7921 ‎(2)‎

• UCREFRP Catalog Number: 7921
• Author: Trembly, T. L. and G. A. Gould.
• Title: Opportunities To Protect Instream Flows In Colorado And Wyoming.
• USFW Year: 1987.
• USFW - Doc Type: Biological Report 87‎(10)‎,
• Copyright Material: NO

Larval. Dissolved oxygen concentrations of 2.0 mg/1 and less are
considered detrimental to striped bass larvae (Dorfman and Westman 1970;
O'Mally and Boone 1972). Levels of 2.0 to 3.5 mg/1 have been responsible for
the absence of eggs and larvae in the Delaware River (Murawski 1969; Chittenden
1971a). Chittenden (1971b) concluded that larvae need a minimum level of
3.0 mg/1 to survive. A level of 4.0 mg/1 may be too low for successful
reproduction (Talbot 1966). Even moderate reductions in dissolved oxygen
concentrations (from 5.0 to 4.0 mg/1) may decrease the survival of eggs and
larvae (Turner and Farley 1971).
Current velocity (V3~.
Adult. Water current probably is an attractant for striped bass that are
preparing to spawn (Dickson 1958).
Egg. Striped bass eggs are semibuoyant. Without sufficient current, the
eggs slowly settle to deeper water or the bottom and may suffocate due to a
deficiency in dissolved oxygen (May and Fuller 1965). Continuous suspension
and movement of eggs appear to be essential to survival and successful hatching
in streams (Surber 1958; Fish and McCoy 1959; May and Fuller 1965; Barkuloo
1970). Albrecht (1964) and Bayless (1968) demonstrated, in the laboratory,
that eggs not held in suspension could be hatched, but success was limited.
Eggs kept on the bottom during. incubation had a poor chance of survival. Eggs
probably hatched successfully in the absence of turbulent current in Lake
Powell, Utah, where the dissolved oxygen concentration was 13.2 mg/1 at the
substrate surface where the eggs settled (Gustaveson et al. 1984).
A minimum current velocity of about 30.5 cm/s (1 ft/s) is required to
suspend striped bass eggs in freshwater (Albrecht 1964). However, the absolute
minimum velocity required can be site and time specific, depending on the
density of the water and the eggs. Water density varies with temperature,
salinity, and total dissolved solids. Egg density varies with age and/or
condition of the female and other factors (Schrader 1979). A velocity of
15 cm/s (0.5 ft/s) may keep eggs suspended once they become water hardened
(Crance 1985).
Surface water velocity in areas where striped bass eggs have been
collected ranged from 12.2 to 88.4 cm/s (0.4 to 2.9 ft/s) in Virginia streams
(Tresselt 1952), 18.3 to 88.4 cm/s (0.6 to 2.9 ft/s) in California waters
(Albrecht 1964), and 50.0 to 83.5 cm/s (1.6 to 2.7 ft/s) in the Arkansas
River, Oklahoma, where striped bass spawned 3 consecutive years (Combs 1979).
Current velocity in the Roanoke River below Weldon, North Carolina, was about
49 cm/s (1.6 ft/s) near a major spawning area for striped bass (Dickson 1958).
Spawning occurred in areas of the Santee River, South Carolina, where water
velocity was less than 29.9 cm/s (0.98 ft/s) (Crance 1985). Velocities of
about 240 cm/s (7.9 ft/s) may create shears approaching the damaging range for
eggs (Marcy 1971, 1973; Morgan et al. 1976). It was reported that eggs have
been observed in water with velocities up to 270 cm/s (8.9 ft/s) and that a
velocity of about 400 cm/s (13.1 ft/s) is likely the maximum for survival
(Crance 1985). •
15