days absent so that alternative specifications 

 of the equations could not be run. Days absent, 

 however, was not as important a variable in 

 this fishery as in the trawl fishery. The reason 

 for this may be that there is a basic difference 

 in the way the vessels in these fisheries operate. 

 The trawl fishery is a wetfish fishery so that the 

 vessels are constrained by time when they go 

 to sea, whereas the tuna boats are freezers, 

 and they stay at sea until their holds are filled; 

 hence, there is a different connotation to the 

 fishing time variable. 



The vessel size variables used in the final 

 equation were capacity and horsepower. Capacity 

 was the more important of these variables. This 

 indicates that the industry is justified in using 

 capacity as an index of a vessel's fishing power. 

 Several tests were run with gi'oss tonnage in 

 place of capacity, but the results were not as 

 good, although they were still meaningful. 



Horsepower makes an important independent 

 contribution to explanation of output. The con- 

 tribution of horsepower to the increase in the 

 coefficient of determination, though small at 

 any point in time, may be important in the 

 maintenance of an effort series as the com- 

 position of a fleet changes. 



Tests were run using crew size but results 

 were poor, presumably because there is such 

 small variation of crew in this fleet (12-14 

 men). In addition, crew size is defined by custom 

 and union contract according to the capacity 

 of a vessel, hence crew size does not give 

 additional information. 



The tuna fleet has two main bases: Puerto 

 Rico and southern California. To test whether 

 vessels located in Puerto Rico were more pro- 

 ductive, a dummy variable was created that took 

 the value one if a vessel's home port was Puerto 

 Rico and was zero otherwise. The results were 

 generally positive but not statistically signifi- 

 cant. This indicates that the fleet's shift toward 

 Puerto Rico is because of reasons other than 

 catching more fish (see Appendix Table 2). 



Tests to see if the age of the vessels could 

 explain some of the variation in output generally 

 showed that older vessels were less productive 

 in the linear forms of the equations. When the 

 logarithmic transformations were made, the 

 age variable became nonsignificant; hence, it 

 is not included in the final equations. 



The original purse seine fleet consisted of 



vessels converted from either military craft 

 or bait boats. There has been a major expansion 

 of this fleet since 1963 with vessels designed 

 specifically for purse seining. To see if these 

 vessels were superior in a way that could not 

 be accounted for by either horsepower or capaci- 

 ty, a dummy variable was created that took the 

 value one if a vessel were built after 1962 and 

 zero if built before 1963. It was hoped that 

 this would pick up technological change. The 

 results using this were generally positive and 

 sometimes statistically significant, but the 

 dummy variable is not included in the final 

 equations because it was not statistically sig- 

 nificant in them. 



We conclude that for the tuna fishery the 

 best production function is given by Table 3, 

 Problem 3, where weighted total pounds is the 

 dependent variable, days absent is the measure 

 of fishing time, and capacity and horsepower 

 are measures of the capital used. 



CONCLUSION 



The basic assumption underlying this work 

 is that a production function can adequately 

 describe the productivity of vessels. The stability 

 of the estimates arrived at using this technique 

 rely most upon the constant patterns of economic 

 behavior. The coefficients would have to be 

 re-estimated if the ratio of days absent to days 

 fishing changed significantly in a fleet, or if 

 the form of regulation changed the pattern of 

 fishing. Pattern changes are undoubtedly taking 

 place in the tuna fishery where the quota system 

 of regulation makes it imperative for vessels 

 to leave the home port the day the season opens 

 and to fish as intensively as possible. This makes 

 vessel utilization in the first part of the year 

 much higher than it has been historically or 

 would be without the quota regulation system. 

 It has probably had the effect of changing the 

 effective productivity markedly by putting a 

 premium upon running speed. 



Once an estimating equation has been deter- 

 mined suitable, it should be used as long as 

 possible, say up to 10 years to provide continuity. 

 Checks should be made periodically to see if 

 the equation being used is still appropriate. 



The technique of using dummy variables to 



51 



