25 



15 



s' V^ 



7< 



20 

 10 



% 



10 



M 



20 

 10 



110 



100 



90 



Figure 6. — Subareas selected for examination of striped 

 marlin size composition. 



From June, the area of good fishing off the coast 

 from Acapulco to Mazatlan begins to expand sea- 

 ward to about long. 115°W. A small, localized area 

 of good fishing is also located at the entrance of the 

 Gulf of California. By July, the area of good fishing 

 has expanded seaward and along the coast and by 

 August the good fishing grounds form a broad and 

 continuous band throughout the waters of Baja 

 California. The seaward expansion of good fishing 

 continues into September and extends as far west as 

 long. 1 17 C W. This shift in good fishing into the 

 offshore waters, however, is accompanied by a de- 

 cline in catch rates in the more coastal waters. In 

 October, the fishing ground becomes narrow and is 

 located farther east. This phenomenon coincides 



Sub-area S' 



" 111 

 N. 394 



N. 5,640 



11 19 27 35 43 51 59 67 |<g 11 19 27 35 43 51 59 67, 



Sub-area M' 



N. 1,262 



11 19 27 35 43 51 59 67, 



Figure 7. — Weight-frequency distributions of striped mar- 

 lin in subareas S' and M' shown by quarters of the year. 



with the decreasing trend in catch rates after Oc- 

 tober in subarea SW as shown in Figure 2. In 

 November, the area of good fishing is narrower 

 than in October and is divided into two areas; one is 



100 120 

 Longitude 



Figure 8. — Monthly thermocline topography for the eastern tropical Pacific 

 Ocean (after Robinson and Bauer 1971). The numbers on the contour lines rep- 

 resent the depth to the top of the thermocline in hundreds of feet. 



305 



