IIMYC   23581
INSTITUTO DE INVESTIGACIONES MARINAS Y COSTERAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Abundance and distribution of isolated populations of franciscana dolphin in southeastern Brazil: red alert for local extinctions
Autor/es:
DANILEWICZ, D; ZERVINI, A.; SUCUNZA, F.; ANDRIOLO, A.; FERREIRA, E.; DENUNCIO, P; SECCHI, E.; FLORES, P.A.
Lugar:
San Francisco
Reunión:
Conferencia; 21st Biennial Conference on the Biology of Marine Mammals: Bridging the Past Toward the Future; 2015
Institución organizadora:
Society for Mammalogy
Resumen:
The franciscana (Pontoporiablainvillei) is endemic of the coastal waters of Brazil, Uruguay and Argentina and is currently regarded as the most threatened small cetacean in South America due mainly to high bycatch levels. Four Franciscana Management Areas or (FMAs) were defined. FMA I corresponds to the coasts of the Brazilian states of Rio de Janeiro (RJ) and Espírito Santo (ES), and represent the two northernmost isolated and poorly studied populations. In December 2011 and January 2012 aerial surveys were conducted to assess the distribution and to estimate abundance of franciscanas in this area. A total of 20 franciscana groups were sighted along 2,242.6 km surveyed. Average group size was 2.2 (SE = 0.305). Abundance corrected for perception and availability bias was estimated to be 1,998 (CV=0.48, 95% CI: 796-5,013) with the most supported detection probability model. These are the lowest across all estimates along the franciscana range, which is consistent with the remarkable low genetic diversity observed in these populations. Franciscanas were recorded from turbid waters of surf zone to clearer waters as far as 13km from the shore (19m deep) in RJ. No on-effort sighting was done in ES. The surveys confirmed the isolation of FMAI from the southern populations, as well as a stretch of 180km between RJ and ES without records. The most recent (2001-2002) estimates of incidental mortality in this area correspond to 5.5% (2.2-13.8%) of this estimated population size, indicating unsustainable bycatch. The risk of local extinction increases with the degree of isolation from conspecific populations, since isolated populations tend to be smaller and have a higher likelihood to be sensitive to demographic/environmental stochasticity and genetic drift. Because of their isolation, low abundance and unsustainable bycatch mortality, franciscanas in RJ and ES clearly constitute a conservation priority for cetaceans in Brazil. Funding:SMF-IWC and ICMBio (MMA).