Pontoporia blainvillei is the scientific name of a small dolphin known as "Franciscana". In Brazil, the species is popularly known as "toninha", however, regional variations include other names, for example, "manico" and "boto-cachimbo." Franciscana is the common name used in Spanish-speaking countries where the species occurs. Its distribution is restricted to the coastal waters of Brazil, Uruguay and Argentina and it is the most endangered dolphin species, mainly due to by-catch in fishing nets.
Despite the regional variations in size, its maximum length is around 1.7 m. It features an extremely long rostrum (beak) with approximately 200 small teeth. The brownish-gray color makes it difficult to contrast with the coastal muddy waters of the region.
They are shy, do not approach vessels, they are very discrete when rising to the surface to breathe. Unlike other dolphins they do not jump and, therefore, are rarely seen in nature. They generally form small groups of 2 to 5 individuals, which genetic studies have often shown to be families.
The Franciscana occurs from Itaúnas (18°25'S), State of Espírito Santo (ES), Brazil, to the Gulf of San Matias (~42°S), Chubut Province, in Argentina. Preferably inhabits shallow waters with less than 50m and some estuaries.
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Its distribution is not continuous. Between Regência, ES (19°40'S) and Barra do Itabapoana, State of Rio de Janeiro (RJ) (21°18'S); and between Macaé (22°25'S) and the Bay of Ilha Grande (23°S), in RJ, the Franciscana is apparently absent.
Conhecer o tamanho das populações de Toninhas é fundamental para sua conservação. As estimativas são feitas de barco ou com pequenos aviões bimotores voando em baixas altitudes.
Estes estudos já foram realizados no Rio Grande do Sul e na FMA II. As estimativas indicam que as populações são pequenas e, portanto, muito vulneráveis às capturas acidentais em redes de pesca.
Na Baia da Babitonga, localizada no litoral norte de Santa Catarina, as Toninhas são avistadas ao longo de todo ano e a bordo de pequenas embarcações a população foi estimada em 50 animais.
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Among cetaceans, the Franciscana is one of the species with the shortest life cycle and biological studies indicate that sexual maturity is reached between 2 and 4 years old, with little difference between males and females. The maximum known age of a Franciscana is 23 years.
Females give birth to a calf every year or two. The gestation period lasts around 11 months and total length at birth varies between 70 and 80 cm. Lactation may reach 9 months and births occur mainly in spring and summer.
The Franciscana feeds on a wide variety of prey, with approximately 80 items already recorded as part of their diet in Brazil, Uruguay and Argentina. The diet composition includes mainly small bony fish and squid in estuarine and coastal regions. Whole fish ingestion probably starts when Franciscanas have reached 2 or 3 months of age and 75-80 cm long, a phase in which shrimp are important components of the diet. Seasonal variations have been recorded, following prey availability in these areas.
Fishing stocks' depletion can also force diet variations in the Franciscanas. As an example, historical records of the commercial catch have shown a decline in annual landings of whitemouth croaker (Micropogonias furnieri), king weakfish (Macrodon ancylodon) in southern Rio Grande do Sul.
This fact is consistent with the reduction in the occurrence of these two species in the Franciscana's diet. Moreover, the frequency of occurrence of the largehead hairtail, Trichiurus lepturus, and the argentine croaker, Umbrina canosai increased in the Franciscana's diet at about 5% and 3%, in the late 1970's to about 39% and 20%, respectively, in the mid-1990s. While the weakfish has always been an important prey item, the hairtail had a lower importance in the past, making it currently one of the most important species in the Franciscana's diet. These figures suggest that changes in their diet followed variations in the availability of some species exploited by commercial fisheries.
Oil spills in coastal areas have affected several marine species (e.g. penguins, seals and sea lions), but their potential effects on the Franciscana are unknown.
Trace elements (Ag, As, Cd, Cu, Hg, Mn, Pb, Se e Zn) and organic persistent pollutants (POPs), especially polychlorinated biphenyls and chlorinated pesticides, have been detected in tissues of Fraciscanas.
In general, the levels of contaminants found are relatively low compared to concentrations recorded in Northern Hemisphere dolphins. Environmental conditions (more or less polluted sites) and food preferences (for example, higher intake of young fish) can influence these concentrations. As an example, higher concentrations of total mercury and organic mercury were found in populations of Rio Grande do Sul than in Rio de Janeiro.
Plastic ingestion of by cetaceans has been a cause of global concern and the analysis of Franciscanas' stomach contents has shown that this species is also vulnerable to the ingestion of various types of waste, including the ingestion of nets and fishing line.
The causes of natural mortality of Franciscanas are still poorly known. Predation by some species of sharks and orcas has been recorded.
With regards to disease, studies performed by the School of Veterinary Medicine at the University of São Paulo (LAPCOM, FMVZ, USP), have analyzed tissues of different organs, blood, fluids and swabs collected during necropsies. These studies revealed that lesions were most often recorded in the lungs and these were edema, emphysema and congestion. These lesions are consistent with those described in other species that eventually died from asphyxia after incidental capture in fishing nets. Recent studies have also reported changes in muscle that can impair the cardiac function and the presence of cholesterol crystals causing pneumonia.
The following organisms have been previously isolated: Plesiomonas shigelloides, Aeromonadaceae, Pseudomonas aeruginosa, Vibrio spp., Aeromonas spp. (bacteria), Micrococcus spp. (fungi).
Several are considered opportunistic and occur in the microbiota of healthy animals, but can cause lesions in individuals with impaired immunity. In some occasions it was possible to correlate the microorganism with disease occurrence, such as in the case of P. aeruginosa, which may have caused death by septicemia in a Franciscana newborn, in Sao Paulo.
The parasitological infection has revealed differences among Franciscanas' populations. They have different helminthofauna along their distribution, which may consist of one or more species of parasites, especially nematodes, trematodes and acanthocephalans. An ongoing assessment of the parasitic infection and other diseases may determine their role in Franciscanas' health along the Brazilian coast.
Single individuals are commonly observed and also groups of 2-5 individuals; however, they can form groups with more than 10, especially while feeding and socializing. The species tends to avoid approaching motorboats. Aerial behaviors are unusual.
The first study monitoring Franciscanas using remote equipment was conducted in 2005, at Baía de Samborombón, mouth of the La Plata River, Buenos Aires Province, Argentina. At the time VHF transmitters were used. More recently satellite transmitters have been used for tracking Franciscanas in the Bays of San Blas and Samborombón.
All the individuals that were satellite-tracked displayed localized movements and had small territories, between 150 and 345 km2, where there are intense artisanal fishing activities. This information helps to identify the Franciscanas' preferred areas and propose fishing zones that have little or no overlap with the animals' distribution.
A detailed field study was also conducted at Baía de Babitonga, SC, Brazil. In this area the Franciscanas are seen throughout the year and the study presents the preferred areas for foraging and socializing. The absence of records at the Bay's entrance suggests that this is a resident population, and recently, five animals received satellite transmitters to confirm this hypothesis.
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There is a need to implement environmental education programs within the fishing communities, aiming at better understanding and increased participation in the species' conservation. These programs should include the preparation and distribution of booklets, leaflets, posters, t-shirts, caps, videos and educational games. Public lectures and interactive events like meetings, exhibitions and cultural festivals inviting the local schools and community associations.
It is also essential to seek federal and state agencies' involvement through financial support, turning campaigns for the species' conservation in activities with national responsibility.
The greatest threat to the Franciscana is undoubtedly bycatch throughout their distribution. Additionally, they suffer with habitat degradation and depletion of fish stocks, which forces changes in their diet.
The species is the only small cetacean on IBAMA-MMA's National List of Threatened Species (Brazilian Institute of the Environment and Renewable Natural Resources, Ministry of the Environment). Francisacanas are also included on international endangered species lists and it is considered one of the world's most threatened small cetaceans by WWF (The World Wide Fund for Nature).
It is listed on the CMS (Convention for Migratory Species) on Appendices I and II; and on CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) as Appendix II.
It is shown as vulnerable on the Red List of Threatened Species IUCN (International Union for Conservation of Nature and Natural Resources), based on a suspected decline of 30% over three generations. The population most probably will keep declining due to the expansion of fishing activities and the lack of mitigation measures.
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