extraction with carbon tetrachloride or petroleum ether. Total N of flesh 

 was done after Kjeldahl digestion of 2 g of meat. Carbohydrate was 

 determined as glucose. Clams were taken from shore along the outfall 

 channel of a power station in Southampton Water. A few came from experi- 

 mental sites elsewhere. Condition was expressed as ratio of wet flesh 

 weight to total weight in percent. Condition was lowest, about 11%, in 

 Feb. Values rose through Mar to May inclusive, parallel with the rise in 

 spawning potentiality. Condition index reached a peak of 15.5% in early 

 June, as did spawning potentiality, then both values fell as spawning began. 

 In late July these values rose again, then fell to the end of Sept. 

 Condition index remained fairly steady during Sept to Nov inclusive, then 

 fell to a minimum in late winter. Dry flesh weight expressed as a per- 

 centage of total weight showed a similar seasonal cycle, from a minimum of 

 2 to a maximum of 3%. Condition may vary from year to year. Large clams 

 showed a different seasonal cycle than small animals. In winter, condition 

 was correlated positively with size. In spring, condition of smaller clams 

 increased relatively more rapidly, so that by early June all clams had same 

 average condition factor. Differences in condition between 1961 and 1962 

 appeared to be related to spawning potentiality, suggesting that 1962 was a 

 "good" spawning year, 1961 less favorable. No extensive spatfall was noted 

 in 1961. Biochemical analysis on clams collected on 3 April 1962 gave the 

 following results: small clams (2.5 to 4.5 cm shell length) - moisture 

 82.1%; protein (=Nx6.25) 11.1% wet, 62% dry; lipid 0.3% wet, 1.7% dry; 

 carbohydrate 3.3% wet, 18.4% dry; ash 1.6% wet, 8.9% dry. Large clams 

 5.75-9.5 cm): moisture 81.1%; protein 11% wet, 58.2% dry; lipid 0.5% wet, 

 2.6% dry; carbohydrate 4.2% wet, 22.2% dry; ash 2% wet, 10.6% dry. Lipid 

 showed little significant seasonal variation. Percent protein fell steadily 

 from maximum in Feb to minimum from June to Sept inclusive. Carbohydrate in 

 small clams rose from minimum in March to maximum in July; in large clams 

 carbohydrate fluctuated but showed no significant seasonal trend. Analysis 

 of adductor muscle, mantle, siphons, visceral mass, digestive gland, and foot 

 showed little significant seasonal change in most, with possible exception 

 of foot, mantle, and siphons, in which carbohydrate fell steadily from Jan- 

 Feb to May- June and protein rose. Lipid content of digestive gland was high 

 compared to that of other orqans , which agrees with its suggested function 

 in part as a site for fat storage. Gonad had much higher carbohydrate than 

 any other organ. Changes in carbohydrate composition of small clams 

 therefore must be caused by proliferation of gonad, arising from consequent 

 increase in ratio of gonad weight to meat weight. In other areas pre- 

 liminary analyses showed clams to have higher condition indices. It was 

 suggested that in sparse populations gametes are too sparse in the water to 

 stimulate mass spawning, thus spawning rarely occurs and loss of condition 

 is slight. Some conclusions could be drawn from the study about organic 

 production represented by gonad development and the contribution of this 

 to total production from all growth processes. During 1962, a 4 cm clam 

 of 2.4 g initial wet meat weight added about 2 g organic wet material by 

 growth. In this period gonad material of about 3 g wet meat was developed, 

 of which about 2.6 g was released in spawning. Total increment retained 

 was therefore about 2.4 g wet flesh. About 52% of total organic production 

 was released as spawn. Contribution to organic production by gonad de- 

 velopment and spawning also can be estimated from changes in carbohydrate/ 

 protein ratio. The estimate corresponded closely with that derived from 

 wet flesh weight. Male and female gonads when ripe may make up to 50% of 

 total body weight. There is apparently no antagonism between gonad de- 

 velopment and body and shell growth. - J.L.M. 



103 



Ansell, Alan D., J. Coughlan, K. F. Lander, and F. A. Loosmore . 1964. 



Studies on the mass culture of Phaeodactylum. IV. Production and nutrient 

 utilization in outdoor mass culture. Limnol . Oceanogr. 9(3): 334-342. 



30 



