11. HYDROSTATIC PRESSURE
447
major exception to this situation is Lake Baikal in Siberia, which is 1620
meters deep. Baikal is the deepest known lake, is aerobic throughout its
volume, and supports an abundant and diverse fish fauna down to its
greatest depths (Kozhov, 1963).
A much larger proportion of marine fishes encounters high pressures.
Considerable numbers of bottom-dwelling fishes have been collected
by many expeditions at depths in excess of 3000 meters (Grey, 1956).
Recent observations with underwater cameras indicate such fishes are
more abundant, and they are often of far larger size than had been
suspected (Hersey, 1967). Water depths between 3000 and 6000 meters
occupy about 83% of the area of the oceans (Sverdrup et al., 1942).
Very few fishes have been collected from depths greater than 6000
meters. Only three genera belonging to two families are known. These
are Grimaldichthys (family Brotulidae ) , maximum collection depth 6035
meters in the Atlantic Ocean, Bassogigas (family Brotulidae) , maximum
collection depth 7160 meters in the Sunda Trench, and Careproctus
(family Liparidae), maximum collection depth 7579 meters in the
Japan Trench (Rass, 1958; Wolff, 1960). Water depths greater than 6000
meters occupy about 1.3% of the area of the oceans. The greatest depth
known is near 11,000 meters, in the Marianas Trench. Our ideas on
maximum depth of fish occurrence, also variety and abundance of hadal
fishes, will almost certainly change dramatically as collecting and observing techniques are improved.
A variety of transitory and /or fluctuating pressure fields are superimposed upon the steady pressures just described. These include fields
from wave phenomena of many kinds, ranging from wind driven surface
waves to tides and including sound waves. Most of these fields are of
relatively small amplitude compared with the ambient steady pressure
field. Their physiological effects lie primarily in the area of sensory
physiology; hence, they will not be considered here.
Exceptions to this situation are the transitory pressure fields associated
with violent events such as explosions. Explosions affect fishes often
fatally, both as a result of the very high compressive pressures often
associated with their primary shock waves (rising to hundreds of atmospheres above ambient in substantial water volumes around even quite
small explosions) and because of the rarefaction waves which usually
follow the shock waves (Hubbs and Rechnitzer, 1952).
C . Physicochemical Effects of Pressure
Pressure has multiple effects on both nonliving and living systems.
Reviews of basic principles for nonliving systems include those by
447
major exception to this situation is Lake Baikal in Siberia, which is 1620
meters deep. Baikal is the deepest known lake, is aerobic throughout its
volume, and supports an abundant and diverse fish fauna down to its
greatest depths (Kozhov, 1963).
A much larger proportion of marine fishes encounters high pressures.
Considerable numbers of bottom-dwelling fishes have been collected
by many expeditions at depths in excess of 3000 meters (Grey, 1956).
Recent observations with underwater cameras indicate such fishes are
more abundant, and they are often of far larger size than had been
suspected (Hersey, 1967). Water depths between 3000 and 6000 meters
occupy about 83% of the area of the oceans (Sverdrup et al., 1942).
Very few fishes have been collected from depths greater than 6000
meters. Only three genera belonging to two families are known. These
are Grimaldichthys (family Brotulidae ) , maximum collection depth 6035
meters in the Atlantic Ocean, Bassogigas (family Brotulidae) , maximum
collection depth 7160 meters in the Sunda Trench, and Careproctus
(family Liparidae), maximum collection depth 7579 meters in the
Japan Trench (Rass, 1958; Wolff, 1960). Water depths greater than 6000
meters occupy about 1.3% of the area of the oceans. The greatest depth
known is near 11,000 meters, in the Marianas Trench. Our ideas on
maximum depth of fish occurrence, also variety and abundance of hadal
fishes, will almost certainly change dramatically as collecting and observing techniques are improved.
A variety of transitory and /or fluctuating pressure fields are superimposed upon the steady pressures just described. These include fields
from wave phenomena of many kinds, ranging from wind driven surface
waves to tides and including sound waves. Most of these fields are of
relatively small amplitude compared with the ambient steady pressure
field. Their physiological effects lie primarily in the area of sensory
physiology; hence, they will not be considered here.
Exceptions to this situation are the transitory pressure fields associated
with violent events such as explosions. Explosions affect fishes often
fatally, both as a result of the very high compressive pressures often
associated with their primary shock waves (rising to hundreds of atmospheres above ambient in substantial water volumes around even quite
small explosions) and because of the rarefaction waves which usually
follow the shock waves (Hubbs and Rechnitzer, 1952).
C . Physicochemical Effects of Pressure
Pressure has multiple effects on both nonliving and living systems.
Reviews of basic principles for nonliving systems include those by