Ma. Smale et Cf. Rabeni, HYPOXIA AND HYPERTHERMIA TOLERANCES OF HEADWATER STREAM FISHES, Transactions of the American Fisheries Society, 124(5), 1995, pp. 698-710
We developed a reference base of relative hypoxia and hyperthermia tol
erance rankings for many of the common fish species that inhabit small
streams in Missouri. We also investigated the influences of geographi
c variation and of fish size on these tolerances. Fish collected From
the wild were acclimated to laboratory conditions over a 63-160-d peri
od. They were then exposed to either progressively increasing temperat
ures or to decreasing dissolved oxygen concentrations over a 4-6-h per
iod. The temperature at which a fish lost equilibrium or the oxygen co
ncentration at which it ceased ventilating was recorded as the end poi
nt. No significant differences in critical maximum temperatures (hyper
thermia tolerance) or critical minimum oxygen concentrations (hypoxia
tolerance) occurred in any of the five comparisons between fish of the
same species collected from different locations in Missouri. Neither
the hypoxia nor hyperthermia tolerance values varied with fish size fo
r any species. Among the 35 species tested, hypoxia tolerance means ra
nged from 0.49 to 1.59 mg/L. Among the 34 species tested, hyperthermia
tolerance means ranged from 34.9 to 3S.8 degrees C. The mean hypoxia
tolerances of species were significantly, but poorly, correlated with
their mean hyperthermia tolerances.