326 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



near Halifax harbor in 1922 (Vladykov, 1935), 

 and one was captured by the Woods Hole Oc«an- 

 ographic Institution research vessel Bear at lati- 

 tude 39°45' N., loiisitiide 73°00' W. in September 

 1956 (Mather and Gibbs, 1957). In addition, al- 

 bacore have been taken on longline gear around 

 the island of Bermuda by Mowbray (1956). 

 Other reports of albacore captures exist but are 

 unconfirmed. 



BIGEYE TUNA 



Captures of bigeye tuna have been reported 

 from sport fishery catches on the Continental Shelf 

 off North Carolina and Maryland, and Mowbray 

 (1956) has recorded the capture of bigeye off Ber- 

 muda. The species was unrecorded from the 

 oceanic region off the United States and Canada 

 prior to the Bureau's exploratory studies. 



OTHER TUNA SPECIES 



Blackfin tuna are recorded from the Bermuda 

 area by IVfowbray (1956) and from oceanic wa- 

 ters of tlie northwestern Atlantic by Mather and 

 Day (1954). One of the two specimens consti- 

 tuting the latter record was taken near latitude 

 32°21' N. and longitude 64°37' W. by the Atlantis 

 in June 1948. Tlie other specimen was taken 300 

 miles east of Cape Hatteras by the same vessel in 

 August 1953. A number of specimens has been 

 taken in inshore areas, and Mather (Mather and 

 Day, 1954) believes that the species does not nor- 

 mally range far beyond the 100-fathom curve. 

 The northernmost record of the species is the cap- 

 ture of one blackfin about 75 miles south of Mar- 

 tha's Vineyard (latitude 40°04' N., longitude 

 70°42' W.) by the Cai^n in October 1948 (Mather 

 and Schuck, 1952). 



Little tuna are common inhabitants of inshore 

 areas, especially from New York south, and have 

 been reported from the Gulf of Maine by Schuck 

 (1951). Little tuna do not, apparently, range 

 into deep waters. Sporadic attempts have been 

 made, along the Middle Atlantic coastline, to util- 

 ize little tuna commercially. 



EXPLORATORY GEAR AND PROCEDURES 



The Bureau research vessel Delaware traveled 

 over 17,900 nautical miles during the explorations 

 in the northwestern Atlantic (fig. 2). 



FISHING GEAR 



The longline fishing gear used in the explora- 

 tions (fig. 3) is identical in basic design and con- 

 struction to that used by the Bureau research 

 vessel Oregon in exploring the tuna resources of 

 the Gulf of Mexico (Captiva, 1955) and Carib- 

 bean. The method of longlining used by the 

 Delaware was essentially the same as that used by 

 the Japanese for tuna fishing operations in the 

 Pacific, Indian, and Atlantic Oceans. 



FISHING PROCEDURE 



On station, the fishing gear and bait were pre- 

 pared for setting at about 0630 hours. A set of 

 60 tubs of longline gear (600 hooks) was selected, 

 following initial operations, as the unit that would 

 give a reasonable representation of fish in the area, 

 but this set would still be convenient to handle 

 when large numbers of large fish were caught. 

 Atlantic herring, Clupea harengus harengus Lin- 

 naeus, were used as bait. The gear was allowed 

 to drift for about 2 hours after the last tub had 

 been set, and hauling was then begun with the aid 

 of a Japanese longline hauler. The vessel was 

 moved slowly ahead as the gear was being re- 

 trieved so that the line was kept on the starboard 

 quarter. 'N^Hien a fish was brought to the side of 

 the vessel, the branchline l)earing the fish was re- 

 moved from the mainline, another branchline was 

 tied on, and hauling was continued. The fish, on 

 its separate branchline, was then gaffed and hauled 

 aboard or tagged and released. Tagging was car- 

 ried out in cooperation with the Woods Hole 

 Oceanographic Institution. Setting the gear re- 

 quired four to five men ; retrieving it required six 

 to seven. 



TEMPERATURE DETERMINATIONS 



Several workers (Murphy and Shomura, 1955; 

 Bullis, 1955; and Wathne, 1959) have stated that 

 longline sections do not function with uniform effi- 

 ciency or at uniform depth, owing to the many 

 variables to which the gear is subjected. These 

 variables include lengths of mainline, branchlines, 

 and buoylines, as well as the amount of tension 

 ajiplied to the mainline when the gear is set, the 

 force and direction of the wind, and the strength 

 and direction of the cun-ent. 



