100 



200 



P 

 ul 

 i^300 



X 



fL400 



Q 



500 

 600 



T T 



1 1 \ r 



SFATH FLQATLINE 

 ISFIITH FLQATLME 



5FATH FLQATLINE- 

 ISaTH FLOftTLINE- 



-5FaTHFUlftTL»C- 

 iSFiTM FLOATLIft- 



300 400 500 600 700 800 900 1000 1100 1200 

 DISTANCE BETWEEN LONGLINE BUOYS(FEET) 



Figure 7. --The theoretical relation of the 

 distance between baoys to the depths of vari- 

 ous hooks on a basket of albacore longline. 

 Droppers have been omitted. 



SUMMARY 



grounds in 1939. Fisheries Bureau, 

 Ministry of Agriculture and 

 Forestry, Japan. (Translation 

 issued as U. S. Fish and Wildlife 

 Service, Spec. Sci. Rept. --Fish. 

 No. 33. 175 p.) 



1955. Albacore tuna scarce in eastern 

 North Pacific in May reports N. B . 

 Scofield (cruise 55-S-3). U.S. Fish 

 and Wildlife Service, Connm.Fish. 

 Rev. 17(9): 44-46. 



BULLIS, H. R. , JR . 



1955. Preliminary report on exploratory 

 long-line fishing for tuna in the Gulf 

 of Mexico and the Caribbean Sea. 

 Part I. Exploratory fishing by the 

 Oregon . U. S. Fish and Wildlife 

 Service, Comm. Fish. Rev. 17(10): 

 1-15. 



1. A brief summary of methods used to 

 estimate the fishing depth of longline by 

 various investigators is given. 



2. Comparisons of field data with laboratory 

 tests show that sounding tubes measure 

 depth of longline gear in the field with 

 considerable accuracy. 



3. A method used to plot the observed "hang" 

 of a given basket of gear and the theoretical 

 "hang" is described. The results obtained 

 suggest that the configuration of the main- 

 line in the individual baskets does not 

 conform to a catenary. We conclude that 

 the skewness in the shape of the line did 

 not occur during the fishing period, but 

 rather during retrieving operations when 

 slack formed in hauling allowed a portion 

 of the gear to sink below the maximum 

 fishing depth. It is suggested this may be 

 averted by placing sounding tubes on a pair 

 of the shallower hooks in a basket of gear 

 and accepting the shoalest reading of the 

 two. 



4. It i s suggested that in areas where the 

 environment, such as currents and winds, 

 does not distort the "hang" of a basket of 

 longline, maximum fishing depths for indi- 

 vidual hooks along an entire set can be 

 estinnated. An applicable method is given. 



LITERATURE CITED 



ANONYMOUS 



1940. Results of encouragennent for the 

 developnnent of albacore fishing 



GRAHAM, J. J. 



1957. Central North Pacific albacore 

 surveys. May to Novennber 1955. 

 U. S. Fish and Wildlife Service, 

 Spec. Sci. Rept. --Fish. No. 2 12. 

 38 p. 



IVERSEN, E. S. , and H. O. YOSHIDA 



1957. Longline and troll fishing for tuna 

 in the central equatorial Pacific, 

 January 195 5 to February 1956, 

 U. S. Fish and Wildlife Service, 

 Spec. Sci. Rept. --Fish. No. 203. 

 38 p. 



KNIGHT, A. M. 



1945. Modern seamanship. Eleventh edition 

 rewritten and revised by Robert A. 

 Hall. New York: D. Van Nostrand. 

 948 p. 



MANN, H. 

 1955. 



Construction details of improved 

 tuna long-line gear used by Pacific 

 Oceanic Fishery Investigations. 

 U. S. Fish and Wildlife Service, 

 Comm. Fish. Rev. 17(12): 1-10. 



MORITA, T. , T. HUZITA, and T. TANOUE 



1955. On the curve of tuna longline. 

 Memoirs of the Faculty of 

 Fisheries, Kagoshima University 

 4: 8-1 1. 



MURPHY, G. I., and R. S. SHOMURA 



1953. Longline fishing for deep-swimming 

 tunas in the central Pacific, 

 January - June 1952. U. S. Fish 



