756 



Fishery Bulletin 93(4), 1995 



annual differences were found in 

 mean female mass at the other 

 three sites or in male masses at 

 any site. Both female {F=8.6, 

 P<0.01) and male (F=12.9, P<0.01) 

 pups weighed at Marmot Island in 

 1993 were significantly heavier 

 than pups weighed at the rookery 

 in 1975, though the weighings oc- 

 curred a week later in 1975. Mean 

 mass of pups weighed at Sugarloaf 

 Island in 1965, 1975, and 1992 

 were not significantly different for 

 either female {F=3. 1, P=0. 1) or male 

 (F=1.3, P=0.5) pups. However, two 

 of the 1965 and 1975 weighings 

 were conducted two weeks later 

 than the 1992 weighing. 



Mean male mass increased significantly in the Gulf 

 of Alaska during the 26 June-8 July weighing pe- 

 riod (£=2.9, P=0.05, r 2 =0.68). However, there was not 

 a significant relationship between weighing day and 

 mean mass for males in Oregon or the Aleutian Is- 

 lands, nor for females in any of the three geographic 

 areas. The slopes of the regression of mean pup mass 

 against weighing day were not significantly differ- 

 ent for the Gulf of Alaska and Aleutian Islands for 

 female (£=0.26, P>0.5) and male (£=0.57, P>0.5) pups. 



Mean mass increased significantly for both sexes 

 from Oregon to Southeast Alaska to the Gulf of 

 Alaska and Aleutian Islands. Oregon female (£=105.1, 

 P<0.01) and male (£=79.3, P<0.01) pups were signifi- 

 cantly lighter than their counterparts in Southeast 

 Alaska (Fig. 2). Mean mass of Southeast Alaska fe- 

 male (£=29.4, P<0.01) and male (£=36.9, P<0.01) pups 

 was significantly less than that of Gulf of Alaska 

 pups. Gulf of Alaska female and male pups were both 

 significantly lighter than Aleutian Island female 

 (P=6.0, P=0.03) and male (P=16.3, P<0.01) pups. 



Discussion 



Our expectations in this study were either that there 

 would be no significant differences in mean pup mass 

 between rookeries or that pups at rookeries with 

 declining populations would be smaller than pups at 

 rookeries with increasing populations. Considerable 

 research by scientists at NMFS, ADF&G, and other 

 research facilities has focused on comparing the con- 

 dition of pups between Southeast Alaska and the Gulf 

 of Alaska, because it has been assumed that the op- 

 posing population trends in the two areas were a 

 result of some limiting factor (e.g. lack of food or dis- 

 ease) affecting only the Gulf of Alaska population, 



