Figure 38, — Two pairs of sea lampreys spawning on a transverse 



gravel bar; a continuous nest v#iich has been reworked 

 by late spawners so that outlines of original nests 

 have been obliterated. (Ocqueoc River, Station IL-M, 

 June 10, I9U8.) 



Although a considerable amount of spawning in the Ocqueoc River 

 occurred in this zone, nest-building and spawning conditions are 

 obviously less suitable thgin those areas characterized by gravel 

 bars and ridges in Zone 1. Initially, bottom contours, particularly 

 in most riffles, are low or flat and offer neither resting places 

 for the working sea lamprey nor sites which facilitate the con- 

 struction of a nest as would the abrupt upstream face of a gravel 

 bar. Heavy and/or unwieldy pieces of rubble must be cleared from 

 the nesting site with some considerable effort by the sea lampreys. 

 These larger materials and the inadequate amounts of gravel avail- 

 able do not permit formation of an adequate nest structure. Swift 

 currents over the riffles hinder nest construction and combined 

 with inadequate nest structures result in the sweeping away and 

 probable mortality of many newly-spawned eggs. 



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