404 



Fishery Bulletin 98(2) 



October 95; n= 1487 



25 

 20 

 15H 



10 

 5 

 



25 



20 



o 15 

 § 10 



■i= 



r^nW^ 11 1 P 



March 96; n = 9561 



, , Ik , 4^ 



July 96; n= 1864 



25-1 



20- 



15 



10 



5 







lu 



-I — I — I — 1 — I — I — I — r 



35 70 105 140 175 210 245 280 315 350 385 



Fork length (mm) 



Figure 3 



Percent size-frequency distributions of walleye pollock, 

 Theragra chalcogramma (fork length mm), collected during 

 three acoustic surveys of Prince William Sound, Alaska, in 

 1995 and 1996 (/!=count). 



and outside the bay.s in deeper water (31-60 m ) and 

 throughout the water columns in July 1996 (Table 

 2). Deeper waters, where Pacific herring were aggre- 

 gated, inside the bays were warmer than outside the 

 bays, 0.28°C (31-60 m) in March 1996. 



Pacific herring and walleye pollock I3NSD distri- 

 butions differed from randomly calculated Z3NSD 

 distributions during all three surveys (Table 3; Fig. 

 6). In October 1995, age-0 and 1-2 year old Pacific 



herring aggregated at the heads of bays with S3NSD 

 values <3 km (Fig. 6). Adult Pacific herring were 

 aggregated in passages or along the open coast (Fig. 

 6). Walleye pollock distribution was also significantly 

 aggi-egated within bays but not as tightly as age-0 

 and 1-2 year old Pacific herring (Table 3; Fig. 6). In 

 March 1996, all size modes of Pacific herring and 

 walleye pollock had greater than expected X3NSD 

 values, ranging between 4 and 10 km (Table 3; Fig. 

 6). In July 1996, age-0 Pacific herring were highly 

 aggi'egated at the heads of bays (57.19f of Z3NSD 

 <1 km; Fig. 6). Age 1-2 year old Pacific herring were 

 also aggregated at the head of bays (<2 km). Adult 

 Pacific herring were aggi'egated within bays (<2 km I, 

 but more than expected had I3NSD values of 6 to 

 7 km (Fig. 6). In July 1996, walleye pollock were 

 aggi'egated within bays and the majority of X3NSD 

 values were <3 km (Table 3; Fig. 6). 



Discussion 



Pacific herring was the most abundant fish aggi-egat- 

 ing in the east-northeast and west southwest areas 

 of Prince William Sound. Bays appeared to be nurs- 

 ery areas for age-0 and 1-2 year old Pacific herring. 

 Water conditions within bays fluctuated less than 

 conditions within passages and along the open coast. 

 In October 1995 and July 1996 water temperatures 

 in the upper 30 m were cooler inside these bays than 

 within passages or along the open coast. In March 

 this pattern was reversed and deeper waters, where 

 the Pacific herring were aggi'egated, were warmer 

 within the bays than within passages or along the 

 open coast. Although, these fluctuations were small, 

 they may have affected juvenile Pacific herring met- 

 abolic rates. Temperature and length of winter are 

 critical factors in determining juvenile Pacific her- 

 ring growth and over-winter survival ( Paul and Paul, 

 1998; Paul et al., 1998; Foy and Paul, 1999). 



