Inventory of U.S. Exploratory Longline Fishing 



Effort and Catch Rates for Tunas and Swordfish 



in the Northwestern Atlantic, 1957-65 



By 



PETER C. WILSON, Fishery Biologist, Bureau of Commercial 



Fisheries Exploratory Fishing and Gear Research Base, 



Gloucester, Mass. 01930, and MARTIN R. BARTLETT, 



Research Assistant, Woods Hole Oceanographic 



Institution, Woods Hole, Mass. 02543 



ABSTRACT 



This report summarizes the results of longline explorations for tunas and 

 swordfish by the Bureau of Commercial Fisheries and the Woods Hole Oceano- 

 graphic Institution in the Northwestern Atlantic from March 1957 to June 1965. 

 Fishing log data from 31 exploratory cruises are summarized in 12 monthly 

 tables that give the date, time, position, number of hooks fished and catch for each 

 longline set. The total and monthly fishing effort (number of longline sets and hooks 

 fished within each 1° latitude and longitude square) is shown by 1 3 figures. Similar 

 figures show the total and monthly average and maximum number of bluefin, 

 yellowfin, albacore, and bigeye tunas, and swordfish caught per 100 hooks within 

 each 1° square. Two figures show the monthly catch rates for blackfin and skipjack 

 tunas by 1° squares. 



INTRODUCTION 



Tunas and swordfish have been under in- 

 vestigation in the Northwestern Atlantic by 

 two U.S. research agencies to determine the 

 distribution, abundance, migration, and avail- 

 ability of several species.^ A major aim of 

 the BCF (Bureau of Commercial Fisheries) 

 Exploratory Fishing Base, Gloucester, 

 Mass., has been the assessment of this 

 resource in oceanic waters off the east coast of 

 the United States to provide long-range sup- 

 porting knowledge necessary for the develop- 

 ment of Atlantic coast tuna and swordfish 

 fisheries. WHOI (Woods Hole Oceanographic 

 Institution) has studied the life histories of 

 these species, with particular emphasis on 

 bluefin tuna. The agencies have coordinated 

 efforts and aims through joint cruises and 

 exchange of equipment, personnel, and data. 



•■^ Swordfish explorations began in 1961. 



^ Bluefin tuna ( Thunnus thynnus ), yellowfin tuna (T. 

 albacares ), albacore (T. alalunga), bigeye tuna (T.qbesus), 

 blackfin tuna (T. atlanticus ), skipjack tuna ( Euthynnus 

 pelamls ), and swordfish (Xlphlas gladlus ). 



•* Located at East Boston, Mass., 1954-59. 



Between March 1957 and June 1965, the 

 Bureau's research vessel Delaware , various 

 WHOI research vessels, and chartered or 

 cooperatively engaged vessels made 31 ex- 

 ploratory fishing cruises in the North Atlantic 

 Ocean and Caribbean Sea to explore the dis- 

 tribution and abundance of tuna and swordfish 

 (table 1). This report covers the portions of 

 the explorations within the area of the North- 

 western Atlantic bounded on the northwest by 

 the 100-fath. (fathom) contour of the North 

 American Continental Shelf, on the south by 

 lat. 35° N., and on the east by long. 49° W. 

 (fig. 1). Many of these cruises have been re- 

 ported individually (Bureau of Commercial 

 Fisheries, 1957a, 1957b, 1958a, 1958b, 1958c, 

 1959a, 1959b, 1960, 1962, 1963, 1964a, 1964b, 

 1965b, 1965d; Mather and Bartlett, 1962). Tuna 

 distribution data from Delaware cruises 

 through I960 have been sumnnarized by Squire 

 (1962b), and extracted data from these cruises 

 and other sources have been treated by Mather 

 (1962, 1964) and Squire and Mather (1963). 

 Incidental captures of swordfish were reported 

 by Mather and Bartlett (1962) and Squire 

 (1962a), 



