BEARDSLEY and CONSER: AN ANALYSIS OF CATCH AND EFFORT DATA 



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NORTHERN GULF OF MEXICO 



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WESTERN GULF OF MEXICO 



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1971 



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'72 



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'74 



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'75 



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'76 



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 '77 



'78 



FIGURE 15. — CPUE, in number offish hooked per hour of fishing, 

 from the recreational fishery for sailfish in the northern and 

 western Gulf of Mexico, 1971-78. 



Although trends in CPUE for blue marlin in the 

 Gulf of Mexico and in the Atlantic are similar for 

 some years, the detailed analysis of data from the 

 gulf indicates that caution should be exercised in 

 interpreting catch and effort statistics for blue 

 marlin. In the gulf, little agreement or consistency 

 could be found among the three data sources, and 

 it appears that the basic catch model is not appro- 

 priate. Some of the competition effect models dis- 

 cussed by Rothschild (1977), in which catchability 

 decreases as effort increases, may be more appro- 

 priate for these data. Rothschild et al. (1970) also 

 demonstrated that the fishing power of various 

 gear types, relative to one another, can change as a 

 function of stock abundance. Declining blue mar- 

 lin abundance during the analysis period (Conser 

 and Beardsley^; Kikawa and Honma^) may have 

 caused this situation to occur in the northern gulf 

 It must be pointed out, however, that white marlin 

 abundance was declining during the same period, 

 but this change in relative fishing power did not 

 occur. 



^Conser, R. J., and G. L. Beardsley. 1979. An assessment of 

 the status of stocks of blue marlin, Makaira nigricans, and white 

 marlin, Tetrapturus albidus, in the Atlantic Ocean. Collect. 

 Vol. Sci. Pap. 8(2):461-489. Int. Comm. Conserv. Atl. Tunas, Gen- 

 eral Mola 17, Madrid, Spain. 



•^Kikawa, S., and M.Honma. 1979. Status ofwhite and blue 

 marlins caught by the longline fisheries in the North Atlantic 

 Ocean. Collect. Vol. Sci. Pap. 8(2):513-515. Int. Comm. Conserv. 

 Atl. Ttmas, General Mola 17, Madrid, Spain. 



In the analysis of Gulf of Mexico data, the pro- 

 portionality of catchability over time for the vari- 

 ous data sets was examined using correlation 

 analysis of the CPUE's, but the available data did 

 not allow testing the constancy of catchability over 

 time. The results show that the catchability was 

 proportional for all data sets with white marlin 

 and sailfish. Therefore, if any change in catchabil- 

 ity occurred, it would have been in the same direc- 

 tion for all data sets. This appears unlikely, how- 

 ever, since any change in catchability for the 

 recreational fishery would probably have been an 

 increase due to improvements in gear and equip- 

 ment, but an increase in catchability for the 

 longline fishery is unlikely because the fishery 

 has been targeting more on bluefin tuna in recent 

 years, and joint occurrences of billfishes and the 

 tropical tunas tend to be more frequent than joint 

 occurrences of billfishes and the temperate tunas, 

 i.e., bluefin (Fox''). It appears reasonable, there- 

 fore, to assume that catchability has been constant 

 for white marlin and sailfish, but this assumption 

 would be tenuous for blue marlin in the northern 

 Gulf of Mexico. 



ACKNOWLEDGMENTS 



We express our sincere appreciation to all.of the 

 anglers, captains, and crew members that partici- 

 pate in the recreational fishery for billfishes for 

 their patience and courtesy in providing the data 

 that form the basis for this report. We also ac- 

 knowledge with gratitude the support of the many 

 charterboat associations, big-game fishing clubs, 

 and tournament committees throughout our sam- 

 pling area. Many of these groups made special 

 arrangements for our samplers so that they could 

 conduct their interviews. We also acknowledge the 

 cooperation of the Government of the Bahamas 

 and the Commonwealth of Puerto Rico and ex- 

 press our thanks for allowing us to sample in their 

 areas. We particularly thank the Florida Depart- 

 ment of Natural Resources, the Georgia Depart- 

 ment of Natural Resources, and the South 

 Carolina Marine Resources Department for sam- 

 pling tournaments in their respective states and 

 providing us with the data. We thank Dade 

 Thornton for his continuing support and assis- 

 tance through the years. This research was sup- 



^Fox, W. W. 1971. Temporal-spatial relationships among 

 tunas and billfishes based on the Japanese longline fishery in the 

 Atlantic Ocean, 1956-65. Univ. Miami Sea Grant Program, Sea 

 Grant Tech. Bull. 12, 78 p. 



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