Size in Square Kilometres
4 898 km2
Qualifying Species and Criteria
Franciscana dolphin – Pontoporia blainvillei
Criterion A; B (1)
Marine Mammal Diversity
Criterion D (1)
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This IMMA encompasses the range of the northernmost population of the threatened franciscana (Pontoporia blainvillei) located off the northern coast of Espírito Santo State, Brazil. The population is estimated at ~1000 dolphins, and is among the smallest and the most restricted in distribution of this species. Habitat degradation, due to agriculture/industrial activities and environmental disasters, is potentially reducing the available habitat for these dolphins, increasing the exposure of individuals to threats. Feeding behaviours have been consistently observed near the Doce River mouth, a high-density area within this IMMA. This area also provides foraging habitat for other cetacean species such as Guiana dolphins (Sotalia guianensis). Groups of rough-toothed dolphins (Steno bredanensis) and common bottlenose dolphin (Tursiops truncatus) are commonly seen off the area as well as groups of humpback whales (Megaptera novaeangliae) during the species’ breeding season in the austral summer.
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
The franciscana (Pontoporia blainvillei) is endemic to the coastal waters of Brazil, Uruguay and Argentina. The species is currently listed as “Vulnerable” in the IUCN Red List of Threatened Species (Zerbini et al. 2017) and “Critically Endangered” by the Brazilian Government (MMA/ICMBio 2022). Franciscana abundance in Franciscana Management Area Ia was estimated at 1,183 (CV = 0.76, 95% CI = 163 – 3,150) individuals based on aerial surveys conducted in 2018 (Sucunza et al. 2023). The authors of that study suggested that the population would qualify for listing as an “Endangered” population under the IUCN Red List Criterion C2a(ii), because of the small size (less than 2,500 mature individuals) and because of an inferred decline in mature individuals and of least 95% of mature individuals in one subpopulation (Zerbini et al. 2017, Sucunza et al. 2023). Habitat degradation, due to agriculture/industrial activities and environmental disasters, is potentially shrinking available habitats for franciscana dolphins, increasing the exposure of individuals to threats (Pinheiro et al. 2019, Domit et al. 2022).
Criterion B: Distribution and Abundance
Sub-criterion B1: Small and Resident Populations
The northern coast of Espírito Santo State (ES) encompasses the range of a small and isolated population of franciscanas known as FMA Ia (Siciliano et al., 2002, Cunha et al. 2014, Amaral et al., 2018, Nara et al. 2022). A hiatus of ~180 km with no known historical or recent records exists between the southern limit of FMA Ia and the next FMA Ib further to the south in Itabapoana (21.34oS; 40.95oW) (Siciliano et al. 2002, Amaral et al. 2018). In 2018, aerial surveys following line transect distance sampling methods were conducted and abundance, corrected for visibility and group size biases, was estimated at 1,183 individuals (CV = 0.76) (Sucunza et al. 2023). In addition, aerial surveys indicate that franciscanas occurring off the north ES coast are limited to nearshore waters, extending only as far as the 30 m isobath (Danileiwcz et al. 2009), between Conceição da Barra in the north (18o35’S) and Santa Cruz in the south (19o56’S), which results in an estimated area of occupancy of only 1400km2 (Sucunza et al. 2023).
Franciscana dolphins have been recorded year-round off this IMMA during drone-monitoring and beach surveys for stranded specimens (Mayorga et al. 2020, Giacomo et al. 2021). In addition, stranding and bycatch events of franciscana adults, juveniles and calves (Siciliano 1994, Marcondes et al. 2018, Mayorga et al. 2020) as well as records of franciscana mother and calf pairs during aerial surveys and drone-monitoring (Giacomo et al. 2021, Sucunza et al. 2023) indicate that the reproductive cycle of franciscanas in ES occurs within this IMMA. Feeding occurs within this IMMA (e.g., Rupil et al. 2019, Giacomo et al. 2021). Feeding behaviours have been consistently observed near the Doce River mouth, which hosts high densities of franciscanas and is also a foraging habitat for other cetacean species such as Guiana dolphins (Sotalia guianensis) (Rupil et al. 2018, Rodrigues et al. 2020).
Criterion D: Special Attributes
Sub-criterion D1: Distinctiveness
Based on mitochondrial and nuclear data available related to stock structure across the range of the franciscanas range, Cunha et al. (2020) proposed the existence of 11 Franciscana Management Areas (FMAs). These areas have been recognized as appropriate units for assessment of the species by the International Whaling Commission (IWC in press). The northern coast of Espírito Santo (ES) corresponds to the range of the northernmost population, which is geographically, demographically and genetically isolated from all other franciscana populations (Siciliano et al. 2002, Nara et al. 2022, Sucunza et al. 2023). Genetic variability decreases from south to north throughout the species’ range, and franciscanas in ES are one of the most genetically differentiated populations, with extremely low genetic diversity (Cunha et al. 2014, Cunha 2022).
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