upper stretch; and sand and areas of exposed rock 

 ledge are in the lower section (Armour 1966). 



Methods 



The number of striped bass passed daily by the 

 Holyoke fish lifts from 1979 to 1986 was counted 

 by personnel of the Massachusetts Cooperative Fish- 

 ery Research Unit (MCFRU). Maximum daily river 

 temperature recorded at the dam was used to char- 

 acterize the temperature regime for the striped bass 

 lifted each day. The daily records of each year's run 

 were used to make frequency distributions of the 

 number of fish lifted and the daily maximum tem- 

 perature. We used the statistics of mean, median, 

 standard deviation, and range of temperatures to 

 visually compare the temperatures when striped 

 bass entered the lifts. 



All striped bass used for telemetry were captured 

 during 1981 and 1982 in the fish trap at the lifts. 

 To help reduce mortality caused by handling, we 

 marked only the largest fish captured (280-365 mm 

 fork length). Fish were held at the dam for a max- 

 imum of 5 d in a 1,325 L circular tank supplied with 

 river water. At the release sites (Fig. 1), we inserted 

 into the fish a transmitter which went directly 

 through the mouth and into the stomach, a proce- 

 dure that did not interfere with subsequent feeding 

 (Warner 1983). 



Radio transmitters were constructed using the 

 design of Knight (1975) or with the modifications 

 of Buckley (MCFRU). The transmitters measured 

 12 mm in diameter and 45 mm long, weighed 3.5-5.5 

 g in air, and transmitted for 7-21 d. Weight of the 

 transmitters never exceeded 3.4% of the body 

 weight of the fish. Individual fish were identified by 

 12 frequencies (30.05-30.25 MHz) and by variations 

 in the pulse rate of each frequency. 



We tracked striped bass from a boat using an 

 omnidirectional antenna (1/8-wave, base loaded) to 

 locate fish to within about 100 m and a directional, 

 tuned-loop antenna to locate fish to within about 10 

 m. Locations of fish were noted on contour maps 

 of the river. Initially, we tracked striped bass from 

 4 to 30 h, but tracking each fish was not continuous 

 and depended on the speed of dispersal. Later, we 

 surveyed the study area daily. Some striped bass 

 moved actively and others were sedentary; there- 

 fore, we tracked the active fish continually for as 

 long as 6 h, but only periodically noting the locations 

 of others. In addition to the daily surveys, we ob- 

 served some fish continually for 24 h to determine 

 the diel movement; we conducted three diel surveys 

 in 1981 and nine in 1982. 



The upstream and downstream rates of movement 

 (ground speed) were determined by using the con- 

 tinuous observations of striped bass that had been 

 free longer than 1 h. Locations where striped bass 

 remained longer than 90 min were designated as 

 "holding areas". The physical characteristics of 

 these areas were determined from visual observa- 

 tions and contour maps. 



Results and Discussion 



Passage in the Lifts and Temperature 



Activity at the fish lifts appeared to be related to 

 temperature (Fig. 2). Striped bass first entered the 

 lifts when river temperatures were 17°-19°C (late 

 May or early June), and in some years a few were 

 still entering the lifts at 25°-28°C when lift opera- 

 tion ceased. The mean temperature of activity when 

 striped bass entered the lifts ranged from a low in 

 1980 of 10.0°C to a high in 1983 of 23.4°C (Fig. 2). 

 For the 7-yr period, the mean temperature of peak 

 movement was 21.3°C (SD, 1.7°C) with 72% of the 

 fish passage from 20°C to 24°C (85% of passage 

 between 19° and 24 °C). 



15 



o 



o 



-' 10 



lU 



=) 



< 



tr 



UJ 

 CL 



LlI 



I- 



21 



2-1 



27 



231 



n--86 



MO 



standard J -I- mean 

 deviolion S V mcdion 



, range 



493 



346 355 



110 



\ 



■o- 



187 



V - 



J_ 



_L 



J_ 



_1_ 



1979 1980 1981 1982 I9B3 1984 1985 1985 



YEAR OF RUN 



Figure 2.— Mean, median, standard deviation, and range of 

 temperatures when subadult striped bass were passed in the 

 Holyolie Dam fish lifts, 1979-86. 



A recent hypothesis proposed that, as striped bass 

 advance in age, they prefer cooler water (Coutant 

 1985). Further, the thermal niche of subadults (43-68 

 cm total length) in Tennessee reservoirs was 20°- 

 24° C, when these temperatures were available (Cou- 

 tant and Carroll 1980). This is essentially the same 

 range as most upstream movement into lifts in this 

 study. Although the movement of striped bass into 



144 



