way. Complete absence of a negative factor 

 refers to optimal conditions, and therefore, is 

 designated zero, wliile the degrees by which the 

 factor adversely affects an oyster population are 

 assigned the numbers diminishing from nine, 

 for 90 percent of negative influence, to one. 

 which denotes 10 percent or less of harmful effect. 

 The zero value of a positive and 10 value of a 

 negative factor are omitted because under the 

 proposed system such values denote complete 

 unsuitability of environment for the existence of 

 an oyster population. 



A combination of environmental conditions 

 which determine the producti\'ity of an oyster 

 bottom is summarized in simple tabular form by 

 listing in two separate columns all positive ( + ) 

 and all negative ( — ) factors and assigning to them 

 their rank. As an example of the method, the 

 data for one of the highly productive areas in the 

 northern Cape Cod area, where observations were 

 made for several years, are presented in table 46. 

 In this area, which approaches ideal conditions, 

 the presence of predators is the only serious 

 problem. 



The overall evaluation is inade by summing up 

 all positive factors, 2 f"^ and all negative factors, 

 2 f" and by deducting the sum of the negative 

 factors from the sum of the positive. Under this 

 system the highest score of 50 refers to a theoreti- 

 cal situation where all positive factors are optimal 

 and negative factors are absent. The low score 

 of 10 and less refers to marginal conditions. 

 Tabulation of factors is of great practical ad- 

 vantage because it shows at a glance the causes of 

 low productivity and how it can be improved. 

 The following tabulation shows the scores that 

 in my opinion apply to various degrees of pro- 

 ductiveness of oyster bottoms: 



Excellent 41-50 



Good 31-40 



Average 21-30 



Poor 11-20 



Marginal 10 and less. 



Table 46. — Evaluation oj the productiveness of an oyster 

 ground in the northern part of Cape Cod 



Note. — Overall score 45-7=38; in negative score indicates absence of 



a factor. 



In its present form, the method obviously over- 

 simplifies the problem because it considers all the 

 factors as equally significant, which may not be 

 true. The present lack of understanding of the 

 interaction within a complex ecological system 

 bars expression of this interrelation in a more 

 precise form. Growing interest in studies of the 

 sea and its resources, however, gives promise of 

 rapid progress in determining the intricate rela- 

 tionships among the principal factors that govern 

 the prosperity of marine populations. The result- 

 ing knowledge will pro\'ide the basic data for 

 designing effective methods of utilization and 

 conservation of the renewable resources of the sea. 



BIBLIOGRAPHY 



Abbott, R. Tucker. 



1954. American seashells. D. Van Nostrand Co., 

 Inc., New York, 541 pp. 

 Agostini, Angela. 



1929. Sulle alghe perforanti la conchiglia di Ostrea 

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 Andrews, Ethan A. (editor). 



1907. A new Latin dictionary, founded on the trans- 

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 Andrews, E. A. 



1915. Distribution of Folliculina in 1914. Biological 



Bulletin, vol. 29, No. 6, pp. 373-380. 

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 Andrews, Jay D., John L. Wood, and H. Dickson 



HOESE. 



1962. Oyster mortality studies in Virginia: 111. 

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 Barnes, H. 



1957. Processes of restoration and synchronization 

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