FISHERY BULLETIN: VOL. 79, NO. 3 



opment stage and gonad size increases. The ac- 

 cumulation of reserves is almost certainly due 

 to spring phytoplankton blooms. Following this 

 general buildup of energy reserves and continued 

 maturation of gametes, a marked shift in the 

 condition of the digestive gland and adductor 

 muscle occurs. From June through July and prob- 

 ably into August, there is a sharp drop in DGI and 

 QAI (Figure 2), lipid levels in the digestive gland 

 (Figure 4), and carbohydrate in both the digestive 

 gland and quick component of the adductor muscle 

 (Figure 5). During this time, gametes are ripen- 

 ing, GMI values reach their peak and lipid gen- 

 erally reaches its highest level in the gonad. 

 The completion of gametogenesis therefore seems 

 largely dependent on energy reserves which were 

 accumulated earlier in the spring. 



Gonadal weight, glycogen, and lipid concentra- 

 tions are inversely related to the weight and 

 energy reserves of somatic tissues in a variety of 

 other pectinids. In queen scallop, Chlamys oper- 

 cularis, lipid content of body tissues declined as 

 gonadal lipid increased (Taylor and Venn 1979). 

 Similarly, inverse relationships have been shown 

 for adductor and gonadal dry weights in Pecten 

 maximus by Comely (1974) and digestive gland 

 and gonadal indices in bay scallop, Argopecten ( = 

 Aequipecten) irradians, by Sastry (1966, 1970). 

 Sastry (1966) has proposed however that the 

 reciprocal relationship between index values may 

 indicate that nutrients supplied by feeding might 

 be rapidly utilized for growth and development 

 without prior storage. Thus a decline in DGI 

 would not represent a drop in actual digestive 

 gland wet weight. However, direct evidence for 

 the transfer of some quantity of materials from 

 body tissues to the gonad has been demonstrated 

 in A. irradians using ^^C-leucine (Sastry and 

 Blake 1971), in C. hericia using lipid ^'^C-labeled 

 Chlorella extract (Vassallo 1973) and in other 

 bivalves (vide Gabbott 1975; Sastry 1979). 



During the spring and summer, the loss of 

 energy stores from the digestive gland and 

 adductor muscle could not have been due solely to 

 the transfer of these substances to the gonad. 

 From 13 April to 13 July, more calories were lost 

 from the quick adductor and digestive gland 

 (male, -4.75 kcal; female, -6.00 kcal) than were 

 gained by the gonadal mass (male, -1-1.57 kcal; 

 female, -1-2.27 kcal). The real energy loss was 

 probably greater than indicated by these calcula- 

 tions, since contributions from the catch compo- 

 nent of the adductor and other somatic tissues 



were not included in the calculations. Metabolic 

 demands, due to warmer water temperatures and 

 the completion of gonadal maturation probably 

 accounted for the remainder of the lost energy 

 reserves. The possibility that these reserves were 

 used entirely for metabolic needs, while gonadal 

 maturation depended solely on food intake, seems , 

 remote. 



Following spawning, the condition of the diges- 

 tive gland and adductor muscle improves, as 

 evidenced by the increase in QAI, CAI, digestive 

 gland lipid, and quick adductor carbohydrate. 

 Reserves do not reach or exceed their springtime 

 levels, such as occurs in P. maximus, (Comely 

 1974), C. opercularis (Taylor and Venn 1979), and 

 C. septemradiata (Ansell 1974) populations from 

 the Clyde Sea area. Postspawned Placopecten 

 magellanicus from Georges Bank attain total fat 

 levels as high as those reached during the spring- 

 time (Idler et al. 1964) whereas P. magellan- 

 icus from a southeast Newfoundland population 

 (Thompson 1977) do not show postspawning, 

 autumn increases in either carbohydrate, lipid or 

 dry weight within the gonad, or somatic tissue. 

 The autumn recovery pattern in Boothbay scal- 

 lops appears to be intermediate between the 

 Georges Bank and Newfoundland populations. 



Reproduction is dependent to varying degrees 

 on available food levels and energy reserves in 

 different temperate marine bivalves. In C. oper- 

 cularis (Taylor and Venn 1979) and Pecten maxi- 

 mus (Comely 1974) for example, energy reserves 

 are utilized for both the initiation of gametogen- 

 esis and for subsequent gonadal growth. Reserves 

 are apparently required for both these activities in 

 the intertidal mussel, Mytilus edulis, as well 

 (Gabbott 1975). In other bivalves, however, intake 

 of food is necessary for vitellogenesis and gonadal 

 growth and often for the initiation of gametogen- 

 esis. Gonadal growth in A. irradians cannot occur 

 without feeding, since reserve material from the 

 digestive gland and other body tissues are not 

 adequate to sustain maturation (Sastry 1966, 

 1968, 1970). However, reserves within the diges- 

 tive gland may supplement nutritional intake 

 needed for gonadal proliferation (Sastry and 

 Blake 1971). Similarly, in Crassostrea gigas and 

 C. virginica (Gabbott 1975), gonadal growth is 

 accompanied both by springtime feeding and de- 

 creased glycogen content of the tissues. Gonadal 

 growth however is supported directly by spring- 

 time feeding in Chlamys septemradiata (Ansell 

 1974), although gametogenesis begins during the 



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