262 



American Fisheries Society 



lapping groups of averages in which each fish appears are 

 shown in the following table: 



Groups Into Which Individual Yellow and Blue Pike of 

 Approximately Same Length Fall 



HEAD MEASUREMENTS 



Distance from Tip of Snout to Posterior Edge of Preopercle. 

 The averages show a converging difference from the smaller 

 to the larger fish, thus indicating a decrease in the distance 

 with increase of size of the yellow pike, and an increase of 

 distance with increase of size of the blue pike, the yellow pike 

 having the greater average. The average of Group 4, of the 

 blue pike, reaches the average of Group 2, of the yellow pike, 

 which are respectively composed of fish averaging 367 and 

 269 mm. in total length. The six individuals of each form 

 show that this dimension in the second yellow pike 295 mm. 

 long equals that of the fourth blue pike, 327 mm. long, the 

 yellow pike being immature and the blue pike a mature fish; 

 this suggests that youthful characteristics of the yellow pike are 

 maintained in older or larger blue pike. 



Interorbital Width. — A narrower interorbital width ob- 

 tains in the general average of the blue pike than in the yellow 

 pike. The yellow pike changes but little from the smaller to 

 the larger fish, while the blue pike, at first considerably 

 narrower than the smallest yellow pike, approaches the yellow 

 pike in Groups 4 and 5 of larger fish. The next to the largest 



