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

temperatures, appeared to repel the fish (Neal 1976). Fish and McCoy (1959)
concluded that a section of the Roanoke River became progressively more
attractive to striped bass spawners as sustained minimum flows increased above
157 m3/s (5,550 cfs) and that most of the spawners were driven out of the
spawning area when minimum river flow decreased to 110 m'/s (3,900 cfs).
Successful spawning in the Apalachicola River, Florida, was associated with
years when water flows of 255 to 8,213 m3/s (9,000 to 290,000 cfs) occurred
(Crance 1985).
Suspended sediments and turbidity. Reports indicate that striped bass
have a relatively high tolerance to silt-laden and turbid waters (Mansueti
1961, 1962; Talbot 1966) and that high concentrations of suspended sediments
1 i kely do not affect the eggs or larvae (Schubel and Wang 1973) .
Sediment levels up to 500 mg/1 did not affect the hatching success of
eggs (Schubel and Wang 1973; Schubel and Auld 1974). However, sediment levels
of 1,000 mg/1 significantly reduced hatching success (Schubel and Auld 1974;
Auld and Schubel 1978). Levels over 100 mg/1 delayed hatching several hours
(Schubel and Wang 1973). Morgan et al. (1973, 1983) concluded that hatch of
striped eggs was not significantly affected by suspended sediment concentra-
tions ranging from 20 to 2,300 mg/1, but embryo development was slowed signif-
icantly at concentrations above 1,300 mg/l.
The LC50 concentration of suspended sediments for striped bass larvae was
4,850 mg/1 at 24 h and 2,800 mg/1 at 48 h (Sherk et al. 1975). The mortality
rate of yolk-sac larvae increased significantly when exposed to suspended
sediment levels of 500 and 1,000 mg/1 for 48 to 96 h (Auld and Schubel 1978).
Turbidity may indirectly benefit striped bass because it reduces light
penetration (Crance 1985). Intense light may be harmful to striped bass. In
addition, gizzard shad and threadfin shad concentrate at times in warm, turbid
water and become more vulnerable as prey.
Salinity and total dissolved solids. Farley (1966) concluded that no
significant spawning occurred during 1963 and 1964 in areas of the Sacramento-
San Joaquin River systems in California where concentrations of total dissolved
solids (TDS) were above 180 mg/1. In addition, TDS concentrations over
180 mg/1 prevented striped bass from migrating above Stockton, California, in
the San Joaquin River. Murawski (1969) noted that striped bass spawned in the
Delaware River where the TDS concentration was 180 mg/1 or less. Radtke and
Turner (1967) concluded that 350 mg/1 TDS was the critical concentration for
blocking upstream spawning migrations. However, prespawning adults did not
avoid 954 mg/1 TDS in Keystone Reservoir, Oklahoma (Summerfelt and Moiser
1976), and adults migrated through waters in the Arkansas River tributary of
Keystone Reservoir where the TDS level was 303 to 1,920 mg/1 to reach spawning
sites (Combs 1979).
Albrecht (1964) concluded that low salinity (920 to 948 mg/1 chlorides)
enhanced egg and larval survival and that moderate salinity (4,595 to
4,740 mg/1 chlorides) was not detrimental. The idea that striped bass larvae
do better in low salinity water than in fresh water is supported by Rathjen
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