384 



STATISTICAL SURVEY PROCEDURE 



Incidental Catch --The term "incidental catch" refers to the catch of certain species by 

 a type of gear which ordinarily does not capture such species. 



Percentages - -Percentages are usually shown as whole numbers . Fractions of percents 

 are dropped if less than five-tenths, anJ the percentage is raised to the next higher integer if the 

 fraction is greater than five-tenths. If the fraction is exactly five-tenths, odd integers are raised 

 to the next even figure while even integers remain unchanged. 



Converting - -Many of the figures shown in the summary tables published herewith have 

 converted to thousands of pounds or thousands of dollars. In making these conversions the sum 

 of the items in a table is raised or lowered to the nearest thousand in accordance with standard 

 statistical procedures. The individual items are adjusted to conform to the total thus obtained. 



Confidential Data --The statistical data collected by thu Service are confidential, and, 

 unless specific authorization is given, are not released in a manner that would divulge private 

 enterprise . 



CONVERSION FACTORS 



It is the policy of the Service to show detailed catch figures of all products in pounds for the 

 sake of uniformity and for the purposes of comparison. This represents little difficulty in the 

 case of fish, since in very rare instances are fish reported in units of measure other than pounds. 

 For shellfish, however, the units of measure may be bushels, sacks, barrels, numbers, gallons 

 of meats, etc. So many units make standardization difficult, and when combined with the wide 

 variation in the requirements or definitions of some of these units in the various States, the prob- 

 lem becomes even more complex. 



All univalve and bivalve mollusks {except fresh-water mussel shells) are reported in pounds 

 of meats in the detailed catch tables presented in this report. In addition, there are included 

 supplementary tables for most of the sections, which give data on the production in bushels. 

 These supplementary tables also give the production in number of certain other shellfish, such as 

 crabs. There also is included in the General Review section of this report a table containing data 

 on the shell weight of univalve and bivalve mollusks taken. 



Oysters - -Probably the greatest problem in the presentation of fishery statistics in uniform 

 units of measure is in the case of oysters. Usually the production of oysters on the Atlantic and 

 Gulf Coasts is reported to NMFS personnel in bushels. Prior to the data obtained for the year 

 1930, bushels were converted to pounds of meats on the basis of a uniform yield of 7 pounds of 

 meats to the bushel. However, it was found that there was considerable variation in the yield of 

 oysters per bushel particularly in Southern States where the yield has ranged as low as half the 

 conversion factor used prior to 1930. There follows a table which gives the measures used for 

 oysters in the various States and the average yields per bushel. The statistical tables in this 

 report are based on these average yields. 



