The duration of spanning activity was very brief in Zone 2, 

 lasting from 9 {191x1) to 17 (19U8) days. This brevity is attri- 

 buted to several factors: (1) The spamiing run in this zone 

 appears to be composed of early migrants which seem to seek the 

 farthest reaches of the watershed for spawning. Their greater vi- 

 tality, and high and favorable water levels at the Ocqueoc Falls, 

 facilitate their passage over this obstruction; (2) Later migrants, 

 which might prolong the spawning activity in this zone, are denied 

 access to it by their decreased vitality and increasingly less 

 favorable water levels for passage over the falls. This may, in 

 part, account for the prolonged spawning season and overcrowding of 

 nesting sites immediately below the falls in the last third of the 

 spawning season; (3) The sea lampreys present in Zone 2, having 

 delayed their spawning activity at suitable spawning temperatures 

 while searching for optimum nesting sites, which did not exist, 

 were compelled (by an increasing urge to spavm) to build their nests 

 and spairvn in the briefest possible period. 



The appearance, late in the season, of spawning sea lampreys 

 below Ocqueoc Lalce has been noted previously. This shift of 

 spasming activity to the lowermost reaches of the river concludes 

 the spawning season. Spawning areas here are scattered and poor 

 and the occurrence of such activity is attributed to migrants, 

 ii^ich, being unable to locate the inlet of Ocqueoc Lake, eventually 

 drop downstream (through the outlet) in order to spawn. Further- 

 more, some late migrants of low vitality may elect to spawn here 

 without attempting to travel further. 



Spawning h abits and behavior 



(1) Pre -spawning behavior 



As has been observed in a previous section, adult sea lampreys 

 of both sexes are present in the watershed in the spawning areas 

 for as much as six to eight weeks prior to any attempt on their 

 part to initiate spawning activity. Anatomical studies and the 

 absence of external secondary sexual structures indicate that 

 these early migrants are much less mature sexually than later 

 migrants and evidently must complete the maturation process while ■ 

 in the spawning stream. Later migrants displayed more advanced 

 stages of maturity on entry into the stream. Individuals attain- 

 ing the nesting areas during and after the peak of spawning activ- 

 ity commence their nest building and spasming in a very short period 

 of time. 



The first evidence of spawning activity on the part of either 

 sex is the construction of a nest in which the fertilized eggs 

 ■will be deposited. This is done by clearing the gravel, rubble, 

 and small stones from a more or less circular area and by depositing 

 them in a crescentic ring about the doimstream margin of the clear- 

 ing (Figure 30 to 38). Occasionally, gravel or stones are moved 



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