FisuJ^e 30. llale and female sea lampreys at moment of extru- 

 sion of eg£;s and milt. (Ocqueoc River, 

 Stations 2L-M, June 9, 19U8 . ) 98 



Figure 3I. Male and female sea lampreys in spawaing act, 



(Ocqueoc River, Stations 2L-M, June 9^ 19)48.) 98 



Figure 32. Diagramatic sketches of the distribution in 

 depth and area of the eggs in some typical 

 sea lamprey nests 100 



Figure 33. Sea la-iprey nest; type characteristic of graveled 

 or gravel bar areas. (Ocqueoc River, Zone 1, 

 Station BI, June 10, 19U8.) 101 



Figure 3U. Diagram of a gravel riffle in the Ocqueoc River 

 utilized by sea lampreys for spa-svning. (Station 

 IL-M, 19li7) 103 



Figure 35. Diagram of the location of sea lamprey nests on a 

 series of crescentic gravel bars in the outside 

 of a bend in the river. (Ocqueoc River, Station 

 20, June, 19U7.) lOU 



Figure 36. Diagram of the location of four sea lamprey 

 nests on a gravel bar in a small stream. 

 (Little Ocqueoc Eiver, Station ^B, June, 19h7.)'" 10^ 



Figure 37. Sea lamprey nests (see text for discussion) IO7 



Figure 38. Two pairs of sea lampreys spavming on a trans- 

 verse gravel bar; a continuous nest which has 

 been reworked by late spaivners so that outlines 

 of original nests have been obliterated. 

 (Ocqueoc River, Station IL-II, June 10, 19U8.) 110 



Figure 39. Spent male sea lamprey clinging to nest after 

 the completion of spa'wning. (Ocqueoc River, 

 Station IM, June 8, 19U8.) 113 



Figure UO. Section of intestine of sexually immature and 

 actively feeding adult taken in Grand Traverse 

 Bay; total length — 9.6 inches; color of liver — 

 orange. X23.2 123 



Figure hi. Section of intestine of migrant sea lamprey; 

 male; total length — I3.I inches; color of 

 liver — orange. X23.2 12l| 



Figure U2. Section of intestine of migrant sea lamprey; 

 female; total length — 16. 5 inches; color of 

 liver — brown-green. X23.2 12^ 



VI 



