434 



Abstract — To estimate postrelease 

 survival of white marlin (Tetraptu- 

 rus albidus) caught incidentally in 

 regular commercial pelagic longline 

 fishing operations targeting sword- 

 fish and tunas, short-duration pop- 

 up satellite archival tags (PSATs) 

 were deployed on captured animals 

 for periods of 5-43 days. Twenty 

 (71.4%) of 28 tags transmitted data 

 at the preprogrammed time, includ- 

 ing one tag that separated from the 

 fish shortly after release and was 

 omitted from subsequent analyses. 

 Transmitted data from 17 of 19 

 tags were consistent with survival 

 of those animals for the duration of 

 the tag deployment. Postrelease sur- 

 vival estimates ranged from 63.0% 

 (assuming all nontransmitting tags 

 were evidence of mortality) to 89.5% 

 (excluding nontransmitting tags from 

 the analysis). These results indi- 

 cate that white marlin can survive 

 the trauma resulting from interac- 

 tion with pelagic longline gear, and 

 indicate that current domestic and 

 International management measures 

 requiring the release of live white 

 marlin from this fishery will reduce 

 fishing mortality on the Atlantic-wide 

 stock. 



Survival of white marlin (Tetrapturus albidus) 

 released from commercial pelagic longline gear 

 in the western North Atlantic* 



David W. Kerstetter 



John E. Graves 



Virginia Institute of Marine Science 



College of William and Mary 



Route 1208 Create Road 



Gloucester Point, Virginia 23062 



Present address ((or D, W. Kerstetter): Cooperative Institute for Marine and Atmospheric Studies 



Rosenstiel School for Marine and Atmospheric Science 



University of Miami 



4600 Rickenbacker Causeway 



Miami, Florida 33149 

 E-mail address (for D W Kerstetter) dkerstetteriSrsmas miami edu 



Manuscript submitted 7 March 2005 

 to the Scientific Editor's Office. 



Manuscript approved for publication 

 6 Ocotber 2005 by the Scientific Editor. 



Fish. 104:434-444(2006). 



White marlin (Tetrapturus albidus 

 Poey 1860) is an istiophorid billfish 

 species widely distributed in tropi- 

 cal and temperate waters through- 

 out the Atlantic Ocean, including the 

 Caribbean Sea. There is substantial 

 international concern regarding the 

 population levels of this species. The 

 standing committee for research and 

 statistics (SCRS) of the International 

 Commission for the Conservation of 

 Atlantic Tunas (ICCAT) last assessed 

 the Atlantic -wide stock of white marlin 

 in 2002 and in its continuity-case 

 assessment the committee indicated a 

 total biomass of approximately 12% of 

 that necessary to produce maximum 

 sustainable yield. It was also esti- 

 mated that the current international 

 fishing mortality level for this species 

 is equivalent to more than eight times 

 the replacement yield, contributing to 

 further decline of the overfished stock 

 (ICCAT, 2005). 



Both recreational and commercial 

 fisheries contribute to the mortality 

 of white marlin. A directed recre- 

 ational fishery exists throughout the 

 tropical and temperate Atlantic (with 

 considerable effort off the coasts of 

 Brazil and Venezuela), as well as off 

 the U.S. mid- Atlantic coast, and there 

 is a growing trend towards catch- 

 and-release practices in all directed 

 recreational billfish fisheries. In con- 

 trast to the catches by this directed 

 recreational effort, white marlin are 

 an infrequent bycatch or a retained 



incidental catch of the international 

 pelagic longline fishery, which targets 

 tunas (Thiinnus spp.) and swordfish 

 iXiphias gladius). Although white 

 marlin catches in the pelagic long- 

 line fishery are relatively rare, the 

 fishery accounts for the majority of 

 the total fishing mortality on this 

 species simply because of the sheer 

 magnitude of pelagic longline effort 

 exerted throughout the Atlantic (IC- 

 CAT, 2005). 



Both domestic and international 

 management measures are currently 

 in effect for white marlin. The U.S. 

 recreational fishery is managed with 

 a 66" lower jaw-fork length federal 

 minimum size and a binding ICCAT 

 recommendation that limits the an- 

 nual U.S. recreational landings to a 

 total of 250 blue marlin (Makaira ni- 

 gricans) and white marlin combined 

 (ICCAT, 2000). U.S. commercial fish- 

 ermen have been prohibited from 

 landing or possessing white mar- 

 lin since the implementation of the 

 National Marine Fisheries Service 

 (NMFS) Fishery Management Plan 

 for Atlantic Billfish (NMFS, 1988). 

 ICCAT has responded twice to the 

 decreasing biomass of white marlin 

 and blue marlin by adopting binding 



Contribution 2695 from the Virginia 

 Institute of Marine Science, College of 

 William and Mary, Gloucester Point, VA 

 23062. 



