398 



Fishery Bulletin 88(2). 1990 



10 CM 



TRANSMITTER 



I^-- 



Figure 1 



Tag attachment system for Pacific blue marlin. A stainless steel ar- 

 rowhead, with downcurved tines and central notch to accommodate 

 the prong of the applicator pole, is attached to the transmitter body 

 with a 10-cm length of 130-lb test monofilament crimped in two 

 places. 



used by Yuen et al. (1974) and Carey and Robison 

 (1981). The arrowhead fitted into the tip of a standard 

 tagging pole to which the transmitter was loosely 

 bound with rubber bands (Yuen et al. 1974, Holland 

 and Bayliff 1986). The fish was harpooned in the trunk 

 musculature, thereby allowing the transmitter to lie 

 against the surface of the fish alongside the forward 

 half of the dorsal fin. Once the transmitter was at- 

 tached, the fish was released by cutting the leader, leav- 

 ing the hook in place. 



Fish were caught by surface trolling with artificial 

 lures and standard sportfishing rods and reels. Two of 

 the fish were caught on the tracking research vessel 

 Kaahele'ale, and four were caught by teams par- 

 ticipating in the 1988 and 1989 Hawaii International 

 Billfish Tournaments (HIBT). In these latter cases, the 

 transmitter and applicator pole were passed to the 

 anglers' vessels during the fighting of the fish. Crew 

 members then tagged the fish while the tracking vessel 

 stood by ~100 m away. Once the fish had been re- 

 leased, tracking began. 



To replicate tracks from one well-defined area, three 

 tracks were initiated on the fishing grounds off Keahole 

 Point, Hawaii. This is an area approximately 5 nautical 

 miles (nmi) long and 2 nmi wide that is renowned for 

 high catch rates of marlin during certain periods of the 

 summer. For comparison, two other tracks were ini- 

 tiated from locations ~12 nmi south of the Keahole 

 grounds, and one fish was tracked off Barbers Point, 

 Oahu. 



Results 



Six Pacific blue marlin were tracked. The three Kea- 

 hole fish were all caught within a 1-nmi radius over a 

 span of 19 days in 1988; one track was 24 hours, and 

 two were of 42 hours duration each (Fig. 2). In 1989, 



Figure 2 



Horizontal movements of five Pacific blue marlin tagged off the Kona 

 coast of Hawaii: three off Keahole Point and two off Keauhou. Lines 

 perpendicular to the tracks represent hourly positions. 



over a period of 4 days, two marlin were tracked from 

 starting points ^^4 nmi apart off Keauhou and were 

 tracked for 26 and 29 hours (Fig. 2). The Barbers Point 

 fish was tracked for 7 hours. Thus, all fish survived for 

 at least 7 hours after release, and there is no reason 

 to believe that any of the fish subsequently died as a 

 result of the capture and tagging procedure. 



Synopsis of tracks 



Fish 8710 (weighing ~150 kg) was caught on a single- 

 hooked artificial lure trolled behind the tracking vessel 

 Kaahele'ale at a location 7 nmi west of Barbers Point, 

 at 0904, 18 October 1987. After a fight time of 30 

 minutes, the fish was brought to the side of the boat. 

 The fish was cleanly hooked through the bill and was 

 immobile. The transmitter was embedded dorsolater- 

 ally, about a third of the way back along the dorsal fin. 

 After release, the fish glided downwards and away 

 from the boat and swam away on a southwesterly (off- 

 shore) course, which it maintained for the duration of 

 the track. After 7 hours the fish was lost while at the 

 surface. Data on the rate of horizontal movement for 



