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RETENTION OF JUVENILE WHITE STURGEON, 

ACIPENSER TRANSMONTANUS, BY PERFORATED1/21 PLATE AND WEDGE-WIRE SCREEN MATERIALS --

Harvey H. Reading -

3/ 

Bay-Delta Fishery Project 

4001 North Wilson Way 

Stockton, CA 95205 

ABSTRACT 

The Fish Facilities Study, part of the Interagency Ecological Study Program 

for the Sacramento-San Joaquin Estuary, evaluated the potential of perforated 

plate and wedge-wire materials for screening juvenile white sturgeon ranging 

in size from 17.0 to 63.0 mm (0.7 to 2.5 in)total length (TIL). Experimental 

sturgeon hatcheries provided test fish �or the study. Evaluations employed 

various screen opening sizes and approach velocities as variables to determine 

their effects on screening young sturgeon. Sturgeon 27.0 mm TL and longer 

were retained by 3.96 mm (5/32 in.) diameter perforated plate and 2.38 mm 

(3/32 in.)sfot width wedge-wire at 6.1 cm/s (0.2 ftfs), the lowest approach 

velocity tested. Impingement of over 20% of the fish tested occurred at 6.1 

cm/s, while at 18.3 cmls (0.6 ft/s) the highest approach velocity tested, 

total impingement occurred within 5 min. 

-1/ This study was conducted as part of the Interagency Ecological Study 

Program for the Sacramento-San Joaquin Estuary whose members include: 

California Department of Fish and Game, California Department of Water 

Resources, U. S. Bureau of Reclamation, and U. S. Fish and Wildlife 

Service. 

-2/ Anadromous Fisheries Branch Administrative Report No. 82-6. Submitted 

March, 1982. 

-3/ Current Address: Department of Fish and Game, P. 0.Box 607, Red Bluff, 

CA 96080. 
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INTRODUCTION 

Downstream migrant sturgeon will be exposed to the fish screens at the proposed Peripheral Canal water intake near Hood, California. It is necessary 

to determine how effectively juvenile sturgeon can be screened by.perforated 

plate and wedge-wire screen materials to help formulate a plan of protection 

for this species. 

Prior to this study, information regarding the screening of juvenile sturgeon 

was lacking, as they were not available in numbers sufficient for conducting 

a study program. In 1980, hatchery-reared juvenile white sturgeon were obtained from the experimental sturgeon hatchery at the University of California, 

Davis, California. . In 1981, the Elk Grove-Florin Catfish Farm near Sacramento,' 

California provided test fish. 

Previous studies indicate that perforated plate with 3.96 mm (5132 in.) openings or wedge-wire screen with 2.38 mm (3132 in.) width slots adequately protect juvenile chinook salmon, Oncorhynchus tshawytscha, and American shad, 

Alosa sapidissima. This study evaluated the effectiveness of these and other 

screen opening sizes to determine their potential for screening juvenile white 

sturgeon. To accomplish this goal, sturgeon were exposed to these materials 

under controlled conditions using water approach velocity and screen opening 

size as variables. 

METHODS 

The testing program was conducted during 1980 and 1981 at the Fish Screen Testing Facility at Hood, California. Pumps at the facility supplied unfiltered 

Sacramento River water for holding and testing juvenile white sturgeon ranging 

in size from 17.0 to 63.0 mm TL (Table 1). a 

Transportation of juvenile sturgeon from the hatchery sources to the test facility, accomplished using ice chests lined with plastic bags containing aerated water, took less than 1-h per trip. At Hood, a 1-h acclimation period, 

during which Sacramento River water gradually replaced hatchery water in the 

transport bag, preceded transferring the fish to a 757-1 (200-gal) circular 

fiberglass tank for holding prior to tests. Sacramento River water flowed 

through the tank at approximately 35 l/min (3 gal/min). Exclusive use of

river water resulted in identical water conditions for both holding and testing young sturgeon. 

To provide the means for confining test fish in close proximity to the screen 

materials chosen for evaluation, tests were conducted in a 19.7 crn (7.75 in.) 

diameter transparent plastic cylinder, similar to one used by Fisher (1978). 

The cylinder was fitted with test screen discs of various opening sizes and 

was screened at both ends to prevent fish from escaping frm the cylinder 

(Figure 1). Submerging the cylinder in ambient water with an adjustable rate 

of flow allowed selected water (screen approach) velocities inside the cylinder. Water velocity within the cylinder was measured with a Gurley mode1 
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TABLE 1. Average and Range of Total Lengths of Juvenile 

White Sturgeon at Various Test Parameters. 

Approach Screen type Average total Range of total 

velocity P = Perf. plate length lengths 

(cm/s> W = Wedge-wire (m> (mm> 

6.1 P 31.3 19.0 - 63.0 

6.1 W 32.0 17.0 - 61.0 

12.2 P 36.7 19.0 - 63.0 

12.2 w 32.2 19.0 - 63.0 

18.3 P 45.6 31.5 - 63.0 

18.3 W 38.1 . 21.0 - 61.5
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560680 pigmy current meter mounted inside the cylinder at its downstream end. 

Screen discs, arranged in the cylinder in a stepwise manner, presented test 

fish, initially placed in the upstream end of the cylinder, with screen discs 

having successively smaller hole sizes as they passed downstream through the 

cylinder. Test fish failing to pass through a disc at the end of a 3-h test 

were considered retained by the hole size associated with that disc. 

Tests during 1980 evaluated perforated plate hole diameters of 6.35, 4.76,and 

3.96 mm (lf4, 3/16,and 5/32 in.). In 1981, testing w5t.h perforated plate included 3/96 mm and 3.18 mm (118 in.)diameter holes. Tests during both years 

evaluated 3.18 and 2.38 mm (3/32 in.)wedge-wire slot widths. 

Screen approach velocities evaluated were: 6.1, 12.2,and 18.3 cm/s (0.2, 0.4, 

and 0.6 ft/s) during both years. The test group size in 1980 was 50 fishftesr, 

In 1981, with fewer fish available, the group size was 25 fishltest. 

Following a test at a given combination of screen type and approach velocity, 

each fish was measured to the nearest 0.5 mm TL and the screen disc that retained that fish was noted. Length data were grouped into 2-mm length-class 

intervals �or the various combinations of screen type, hole size,and approach 

velocity. 

In addition to retention data, records were kept of the number of fish impinged 

on the screen discs at the -conclusionof a test. This data allowed calculation 

of a simple regression equation which helped describe the relationship between 

approach velocity and impingement. 

RESULTS 

No mortality was experienced during transportation of juvenile sturgeon from 

the hatcheries to the test facility at Hood. 

Perforated plate with 3.96 mm holes retained sturgeon 27.0 mm TL and longer 

with an approach velocity of 6.1 cm/s (Table 2). At 12.2 cm/s, this same material retained sturgeon 29.0 mm TL and longer. Sturgeon as small as 21.0 mm 

TL were retained by perforated plate with 3.18 mm holes. 

During 1980 evaluations, wedge-wire screen with opening size of 2.38 mm retained sturgeon 27.0 m TL and longer at 6.1 cm/s, and at 12.2 cm/s this material retained sturgeon 29.0 mm TL. These results are similar to those obtained with 3.96 mm perforated plate. 

During 1981 evaluations, 2.38 mm wedge-wire retained sturgeon 23.0 rnm TL at 

6.1 cm/s and 25.0 mm TL at 12.2 cm/s (Table 2). 

A strong positive relationship exists between screen approach velocity and 

impingement of juvenile white sturgeon (Figure 2). Impingement at each velocity was similar for both perforated plate and wedge-wire material. At 18.3 

cm/s, complete impingement of test fish occurred within 5 min. 
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TABLE 2. Total Lengths at Which Juvenile White Sturgeon Were 100% 

and 0% Retained at Various Combinations of Screen Type, 

Hole Size, and Approach Velocity. 

Screen type Screen Approach . 100% 0% 

Year 

wedge-wire (W) (mm) (CRI~S) (IIBII TL) (m TL) 

1980 P 6.35 6.1 45.0 34.0 

1980 P 4.76 6.1 31.0 19.0" 

1980 P 3.96 A. 1 27.0 19.0" 

1981 P 3.96 6.1 27.0 19.0 

1981 P 3.18 6.1 21.0 19.0 

1980 P 6.35 12.2 43.0 33.0 

1980 P 4.76 12.2 31.0 21 -0 

1980 P 3.96 12.2 29.0 21 .o 

1981 P 3.96 12.2 25.0 19.0 

1981 P 3.18 12-2 25.0 13.09: 

1980 W 3.18 6.1 31.0 13.0;' 

1981 W 3.18 6.1 29.0 '19.09: 

1980 W 2.38 6.1 27.0 15.0 

1981 W 2.38 6.1 23.0 19.0 

1980 W 3.18 12.2 33.0 19.0 

1981 W 3.18 12.2 33.0 23.0 

1980 W 2.38 12.2 29.0 17.0 

1981 W 2.38 12.2 25.0 19.0 

perf-plate (PI opening velocity retention retention 

* Calculated values. 
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Average Percent 

I mpin gement 

50 

oi J/ I I I

2'-3 6-1 I!?-2 18.3 

Approach Velocity 

(cm/s) 

FIGURE 2. Average percent impingement of juvenile white sturgeon on 

test screen discs at three approach velocities �or perforated plate (A) and wedge-wire (0). A = Calculated line 

based on impingement results from 3 approach velocities. 

B = Line fit to the 2 points where impingement was less than 

100%. 
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DISCUSSION 

Both 3.96 mm perforated plate and 2.38 mm wedge-wire effectively screen juvenile white sturgeon 27.0 mn~TL and longer at approach velocities of 6.1 cm/s 

and less. Juvenile white sturgeon as small as 10 mm (0.4 in,.)have been 

collected in the Sacramento River downstream from Hood (Stevens and Miller 

1970). Exptected losses for white sturgeon less than 27.0 mm TL exposed to 

these screen opening sizes would be high. 

The impingement results indicate that a significant proportion of white sturgeon in the size range tested fail to maintain their position against currents 

as low as 6.1 cm/s, over a 3-h period. A calculated approach velocity of no 

less than 2.3 cm/s (0.075 ft/s) appears necessary to completely prevent impingement (Figure 21, however additional testing should be conducted to more 

accurately determine acceptable approach velocities. 

Additional studies are necessary to develop safe and effective criteria for 

screening juvenile white sturgeon. The location of juvenile sturgeon in the 

water column, their daily activity patterns, and their susceptibility to diversion into the Peripheral Canal .intake are essentially unknown at this time; 

however,a benthic association is suggested by the literature (Stevens and 

Miller 1970; Kohlhorst 19761, and a sill at the base of the intake has been 

provided to reduce entrainment of benthic species. If it is determined that 

large-scale entrainment of young sturgeon is likely, then criteria for screen 

opening size and approach velocities should be considered. 

ACKNOWLEDGMENTS 

Serge Doroshov, Department of Animal Science, University of California, Davis, 

and the staff of the Elk Grove-Florin Catfish Farm supplied fish for testing. 

Ronald Lunsford and James Gibboney, California Department of Water Resources, 

provided engineering expertise and maintained the test facility. Alan Pickard 

and Dan Odenweller, California Department of Fish and Game, designed the studies and provided support and editorial assistance. To these, and especially 

to the seasonal employees associated with the study program, a great deal of 

gratitude is due. 
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REFERENCES 

Fisher, F. W. 1978. Retention of young king salmon, American shad, and striped 

bass by perforated plate and woven-wire screens. Calif. Dept. Fish and 

Game, Anad. Fisheries Branch Admin. Rept. No. 78-18:19 pp. 

Kohlhorst, D. W. 1974. Sturgeon spawning in the Sacramento River in 1073, as 

determined by distribution of larvae. Calif. Fish Game, 62(1):32-40. 

Stevens, D. E., and L. W. Miller. 1970. Distribution of sturgeon larvae in the 

Sacramento-San.Joaquin River system. Calif. Fish Game, 56(2):80-86.