TABLE 3-1  Synopsis of release and recapture (tagging experiments) of western Atlantic bluefin tuna. Data are from Mather (1980) and Brunenmeister (1980).

Tag locality

# Released

Size

# Recaptured

 

Bahamas

1,709

Giant fish

17

 

NW Atlantic Ocean

1,881

Giant fish

81

 

US Coast*

468

Medium fish

10

 

NW Atlantic Ocean

>17,700

Small fish

>2,180

 

Bahamas to eastern Atlantic Ocean

9 [giant fish]

 

 

US Coast* to eastern Atlantic Ocean

1 [medium fish]

 

 

NW Atlantic to eastern Atlantic Ocean

46 [small fish]

 

 

Trans-Atlantic giant fish released in Bahamas

9/17

52.9%

Trans-Atlantic giant fish released in W Atlantic Ocean

9/98

9.2%

Trans-Atlantic medium fish released off US Coast*

1/10

10.0%

Trans-Atlantic small fish released in NW Atlantic Ocean

46/2,180

2.1%**

* From Mather (1980): "mostly" medium fish were released north of 35°N and west of 60°W.

** More than 2,180 fish released; estimate of 2.1% is maximum.

Recaptures through 1978 of large fish released in the Bahamas in the 1960s, and of small fish released along the U.S. Atlantic coast, document unequivocally that transatlantic migration occurs (Table 3-1). Transatlantic migrants include nine giant fish taken off the Norwegian coast, one medium fish (recovered as a giant tuna over 10 years later) taken off the southern coast of Spain, and 46 small fish taken chiefly from the Bay of Biscay. Estimates of the total proportion of fish tagged in the western Atlantic Ocean in eastern Atlantic samples (Table 3-1) range from 9.3% for giant fish and medium fish to 2.1% for small fish. Estimates for giant and medium fish differ slightly from those given in Mather (1980), who found a total of 10 western migrants in 126 eastern Atlantic recaptures (10/126 = 7.9%). Suzuki (1990) estimated an "overall" proportion of western-tagged fish in eastern Atlantic samples of 3.2% as of 1988.

Estimates of west to east transatlantic movement are variable and depend on the size of fish tagged and tagging locality. All but one of the giant fish transatlantic recoveries were tagged near the Bahamas, and five of the nine migrants were recovered in Norwegian waters in the same year. These results indicate that giant bluefin tuna can travel long distances; only one of the remaining 91 giant tuna or medium fish tagged in the western Atlantic Ocean was recovered in the eastern Atlantic Ocean. This fish was tagged near Bermuda and recovered 10 years later. Mather (1980) hypothesized that the transatlantic migration of



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