20° 0' 



Figure 36. Geographic references in the eastern Atlantic 



a. Northeastern Atlantic 



Le Gall (1927, 1929) described 

 the distribution of bluefin in the north- 

 easlcm Atlantic and the North Sea 

 (Figure 36) The species was re- 

 corded in abundance off the south- 

 west coast of Ireland in July and off 

 the north coast in July and August 

 They were also observed off the west 

 coast of Scotland in July, and off the 

 south and west coasts of Norway, 

 and in the Skagerrak and the Kattegat 

 from July to October Hemng boats 

 encountered them in July and Au- 

 gust east and south of Fair Isle, then 

 north and west of Dogger Bank In 

 late September and October, bluefin 



were observed on the west edge of 

 Dogger Bank In November and De- 

 cember, trawlers on the Great Sole at 

 the edge of the continental shelf en- 

 countered schools of them surfacing 

 l.e Gall related the occurrences of 

 bluefin in the North Sea and its tribu- 

 taries to the seasonal "transgressions" 

 of Atlantic and Atlantic slope wa- 

 ters, with salinities of about 35 o/oo 



b. Norway 



Bluefin tuna have been taken by 

 harpoon and angling gear in Norwe- 

 gian waters for many years, but the 

 introduction of the purse seine 

 method in the late 1940s greatly in- 

 creased the catch The fishen', includ- 



ing the catch and its size composi- 

 tion (Figure 37), has been described 

 by I lamre ( 1 97 1 ). The catch increased 

 from a few hundred tons in the 1 940s 

 to over 1 1 ,000 tons in 1952, but de- 

 creased after 1962 to 2,500 tons or 

 less per year. Hamre attributed the 

 decrease to lack of recruitment, lie 

 showed that the seasonal movement 

 of bluefin tuna through the fishery 

 varied with age of fish. The largest 

 fish (age 7 and older) arrived off 

 Bergen in early July and migrated to 

 the northern Norwegian coast. After 

 feeding there for three or four weeks, 

 they migrated southward into the 

 bank area of the North Sea Fish of 

 ages 6-12 arrived in mid- July south 

 of 62°N latitude, and migrated south- 

 ward along the coast. Catches of fish 

 of this size in late autumn by Swed- 

 ish and Danish fishermen in the 

 Kattegat, including one fish which 

 had been tagged earlier in the same 

 season in Norwegian waters, indi- 

 cated that the migration continued to 

 that area Five and six year old blue- 

 fin arrived in the southern area in 

 September and migrated to the east 

 coast of Norway (Skagerrak). 



I'his general pattern was fol- 

 lowed as long as new vear classes 

 were recruited. Since 1958, when the 

 1952 year class was recruited, there 

 has been no recruitment of younger 

 age groups to the stock (Figures 37- 

 39) This resulted in a decline in the 

 annual catch, and a change in the 

 migration pattern of the fi.sh after the 

 1 962 season. The largest bluefin now 

 rarely migrate to the northward, but 

 usually follow the southerly route pre- 

 viously travelled by the intermediate 

 size (6-12 year old) fish A fev/ large 

 fish, however, were taken in the 

 northern area in 1967-1969 (Figure 

 38) No bluefin have been caught in 

 the German North Sea fishery since 

 1 962, probably because of this change 

 111 migratoiy pattern, but a few have 

 been caught in the Kattegat. Medium 

 sized bluefin have failed to appear in 

 the Norwegian fishery since 1962 

 (Figures 37-39) The annual catch 

 since 1 967 has been less than 1 ,000 

 tons. It fell to a low of 90 tons in 

 1972 and even less in 1973. An in- 

 crease in the modal and minimum 

 sizes of fish taken since 1 957 is evi- 

 dent for botli the northern and south- 



37 



