FISHERY BULLETIN; VOL. 78, NO 4 



during peak months the forecast is within 15% of 

 the observed catch (and is usually within 8-10% of 

 the observed catch), most turning points in the 

 catch trend are predicted, and the important 

 feature of a low, flat catch during the summer 

 months or high, peaked catches are accurately 

 predicted. Moreover, the reasons for forecasts with 

 large errors appear to be related more to fisher- 

 men's decisions in face of weather and economic 

 factors, than to mispredicting the availability 

 of the fish. 



THE DATA AND 

 UNDERLYING MODEL 



The data to be analyzed are landings of skipjack 

 tuna by approximately 12 boats from Oahu during 

 1964 through 1978. The raw data consist of the 

 daily landings (each boat rarely stayed out more 

 than a day or two), broken dovm by boat, and by 

 four skipjack tuna size classes: large, medium, 

 small, and extra small. For purposes of analysis. 



the data were aggregated into monthly totals, 

 with the total number of fishing trips used as the 

 measure of fishing effort. For monthly catch and 

 effort during 1964-78 see Figures 1 and 2. 



There are several causes for the observed sea- 

 sonal variability. First, the tuna are only avail- 

 able in large numbers seasonally. Second, price 

 considerations, particularly around Christmas 

 and New Year when there is large demand, tend to 

 spur fishing even when availability is low. Third, 

 with only 12 boats fishing, if 1 or 2 boats are not 

 able to fish for a few weeks, the catch will drop 

 sharply. Finally, environmental factors, partic- 

 ularly weather (such as bad seas) will affect the 

 landings since the boats are unable to fish. 



Folklore in Hawaii has it that the catch remains 

 similar each year, no matter how many boats fish. 

 Comitini^ examined the fishery using dummy 

 variables and ordinary least squares to estimate 



'Comitini, S. 1977. An economic analysis of the state of 

 thie Hawaiian skipjack tuna fisliery. Sea Grant Tech. Rep. 

 UNIHI-SEAGRANT-TR-78-01. 46 p. 



JFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASOND 



MONTHS 



Figure l. — Level of Hawaiian skipjack tuna catch by month, 1964-78. 



888 



