Table 1. — Number of California baitboats by size 

 category, based on capacity tonnage, 

 1932-58. 



fur 



0-50 

 ton* cap. 



51-100 

 tons cap 



101-200 

 ton i cap. 



»l-}00 

 torn cap. 



301-400 

 tona cap. 



Ovar WO 

 tons cap. 



Total 



** Includaa Puarto Rico Flaat 



baitboats have been and are being converted 

 to purse-seiners. 



We have attempted to combine the data 

 of numbers of vessels of both types, and of 

 the various sizes, by computing an index of 

 potential fishing power of the fleet in 

 terms of the equivalent number of Class k 

 tuna clippers. The methods of computing 

 this index are outlined in the 1957 Annual 

 Report of the Commission. The potential 

 fishing power of the U. S. fleet for the 

 years 1932-58 is shown in figure 3- It may 

 be seen that after a rapid rise, following 

 the end of World War II, to a peak in 1951, 

 there, has been a fairly steady decline in 

 the Ashing power through 1958. 



EFFECTS OF FISHING ON THE 

 STOCK AND YIELD 



One of the essential tasks of the Com- 

 mission is the measurement of the changes 



in abundance of each of the 

 tropical tuna species, as re- 

 flected by catch-per -day's 

 fishing corrected to a vessel 

 of standard size, and the study 

 of the relationships of changes 

 in abundance to changes in fish- 

 ing effort and other factors. 

 Methods of compiling and comput- 

 ing the pertinent statistics 

 are given in detail in the An- 

 nual Reports of the Commission 

 and various research papers of 

 our Bulletin series. 



In figure h, are shown, 

 for the years 193U-57, the 

 total catch of skipjack from 

 the Eastern Tropical Pacific, 

 together with the catch-per- 

 day's fishing, computed from 

 the logbook records of tuna 

 clippers, and also the calcu- 

 lated fishing intensity in 

 terms of thousands of days fish- 

 ing by a Class 3 tuna clipper. 

 It may be seen from this figure 

 that the catch-per-day's fish- 

 ing, which measures the abun- 

 dance of this species as the 

 fishermen see it, fluctuates 

 rather widely from year to 

 year. Part of this variation 

 reflects real changes in the 

 abundance of the stock, but a 

 large proportion is believed to be due to 

 variations in availability of the fish to 

 the fishermen, in response to variations in 

 environmental factors. 



Figure 3.— Potential fishing power, U. S, 

 fleet (vessels fishing tropical tunas), 



38 



