per unit of volume or weight, and obviously have 

 higher nutritive value than the poor ones contain- 

 ing over 92.5 percent water. 



Oysters living under marginal conditions (see 

 chapter XVIII) are usually low in solids through- 

 out the year. A comparison of the mean annual 

 composition of meat based on a series of regular 

 observations discloses these differences. Table 38 

 summarizes the chemical studies made for 2 con- 

 secutive years on oysters from six southern states 

 (Lee and Pepper, 1956; Lee, Kiu-tzman, and 

 Pepper, 1960). The lowest values of total solids, 

 and of proteins, carbohydrates, and fat were found 

 in Georgia and the highest in Louisiana and 

 Alabama oysters. Data on seasonal variation in 

 the composition of meat for the southern oysters 

 were analyzed by Lee and Pepper (1956). Solids 

 increase steadily from 9.5 percent in October to 

 about 13.5 percent in March; in the middle of 

 May they begin to decline and reach the lowest 

 value of 9.2 percent in September. The fat con- 

 tent followed the trend appro.ximately. The 

 changes are associated with the gonad develop- 

 ment and spawning, which in the southern oysters 

 begins earlier and continues longer than in oysters 

 of the northern waters. 



T.\BLE 38. — Proximate mean composition of meat of C. 

 virgiiiica from southern icaters for 2 consecutive years, 

 from October 1954 to October 1956 inclusive, in -percent 

 of their net weight 



YIELD AND QUALITY OF MEAT 



Some idea of geographical differences in the 

 productiveness of oyster bottoms may be gained 

 by comparing the yield of oysters in pounds of 

 meat per bushel. It can be seen from table 39 

 copied from Power (1962) that the recorded yield 

 of market oysters in the waters of Delaware and 

 further north varies from 6.6 to 7.5 pounds per 

 standard bushel and is significantly higher than 

 in the southern states, from Maryland to Texas, in 

 which the yield is from 3.15 to 5.07. 



APR MAY 



Figure 355. — Average protein and carbohydrate content 

 in monthly samples of southern oysters in percent of dry 

 weight. Oysters for analysis were collected at the 

 shucking plant but were not subjected to the routine 

 washing and air bubbhng procedure which causes large 

 salt and fluid lo.sscs. From Lee and Pepper, 1956. 



The quality of oyster meat is related primarily 

 to the amounts of protein and carbohydrates. 

 The ratio between the two components changes 

 with the season and reproductive cycle. The 

 percentage of protein sharply decreases in May to 

 less than 40 percent of the dry weight while at the 

 same time the cai'bohydrates reach their maxi- 

 mum of about 60 percent (fig. 355). The actual 

 changes in the protein content are less pronounced 

 because of the increase in solids due to storage 

 of glycogen. 



Decline in the ash (mineral matter) content of 

 oyster meat from the highest value of almost 25 

 percent (dry weight basis) in October to about 5 

 percent in May (fig. 356) and a gradual increase 

 during May to September are probably related to 

 changes in the salinity of water from which the 



Figure 356. — Average mineral matter and salt content in 

 the montlily samples of southern oysters (unwashed) in 

 percent of dry weight. From Lee and Pepper, 1956. 



382 



FISH AND WILDLIFE SERVICE 



