FISHERY BULLETIN: VOL. 75, NO. 2 



types, most of the bed being "fine sand - grey" 

 while areas of its western edge were "shell hash - 

 often brown - many types of organic contributors." 

 The latter was typical of our sediment sample 14. 

 The area from which sediment sample 20 was 

 taken was characterized as "Coarse sand - very 

 shelly - iron stained"; the experimental area 

 northwest of the main scallop producing area was 

 characterized as "fine sand - iron stained - less 

 than 25% shell material." Median grain size 

 analyses of our data agreed with Newton et al. 



(1971) in that parts of the western edge of the 

 calico scallop bed had coarser sediments than 

 other areas encompassed by the main bed (Figure 

 3); however, no differences were found between 

 the main scalloping area, the experimental area 

 north of the bed, and stations 14 and 20. 



Sanders (1958) and Bloom et al. (1972) 

 suggested that optimal sediment conditions for 

 filter feeders were a fine (about 0.18 mm) and a 

 well-sorted, but positively skewed, grain size. Me- 

 dian sediment sizes found within the 1972 North 

 Carolina calico scallop bed averaged below San- 

 ders' 0.18 mm optimal size for filter feeders. Sub- 

 sequent to this study, plotting the location of the 

 1973 calico scallop fishery off the North Carolina 

 coast on the Newton et al. (1971) sediment chart, 

 revealed that the 1973 fishery was in an area not of 

 fine sand but very coarse shelly sand. This has 

 been further corroborated by personal observa- 

 tions aboard vessels in the fishery. These data may 

 support the contention of McNulty et al. (1962) 

 that other factors besides grain size are important 

 to the well being of filter feeders. 



Sorting coefficient values for most sediment 

 samples ranged from 0.300 to 0.685 (Table 3, a 

 condition considered well sorted), although two 

 samples located northwest of the main fishery had 

 relatively high sorting coefficients (1.100 to 

 1.465). Sediments in these same two samples were 

 also strongly skewed ( -0.615 and 0.500, Table 3). 

 While sorting coefficient values agreed with the 

 conclusions of Sanders (1958) and Bloom et al. 

 (1972), the sediment skewness data did not. Most 

 of the data was only slightly skewed (-0.155 to 

 0.090) and not strongly positively skewed as they 

 suggested. 



Commercial fishermen reported that there were 

 numerous rough areas, including a small low 

 ledge, outside the commercial area which caused 

 great damage to their nets. Porter and Wolfe 



(1972) described the North Carolina scallop 

 grounds as consisting of sand, shell fragments, 



and occasionally large pieces of trent marl and 

 coquina. Porter and Wolfe (1972) and Pearse and 

 Williams (1951) described a small bed southwest 

 of New River which was surrounded by bottom 

 containing large heads of lobe star coral, Sol- 

 enastrea hyades (Dana). During 1972, large mas- 

 ses of trent marl were not infrequently brought up 

 in the scallop nets by the commercial fishermen. 

 Ledgelike outcroppings of marl (?) and large heads 

 of the lobe star coral outside the commercial area 

 were observed in 1972 while aboard the George M. 

 Bowers through use of its remote underwater tele- 

 vision sled RUFAS. While such marl outcrops and 

 coral heads are not uncommon throughout the 

 southern North Carolinian coastal area, known 

 calico scallop beds do not seem to be dependent 

 upon their presence. 



CALICO SCALLOP GROWTH 



Length measurements were taken on 5,180 scal- 

 lops during the sampling period (Table 4). Scallop 

 (865) mean growth in the experimental area was 

 faster than that from the commercial area (Table 

 4); size increase over a 7-mo sampling period was 

 17.8 mm or 2.5 mm/mo. Comparable growth data 

 obtained from 4,315 scallops landed by the com- 

 mercial fishery over the 9-mo sampling period 

 were 8.7 mm or 1.1 mm/mo; their sizes ranged 

 from 35 to 65 mm with no live small scallops being 

 noted. The difference in rate of growth was proba- 

 bly related to the original smaller size of the ex- 

 perimental area scallops, which ranged from 28 to 

 57 mm in length (Table 4). Allen and Costello 

 (1972), reviewing the calico scallop literature, 

 noted growth data of 4.0 mm/mo for scallops hav- 

 ing mean sizes of 13.9 to 37.8 mm and 0.3 mm/mo 

 for scallops having mean sizes of 75 to 80 mm. 



As mentioned above, the scallops from the ex- 



TABLE 4. — Lengths (millimeters) of calico scallops collected 

 monthly from the experimental bed north of the main bed and 

 commercial catch, 1972. 



434 



