Boggs: Estimating capture depths of longline-caught pelagic fish 



657 



shallow sets of the type hypothesized to represent early 

 use of monofilament longline gear in Hawaii would be 

 expected to catch about 40% more billfish and 160% 

 more mahimahi than would regular longline gear. 

 Large increases in longline catches of these fish in 

 Hawaii have occurred in recent years (1989-90, Boggs 

 1991) as the expanding Hawaii fishery adopted a new 

 type of gear. The proposed new gear configuration 

 would be an effective way to reduce the catch of spear- 

 fish and striped marlin by ~70-80% below that of 

 regular gear. 



Hook timers and TDRs are useful in documenting the 

 depth distribution and habitat of pelagic fish and in 

 showing how different configurations of longline gear 

 and the release of live fish can be effective means of 

 reducing fishing mortality for some species. Better 

 methods of identifying the habitats of pelagic fishes 

 should make it easier to estimate real changes in fish 

 abundance by accounting for changes in fishing 

 methods and the environment. 



Acknowledgments 



Several of Hawaii's longline fishermen, especially 

 F. Amtsberg, provided technical advice without which 

 few fish would have been caught. Many of the staff at 

 the Honolulu Laboratory participated in the cruises, 

 and their creativity and hard work contributed substan- 

 tially to this study, especially R.K.C. Chang, A.E. 

 Chun, R. Ito, L.A. Koch, R.A. Skillman, D. Therry, 

 J.H. Uchiyama, and S. Yano. L.A. Koch tabulated the 

 data and produced the figures, and B.S. Kikkawa pro- 

 vided invaluable help in acquiring and manufacturing 

 the hook timers. Volunteer assistance on the research 

 cruises was given by H. Dewer, P. Fields, C. Hayashi, 

 and A. Sesawa. The officers and crew of the NO A A 

 ship Townsend Cromwell also were very helpful, espe- 

 cially LT R. Brainard, LTC B. Dearbaugh, H. Lariosa, 

 and CDR R. Marriner. 



Citations 



Boggs, C.H. 



1990 Longline research on tuna and marlin. In Relatorio, X 

 Semana das Pescas dos Acores, March 12-16 1990, p. 

 249-252. Sec. Reg. Agric. Pescas. Dir. Reg. Pescas, Horta, 

 Faial, Azores. 



1991 A preliminary examination of catch rates in Hawaii's troll 

 and handline fisheries over a period of domestic longline fishery 

 expansion. Admin. Rep. H-91-05, NMFS Southwest Fish. Sci. 

 Cent., Honolulu, 62 p. 



Bushnell. P.G.. R.W. Brill, and R.E. Bourke 



1990 Cardiorespiratory responses of skipjack tuna (Katsu- 

 wonus pelamis), yellowfin tuna (Thunnus albacares), and bigeye 

 tuna {Thunnus obesus) to acute reductions of ambient oxygen. 

 Can. J. Zool. 68:1857-1865. 



Carey, F.G., and R.J. Olson 



1982 Sonic tracking experiments with tunas. Int. Comm. Con- 

 serv. Atl. Tunas Collect. Vol. Sci. Pap. 17:458-466. 

 Foreman, T.J. 



1987 A method of simultaneously tagging large oceanic fish 

 and injecting them with tetracycline. Fish. Bull., U.S. 85: 

 645-647. 

 Grudinin, V.B. 



1989 On the ecology of yellowfin tuna {Thunnus albacares) and 

 bigeye tuna {Thunnus obesu^). J. Ichthyol. 26(6):22-29. 



Hanamoto, E. 



1974 Fishery oceanography of bigeye tuna— I. Depth of cap- 

 ture by tuna longline gear in the eastern tropical Pacific 

 Ocean. La Mer (Bull. Soc. Franco-Japonaise Oceanogr.) 

 12(3):128-136. 



1975 Fishery oceanography of bigeye tuna— H. Thermocline 

 and dissolved oxygen content in relation to tuna longline fishing 

 grounds in the eastern tropical Pacific Ocean. La Mer (Bull. 

 Soc. Franco-Japonaise Oceanogr.) 13(2):58-71. 



1976 The swimming layer of bigeye tuna. Bull. Jpn. Soc. Fish. 

 Oceanogr. 29:41-44. [Engl, transl. no. 21 by Tamio Otsu, 1977, 

 7 p.: avail. NMFS Honolulu Lab., Honolulu 96822-2396.] 



1979 Fishery oceanography of striped marlin— IV swimming 

 layer in the tuna longline fishing grounds. Bull. Jpn. Soc. Sci. 

 Fish. 45:687-690. 



1987 Effect of oceanographic environment on bigeye tuna 

 distribution. Bull. Jpn. Soc. Fish. Oceanogr. 51:203-216. 

 Hanamoto, E., T. Shibata, and H. Okui 



1982 Some considerations on the vertical distribution par- 

 ticularly of the striped marlin in the Indian Ocean and on the 

 fishing characteristics of the tuna longline gear. Kanagawa 

 Prefect. Fish. Exp. Stn. Res. Rep. 4:17-21. 

 Holland, K.N., R.W. Brill, and R.K.C. Chang 



1990 Horizontal and vertical movements of yellowfin and big- 

 eye tuna associated with fish aggregating devices. Fish Bull., 

 U.S. 88:493-507. 



Holts, D., and D. Bedford 



1989 Activity patterns of striped marlin in the Southern Cah- 



fornia Bight. In Stroud, R.H. (ed.), Planning the future of 



billfishes, research and management in the 90's and beyond. 



Part 2: Contributed papers. Mar. Rec. Fish. 13: 81-93. Natl. 



Coalition Mar. Conserv., Savannah, GA. 

 Kawamoto. K.E., R.Y. Ito. R.P. Clarke, and A.E. Chun 



1989 Status of the tuna longline fishery in Hawaii, 1987-1988. 

 Admin. Rep. H-89-10, NMFS Southwest Fish. Sci. Cent., 

 Honolulu, 34 p. 



Nishi. T. 



1990 The hourly variations of the depth of hooks and the hook- 

 ing depth of yellowrfin tuna {Thunnus albacares). and bigeye 

 tuna {Thunnus obesus), of tuna longline in the eastern region 

 of the Indian ocean. Mem. Fac, Fish. Kagoshima Univ. 39: 

 81-98. 



Rockefeller, W. 



1989 Looking to the fiature of billfishes. /« Stroud, R.H. (ed.). 

 Planning the future of billfishes, research and management 

 in the 90's and beyond. Parti: Fishery and stock synopses, 

 data needs and management. Mar. Rec. Fish. 13:11-14. Natl. 

 Coalition Mar. Conserv., Savannah, GA. 

 Saito. S. 



1973 Studies on fishing of albacore, Thunnus alalunga (Bon- 

 naterre) by experimental deep-sea tuna long-line. Mem. Fac. 

 Fish. Hokkaido Univ. 21:107-185. 



1975 On the depth of capture of bigeye tuna by further im- 

 proved vertical long-line in the tropical Pacific. Bull. Jpn. Soc. 

 Sci. Fish. 41:831-841. 



