4.42 Factors causing or affecting mortality 

 No information available. 



4.43 Factors affecting morbidity 

 No information available. 



4.44 Relation of morbidity to mortality 

 rates 



No information available. 



4.5 Dynamics of Population (as a Whole) 



There is not enough information to permit construc- 

 tion of mathematical models for prediction of catch 

 characteristics. 



4.6 The population in the Community and the 

 Ecosystem 



The species composition of the community is that of 

 the pelagic tropical and subtropical habitat. Several 

 species of billfishes and tunas are sympatric and syn- 

 topic with the blue marlin and probably compete with 

 it for food and space. Among those attaining a size 

 comparable to that of young and adult blue marlin are 

 the black marlin;, striped marlin; white marlin; 

 longbill spearfish, Tetrapturus pfluegeri; shortbill 

 spearfish, T. angustirostris; sailfish; bluefin tuna, 

 Thunnus thynnus; bigeye tuna, T. obesus; and 

 yellowfin tuna, T. albacares. In the Atlantic, the blue 

 marlin occurs with white marlin, longbill spearfish, 

 sailfish, bluefin tuna, bigeye tuna, and yellowfin tuna. 

 In the Pacific and Indian oceans, the blue marlin oc- 

 curs with black marlin, striped marlin, shortbill 

 spearfish, sailfish, bluefin tuna, bigeye tuna, and 

 yellowfin tuna. 



Because the blue marlin is a large predator it is con- 

 sidered a climax feeder after reaching the adult stage. 



See 2.22 and 3.32 for information on physical 

 features of the biotope and changes in environmental 

 factors. 



5 EXPLOITATION 



5.1 Fishing Equipment 

 5.11 Gear 



In the commercial fishery the gear in current use is 

 the conventional Japanese longline which is described 

 amply in the literature (Nakamura, 1938; Bullis 1955; 

 Captiva 1955). Off Havana, Cuba blue marlin are 

 taken commercially with palangres, a type of gear 

 similar to the longline but with only a few hooks. 



In the sport fishery, blue marlin are taken by con- 

 ventional rod and reel methods. Natural or artificial 

 baits are trolled at the surface at speeds varying from 



4 to 8 knots. Usually two to four lines are fished 

 simultaneously. Echo sounders or fish detectors are 

 not used, but bathythermographs are used to locate 

 the depth of the thermocline. Longline gear is usually 

 fished above the thermocline. 



In the sport fishery, artificial hookless wobbling 

 lines called "teasers" are trolled close behind the 

 boat. Presumably, the action of these teasers attracts 

 marlin to the bait. It is also the opinion of many 

 anglers and fishing guides that the size of the boat and 

 degree of vibration of the motors are instrumental in 

 attracting the marlin. Nakamura and Rivas (1972) 

 analyzed the effect of boat size in the northern Gulf of 

 Mexico but could not reach any definite conclusions. 



5.12 Boats 



Japanese-type longliners are used in the commer- 

 cial fishery with certain modifications in size and 

 equipment according to locality. The Cuban palangre 

 referred to above is tended from small boats powered 

 by sail and/or motors (inboard or outboard). 



5.2 Fishing Areas 



5.21 General geographical distribution 



The geographic distribution of commercial fishing 

 areas corresponds to the geographic distribution of the 

 species as discussed in 2.1. Sport fishing areas are 

 limited to only a few countries. 



In the United States, sportsmen fish for blue marlin 

 off southern Texas, Louisiana, Alabama, 

 northwestern and southeastern Florida, North 

 Carolina, southern California, and Hawaii. Active 

 sport fishing is also conducted off Puerto Rico and the 

 Virgin Islands. 



In the Bahama Islands, an active sport fishery for 

 blue marlin is conducted off Bimini, Cat Cay, Cay 

 Sal, Grand Bahama, and Walkers Cay. Many blue 

 marlin are caught in the Tongue of the Ocean off the 

 east coast of Andros, the largest island of the group. 



In Mexico, most of the blue marlin sport fishery oc- 

 curs along the Pacific coast. Acapulco, Mazatlan, and 

 the southern tip of Baja California are the most active 

 areas; however, blue marlin are not caught in large 

 numbers in these areas. 



In Central and South America most of the sport 

 fishing for blue marlin takes place along the Pacific 

 coast. There is an active sport fishery off Pinas Bay, 

 Panama and another off Ecuador. Sport fishing for 

 blue marlin in Venezuela is conducted mostly off La 

 Guaira. 



In the central Pacific, blue marlin are commonly 

 taken around the Hawaiian Islands and Tahiti. 



In Africa, blue marlin have been caught by 

 sportsmen off Senegal and the Ivory Coast. A more ac- 

 tive sport fishery, however, is conducted along the 

 coast of South Africa. 



In the Indian Ocean, blue marlin are taken by 



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