Figures 26 and 2? have been fitted by inspection to these mean val- 

 ues. The munber of eggs produced increases quite rapidly with increase 

 in total lengthj hoivever, with increasing weight egg production is 

 more directly proportional. The lo'west egg production recorded, 

 2i|.."021 eggs J, was found in a 12.6-inch (320 mm.) female weighing 

 70 grams. The greatest recorded^ 107,138 eggs, was found in a 

 21.1-inch {^3^ mm.) female weighing 316 grams. Using values 

 obtained from the curve projected in Figure 26, vre find that the 

 mean egg production for females of average length (17. U inches, 

 i4jb.2 mm.) is 6l»500 eggs. Mean egg production data, as estimated 

 from the curve in Figure 26, for successive one-inch size groups are 

 listed in Table h with the mean deviation for each of the groups. 



(d) Percentage of unspawned eggs 



The egg production determined for the sea lamprey in the pre- 

 ceding section represents the basic reproductive potential of the 

 species in the region studied. This potential is obviously never 

 realized in natiire. Many factors inherent in the organism itself 

 and in its environment tend to nullify the potential, and the 

 actual productivity of the species may be very low when these 

 factors are considered. A preliminary experiment in the number of 

 ammocoetes (lanrae) produced per spavming female suggests that the 

 larval hatch per number of eggs produced (and spawned) is quite 

 small. 



One of the inherent factors which may contribute to a low 

 productivity is the percentage of ripe eggs remaining in the female 

 after the spawning act is completed, i.e., the number of unspawned 

 eggs. Forty spent females were collected to determine this per- 

 centage. In order to avoid any doubt as to -vdiether they had com- 

 pleted as much of their spawning act as they were destined to, 

 only dead (30) or obviously dying (10) specimens were collected. 

 Most collections Trere made in the deeper pools below spawning 

 riffles or in sloughs into "vdiich the dying lampreys had drifted. 

 The females obtained ranged from 11.8 inches (300 mm.) to 18.1 

 inches (I1.6O mm. ) in total length. 



For ten specimens, separate counts were made of the partially 

 developed and fully developed eggs. For the remainder, only the 

 fully d^eloped eggs were counted (Appendix F, Table 3)' The 

 partially developed eggs were, as a rule, still trapped in the 

 remnants of the ovary. Some fully developed eggs were found in like 

 position, but when larger numbers of these were present, by far the 

 bulk of them were loose in the coelomo The potential egg production 

 of each female was determined from the curve projected in Figure 26. 

 Using this figure and the number of developed eggs retained in 

 females, the estimated percentage of unspawned eggs was computed 

 (Appenjdix F. Table 3). The partially developed eggs were not con- 

 sidered in estimating this percentage since their occurrence is 

 variable with the length of the fish. They are present in nominal 

 numbers only in all but the very smallest size groups. 



- 82 - 



