Horizontal and Vertical 

 Movements of Pacific Blue Marlln 

 Captured and Released Using 

 Sportfishing Gear* 



Kim Holland 



Hawaii Institute of Marine Biology, P O Box 1346 

 Kaneohe, Hawaii 96744 



Richard Brill 

 Randolph K.C. Chang 



Honolulu Laboratory, Southwest Fisheries Center 

 National Marine Fisheries Service, NOAA, 2570 Dole Street 

 Honolulu, Hawaii 96822-2396 



Despite the commercial and recre- 

 ational importance of Pacific blue 

 marlin Makaira nigricans, little is 

 known about their biology or be- 

 havior. This is due mainly to their 

 large size and pelagic habitat and 

 the difficulty in maintaining them in 

 captivity or observing their behav- 

 ior in the wild. However, two tech- 

 niques are available to elucidate 

 their movements: capturing and re- 

 leasing marlin fitted with identifica- 

 tion tags, and tracking of fish car- 

 rying ultrasonic transmitters. 



The recovery of tagged marlin 

 has enhanced our understanding of 

 the long-term geogi'aphical range of 

 individual fish and their minimum 

 rates of travel (Squire 1974, Squire 

 and Nielsen 1983, Bayliff and Hol- 

 land 1986), and growing interest in 

 the tag and release of marlin by 

 sportfishermen should produce an 

 increasingly precise picture of mar- 

 lin movements. However, this tech- 

 nique cannot answer questions re- 

 garding the vertical movements of 

 marlin, and questions remain con- 

 cerning both the survival of tagged 

 fish following the trauma of capture 

 and the nature of their behavior im- 

 mediately upon release. 



•Sea Grant Publication UNIHI-SEAGRANT 

 JC-90-13. 



Fine-scaJe observations of the hori- 

 zontal and vertical movements of 

 pelagic fish can be obtained for 

 periods of up to a few days by track- 

 ing fish equipped with depth-sensi- 

 tive ultrasonic transmitters (Hol- 

 land et al. 1985, 1990; Bayliff and 

 Holland 1986). For billfishes, this 

 technique has been used to track 

 swordfish Xiphius gladius (Carey 

 and Robison 1981) and striped mar- 

 lin Tetrapturus audax (Holts and 

 Bedford In press). Similarly, Yuen 

 et al. (1974) tracked Pacific blue 

 marlin but used temperature-sensi- 

 tive transmitters to monitor ambi- 

 ent water temperature from which 

 depth was later calculated using 

 bathythermograph data. However, 

 this study heightened concerns about 

 tagging mortality rates because three 

 of the five tagged fish died soon 

 after release. 



Here we report on the movements 

 of six Pacific blue marlin tracked in 

 the waters around the Hawaiian 

 Islands. Of particular interest were 

 survivorship and behavior of the 

 fish immediately upon release, their 

 patterns of vertical movement, and 

 their overall patterns of horizontal 

 movement. To discern any common 

 patterns of movement associated 

 with one particular area of ocean, 

 three fish were caught and tracked 



from one well-defined location on 

 the Kona coast of Hawaii. For com- 

 parison, two other tracks were in- 

 itiated several miles away along the 

 same coast, and one marlin was 

 tracked off the Waianae coast of 

 Oahu. 



Methods 



The ultrasonic tracking techniques 

 employed were identical to those 

 used previously to track yellowfin 

 tuna (HoDand et al. 1985, 1990; Bay- 

 liff and Holland 1986). The transmit- 

 ters used in the present study had 

 a nominal life span of 3 days and a 

 maximum working pressure of 500 

 psi (Vemco, Halifax County, Nova 

 Scotia). The signal, encoding depth 

 information by variable pulse inter- 

 val, was recorded on audiotapes for 

 later onshore plotting of vertical 

 movements of the fish. Horizontal 

 location was determined every 15 

 minutes (or more frequently when 

 necessary) by using a combination 

 of Loran-C, radar, visual, and bathy- 

 metric fixes. Water temperature 

 was measured by expendable bathy- 

 thermographs deployed approx- 

 imately every 3 hours. 



Aggregate depth and tempera- 

 ture distributions were calculated 

 (with 10-m and 1°C bins, respective- 

 ly) as percentages of the total track 

 time spent at any particular depth 

 or temperature. For temperature, 

 the combined distributions of all fish 

 were calculated as the percentage 

 of time spent in the various tem- 

 perature strata relative to the up- 

 per mixed layer. 



Each transmitter was attached 

 with a 10-cm length of 130-lb test 

 monofilament to a stainless steel 

 "arrowhead" (~2.75 x 1.75 x 0.1 

 cm; Fig. 1) modified from the type 



Reference to trade names does not imply en- 

 dorsement by the National Marine Fisheries 

 Service, NOAA. 



Manuscript accepted 5 March 1990. 

 Fishery Bulletin, U.S. 88:397-402. 



397 



