(General Observations) 



In both Zones 1 and 2, some visible current was present at 

 every nesting site. The least current velocity in any one spaiim- 

 ing location was 1.3 feet per second.?/ The maximum velocity 

 in an area -where spa-vming occ-urred was 5.2 feet per second in 

 a rubble and gravel riffle. Current velocities in fo-or long and 

 heavily used riffles ivere 3.6, 3.3, It.O, and k.h feet per second. 

 T1.T0 less extensively used riffles (poor bottom- type) had velo- 

 cities of 1.9 and 2.3 feet per second. In areas other than 

 riffles "where it occurred, velocities of 1.$, 2.3, 2,8, 2.9^ and 

 3.5 feet per second were recorded. 



In the Ocqueoc watershed, there was no evident relationship 

 between the degree of cover and/oi shade and the incidence of 

 spawning activity. The earliest, and subsequently one of the 

 most widely used spasming riffles in the river was relatively 

 shallow, contained no cover within the stream and was completely 

 exposed to the direct rays of the sun throughout the day. At 

 the other extreme,, spawiixig in the Little Ocqueoc River at Sta- 

 tion 5B occurred in dense shade where the sun seldom struck the 

 water. However, since among the earliest spawning sea lampreys 

 some-ii^at more activity was displayed during the hours of darkness 

 than durin.g daylight, I suspect that under optimum conditions^, 

 all other factors being equal, a preference would be shown by 

 the sea lamprey for covered or shaded nesting sites. 



(U) Summary of spawning requirements 



It is concluded from these data collected in the Ocqueoc 

 River that two essential physical conditions, other than suitable 

 ^rnter temperatures, must be fulfilled before sea lampreys may 

 spa-\vn with any degree of success. First, gravel, 3/8-inch to 

 2 inches in diameter, or gr-avel mixed with some other acceptable 

 hard bottom-type (rabble, clamshells, etc.) must be present as 

 the basic elements for nest construction. Furthermore, some 

 small amounts of sand must be available to which the eggs mil 

 adhere and which will imbed them in the interstices of the g.:e.re"L 

 in the nest rim. Excessive amounts of larger hard bottom-types 

 (bed rock., boulders, large rubble) hinder or prevent spawning. 

 In predomin.antly sandy areas, some small amount of gravel m-ast be 

 present before nest construction and spawning ivill be attempt'^d 

 by the sea lamprey. Probably the minimal acceptable quantity of 

 gravel uxjder such circ-omstances is typified in the nesting s' " 

 described on p. 108 (Figure 37e), 



.1 'JT 



7/current velccitys surface velocity X factor of 1.33. 



- Ill 



