750 



Fishery Bulletin 92(4). 1994 



float 



1 70 m 



780 m 



780 m 



line 



Detail of branch I 

 (20 hooks) 



Figure 2 



Longline gear employed from the longliner Humboldt during a set ( 15) on 7 June 1991 

 on seamount K (lat. 24°43'S; long. 170°06'E) and detail of a branch line. Main line is 

 4,000 m long and divided into five sections (each section has 840 hooks [42 branch lines 

 x 20 hooks] and is 800 m longhji, depth recorded on the echosounder at time t { when 



sinker was thrown overboard; d, =1/2 (d l 

 cated to all fish hooked on section i. 



+ d ,) + 10 = mean depth of capture allo- 



Figure 3 



Measurements taken to assess the 

 deviation between the depth pro- 

 file recorded on the echosounder 

 and the actual configuration of the 

 longline on the bottom: (A) current 

 velocity from the Doppler sonar 

 current indicator recorded at dif- 

 ferent depths during the settings 

 of the longline by the Humboldt 

 (rc=694 current measurements); (B) 

 deviations between the depth of the 

 terminal anchor recorded when the 

 line was set and the depth of the 

 bottom recorded at the time the cor- 

 responding buoy was grabbed at 

 the begining of retrieval (n=23 

 sets); (C) depth variations within 

 sections recorded during the fish- 

 ing cruise carried out by the 

 longliner Humboldt (n=290 line 

 sections of 800 m each); (D) depth 

 variations (differences between 

 maximum and minimum depths) 

 for the whole line recorded during 

 the fishing cruises carried out by 

 the longliners Hokko Maru and 

 Fukuju Maru (n=287 longlines of 

 4,000 m). 



5 10 15 20 ?& 30 35 40 45 50 SS 60 

 DEPTH VARIATION WITHIN SECTIONS (m) 



I) 



25 50 75 100 125 150 175 200 225 250 



DEPTH VARIATION OVER WHOl-E UNE (ml 



