446
MALCOLM S. GORDON
1860s and 1870’s. The famous Challenger expedition ( 1873-1876) was
one of the later of these efforts (Murray and Hjort, 1912).
Fishes were among the earliest subjects for the study of pressure
effects. However, experimental efforts involving fishes have since occurred only sporadically. The reviews of Cattell (1936), Johnson et al.
( 1954), Knight-Jones and Morgan (1966), Morita ( 1967), and Fenn
(1967) document the fact that studies of fishes began with Regnard
in France in the 1880s, then were completely neglected for 40 years
until taken up by Fontaine, again in France, in the 1920’s. The 1930’s
saw more activity in this area, especially in the United States and
Germany. The 1940’s and 1950’s were again quiet (thc author found
only two papers). The present decade, however, has produced a burst
of activity. Omitted from this survey and from this chapter are papers
dealing with swim bladder function and with pressure-sensitive sense
organs, since these topics are discussed elsewhere in these volumes.
This pattern of historical development has produced a picture of
pressure effects on fishes which is in many respects vague, fragmentary,
and probably inaccurate. As is also the case in many other fields of
physiology, much of what has been done has been directed at laboratory
phenomena having only limited relevance to conditions encountered by
intact fishes in nature. Our understanding of the effects of hydrostatic
pressure on the lives of fishes is in a primitive state.
B. Pressure in Natural Environments
Steady hydrostatic pressures encountered by fishes in natural environments vary from about 0.5 atm to no more than 1100 atm. Fishes living
in streams and shallow lakes at high altitudes in mountain areas such
as the Andes and Himalayas live at the lower end of the range. Fishes
living in the hadal zones (below 6000 meters) of the great ocean trenches
live near the upper end.
Depths of water (in meters) can be readily converted to equivalent
pressures (in atmospheres) with an error of only a few percent. Ten
meters water depth (either fresh or salt) approximates one atmosphere.
Other conversions frequently used include: 1 atm = 14.7 lb/in’ (psi),
1.03 kg/cm2, 1.01 bars, 101 dynes/cm2, and 760 mm Hg at 0°C.
Very few freshwater fishes encounter pressures higher than 40 atm.
Hutchinson (1957) lists only 18 lakes worldwide known to reach depths
greater than 400 meters. ( H e points out that there may be a few more,
as yet unmeasured, in southern South America.) Most of these very
deep lakes are vertically stratified and essentially permanently anaerobic
(hence devoid of fish life) at depths below about 100-250 meters. The
MALCOLM S. GORDON
1860s and 1870’s. The famous Challenger expedition ( 1873-1876) was
one of the later of these efforts (Murray and Hjort, 1912).
Fishes were among the earliest subjects for the study of pressure
effects. However, experimental efforts involving fishes have since occurred only sporadically. The reviews of Cattell (1936), Johnson et al.
( 1954), Knight-Jones and Morgan (1966), Morita ( 1967), and Fenn
(1967) document the fact that studies of fishes began with Regnard
in France in the 1880s, then were completely neglected for 40 years
until taken up by Fontaine, again in France, in the 1920’s. The 1930’s
saw more activity in this area, especially in the United States and
Germany. The 1940’s and 1950’s were again quiet (thc author found
only two papers). The present decade, however, has produced a burst
of activity. Omitted from this survey and from this chapter are papers
dealing with swim bladder function and with pressure-sensitive sense
organs, since these topics are discussed elsewhere in these volumes.
This pattern of historical development has produced a picture of
pressure effects on fishes which is in many respects vague, fragmentary,
and probably inaccurate. As is also the case in many other fields of
physiology, much of what has been done has been directed at laboratory
phenomena having only limited relevance to conditions encountered by
intact fishes in nature. Our understanding of the effects of hydrostatic
pressure on the lives of fishes is in a primitive state.
B. Pressure in Natural Environments
Steady hydrostatic pressures encountered by fishes in natural environments vary from about 0.5 atm to no more than 1100 atm. Fishes living
in streams and shallow lakes at high altitudes in mountain areas such
as the Andes and Himalayas live at the lower end of the range. Fishes
living in the hadal zones (below 6000 meters) of the great ocean trenches
live near the upper end.
Depths of water (in meters) can be readily converted to equivalent
pressures (in atmospheres) with an error of only a few percent. Ten
meters water depth (either fresh or salt) approximates one atmosphere.
Other conversions frequently used include: 1 atm = 14.7 lb/in’ (psi),
1.03 kg/cm2, 1.01 bars, 101 dynes/cm2, and 760 mm Hg at 0°C.
Very few freshwater fishes encounter pressures higher than 40 atm.
Hutchinson (1957) lists only 18 lakes worldwide known to reach depths
greater than 400 meters. ( H e points out that there may be a few more,
as yet unmeasured, in southern South America.) Most of these very
deep lakes are vertically stratified and essentially permanently anaerobic
(hence devoid of fish life) at depths below about 100-250 meters. The