Bycatch of franciscana dolphins Pontoporia blainvillei and artisanal fisheries dynamics in the species southernmost distribution

NEGRI, M.F.; DENUNCIO, P; PANEBIANCO, M.V. ; CAPPOZZO, H.L.

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Lugar: São Paulo; Año: 2012 vol. 60 p. 151 - 160

1679-8759

In Argentina, the franciscana dolphin is one of the most vulnerable cetaceans regularly entangled in coastal artisanal fisheries. The objective of this paper is to estimate its incidental mortality in the Southern coast of Buenos Aires province through the methods of interviews to the captains of artisanal fishing vessels, in the period 2006­2009. Results: Franciscana bycatch was reported for gillnets and shrimper gears all year round, but at higher frequencies between October and February, at 5 km offshore and 10­20 m of depth. The estimated mean annual incidental mortality was 109 dolphins (CI 95% = 89­131), 92 in gillnets (CI 95% = 74­113) and 17 in shrimpers (CI 95% = 10­27) with a capture per unit of effort of 0.035 dolphins per km of gillnet (CI 95% = 0.024­0.049) and 0.024 per shrimper net (CI 95% = 0.015­0.036). Annual fluctuations were due to differences in gillnetting fishing days. If mortality estimations of the Northern coast are taken into account, values reach a maximum of 362­541 dolphins bycaught in the entire Buenos Aires province, representing 2.5­3.7% of the species abundance in Argentina. Conclusions: This would inevitably lead to the declination of franciscana dolphin populations in the near future unless alternative fishing grounds and gears are identified and implemented.