849 



Geographic patterns in growth of the 



giant Pacific sea scallop, Patinopecten caurinus 



Steve Ignell 



Evan Haynes 



Auke Bay Laboratory 



Alaska Fisheries Science Center 



National Manne Fishenes Service, NOAA 



11305 Glacier Highway 



Juneau, Alaska 99801-8626 



E mail address Sieve Ignellanoaa gov 



Giant Pacific or weathen'ane sea scal- 

 lops. Patinopecten caurinus. were first 

 fished commercially in the Gulf of 

 Alaska in 1967, when 3449 kg of 

 unshucked sea scallops (estimated 341 

 kg of meats) were landed at Kodiak, 

 Alaska (Haynes and Powell, 1968 1. The 

 discovery of commercially exploitable 

 stocks of giant Pacific sea scallops led 

 to a fishery that expanded rapidly, and 

 landings increased to 856 metric tons 

 (t) of schucked meats by 1969 (ADF&G, 

 1979). For the next two decades, scallop 

 landings fluctuated greatly (ADF&G, 

 1987 ), a result of limited stocks, restric- 

 tive regulations, and more lucrative 

 opportunities in other Alaska fisheries 

 (Kaiser, 1986). Since 1990, however, 

 the fishery has changed from a part- 

 time fleet to a dedicated full-time fleet 

 with the influx of larger, more efficient 

 vessels. This change has led to sus- 

 tained near- record harvests (up to 823 

 t) and the adoption of new manage- 

 inent measures for the fishery (Shirley 

 andKruse, 1995;NMFSM, 



Most of the biological literature on 

 giant Pacific scallops relates to fishing 

 exploration (Rathjen and Rivers, 1964; 

 Haynes and Powell, 1968; Ronholt 

 and Hitz, 1968; Haynes and McMul- 

 len. 1970; Bourne, 1988). aquaculture 

 (Beattie, 198.5; Thompson et al., 1985; 



Rhee, 1989), or reproductive biology 

 (Hennick, 1970 and 1971; Robinson 

 and Breese, 1984). Age and growth of 

 giant Pacific scallops have been stud- 

 ied in populations off Oregon (Starr 

 and McCrae, 1983), Washington and 

 the Strait of Georgia (Haynes and Hitz, 

 1971), northern Gulf of Alaska (Kaiser, 

 1986; Hennick2), and the lower Cook 

 Inlet region (Hammarstrom and Mer- 

 ritt, 1985). 



A lack of data on biological produc- 

 tivity has affected recent efforts to 

 develop a fishery management plan 

 (FMP) for Alaska giant Pacific scallop 

 stocks (NMFSM. It has inhibited the 

 development of yield models and a 

 numeric specification of overfishing ( an 

 FMP requirement) and resulted in a 

 simple numeric range given for opti- 

 mal yield. However, there is a renewed 

 interest in acquiring better informa- 

 tion for stock assessments and biolog- 

 ical parameters needed to implement 

 an exploitation-rate harvest strategy 

 for the fishery (NMFSM. 



This note presents results of a com- 

 parative growth study of stocks of giant 

 Pacific scallops in the Gulf of Alaska. 

 Samples for this study were collected 

 during the initial explorations for com- 

 mercial quantities of these scallops in 

 1968 (Havnes and Powell, 1968); thus 



' National Marine Fisheries Service. 1996. 

 Fishery management plan for the scallop 

 fishery off Alaska. Unpubl. document. 

 Natl. "Mar. Fish. Serv.. P.O. Box 21668. 

 Juneau, AK 99802, 123 p. 



- Hennick. D. P. 1973. Sea scallop. Pati- 

 nopecten caurinus. investigations in 

 Alaska. Commer Fish. Res. Develop. Act. 

 project 5-23-R, completion rep. (unpubl.). 

 Alaska Dep. Fish and Game, Juneau, AK 

 99801.. 38 p. 



these data yield prefishery biological 

 parameters that can provide a base- 

 line to evaluate fishery impacts on 

 the giant Pacific scallop populations in 

 Alaska. 



Methods 



Giant Pacific scallops were collected 

 at six locations in the Gulf of Alaska 

 from 27 April to 6 June 1968 (Fig. 1). 

 Sampling was done from the chartered 

 FV Vlkinfi Queen with a standard New 

 Bedford type sea scallop dredge 3.96 

 m wide (equipped with 10-cm rings). A 

 detailed description of this type of gear 

 is given in Posgay (1957) and Bourne 

 (1964). The locations and depths of 

 sampling were 1 ) on Albatross Bank 

 at 92-104 m, 2) on Marmot Flats 

 at 73-104 m, 3) in lower Cook Inlet 

 at 108-122 m, 4) off Cape St. Elias 

 at 91-102 m, 5) off Ocean Cape at 

 82-91 m, and 6) off Lituya Bay at 

 64-75 m. Areas were selected for their 

 geographic separation and likely abun- 

 dance of scallops. Giant Pacific scallops 

 were shucked aboard the vessel, and 

 the upper valves were retained for age 

 and growth analyses. At each location, 

 59-248 scallops were selected (Table 

 1 ); the only criterion for selection was 

 that each sample include a wide range 

 of sizes. Because larger (and rarer) 

 scallops were more likely to be chosen, 

 samples were not selected at random. 

 Within a sample, however, the range of 

 sizes at any given age was not great; for 

 the purpose of fitting gi'owth curves, 

 we assumed that each age class was 

 sampled randomly 



Ages were determined by counting 

 clearly visible annuli (growth rings) on 

 the outer surface of the upper valve. 

 The first annulus is formed halfway 

 during the second year of life; scallops 

 spawn in the summer and the annuli 

 are formed in the winter (Haynes and 

 Hitz, 1971). This aging method has 

 been used extensively to study mol- 

 lusk growth, such as in studies on 

 the North Atlantic sea scallop, Placo- 

 pecten magellanicus (Stevenson, 1934; 

 Stevenson and Dickie, 1954; Merrell et 

 al., 1961), and on the European sea 



Manuscript accepted 13 March 2000 

 Fish. Bull. 98:849-853 (2000) 



