VII. DESERT FISHES
415
the same (temperature range of 44.5°-48.9°C; Miller, 1948). Also,
Norman's (1931) record of a Cyprinodon ( = Aphanias) from Arabia in
water "hot to the hand," and a cichlid (Tilapia) in springs on the eastern
shore of Lake Magadi, Kenya, Africa, at temperatures ranging from 26.7°
to 48.9°C, have not yet been confirmed. Perhaps density currents or similar phenomena explain these records.
Seasonal maxima in shallow, sometimes ephemeral desert waters may
approach the dubious records just discussed (Table I ) . A maximum of
47.2°C for Cyprinodon atrorus was confirmed by use of two thermometers
in August 1968, near Cuatro Ciénegas, Coahuila. Some spring-fed marshes
in that basin have water levels that fluctuate seasonally (Minckley, 1969b),
and the fish were found in a remnant pool of such a marsh. The pool
less than 1 meter in diameter was in full sunlight. The pool averaged about
1 cm deep except for a 3 cm strip, ^ 4 cm deep, produced by passage
of a burro cart. About 25 adults and many hundred young, ranging from
yolk-sac fry to 20 mm in length, were present, hyperactive, but not otherwise evidently in distress. Activity of the adults was confined principally
to the deeper water, and the movements had mixed the water adequately
to create uniform temperatures. Young were in the shallowest, 1 to 5 mm,
areas. A gallon of water was removed, 20 adults were placed in it, and
carried in a truck for about 3 hours. After arriving at camp the temperature of water in the gallon jar remained at 44°C. The adult fish were later
transported to Arizona, where they reproduced to establish a stock still
in existence. On the following afternoon the place was visited again; the
remnant pool had dried, and no living fish were found.
Also in August, 1968, Cole and Minckley studied a number of small
pools adjacent to Laguna de San Pablo, Cuatro Ciénegas basin, where tremendous populations of C. atrorus, plus a few Gambusia marshi, persisted
at temperatures of 43°-44°C. The pools were shallow and elongate, no
more than 20 cm at the deepest and 3-5 meters wide by 8-12 meters long,
with numbers of small bays, and shorelines densely vegetated by sedges
and salt grass. The riparian plants afforded no shading to the water, which
had receded to expose narrow, saline flats. Fish were concentrated in shallows, several males were defending territories, and young were very
abundant. Only large, brightly colored males were dead; other fish seemed
to behave normally.
Cyprinodon n. nevadensis in a marsh associated with Saratoga Spring,
Death Valley, has been found swimming voluntarily at 43°C (Deacon,
1968a). They could be chased into 44°C water. Under experimental confinement in the field this form was killed at 43°-44°C in July and survived
exposure to 43.5°C in early September. Miller (1948) reported short-term
tolerance of 35°-37.8°C for pupfishes in creeks of the Death Valley sys-
415
the same (temperature range of 44.5°-48.9°C; Miller, 1948). Also,
Norman's (1931) record of a Cyprinodon ( = Aphanias) from Arabia in
water "hot to the hand," and a cichlid (Tilapia) in springs on the eastern
shore of Lake Magadi, Kenya, Africa, at temperatures ranging from 26.7°
to 48.9°C, have not yet been confirmed. Perhaps density currents or similar phenomena explain these records.
Seasonal maxima in shallow, sometimes ephemeral desert waters may
approach the dubious records just discussed (Table I ) . A maximum of
47.2°C for Cyprinodon atrorus was confirmed by use of two thermometers
in August 1968, near Cuatro Ciénegas, Coahuila. Some spring-fed marshes
in that basin have water levels that fluctuate seasonally (Minckley, 1969b),
and the fish were found in a remnant pool of such a marsh. The pool
less than 1 meter in diameter was in full sunlight. The pool averaged about
1 cm deep except for a 3 cm strip, ^ 4 cm deep, produced by passage
of a burro cart. About 25 adults and many hundred young, ranging from
yolk-sac fry to 20 mm in length, were present, hyperactive, but not otherwise evidently in distress. Activity of the adults was confined principally
to the deeper water, and the movements had mixed the water adequately
to create uniform temperatures. Young were in the shallowest, 1 to 5 mm,
areas. A gallon of water was removed, 20 adults were placed in it, and
carried in a truck for about 3 hours. After arriving at camp the temperature of water in the gallon jar remained at 44°C. The adult fish were later
transported to Arizona, where they reproduced to establish a stock still
in existence. On the following afternoon the place was visited again; the
remnant pool had dried, and no living fish were found.
Also in August, 1968, Cole and Minckley studied a number of small
pools adjacent to Laguna de San Pablo, Cuatro Ciénegas basin, where tremendous populations of C. atrorus, plus a few Gambusia marshi, persisted
at temperatures of 43°-44°C. The pools were shallow and elongate, no
more than 20 cm at the deepest and 3-5 meters wide by 8-12 meters long,
with numbers of small bays, and shorelines densely vegetated by sedges
and salt grass. The riparian plants afforded no shading to the water, which
had receded to expose narrow, saline flats. Fish were concentrated in shallows, several males were defending territories, and young were very
abundant. Only large, brightly colored males were dead; other fish seemed
to behave normally.
Cyprinodon n. nevadensis in a marsh associated with Saratoga Spring,
Death Valley, has been found swimming voluntarily at 43°C (Deacon,
1968a). They could be chased into 44°C water. Under experimental confinement in the field this form was killed at 43°-44°C in July and survived
exposure to 43.5°C in early September. Miller (1948) reported short-term
tolerance of 35°-37.8°C for pupfishes in creeks of the Death Valley sys-