periods of tifne. A straight line relation 

 (fig. 6) exists between the number of times 

 the propeller, synchronized to the counter, 

 makes a complete revolution, and the speed 

 of the water in feet per second. Therefore, 

 by merely making a note of the number re- 

 corded on the counter register for a given 

 period of time, the velocity of the water 

 being tested can be easily calculated or 

 read from the chart. The meter in its pre- 

 sent form will record speeds up to 6 miles 

 per hour, and can be used at depths less 

 than 3 feet. Greater speeds could be meas- 

 ured by changing the angle of the propeller 

 assembly £Uid recalibrating, while currents 

 at greater depths could be determined by 

 increasing the length of the rod. The maxi- 

 mum water velocity which could be measured 

 by the meter has not been determined. 



SUMMARY 



A photoelectric current meter based 

 on a modified 1-shot cathode-coupled multi- 

 vibrator circuit has been planned, built, 

 and tested. It has been designed to record 

 velocities in the laboratory or field under 

 salt- or fresh-water conditions. In the 

 laboratory it is powered by a 110-volt 

 source and cein record currents encountered 

 by fishes in circular-tank experiments. In 

 the field it is powered by two 9-volt bat- 

 teries and has been designed to measure 

 currents at depths less than 3 feet, and 

 speeds up to 6 miles per hour. Greater 

 speeds could be measured by changing the 

 angle of the propeller Jind recalibrating. 



ACKNOWLEDGMENTS 



We wish to thank A. P. Stickney and 

 Dr. C. J. Sindermann of the Bureau of Com- 

 mercial Fisheries Research Laboratory at 

 Boothbay Harbor, Maine, for valuable sug- 

 gestions in prepeiration of this manuscript. 

 We also wish to thank R. Stanley of Water- 

 town, Massachusetts, for assistance in 

 construction of the meter. 



LITERATURE CITED 



BRETT 



J. 



D. 



AND 



R. , M. HOLLANDS, 



F. ALDERDICE. 

 1958. The effect of temperature on the 

 cruising speed of young sockeye and 

 coho salmon. Journal of the Research 



Figure 6. 



-Relation of revolutions per second to feet 

 per second for the current meter. 



Board of Canada, vol, 

 pp. 587-604. 



15, No, 4, 



DAVIDSON, VIOLA. 



1949. Salmon and eel movement in con- 

 steuit circular current. Journal of 

 the Research Board of Canada, vol. 

 7, No. 7, pp. 432-448. 



FRY, F. E. J., AND J, S, HART. 



1948. Cruising speed of goldfish in 

 relation to water temperature. 

 Journal of Research Board of Canada, 

 vol. 7, No. 4, pp. 169-175. 



PAULIK, G, J., A. C. DeLACY, AND 

 E. F. STACY . 

 1957. The effect of rest on the swim- 

 ming performcince of fatigued adult 

 silver salmon. University of 

 Washington, School of Fisheries, 



