320 U. S. BUREAU or FISHERIES 



titles of fish frozen, for the years from 1920 to 1925, inclusive, and 

 from 1928 to 1933, inclusive. 



Sponge market, Tarpon Springs. — A large proportion of the total 

 output of sponges in Florida is handled through the sponge exchange 

 at Tarpon Springs. In view of this, the Bureau has obtained from a 

 representative of the exchange annual statistics of the quantity and 

 value of the sponges, by variety classification, handled through it 

 annually. Statistics of the quantity of sponges handled through the 

 exchange are not published in bulletin form, but a summary of the 

 year's activities is published in the annual reports of this Division. 

 Statistics of the transactions on the sponge exchange are available for 

 1913, 1914, and for the years from 1917 to 1933, inclusive. 



Foreign fishery trade. — Statistics of the foreign fishery trade are 

 obtained from compilations made by the Bureau of Foreign and 

 Domestic Commerce, Department of Commerce. Statistics of all 

 known fishery products imported or exported have been assembled 

 in one table and published annually in the reports of the Division in 

 recent years. For earlier years they are available in the reports of 

 the Bureau of Foreign and Domestic Commerce, the Bureau of Sta- 

 tistics, the Department of Commerce and Labor, and the Treasury 

 Department. 



PRACTICES AND TERMS 



Certain practices and terms of importance used in the compilation 

 of fishery statistics are explained below. 



Days absent. — In computing "days absent" for vessels landing fares 

 at the various ports, the day of departure and the day of arrival are 

 included; thus, a vessel leaving port on the 8th of the month and 

 returning on the 15th of the month will be shown as being absent 

 8 days. 



Operating units. — Operating units as referred to in this document 

 include persons engaged in the fisheries and fishing craft and gear 

 employed. 



Vessel. — The term ''vessel" refers to a craft having a capacity of 

 5 net tons or more. 



Boat. — The term "boat" refers to a craft having a capacity of less 

 than 5 net tons. 



Incidental catch. — The term "incidental catch" refers to the catch 

 of certain species by a type of gear wliich ordinarily does not capture 

 such species. 



Percentages. — Percentages are usually shown as whole numbers. 

 Fractions of percents are dropped if less than five-tenths, and the 

 percentage is raised to the next higher integer if the fraction is greater 

 than five-tenths. If the fraction is exactly five-tenths, the integer is 

 raised or lowered to make it an even number. 



Converting.- — Many of the figures shown in the statistical tables 

 published herewith have been reduced to thousands of pounds or 

 dollars. In maldng these conversions the largest number from which 

 a group of items is computed is raised or lowered to the nearest 

 thousands place. If the number ends in an even 500, the thousands 

 integer is raised or lowered to make it an even number. The indi- 

 vidual items are changed to conform to the total thus obtained. 



Confidential data. — The statistical data collected by the Division are 

 confidential and are not released except by approval of the Washington 



