Figure 1, — Shaded portion of North Atlantic is the area of tuna and swordfish explorations covered by this inventory. 



regulated by the number of buoys and length 

 of buoylines supporting the mainline units. 

 Most longline sets were buoyed at the ends 

 of each unit with buoylines, which varied on 

 different cruises and sets from 5 to 30 fath. 

 For swordfish explorations some of the gear 

 was fished over a wide depth range, with 

 buoys, and 1 -fath. buoylines at every second, 

 and sometimes third, unit ( Cap'n Bill III 

 cruises 64-1 and 65-1). On other occasions 

 fishing depth distribution was attained by using 

 several different buoyline lengths on the same 

 set. Analyses of the depth distribution of the 

 catch should not be derived from the infor- 

 mation presented in this report because these 

 variations and other factors (current, speed 

 and direction) caused uncertainty in the esti- 

 mated fishing depths of the gear. 



The time period during which longline gear 

 was fished (table 2-13) has varied consider- 

 ably during these investigations. Until June 

 1961 ( Crawford cruise 62), all longline sets 

 were specifically made for tuna and were 

 fished during daylight. Setout generally conn- 

 menced at or shortly after dawn, and hauling 

 was completed well before dusk. Since June 

 1961 a large number of the longline sets have 



been set out at dusk or after dark for sword- 

 fish and were not hauled until dawn of the 

 following day. In son-ie instances when hauling 

 continued well into daylight, the gear took 

 good catches of tuna. 



Principal bait used on most sets has been 

 Atlantic herring (Clupea harengus harengus ). 

 Other baits used in combination with Atlantic 

 herring, with other species, or separately 

 included: alewife ( Alosa pseudoharengus ), 

 silver hake or whiting ( Merluccius bilinearis ), 

 squirrel hake or red hake ( Urophycis chuss ), 

 blue runner or hardtail ( Caranx crysos ), scup 

 ( Stenotomus chrysops ), Atlantic nnackerel 

 ( Scomber scombrus ), ocean pout or eelpout 

 ( Macrozoarces americanus ), butterfish 

 ( Poronotus triacanthus ), common squid 

 ( Loligo pealii ) and flying squid ( Ommastrephes 

 illecebrosa ). Most bait was frozen, but occa- 

 sionally fresh bait was obtained from mid- 

 water or bottom trawl drags over the Con- 

 tinental Shelf. 



Major consideration was given to spatial 

 and temporal coverage on the explorations. 

 Equal importance was assigned to environ- 

 mental features that could be measured or 

 observed and that are known to be related to 



