An overview of franciscana dolphin distribution and abundance in Brazil: implications for its conservation and fishery management

DANILEWICZ, D; SUCUNZA, F.; FERREIRA, E.; DENUNCIO, P; AZEVEDO, R; ANDRIOLO, A.; SECCHI, E.; CREMER, M.; ZERBINI, A

Nova Scotia

Conferencia; 22nd Biennial Conference on the Biology of Marine Mammals; 2017

Society for Marine Mammalogy

Franciscana dolphin (Pontoporia blainvillei) populations have been depleted by fishery bycatch since early 1980´s in Brazil. Two Evolutionary Significant Units (ESUs) divided into five franciscana management areas (FMAs) are currently recognized. Systematic efforts toward abundance estimation through aerial surveys have been conducted from 2008 to 2014, including the complete covering of the potential distribution of franciscana in Brazil. In the southern ESU, abundance estimation in FMA 3 was 9,400 (CV:0.19) animals in 2014, while estimates for FMA II are outdated since 2009 (8,000 and 9,000 individuals; CVs = 0.32-0.35). Regarding the northern ESU, less than 1,000 animals (CV:0.48) inhabited northern Rio de Janeiro (FMA Ib) in 2012 and an even smaller number in Espírito Santo (FMA Ia) (no records during observation effort). About 60% of franciscanas are distributed in waters less than 3.5nm from the coast in all FMAs, except in the southern portion of FMA III (60%>6.5nm). Although seasonal variation should be incorporated, that pattern reinforces the importance of coastal marine protected areas where gillnet fishery is restricted. Franciscana conservation depends on two fishery management strategies: (1) implementation and reinforcement of the existing marine protected areas and (2) reduction and/or regulation of fishery effort. These strategies are not mutually exclusive, although the first may be more effective in smaller populations/areas where artisanal fishery operates, while the second would be preferential in larger open areas where industrial fleet operates. A deep concern is that franciscana bycatch research in Brazil is practically ceased. Research-fishery cooperation has deteriorated and the last published statistics on mortality were achieved in middle 2000´s. This research must be urgently resumed at least in some areas. Moreover, it must be stressed that the isolated and fragmented northern Evolutionary Unit (FMA I) soon will be inviable if urgent actions are not taken by the Brazilian government.