FISHERY BULLETIN; VOL. 69. NO. 2 



This latter situation is ana]og:ous to that off 

 eastern Florida. Little is known about substrate 

 preference. Some beds offering optimum con- 

 ditions may be perpetuated for several years, 

 but competition for space between adults and 

 spat must minimize such occurrences. If spat 

 are unable to compete effectively for substrate, 

 the presence of live adult scallops on the bed 

 may prevent spat set. This question needs to 

 be answered in the near future. 



Yearly distribution and abundance depend on 

 both spawning success and spat set. Commer- 

 cial size and abundance are generally reached 

 by early fall, usually in October. Fishing re- 

 mains optimal until February when catch rates 

 and yield decrease. This is due to spawning and 

 associated factors such as increased mortality 

 and meat deterioration. 



In October 1967 scallops averaged about 45 mm 

 and yielded 75 to 80 meats per pint. During Oc- 

 tober the survey produced an average catch of 

 70 lb. of meats per 30-min drag as compared with 

 20 lb /drag in April. 



A fall and early winter fishery is expected to 

 be most productive. Fishing is not recommend- 

 ed during spring because catch rates and yield 

 are generally low and a spring fishery could 

 have an adverse effect on the spawning popu- 

 lation. 



The nonrandom distribution and variable size 

 of beds make it diflicult to estimate the standing 

 crop from dredge surveys. Scallops were found 

 over approximately 285 square miles of bottom 

 during the survey but less than 14% (37 miles) 

 was covered by the dredge. About 6,500,000 

 scallops were caught during the survey. Scal- 

 lops are not randomly distributed on the grounds 

 but occur in beds where very high densities are 

 often reached. Relatively few individuals occur 

 between beds. Beds are diflicult to measure but 

 some were estimated to be several hundred yards 

 in width and over a half mile in length. 



Photographs taken during the Alummaut dive 

 show that densities of five scallops per square 

 foot occur on some beds (Taylor, 1967). A 

 minimum of 285 square miles of scallop bottom 

 was found during the survey and varied densi- 

 ties occurred over that area. If 10% (28 square 



miles) supported densities approximating those 

 found by the Alumiuaut, then an estimated 

 standing crop of 3,892,000,000 scallops existed in 

 1967-68. This figure is derived from the fol- 

 lowing: 28 X 27.8 million (no. ft= /mile') X 5. 

 That population could easily support 10 boats 

 fishing at a rate of 1,500 lb day. At an average 

 of 70 scallops per pound, 10 boats would take a 

 total of 31,500,000 scallops per month at the 

 above rate. This is approximately I'^'r of the 

 estimated standing crop. 



Recent explorations with RUFAS indicate 

 that densities estimated from the Ahiminaut 

 cruise may be ultraconservative (Cummins et 

 al., see footnote 5). Films from the RUFAS 

 survey indicate that scallops may reach densities 

 as high as 10 or more per square foot providing 

 a standing crop is considerably above that given 

 previously. Findings from the RUFAS survey 

 will be published in the near future by personnel 

 from the Exploratory Fishing Station in Bruns- 

 wick, Ga. 



Yearly variations in distribution and abun- 

 dance may at first glance be discouraging to a 

 fisheiy. However, the remarkable opportunity 

 to predict each fall fishery exists because dis- 

 tributional and abundance jjatterns are estab- 

 lished in spring or early summer — perhaps as 

 early as May or June. Population assessment 

 at that time would provide estimates on the 

 standing crop and determine the success of a 

 fall fishery some 4 or 5 months prior to its onset. 

 The authors tested this hypothesis in the 

 spring and summer of 1970 using the RUFAS 

 vehicle. 



SUMMARY AND CONCLUSIONS 



The survey data show that calico scallops have 

 a short life span of 18 to 24 months. Sjiawning 

 occurs after a 7- to 9-month sexual maturation 

 period in early spring. Some protracted spawn- 

 ing was noted for localized areas. Although 

 growth rates were not determined for sizes 

 smaller than about 5 mm, the estimated growth 

 curve between 5 mm and senility (75 to 80 mm) 

 is sigmoid, rapidly increasing to about 50 mm 

 and then decreasing to death. 



408 



