CRUISE TO-66-1 

 NOVEMBER 1966 



YELLOWFIN TUNA 



SKIPJACK TUNA 



BOTH TUNA SPP. 

 — SURFACE TEMPERATURE, °C. 



I I I RED CRAB, > 40 ML./lO^M.' 



SURFACE CHLOROPHYLL, >0.1 MG./M.^ 



116° W. " 



Figure 14. — Distributions of surface temperature, surface clilorophyll o, and red crabs for cruise 



and locations of contemporaneous catches. 



28° 

 N. 



27° 



26° 



25° 



124° 



r 



22° 



109° 

 TO-66-1 



the otlier hand, the lATTC charts show that yel- 

 lowfin and skipjack tunas are sometimes sought 

 and f aptured offshore, for instance at Alijos Rocks, 

 about 150 nautical miles (278 km.) from the coast 

 (fig. 2) , and even about 1° of longitude to the west 

 of that locality. Nothing suggests that these off- 

 shore tuna are not aggregated in food-rich areas 

 of suitable temperature in the same way as the 

 inshore tuna. Furthermore, one definite record of 

 an offshore commercial tuna catch appears to be 

 associated with a tongue of food-rich water (fig. 



10). This catch was at Alijos Rocks on cruise 

 TO-59-2. The only other cruise in the present 

 series which yielded information about properties 

 at Alijos Rocks was TO-65-1 (see fig. 11, station 

 14). On that occasion, no tongue of biologically 

 rich water reached the Rocks area, concentrations 

 of chlorophyll a and red crabs were low, no tuna 

 were seen or caught while the scientific party was 

 fishing at the Rocks, and no commercial catches 

 were recorded tliere during the cruise period. 

 The other possible objection to the model of 



172 



U.S. FISH AND WILDLIFE SERVICE 



