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Trends in Catch and Effort 



Annual catches of skipjack by the eastern Pacific tuna fleet 

 fluctuate greatly, and there are no obvious trends. During the 1961 to 

 1979 period, the catches ranged from 33,300 mt in 1972 to 170,300 mt in 

 1978 (Table 1). The mean annual catch during the 1976 to 1979 period was 

 129,200 mt: an increase of 76% over the mean catch for the previous 12 

 years. 



The size composition of skipjack tuna samples taken in the lATTC's 

 yellowfin regulatory area during 1967 through 1980 is shown in Figure 2. 

 Differences among years are apparent; the incidence of fish larger than 55 

 cm was highest in 1971-73 and lowest in 1978-79. 



In the eastern Pacific most of the skipjack is caught within 600 

 nautical miles of land, off the coasts of Central America and northern 

 South America (Figure 3). During the 1960's much of the skipjack was 

 caught in waters off Baja California and Ecuador, and in the Gulf of 

 Guayaquil; in the 1970 's the largest catches were usually made offshore 

 between 5° and 15° N latitude and in the Panama Bight. During the past few 

 years, however, the center of abundance in the southern area seems to have 

 shifted to waters off Colombia and Central America. During 1975 to 1979, 

 an average of 73X of the skipjack caught east of 150° W longitude were 

 taken within 200 nautical miles of land. Most of the catch comes from the 

 area south of 15° N latitude (Figure 4). 



In general there is a little seasonal variation in the skipjack 

 fisheries in the equatorial areas. The greater the distance from the 

 equator, the more the catches peak in the summer months. In the Panama 

 Bight skipjack catches are low from August to March and peak from April to 

 July. Near Ecuador they are low from January to April, with a major peak 

 from May to July and a minor one in October and November. 



The numbers of vessels fishing for tropical tunas in the eastern 

 Pacific since 1961 and their total carrrying capacity are given in Table 2. 

 The number of larger purse seiners (> 401 short tons of carrying capacity) 

 increased gradually from 9 in 1961 to 24 in 1967; it then increased 

 rapidly, reaching 158 in 1976, and remained near this level through 1979. 

 The number of baitboats remained fairly constant, between 91 and 116, from 

 1961 to 1976, but decreased rapidly to 45 by 1979. The total carrying 

 capacity of all gears in the fleet increased from 36,600 mt in 1961 to 

 169,000 mt in 1979. The 1979 fleet consisted of 97.7% purse seiners, 2.1% 

 baitboats, 0.2% bolicheras (small purse seiners with < 50 short tons of 

 carrying capacity), and less than 0.1% jigboats in terms of capacity; in 

 terms of numbers, 80.7% were purse seiners, 14.0% baitboats, 4.4% 

 bolicheras, and 0.9% jigboats. 



In the eastern Pacific the logged effort by purse seiners remained 

 fairly constant between 1961 and 1969, ranging from 14,800 to 19,700 days 

 of fishing, standardized to Class-3 vessels (101-200 short tons of carrying 



