COMBINED 



F 

 80 



70 



60 



■50 



30 



20 ; 



10 



12 3 4 5 



STAT 



6 7 8 9 10 



IONS 



»N-T} 



MEAN-I ^ RANGE 



Figure 20. — Range and mean value of each hydrographic variable measured, by station and 

 for stations combined by area, Jamaica Beach area, Tex., 1969. 



Bay. On February 20, we placed two trays of 

 oysters 0.3 m. (1 ft.) below mean low water in 

 each area. Each tray was partitioned into 18 

 squares. The oysters were sorted into eight 

 groups; each group had a shell length range of 

 5 mm. before being placed in trays. Lengths 

 of groups ranged from 25 to 29 nnm. to 60 to 

 64 mm., and four oysters of a size group were 

 placed in each partition. Every size group was 

 represented by at least eight oysters at each 

 station. Every 2 weeks we replaced any dead 

 oysters with live oysters of the same length 

 and a similar shell configuration. Shell length 

 for each oyster was recorded monthly and 

 weight was recorded bimonthly. We analyzed 



only the lengths because the oysters had been 

 weighed only twice. 



The lengths of the oysters in each size group 

 increased more rapidly in the natural area 

 than in the altered area during the 3-month 

 period (fig. 21). Growth in both areas, however, 

 was probably determined to a large extent by 

 the seasonal temperature increase from a low 

 of 12° C. (540 F.) in the first month to a high 

 of 28° C. (82° F.) in the third month. Salinity 

 apparently had little or no effect on oyster 

 growth as concentrations varied no more than 

 2 p.p.t. between the two areas. 



The difference in oyster growth between the 

 two areas may be explained by the relative 



30 



