riverine rather than anadromous. Spawning takes 

 place in the freshwater, tidally influenced zone 30-40 

 km upstream from the river mouth during late March 

 through early May, normally at water temperatures 

 of 16°-20°C (Dudley and Black 1978). After spawn- 

 ing, striped bass in the Savannah River move up- 

 stream and remain in the river until the following 

 autumn (Dudley et al. 1977). The fish may then move 

 downstream to overwinter in estuarine areas, al- 

 though, until now, no direct evidence for this assump- 

 tion has been available except for the existence of a 

 small and unpredictable sport fishery in the estuary 

 during November through January. This note sum- 

 marizes additional information about striped bass 

 movements during the winter and during the spring 

 spawning season. 



Study Area 



The study area extends from the mouth of the 

 Savannah River to the Augusta city dam 370 km up- 

 stream and has been described by Dudley et al. 

 (1977). The tidally influenced section of the river is 

 composed of three branches. Front River, the main 

 shipping channel, flows through the industrial part of 

 Savannah, Ga., and is 10-12 m deep downstream 

 from Highway 17. Back River and Middle River flow 

 through the Savannah National Wildlife Refuge, are 

 bordered by cypress forest and extensive grassy 

 marshlands, and are 1-3 m deep at mean low water 

 (Fig. 1). 



The tide gate, completed by the U.S. Army Corps of 

 Engineers in 1977, was built to control sedimenta- 

 tion in the shipping channel. The gate allows the in- 

 coming tide to flow upstream in Back River but closes 

 when the tide starts to drop, preventing downstream 

 flow. Tidal brackish water and freshwater flowing 

 down upper Back River pass through the diversion 

 canal and increase water velocities in Front River. 

 The gate has changed flow patterns and has in- 

 creased salinity in parts of Back and Front Rivers. 

 Salinity in Back River from the tide gate to Highway 

 17 is l-3%o higher than without tide gate operation, 

 when salinity upstream from the diversion canal is 

 usually zero. With gate operation, salinity in Back 

 River at Highway 17 can reach 3%o (Dudley and 

 Black 1 ). 



During studies conducted in 1973-75 (Dudley et al. 

 1977), Back River was blocked at the site of tide gate 



construction. During the present study the tide gate 

 was operating. 



Methods 



In freshwater a boom-type electrofishing boat with 

 alternating or pulsed direct current was used to cap- 

 ture striped bass. During November through March, 

 attempts were made to capture striped bass with gill 

 nets of 24.3 and 15 cm stretch mesh 30-100 m long. 

 These nets were fished primarily in the Savannah 

 Back River, especially near the tide gate, and in other 

 areas of the downstream 80 km of the river. A 10 cm 

 mesh net was also used but caught mostly smaller 

 fish. Gill nets were checked for fish eveiy 30 min. 



Both ultrasonic and radio transmitters were used. 

 The ultrasonic transmitters (manufactured by 

 Smith-Root 2 of Vancouver, Wash.) are easily detected 

 in the estuary, but difficult to track in upstream areas 

 due to noise generated by water currents and by sand 

 moving along the bottom. Ultrasonic transmitters 

 used in the spring of 1979 weighed 54 g, measured 20 

 mm in diameter and 100 mm long, and had a life ex- 

 pectancy of 6 mo. Those used in the winter of 1979- 

 80 and in the spring of 1980 weighed 40 g, measured 

 20 mm in diameter and 110 mm long, and had a 1-yr 

 life expectancy. 



Radio transmitters (manufactured by AVM Elec- 

 tronics of Champaign, 111.) are easily detected in 

 freshwater but not in saline water. Radio tags 

 measure 70 X 25 X 20 mm, weigh 23 g, and transmit 

 for more than 1 yr. The surgical tagging procedure 

 followed that of Dudley et al. (1977). 



In our studies of winter movements, the down- 

 stream 100 km of the river was searched for tagged 

 striped bass at about weekly intervals. During this 

 time we also tried to capture and tag additional fish. 

 In our studies of spring movements, the downstream 

 60 km, including most side channels, was searched 

 about five times per week. The river in the vicinity of 

 the spawning grounds was divided into nine sections 

 to facilitate comparison of 1980 movements with 

 those observed in earlier studies (Dudley etal. 1977) 

 (Fig. IB). 



We used a chi-square test of independence to com- 

 pare sections used by striped bass in 1980 with sec- 

 tions frequented by striped bass tracked in the 

 earlier, pretide gate study. In that test, river sections 

 E through H were combined, because of the small 

 number of sightings made in them. 



'Dudley, R. G., and K. N. Black. 1979. Effect of the Savannah 

 River tide gate on striped bass eggs and larvae. Final report to the 

 U.S. Army Corps of Engineers on contract DACW2 1-78-C-0073, 46 

 p. + app. 



2 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



421 



