Pontoporia blainvillei (Gervais and d'Orbigny, 1844) — Details

La Plata River Dolphin learn more about names for this taxon

Overview

Distribution

Range Description

Franciscanas inhabit shallow coastal waters (and they sporadically enter the estuary of the La Plata River) of tropical and temperate regions of the western South Atlantic Ocean (Crespo 2002). They are found only along the east coast of South America (Brazil, Uruguay, and Argentina), from the northern Golfo San Matias, central Argentina (ca. 42°10'S), to Espirito Santo, southeastern Brazil (18°25'S) (Siciliano 1994; Crespo et al. 1998). The species is not distributed continuously throughout its range. Surveys (including beach surveys, museum specimens, and interviews with local people) indicate that franciscanas are extremely rare or absent in two areas of the northern parts of their range between Macaé (southern Rio de Janeiro State) and Ubatuba (northern São Paulo State) and in Espírito Santo State (Azevedo et al. 2002; Siciliano et al. 2002; Secchi et al. 2003). The reasons for these gaps are unclear, but because the species prefers shallow, turbid waters (Brownell 1989; Pinedo et al. 1989), water transparency and depth may be among the factors responsible (Siciliano et al. 2002).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states.
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Geographic Range

Franciscana dolphins are found along the costal waters of South America from the Doce River in Brazil south to the Valdez Peninsula in Argentina. Pontoporia blainvillei are also common in the estuaries of the Rio de la Plata, hence the other common name, La Plata dolphin.

Biogeographic Regions: neotropical (Native )

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Physical Description

Morphology

Physical Description

Pontoporia blainvillei is one of the smaller species of cetaceans. They range from 1.25 to 1.74m in length, with the females slightly larger than the males. The cape color of these dolphins is grayish, but the ventral and lateral surfaces is paler. The young are distinguishable from adults by their brownish color, and by seven hairs on the upper rostrum that disappear with age. Their beak is extremely long and slender and is moderately demarked from the bulging forehead. Their blowhole is uniquely transverse and in the shape of a crescent. The dorsal fin is triangular in shape with a rounded tip, and ranges 7.0-10.0cm in height. The neck is distinct and apparent. There are 48-61 teeth in each side of the jaw, with the total ranging from 210-242.

Range mass: 20 to 61 kg.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger

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Ecology

Habitat

coastal and estuarine
  • UNESCO-IOC Register of Marine Organisms
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Habitat and Ecology

Habitat and Ecology
Although sometimes described as a ‘river dolphin’, the Franciscana is not a freshwater species. Franciscanas apparently do not migrate, although seasonal inshore/offshore movements have been documented in some areas (Bordino et al. 1999, Bordino 2002). Predation by both large sharks and killer whales has been documented (Praderi 1985, Ott and Danilewicz 1996, Santos and Netto 2005).

Franciscanas are generally found in turbid waters < 30 m deep (Pinedo et al. 1989, Secchi and Ott 2000). Although they are found mainly in marine waters and only occasionally in estuaries, they are relatively common in the Uruguayan part of the La Plata River estuary (Praderi 1986). Franciscanas are primarily coastal, ranging no farther offshore than the 30 m isobath. Some sightings have been made in waters seaward of the 50 m isobath and 55 km offshore, but the density offshore is very low.

Franciscanas feed on several species of shallow-water fish (e.g., sciaenids, engraulids, gadids, and carangids), cephalopods, and crustaceans (Brownell 1989, Di Beneditto and Ramos 2001, Rodriguez et al. 2002, Danilewicz et al. 2002).

Systems
  • Marine
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Pontoporia blainvillei is the only member of the superfamily Platanistoidea that lives in salt water. They are found in the estuary of the Rio de la Plata during most of the seasons, but during winter they migrate either out to sea or upwards along the coast of Brazil.

Aquatic Biomes: coastal

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Depth range based on 8 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 8.6 - 8.6
 
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Trophic Strategy

Food Habits

The franciscana dolphin inhabits waters that are sometimes murky from sediments. They locate bottom-dwelling species of fish by echolocation and by digging up the bottom with their long snout.

Only a few species account for the majority of the food. In Uruguayan waters the most common fish is Cynoscion striatus. In Brazil, the most common are Paralonchurus brasiliensis, Cynoscion striatus, Macrodon ancylodon, and Micropongonias furnieri.

Females eat more squid, Loligo sanpaulensis, than males. It was also observed that juveniles eat more shrimp, Artemesia longinaris, than adults.

Animal Foods: fish; mollusks; aquatic crustaceans

Primary Diet: carnivore (Piscivore )

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Life History and Behavior

Life Expectancy

Lifespan/Longevity

Average lifespan

Status: wild:
16.0 years.

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Lifespan, longevity, and ageing

Observations: Little is know about the longevity of these animals but it is estimated that they live 15-20 years.
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Reproduction

Unfortunately, nothing is known about the mating system of this species.

The female dolphin has a breeding cycle of two years. Matings happen from December to February, births from September to December. Females lactate until the following August or September, and then rest for several months. The gestation period lasts from 9 to 10.5 months and lactation can take up to 9 months. The young are born about .75-.80m in length and weigh about 7.3-8.5kg. Once the young is born it takes up to 1-3 years for physical maturity and 2-3 years for sexual maturity.

Breeding interval: Females breed once every two years

Breeding season: Matings happen from December to February

Range gestation period: 9 to 10.5 months.

Range weaning age: 8 to 9 months.

Range age at sexual or reproductive maturity (female): 2 to 3 years.

Range age at sexual or reproductive maturity (male): 2 to 3 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

Average birth mass: 7900 g.

Average number of offspring: 1.

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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A3d

Version
3.1

Year Assessed
2012

Assessor/s
Reeves, R., Dalebout, M., Jefferson, T.A., Karkzmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E., Slooten, E., Smith, B.D., Wang, J.Y. , Zerbini, A.N. & Zhou, K.

Reviewer/s
Brownell Jr., R.L. & Cooke, J.

Contributor/s

Justification
The species qualifies as VU under criterion A3d because a projected decline of more than 30% over three generations (36 years, Taylor et al. 2007) is suspected based on the results of a population simulation analysis (Secchi 2006) using actual and potential levels of fishing-related mortality (with bycatch defined as exploitation for purposes of applying the criteria). The rate of decline is probably underestimated because a period of only 25 years was considered and other sources of non-natural mortality were not incorporated into the analysis. The causes of the inferred population decline have not ceased and are likely increasing because of fishery expansion (causing higher bycatch and also potentially reducing prey base) and lack of mitigation actions.

History
  • 2008
    Vulnerable
  • 1996
    Data Deficient
    (Baillie and Groombridge 1996)
  • 1996
    Data Deficient
  • 1994
    Insufficiently Known
    (Groombridge 1994)
  • 1990
    Insufficiently Known
    (IUCN 1990)
  • 1988
    Insufficiently Known
    (IUCN Conservation Monitoring Centre 1988)
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US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: vulnerable

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Population

Population
Morphological and molecular data strongly support the existence of two main subpopulations of Franciscanas. Multivariate analysis of morphometric data revealed two subpopulations: a smaller form in the northern part of the species' range (north of 27°S) (those in the far north are of intermediate size) and a larger form in the coastal waters of southern Brazil, Uruguay and Argentina (south of 27°S) (Pinedo 1991). Analyses of a highly variable region of mitochondrial DNA (mtDNA) also supported these two geographic forms (Secchi et al. 1998). Ott (2002) and Lázaro et al. (2004) compared the mtDNA of Franciscanas from Uruguay and Argentina with those published by Secchi et al. (1998). These studies found support for the existence of a large southern population (composed of animals from Rio Grande do Sul, Uruguay and northern Argentina) that is clearly differentiated from animals in the waters off Rio de Janeiro. In addition, they revealed fixed genetic differences between the populations that suggest essentially no effective genetic exchange (see Secchi et al. 1998, Ott 2002, Lázaro et al. 2004). Ott’s results also clearly showed that individuals inhabiting Paraná and São Paulo waters belong to a genetically distinct subpopulation. This is consistent with morphological data showing that size is not clinal, with animals from Paraná and São Paulo being smaller than those in adjacent populations to the south and north of those States (e.g.. Kasuya and Brownell 1979, Di Beneditto and Ramos 2001, Barreto and Rosas 2006, Barbato et al. 2007) A pairwise analysis of haplotype distances between different geographic locations showed increasing differentiation in the haplotype frequencies with increasing distance, following an isolation-by-distance pattern (Lázaro et al. 2004). Furthermore, recent analysis indicated that haplotype frequencies of samples from Claromecó (in Argentina) were significantly different from those of the rest of the southern population (Ott 2002, Lázaro et al. 2004).

Secchi et al. (2003a) proposed four provisional management units (Franciscana Management Areas, or FMAs) with the following ranges: FMA I - coastal waters of Espírito Santo and Rio de Janeiro states, Brazil (note: confirmation of the hiatus in the Espírito Santo State with increased survey effort will require further division of this FMA); FMA II - São Paulo, Paraná and Santa Catarina states, Brazil; FMA III - coastal waters of Rio Grande do Sul State, southern Brazil and Uruguay; and FMA IV - coastal waters of Argentina, including the provinces of Buenos Aires, Rio Negro and Chubut.

There is no current abundance estimate for the species as a whole, but there is an estimate for the management stock inhabiting FMA III (hereafter referred as the RS/URU management unit). During aerial surveys of coastal waters of Rio Grande do Sul State in 1996 (Secchi et al. 2001), this stock’s abundance was estimated at 42,078 (95% CI 33,047–53,542). This extrapolated result must be used very cautiously, however, because it is based on a density estimate for only a small fraction of the coastline, representing approximately 0.7% of the possible range of the subpopulation (ca. 64,045 sq. km), and there is limited information on the distribution pattern of Franciscanas within their total range. This and other estimates of Franciscana density and abundance need to be interpreted cautiously as they could be either positively or negatively biased. The IWC Scientific Committee concluded, after reviewing the methods and limitations of Franciscana surveys through 2003–2004, that it was not appropriate to consider them as providing minimum estimates of abundance (IWC 2005a).

While the overall abundance of the species would seem relatively high, in most areas the gillnet mortality alone is not thought to be sustainable. Secchi (2006) projected the four management units 25 years into the future based on a stage-structured matrix model using a variety of scenarios of fishing effort. Because there were estimates of Franciscana density and abundance only for FMA III and IV (Secchi et al. 2001, Crespo et al. 2004), Secchi (2006) used the density estimated for FMA III and applied a correction factor based on the ratio of capture per unit of effort (CPUE) between the other areas and FMA III. This was assumed to represent a valid index of abundance because the unit of fishing effort is the same and the fishing gears are similar among management units. The corrected densities were multiplied by the entire area of both FMA I and II to obtain the estimate of total abundance. Uncertainty in the parameter estimates was incorporated through appropriate probability distributions. The scenarios considered most realistic (i.e. those that aimed to compensate for underestimation of the bycatch and that modelled environmental stochasticity) resulted in relatively high probabilities that each management unit would decline by at least 30% below its initial size with the exception of FMA I. However, it should be noted that estimates of bycatch in FMA I come from only one fishing village and it is known that bycatch occurs in other parts of this FMA (e.g. Freitas-Neto and Barbosa 2003).

The modelling exercise described above is considered to underestimate the risk of decline of Franciscanas. The most recent data on bycatch (e.g. Rosas et al. 2002, Bordino and Albareda 2005, A. Zerbini as summarized in IWC 2005b) indicate that the numbers caught annually in FMAs II and IV are roughly twice as high as the values used by Secchi (2006) in his projections. In addition, other sources of potential threat (risk factors, as described in the Threats section below) were not considered in Secchi’s study.

Population Trend
Decreasing
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Threats

Major Threats
The main problem facing the species is incidental mortality in gillnet fisheries (there is no indication of direct exploitation of Franciscanas), which has been observed since at least the early 1940s (Van Erp 1969). In the 1960s, the bycatch in Uruguay alone was as high as 1,500–2,000 animals (Brownell and Ness 1969, Pilleri 1971). Current estimates total at least 2,900 animals per year in all four management stocks, combined (e.g., Ott et al. 2002, Secchi et al. 2003b), but the numbers used to get that total are thought to be underestimated to an unknown extent, primarily due to: (1) captures in other non-monitored types of fisheries (e.g., active gillneting, Secchi et al. 1997; shrimp trawling, Cappozzo et al. 2000); (2) under-reporting of bycatch by fishermen; and (3) dolphins captured sometimes falling from the net before or during haul-out (Secchi et al. 2003b). Bycatch is higher in FMA III with estimates being above 1,300 animals incidentally caught annually (Ott et al. 2002; Secchi et al. 2003b, 2004), followed by FMA IV: approximately 800 individuals (Bordino and Albareda 2005), FMA II: > 700 dolphins (Rosas et al. 2002, IWC 2004), and FMA I: > 110 Franciscanas (Di Beneditto 2003).

Stomach contents of Franciscanas from Rio Grande do Sul have included many kinds of debris: discarded fishing gear such as pieces of nylon net (17% of 36 stomachs), cellophane, and plastic fragments (6%) (Bassoi 1997). This problem has also been reported in northern Argentina, where cellophane, fishing debris, and plastic were found in 45%, 32% and 16% of the stomachs (Bastida et al. 2000; Danilewicz et al. 2002). The effects of such debris ingestion on health status of individual Franciscanas have not been determined, and the subpopulation-level implications are uncertain. However, debris could have a negative effect in at least some areas.

Other potential threats include various forms of habitat degradation (e.g. overfishing; destruction of benthic community and bycatch of small sciaenid fish – main Franciscana prey – by trawling) (e.g. Bassoi and Secchi 2000, Danilewicz et al. 2002, Rodríguez et al. 2002).
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES. Measures are needed to reduce the level of bycatch of this species, and research is needed to monitor bycatch levels more accurately.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

None.

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Economic Importance for Humans: Positive

The local farmers use the franciscana dolphin for pig feed and as a source of oil. Their blubber is a good indicator for scientists studying the pesticide levels in the ecosystems in Brazil, Uruguay and Argentina.

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Risks

IUCN Red List Category

subpopulation Rio Grande do Sul/Uruguay franciscana : Vulnerable (VU)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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IUCN Red List Category

Vulnerable (VU)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

La Plata dolphin

The La Plata dolphin or Franciscana (Pontoporia blainvillei) is found in coastal Atlantic waters of southeastern South America. It is a member of the river dolphin group and the only one that actually lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems.

Taxonomy[edit]

The La Plata dolphin is the only species in its genus, and is often placed in its own family, the Pontoporiidae. It was first described by Paul Gervais and Alcide d'Orbigny in 1844 (the species epithet blainvillei commemorates the French zoologist Henri Marie Ducrotay de Blainville). The La Plata dolphin is also widely known as the Franciscana - the Argentine and Uruguayan name that has been adopted internationally. Other common names are the toninha (the Brazilian name) and cachimbo.

Description[edit]

The La Plata dolphin has the longest beak (as a proportion of body size) of any cetacean — as much as 15% in older adults. Males grow to 1.6 m (5 ft, 3 in) and females to 1.8 m (5 ft, 10 in). The body is a greyish brown colour, with a lighter underside. The flippers are also very large in comparison with body size and are very broad, but narrow on joining the body, so are almost triangular in shape. The trailing edges are serrated. The crescent-shaped blowhole lies just in front of a crease in the neck, giving the impression that dolphin forever has its head cricked upwards. The dorsal fin has a long base and a rounded tip.

The La Plata dolphin weighs up to 50 kg (110 lb), and lives for up to 20 years. The gestation period is around 10–11 months and juveniles take just a few years to mature. Females may be giving birth by the age of five.

Behavior and feeding[edit]

The animal is very inconspicuous - it moves very smoothly and slowly—and can be difficult to spot unless estuary conditions are very calm. They will commonly swim alone or in small groups. Exceptional groups as large as 15 have been seen. La Plata dolphins are bottom feeders and gut inspections have revealed they eat at least 24 different species of fish, depending on which species are most common. They will also take octopus, squid and shrimp. They are, in turn, hunted by killer whales (orcas) and several species of sharks.

Range and habitat[edit]

The La Plata dolphin is found in the coastal Atlantic waters of southeastern South America, including the Río de la Plata estuary. Its distribution ranges from the Tropic of Capricorn near Ubatuba, Brazil, south to Península Valdés, Argentina. It is the only member of the river dolphin group that actually lives in the ocean and saltwater estuaries, rather than freshwater. Although some members of the species do spend portions of their lives outside of river systems, many individuals live their entire lives within rivers, never venturing into the ocean proper.

Conservation[edit]

The La Plata dolphin is listed as "Vulnerable" in the IUCN Red List of Threatened Species. However, the Franciscana is a particular conservation concern because of its restricted distribution and vulnerability to incidental capture in fishing gear. Large numbers are killed in gillnets. Although the largest documented catches in the 1970s were in Uruguay, catches in recent decades have also been high in southern Brazil and Argentina. Scientists from all three countries have voiced their concerns, and asked for international assistance in highlighting the plight of the dolphin (see Reeves et al., pg. 53).

The species is listed on Appendix I[2] and Appendix II[2] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I[2] as this species has been categorized as being in danger of extinction throughout all or a significant proportion of its range, and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. It is listed on Appendix II[2] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

A young La Plata dolphin was rescued in 2011 off of Montevideo, Uruguay. Images of the infant dolphin became viral on Facebook, highlighting the plight of the species. [3]

See also[edit]

References[edit]

  1. ^ Reeves, R., Dalebout, M., Jefferson, T.A., Karkzmarski, L., Laidre, K., O’Corry-Crowe, G., Rojas-Bracho, L., Secchi, E., Slooten, E., Smith, B.D., Wang, J.Y. , Zerbini, A.N. & Zhou, K. (2012). "Pontoporia blainvillei". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 January 2013.  Database entry includes a brief justification of why this species is of vulnerable.
  2. ^ a b c d "Appendix I and Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.
  3. ^ http://www.buzzfeed.com/mjs538/adorable-pictures-of-man-taking-care-of-an-orphane
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