderately heavy-bodied forms
live on or near the bottoms. In rocky areas or dense beds of aquatic
vegetation, laterally compressed, deep-bodied, or elongated, snake-like
forms may occur (Nikolsky, 1961, 1963; Lagler et ai, 1962).
In habitats between extremes, creeks of intermediate gradient, for example, a major proportion of the fishes are typically small, with rounded
bodies and moderately expansive fins. A limbo of variability in such environments, from torrent in flood to pool in drought, dictates a highly
adaptable body form and function. With a few notable exceptions, fishes
successful in desert waters display generalized shapes. A few minor adjustments in form and function allow their successful exploitation of the sometimes harsh environments.
Coverage in this chapter emphasizes hotter deserts of southwestern
United States and northern Mexico, which are the geographic focus of our
researches. Information on fishes and aquatic habitats of those regions
not specifically attributed to other sources is compiled from our unpublished data. We follow Cole (1968) in embracing a broader definition of
desert than might a terrestrial ecologist, since many waters discussed here
transcend a number of biomes. With the exception of springs fed by
subterranean waters, aquatic habitats of arid lands depend upon surface
flow or subsurface infiltration of water from adjacent, more mesic zones
(Smith, 1968). Special adaptations of fishes to aquatic circumstances in
nondesert regions, which parallel those of desert species, are also drawn
upon. However, discussion of fish species alien to deserts, but now present
there, is limited generally to effects they have had upon systems into
JAMES E. DEACON AND W. L. MINCKLEY
have disappeared as new ones arose. Some fish species have been dispersed widely, by accident or design. Other, native ones, have been
extirpated, or their stocks were greatly depleted forcing them back into the
most inaccessible parts of their ranges. In this chapter we stress, insofar as
possible, the inland, indigenous fishes of deserts; their habitats in the
pristine state; and their behavioral, morphological, and physiological
adaptations for life.
Fishes as a group are remarkably diversified, reflecting in considerable
detail the rigorous environmental forces under which they operate. Special
environmental features require special adaptations, "adjustments . . . to diverse niches in the environment" (Hubbs, 1941a). Thus, some perpetually torrential streams support highly specialized fishes and other animals
that have evolved sucking discs or hooks. Modifications of their mouths,
fins, or other body parts hold against the constant turbulence and thrust of
current (Hora, 1922). At the other extreme, downstream parts of rivers,
lakes, or quiet springs are lentic in nature, and deep-bodied, slowly moving
fishes may predominate. In open water of quieter places, small, slim,
silvery species occupy pelagic space. Some moderately heavy-bodied forms
live on or near the bottoms. In rocky areas or dense beds of aquatic
vegetation, laterally compressed, deep-bodied, or elongated, snake-like
forms may occur (Nikolsky, 1961, 1963; Lagler et ai, 1962).
In habitats between extremes, creeks of intermediate gradient, for example, a major proportion of the fishes are typically small, with rounded
bodies and moderately expansive fins. A limbo of variability in such environments, from torrent in flood to pool in drought, dictates a highly
adaptable body form and function. With a few notable exceptions, fishes
successful in desert waters display generalized shapes. A few minor adjustments in form and function allow their successful exploitation of the sometimes harsh environments.
Coverage in this chapter emphasizes hotter deserts of southwestern
United States and northern Mexico, which are the geographic focus of our
researches. Information on fishes and aquatic habitats of those regions
not specifically attributed to other sources is compiled from our unpublished data. We follow Cole (1968) in embracing a broader definition of
desert than might a terrestrial ecologist, since many waters discussed here
transcend a number of biomes. With the exception of springs fed by
subterranean waters, aquatic habitats of arid lands depend upon surface
flow or subsurface infiltration of water from adjacent, more mesic zones
(Smith, 1968). Special adaptations of fishes to aquatic circumstances in
nondesert regions, which parallel those of desert species, are also drawn
upon. However, discussion of fish species alien to deserts, but now present
there, is limited generally to effects they have had upon systems into