for netting. That these situations make up 

 a good part of the vast majority of trips 

 points to the need for more knowledge about 

 the fish and their ocean environment. Such 

 information can come from studies of ocea- 

 nography and biology. 



Study of the geographic distribution 

 of tuna catches from logbook records of 

 fishing vessels shows that tunas are not 

 evenly distributed over the Eastern Pacific 

 but tend to concentrate in certain general 

 areas. The tropical tunas congregate off 

 Baja California, the Revillagigedo Islands, 

 the Gulf of Tehuantepec, Central America, 

 northern South America, and the Galapagos 

 Islands. The concentration of the fish in 

 these general regions is remarkedly con- 

 sistent. However, notable variations do 

 occur from year to year and season to 

 season in the location of the center of 

 good fishing within these general regions, 

 and wide variations also occur in the 

 relative abundance of the tunas within 

 these localities. This also occurs in the 

 broad area of the albacore and bluefin 

 fishery. These variations are responsible 

 for the time the fishermen waste scouting. 



Oceanographic studies by Scripps 

 Institution of Oceanography, the Inter- 

 American Tropical Tuna Commission and the 

 Bureau of Commercial Fisheries during the 

 past several years have provided a rather 

 good understanding of the general circula- 

 tion of the Eastern Pacific Ccean and the 

 reason for the concentration of tunas in 

 the particular regions mentioned. It is 

 in these general areas, as might be ex- 

 pected, that the tunas encounter the best 

 feeding conditions. The regions include 

 features of the ocean circulation which 

 bring nutrient-rich deeper waters into the 

 euphotic zone or layer of light penetration 

 where production of phytoplankton is stim- 

 ulated. This in turn leads to large crops 

 of forage organisms and finally to con- 

 centrations of tuna. 



Basic productivity is highest and is 

 accompanied by tuna concentrations where 

 upwelling occurs, as off Baja California 

 and Peru, in the vicinity of thermal anti- 

 clines (regions where a strongly developed 

 thermocline rises close to the surface) as 

 off Costa Rica and Panama Bight, along 

 transitions between water masses, and where 

 vertical mixing is particularly strong. 

 However, we have also noted that towards 



the extreme ranges of the tropical tuna 

 fishery, aggregations are more seasonal, 

 less persistent throughout the year, and 

 appear to be related in a general way to 

 the distribution of temperature more than 

 food. The distribution of albacore is 

 likewise affected by temperature, although 

 there are probably other properties con- 

 trolling or affecting its distribution. 



As yet oceanography has not demon- 

 strated anything new to the fishermen about 

 the distribution of tuna and scientists are 

 not yet able to predict where fish will be 

 most available at any particular time. The 

 tasks of research, therefore, are: (l) to 

 determine what features stimulate organic 

 production, (2) to elucidate the processes 

 by which marine life is supported, (3) to 

 discover the causes of temporal variations 

 in these features and processes, and (U) to 

 relate the latter variations to the tuna's 

 distribution and abundance. When the 

 causes and mechanisms of changes in tuna 

 availability are better understood, scien- 

 tists will better be able to assist 

 fishermen by predicting areas of tuna 

 concentration. 



An investigation with such a goal is 

 now underway at Scripps Institution of 

 Oceanography. It is devoted to the area 

 of the tropical tuna fishery and is financed 

 by contract with the Bureau of Commercial 

 Fisheries. It is being augmented by allied 

 research programs at Scripps Institution 

 and by the oceanographic studies of the 

 Inter-American Tropical Tuna Commission. 

 Its ultimate objective - accurately fore- 

 casting changes in tuna availability - will 

 not be attained for some years. However, 

 it should not be long before this program 

 provides useful information which will 

 assist fishermen in locating fish more 

 rapidly than is now possible on the basis 

 of their own knowledge and information. 



What benefits are the albacore fisher- 

 men receiving from oceanographic research? 

 The California Cooperative Oceanic Fishery 

 Investigation (CCOFI) has made a tremendous 

 number of observations in the area of the 

 albacore fishery during the course of its 

 studies of the California sardine, anchovy 

 and mackerels. Mr. Clemens utilized data 

 collected by CCOFI in his study of albacore 

 distribution as it relates to temperature 

 and for predicting occurrence. It is 

 reasonable to assume that much of the 



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