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Figure 12.— Catch and temperature data by block area for Pacific barracuda 

 caught off southern California. 



PART n— SEA SURFACE TEMPERATURE AND ITS 

 RELATION TO THE CATCH OF THE PELAGIC 



MIGRATORY SPECIES OF YELLOWTAIL, 



PACIFIC BONITO, AND PACD7IC BARRACUDA 



OFF SAN DffiGO 



The airborne temperature surveys described in Part I were con- 

 ducted monthly over a large geographical area. The survey track 

 lines were not specifically designed to cross the geographical centers 

 of sportfishing. Sportfishing effort is concentrated in localized areas 

 along the southern California coast and around the offshore islands 



(Squire and Smith 1977). Two of the important marine sportfishing 

 areas in southern California are located off San Diego. The Coronado 

 Islands, located southwest of San Diego in Mexico, are in block area 

 916, a high catch area for yellowtail by the sportfishing fleet. The 

 second high catch area for yellowtail is block area 860 off Point La 

 Jolla. Block area 860 is also the leading catch area for the Pacific bar- 

 racuda and Pacific bonito, while block area 916 is the third-ranking 

 catch area for Pacific bonito. 



In order to examine the relation of temperature changes to catch, a 

 series of weekly airborne surveys, using an infrared radiometer to 

 measure the surface temperature, were conducted over a 3-yr period, 

 April through October 1972-74. The survey track lines (Fig. 20) 

 were plotted to pass over the sportfishing area directly off Point La 

 Jolla, and the heavily fished kelp bed areas off Pacific Beach and 

 Point Loma. The flight track also passed over the kelp bed located 

 nearshore just south of the United States-Mexico border These 

 coastal kelp beds are important fishing areas for sportfishing. The 

 survey track also passed near the north end of the North Coronado 

 Islands, an intensively fished area, and over the kelp bed area south 

 of the south Coronado Island (South Kelp). Track lines were flown 

 out to 15 nmi offshore to obtain sufficient data to allow the drawing 

 of isotherm charts. The charts depicted the temperature patterns 

 observed within the coastal area off Torrey Pines State Beach Park, to 

 about 8 nmi below the United States-Mexico border, and to about 15 

 nmi offshore. Temperatures were calibrated to a "ground truth" mea- 

 surement, obtained by a simultaneous sea surface temperature mea- 

 surement made while passing directly over the U.S. Navy Undersea 

 Center (NUC) Oceanographic Tower located about 1.5 nmi offshore 

 from Mission Beach. The results of temperature observations made 

 during the 90 surveys over the 320 nmi survey track conducted dur- 

 ing the 3-yr period, and a review of isotherm patterns observed, were 

 published by Squire (1978). 



Results 



The average temperatures by month obtained over the Naval 

 Oceanographic Tower (NUC) during the 1972-74 series of surveys 

 were similar to those observed in the same monthly time period dur- 

 ing the U.S. Coast Guard surveys in 1963-68 (Part I). The NUC 

 tower was used as a "ground truth" calibration point during both sur- 

 veys. Data pertaining to catch in numbers offish, in numbers offish 

 per day, and effort in numbers of anglers per day, were obtained 

 through the cooperation of the CF&G for the 31 wk from April 

 through October 1972-74. 



The following is a general description of the temperature patterns 

 from the areas where the fish catch and angler effort data for this 

 study were taken. 



The area to the north and northwest of Point La Jolla (blocks 842, 

 843) usually has temperatures that are greater than those found in 

 other locations in the survey area. An area of upwelling with gener- 

 ally lower temperatures than those observed to the northwest occurs 

 from off Point La Jolla to Pacific Beach, continuing offshore to the 

 southwest (blocks 860, 861). This coastal upwelling area is also indi- 

 cated by a temperature decline west of the NUC tower (block 860). 

 The kelp bed area west of Point Loma (block 860) appears to be 

 slightly warmer than the area to the north off Pacific Beach. South of 

 Point Loma and about the San Diego harbor entrance channel (block 

 878), a significant drop in temperature is usually observed. Tempera- 

 tures south of Point Loma peninsula tend to remain lower than those 

 found to the west, and remain low to the southeast of Point Loma and 

 off the Coronado Strand, increasing slightly inshore off Imperial 

 Beach. 



