NOTE Kerstetter et al : Use of satellite archival tags to demonstrate survival of Makaira nigricans 947 



The reason that two tags did not report data could have 

 been result of mortality (the blue marlin died and sank 

 to a depth at which the tag was crushed or lost positive 

 buoyancy) or of other factors, such as tag malfunction or 

 mechanical damage to the tag. Neither tag contained pre- 

 release software or an emergency release device. There did 

 not appear to be a relationship between the weight of the 

 fish and a nonreporting tag. Both fish with nonreporting 

 tags were hooked in the jaw with "J" hooks. The blue marlin 

 with tag 5D-3 was in excellent condition and actively swam 

 away from the vessel, whereas the fish that received tag 

 5D-6 was in good condition and actively swam away from 

 the vessel, albeit more slowly than several of the others. It 

 is worth noting that this fish also had an orange streamer 

 tag attached to it from a previous capture, but it was not 

 possible to retrieve this tag without compromising the 

 release protocol. 



The results of the present study can be used to generate 

 rough estimates of postrelease survival rate for blue marlin 

 released from the western North Atlantic pelagic longline 

 fishery. This project observed that seven of nine deployed 

 PSATs reported data as programmed (if the two nonreport- 

 ing tags were indeed mortalities); this results in a 77.8% 

 postrelease survival rate. Combining postrelease mortali- 

 ties with estimates of mortality at the time of haulback, 

 the compounded mortality for blue marlin conservatively 

 ranges from 65.4% (Jackson and Farber, 1998) to 53.5% 

 (Cramer, 1998). However, the relatively small number of 

 tags deployed in this study clearly limits the general ap- 

 plicability of the these results, as did the prior limitation 

 that only live fish greater than 100 pounds, without clearly 

 mortal wounds, would be tagged. Fortunately, all of the fish 

 encountered alive (one was dead on haulback) met these 

 two requirements. The 11 .S% estimate of postrelease sur- 

 vival is nevertheless comparable with the 89% survival 

 rate (8 of 9 reporting PSAT tags) reported by Graves et al. 

 (2002) for blue marlin caught in the recreational fishery 

 off Bermuda — a fishery in which many blue marlin are 

 resuscitated prior to release. 



The sample size required for an Atlantic-wide estimate 

 of postrelease mortality would be large given the need 

 to account for different gear configurations, as well as 

 variables such as environmental conditions, season, and 

 geographic area (Goodyear, 2002). Such a project would 

 be extremely expensive with current technology. However, 

 evolving PSAT technology presents the opportunity for ad- 

 ditional work describing the interactions between pelagic 

 longline gear and catch species, such as the billfishes. New 

 high-resolution PSATs provide fine-scale data on habitat 

 preferences and behavior, allowing the eventual refine- 

 ment of models that standardize historical catch-per-unit- 

 of-effort data for pelagic longline gear (e.g. Hinton and Na- 

 kano, 1996; Hinton, 2001). Such standardization efforts, if 

 correctly applied, may permit more accurate blue marlin 

 stock assessments (Venizelos et al., 2001). 



This study demonstrates that PSAT technology is well 

 suited to estimate postrelease survival rates for blue 

 marlin from the pelagic longline fishery, with minimal 

 interference to normal commercial fishing operations. The 

 relatively high rate of survival of blue marlin inferred 



from these data for five and thirty days following release 

 from pelagic longline gear demonstrates that management 

 measures requiring live release, such as those recently ad- 

 opted by ICCAT, can significantly reduce fishing mortality 

 on Atlantic blue marlin. 



Acknowledgments 



The authors would like to thank Captains Bobby Lamb ( FV 

 Ark Angel), Keith Garner (FV Deliverance), David Kolesar 

 (FV Triple Threat), Greg O'Neil (FV Carol Ann), and Baker 

 Dunn (FV Triple Threat), as well as their crews, for provid- 

 ing assistance in deploying the pop-up tags. We would also 

 like to thank vessel owners Willie Etheridge and Vince Pyle 

 for their assistance in coordinating available vessels. Paul 

 Howey, Roger Hill, and Melinda Braun provided technical 

 assistance with the tags, and Heidi Dewar kindly assisted 

 with the interpretation of the tag data. John Hoenig help- 

 fully assisted with some of the statistical methods. Support 

 for this project was provided by the Bermuda Department 

 of Agriculture and Fisheries, the U.S. National Marine 

 Fisheries Service, and the Hewit Family Foundation. 



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