Notes on the Tracking of the Pacific Blue Marlin, 



Makaira nigricans 



HEENY S. H. YUEN, ANDREW E. DIZON. and JAMES H. UCHIYAMA' 



ABSTRACT 



In July of 1971 and 1972 five Pacific blue marlin, Makaira nigricans, were tagged with temperature 

 sensing, ultrasonic transmitters off the west coast of Hawaii. These were tracked for durations up to 22 V2 

 h. The paths of three showed movement in a northerly direction. The other two showed no movement. 

 Average swimming speed ranged from 2.2 km/h to 3.4 km/h for the three fish tracked. Swimming depths 

 differed considerably among the three. 



The Pacific blue marlin, Makaira nigricans, 

 found off the Kona coast on the west side of the 

 island of Hawaii has attracted sport fishermen from 

 all over the world. Veteran anglers of that area usu- 

 ally fish where the bottom slopes steeply from 200 

 to 2,000 m; but movement patterns of this prized 

 fish, if patterns do indeed exist, are unknown. 



The Honolulu Laboratory of the National Marine 

 Fisheries Service initiated a project in 1971 to study 

 the movements of the blue marlin using a fish tag 

 that transmitted ultrasonic pulses. The research 

 ship, Charles H . Gilbert, tracked one blue marlin 

 during 13-16 July 1971, and four during 24-29 July 

 1972. Fish were tracked for periods ranging from 1 

 to TlVi h. Path, depth, and speed of swimming are 

 reported. 



MATERIALS AND METHODS 



Transmitter and Receiving Equipment 



The basic unit of the system is the ultrasonic tag. 

 The tag, cylindrical with faired ends, measures 16.5 

 cmlongand 1.8 cm in diameter (Fig. la). Itproduces 

 a 50 kHz carrier signal with a pulse rate that is a 

 function of the surrounding water temperature. Es- 

 timation of depth offish is then possible. The tags 

 have a temperature range of 7°-27°C, an active life of 

 10 days, and a reception range of about 1 .2 km with 

 the equipment aboard Charles H. Gilbert. 



The tags are attached to the fish with a leader of 

 fine monel wire rope (0.7 mm diameter). The 25-cm 

 leader is embedded at one end of the tag and crimped 

 to an anchor plate of curved, stainless steel (Fig. lb). 

 The plate is 7.4 by 1.8 cm with a sharpened end. A 

 specially tooled rod at the end of 2Vi m pole (Fig. Ic) 

 is used to force the anchor plate into the back of the 

 marlin. The drag of the tag and the curvature of the 

 plate move the plate into position under the skin. 

 The toughness of the skin holds the plate in place. 



Ultrasonic signals are received via a hydrophone 

 (Honeywell, model HX-74C^) mounted in a well in 

 the hull oi Charles H. Gilbert and a low-frequency 

 receiver (Lawson) mounted on the bridge. Pulse fre- 

 quency is determined by visually displaying output 

 signals on a storage oscilloscope (Tektronix, model 

 564). Sensitivity of the hydrophone to 50 kHz trans- 

 mission is minus 70 db volt/microbar. The cone- 

 shaped beam of the hydrophone has a width of 25° at 

 the minus 3 db level. The hydrophone can be rotated 

 horizontally 125° on both sides of the bow and verti- 

 cally 90° by electric scan motors controlled by the 

 tracker on the bridge. 



Capture and Tagging of Blue Marlin 



Bart Miller and his sport fishing boat, Christel, 

 (Kona, Hawaii) were engaged to catch and tag mar- 

 lins. Fish were caught by trolling. As soon as a 

 marlin struck, the line was pulled in by hand to bring 



' NOAA, National Marine Fisheries Service, Southwest 

 Fisheries Center, Honolulu Laboratory, Honolulu, HI 96812. 



' Reference to trade names in this publication does not imply 

 endorsement of commercial products by the National Marine 

 Fisheries Service. 



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