668 



Fishery Bulletin 103(4) 



For blue marlin larvae <6.2 mm SL, Serafy et al. 

 (2003) found problems with estimating age from size 

 with the larval growth equations reported by Prince et 

 al. (1991). Serafy et al. (2003) suggested an exponen- 

 tial growth curve with an assumed size-at-hatching 

 of 2.5 mm SL yielded more realistic larval age values 

 for this growth stanza (<6.2 mm SL). Application of 

 the Serafy et al. (2003) growth model to the larval 

 blue marlin collected in the present study indicates 

 that larvae 3 mm SL were 2 days old, 4-mm-SL larvae 

 were 5 days old, and 5-mm-SL larvae were over 7 days 

 old. It seems possible that blue and white marlin have 

 similar size-at-hatching and growth rates at this early 

 stage of development. Given this assumption, the fact 

 that half of the white marlin larvae (4 out of 9) and a 

 third of the blue marlin larvae sampled in this study 

 were 3-4 mm long (i.e., only a few days old) indicates 

 that spawning activity was taking place in the same 

 general area where these larvae were captured and 

 where the recreational fishery for these species was 

 being pursued. This statement may not hold true for 

 the larval marlin in our collections over 4 mm SL 

 because increases in size and age add increased un- 

 certainties concerning possible spawning locations. 

 Providing a more precise estimate of spawning loca- 

 tion was beyond the scope of our study, although we 

 would expect that the upstream spawning locations 

 (assuming minimal mobility of larvae) of both marlin 

 species to be a function of the prevailing currents 

 and oceanographic features in the Punta Cana area 

 and the elapsed time between the spawning event and 

 sample collection. Future research should focus on a 

 more rigorous and comprehensive estimate of spawning 

 location for all sizes and ages of larvae. This would 

 require both a significant increase in the spatial and 

 temporal larval sampling scheme, as well as direct 

 aging methods for both species and sizes of marlin 

 larvae collected. 



Implications for managment and future research 



The current stock status of Atlantic white marlin indi- 

 cates that biomass is only at about 12% of the level nec- 

 essary to maintain maximum sustainable yield (MSY) 

 and continues to decline (ICCAT, 2002). The stock has 

 been estimated to be incurring fishing mortality at 

 a rate about eight times higher than the population 

 can sustain to produce MSY (ICCAT, 2002). Although 

 the Atlantic blue marlin stock is also considered to be 

 overexploited, its status is not as precarious as that of 

 white marlin (ICCAT, 2001). The characterization of 

 adult movements and larval distribution in a potentially 

 important spawning area is seen as a necessary "first 

 step" toward improved management and rebuilding of 

 depressed Atlantic billfish stocks, possibly with gear 

 restrictions (e.g., use of circle hooks. Prince et al., 2002b; 

 Horodysky and Graves, 2005). Improved management 

 seems particularly relevant in the area of Punta Cana 

 because the target of the 40-year-old Cabeza de Toro 

 tournament is, and probably always has been, a repro- 



ductively active aggregation of white marlin. In light of 

 the ICCAT recommendation to reduce mortality on the 

 overexploited marlins from all Atlantic fisheries (ICCAT, 

 2002), a shift to catch-and-release requirements for the 

 white marlin recreational fishery off Punta Cana, and 

 the use of circle hooks during the spring months, may 

 be suitable options. In terms of spawning, there is an 

 obvious need for more detailed spatiotemporal informa- 

 tion on the distribution of marlin reproduction and on 

 the identification of nursery areas to help managers 

 make informed decisions regarding conservation of the 

 resource. In addition, more fine-scale data on adult 

 movement patterns in relation to horizontal and verti- 

 cal use of the water column, including identification of 

 spawning depth, are necessary. 



Acknowledgments 



This work was made possible through Cooperative 

 Research and Recover Protected Species Candidate 

 Plus Program funds of the National Marine Fisheries 

 Service and additional support from The Billfish Founda- 

 tion and the Lmiversity of Miami, Center for Sustainable 

 Fisheries, Billfish Research Initiative. We thank Noretta 

 Perry at the Florida Fish and Wildlife Commission's 

 Fish and Wildlife Research Institute for histological 

 slide preparations. 



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