NOTE Ignell and Haynes: Growth patterns of Patinopecten cauiinus 



851 



indicated highly significant differences 

 (P<0.003) in growth between scallops 

 from each area. 



Results and discussion 



Sea scallops from the Gulf of Alaska 

 showed a consistent trend in growth geo- 

 graphically: from southeastern Alaska 

 northward and then westward around 

 the perimeter of the Gulf of Alaska, sea 

 scallops tended to be larger. Differences 

 in mean shell height were small at early 

 ages but became more pronounced as 

 the scallops grew older (Fig. 2). 



This geographic trend in growth was 

 probably not related to time and depth 

 of sampling. Time of sampling varied 

 little between areas; all areas were 

 sampled within a period of 45 days. 

 Depth of sampling did vary between 

 areas, however, because scallop growth 

 rates are known to vary by water depth, 

 e.g. scallops off Oregon are smaller 

 in deeper waters and have reduced 

 asymptotic lengths (Ronholt and Hitz, 

 1968; Starr and McCrae, 1983). If this 

 depth-size relationship holds true in 

 Alaska waters, then current estimates 

 of asymptotic size for scallops from the 

 northern areas are biased downwards 

 compared with those from Lituya Bay, 

 where scallops were sampled in shal- 

 lower waters. 



Comparisons of our growth results 

 with two analyses of giant Pacific scal- 

 lop samples taken after the start of 

 commercial fishing (Kaiser, 1986; Hen- 

 nick-) showed significantly different 

 estimates of asymptotic size. For scal- 

 lops off Kodiak, values of /^ from Hen- 

 nich's data (182.8 mm) and Kaiser's 

 data (189.8 mm) are larger than our 

 estimate (175.7 mm); for scallops off 

 Yakutat, values of /„ from Hennick's 

 data (151.5) and Kaiser's data (143.7 

 mm) are smaller than our estimate 

 ( 158.6 mm). Scallop fishing before 1980 

 occurred entirely in these two areas 

 (Shirley and Ki'use, 1995). The reduc- 

 tion in asymptotic size for scallops off 

 Yakutat may indicate an increase in 

 fishing mortality on larger individuals. 

 Both analyses also showed that giant 

 Pacific scallops for a given annular ring 

 are larger from the Kodiak area than 

 from Yakutat, a result that supports 

 our conclusions of geographic growth 

 trends for the giant Pacific sea scallop. 







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