V I I . DESERT FISHES
407
streams also may be cyclical, oscillating with vagaries of inflow from
springs or tributary streams (Kosswig, 1961; Minckley, 1969b; Minckley
and Barber, 1971).
Information on specific effects of drought on fishes of deserts in western
North America and elsewhere is largely general and widely scattered. However, a number of workers have dealt with effects of low water on fishes
of eastern United States: James (1934), Stehr and Branson (1938),
Paloumpis (1957, 1958), Larimore et al, (1959), Deacon (1961), and
Deacon and Metcalf (1961), to name but a few. Their results generally
correspond with data we have accumulated in low-elevation, desert
streams. Survival of fishes in remnant pools is similar in all kinds of climate. Crowding is extreme and diseases may decimate them, as may starvation and heavy prédation by a broad spectrum of other animals, ranging
from mammals to dytiscid coleopterans and decapod crustaceans (James,
1934; Minckley and Barber, 1971). Cannibalism by larger fish also seems
to occur, or young succumb to environmental extremes in a differential
manner.
The presence of a single, large, predatory fish in a drying pool may
spell doom for all other fishes similarly trapped. Accumulation of organic
matter such as leaves in intermittent pools (Larimore et al., 1959), a rare
event in sparsely vegetated deserts, death and decomposition of part of
the biota, or the simple presence of a large number of fishes (Lowe et
al, 1967) may deplete dissolved oxygen, and only those species capable
of using atmospheric oxygen or oxygen from the thin surface film may
survive.
Numerous groups of fishes have species adapted for survival in foul
water, or in essentially dry habitats. Auxiliary respiratory surfaces are developed in the bucco-pharyngeal region as invaginations, pouches, or special epibrachial organs, in the digestive tract, and even in external skin
(Black, 1951; Todd and Ebeling, 1966; Teal and Carey, 1967). The
lungfishes (Dipnoi) have gas bladders that are respiratory, as in the lungs
of higher vertebrates, and many physostomus fishes are facultative airbreathers, utilizing vascularized tissues associated with their gas bladders.
Even in physoclistous species, a considerable respiratory advantage is imparted to those forms having a dorsally oriented mouth (Poeciliidae and
Cyprinodontidae, among others), since they have far greater access to the
air-water interface (Lowe et al., 1967; Lewis, 1970). Physiological
mechanisms also exist that allow greater tolerances to low levels of dissolved oxygen and to other parameters in fishes frequenting harsh environments (Lowe et al., 1967).
Highly developed capabilities for land locomotion, ranging from refined
"walking" in some species to a mere flipping from pool to pool, are de-
407
streams also may be cyclical, oscillating with vagaries of inflow from
springs or tributary streams (Kosswig, 1961; Minckley, 1969b; Minckley
and Barber, 1971).
Information on specific effects of drought on fishes of deserts in western
North America and elsewhere is largely general and widely scattered. However, a number of workers have dealt with effects of low water on fishes
of eastern United States: James (1934), Stehr and Branson (1938),
Paloumpis (1957, 1958), Larimore et al, (1959), Deacon (1961), and
Deacon and Metcalf (1961), to name but a few. Their results generally
correspond with data we have accumulated in low-elevation, desert
streams. Survival of fishes in remnant pools is similar in all kinds of climate. Crowding is extreme and diseases may decimate them, as may starvation and heavy prédation by a broad spectrum of other animals, ranging
from mammals to dytiscid coleopterans and decapod crustaceans (James,
1934; Minckley and Barber, 1971). Cannibalism by larger fish also seems
to occur, or young succumb to environmental extremes in a differential
manner.
The presence of a single, large, predatory fish in a drying pool may
spell doom for all other fishes similarly trapped. Accumulation of organic
matter such as leaves in intermittent pools (Larimore et al., 1959), a rare
event in sparsely vegetated deserts, death and decomposition of part of
the biota, or the simple presence of a large number of fishes (Lowe et
al, 1967) may deplete dissolved oxygen, and only those species capable
of using atmospheric oxygen or oxygen from the thin surface film may
survive.
Numerous groups of fishes have species adapted for survival in foul
water, or in essentially dry habitats. Auxiliary respiratory surfaces are developed in the bucco-pharyngeal region as invaginations, pouches, or special epibrachial organs, in the digestive tract, and even in external skin
(Black, 1951; Todd and Ebeling, 1966; Teal and Carey, 1967). The
lungfishes (Dipnoi) have gas bladders that are respiratory, as in the lungs
of higher vertebrates, and many physostomus fishes are facultative airbreathers, utilizing vascularized tissues associated with their gas bladders.
Even in physoclistous species, a considerable respiratory advantage is imparted to those forms having a dorsally oriented mouth (Poeciliidae and
Cyprinodontidae, among others), since they have far greater access to the
air-water interface (Lowe et al., 1967; Lewis, 1970). Physiological
mechanisms also exist that allow greater tolerances to low levels of dissolved oxygen and to other parameters in fishes frequenting harsh environments (Lowe et al., 1967).
Highly developed capabilities for land locomotion, ranging from refined
"walking" in some species to a mere flipping from pool to pool, are de-