$262.50 per season. This applies in those lake basins where the sea 

 lamprey's spawning run season lasts an average of 3 l/2 months and is 

 based on an average hourly rate (in 1952) for laborers of $1.25. 



Recommendations 



At the present time, no single electrical mechanism for gen- 

 eral use in all sea lamprey spawning streams is recommended. In streams 

 where simultaneous fish runs must be protected, an electromechanical 

 weir and trap is required. Considerable care should be taken in advance 

 to determine the primary path of upstream movement of migrant fishes at 

 the site of installation. Weir-traps should be installed directly in 

 this path and the electrode array "tailored" to provide "leads" to the 

 trap. 



A multiple-row, suspended electrode system is recommended where 

 any, or a combination of, the following conditions obtain at the locus 

 of installation: 



(1) Maximum flood depths are greater than 5 feet 



(2) Stream velocities are less than 1.0 f.p.s. 



(3) Stream bed materials are soft or floculent 



In general, a two-row electrode system creating a uniform electrical 

 field should suffice in such locations. A recommended design for an elec- 

 tromechanical weir and trap of this type is presented in Figure 18. 



At sites where very sluggish water exists (0.5 f.p.s. or less), 

 observations during operation of the above device may indicate that some 

 fish mortality results due to the ability of some migrants to propel them- 

 selves into the strongest areas of the electrical field. Should this 

 occur, it would be desirable to alter the device to a three-row system 

 with an incremental electrical field. Modification of the structure de- 

 tailed in Figure 18 to accommodate a third row of electrodes may be accom- 

 plished as follows: 



(1) Remove 5-foot, channel iron crosspiece at top of each pair 

 of suspension towers. 



(2) Replace with similar crosspiece measuring 10 feet longj 

 crosspiece should be centered on centerline between dual suspension towers, 



(3) Install suspension cables for three rows of electrodes on 

 U l/2-foot centers with middle row on centerline between towers. 



U5 



