Alternate Title

Fishery and Biology of Blackfin Tuna Thunnus atlanticus off Northeastern Brazil

Document Type



Blackfin tuna, Thunnus atlanticus, is the target species of a handline artisanal fishery off northeastern Brazil in September–January, but it is also caught by anglers and as by-catch in industrial fisheries. The population structure, morphometric relationships, mortality, reproduction, and fishery dynamics were studied during 2 fishing seasons (1996 and 1997). The maximum length and weight observed were 87 cm FL and 10 kg Wd, respectively. Males were larger and predominant (1.9:1). The length at 50% maturity was 49.8 cm FL for females and 52.1 cm FL for males. This species uses the area for reproduction, although a spawning peak was not observed. The length at first capture (58.1 cm FL) was higher than the length at 50% maturity. The total, natural, and fishing mortality rates were 2.34, 0.94, and 1.40 year-1, respectively. The total length-fork length and the total length-standard length relationships were TL = 1.35369 + 1.0462 FL and TL = 6.37742 + 1.0544 SL, respectively (sexes grouped). The length-weight relationship estimated for both sexes was Wd = 0.00003 FL2.8569. Annual catches decreased from 154 t year-1 in the 1970s to 33.5 t year-1 in the 1990s. It seems that there was not much change in the structure of this stock after 30 years, but the lack of a proper collection system of catch data and the increasing interest in recreational fisheries raise reasons for concern.

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