18 Gomez Salazar et al.pmd

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4 C.GÓMEZ-SALAZAR et al.Figure 2. Sightings (2006–2009) of Sotalia sp. in the Venezuelan Orinoco basin.Figure 3. Distribution of Sotalia in the Amazon (Colombia, Ecuador, Peru), Orinoco (Venezuela) and Suriname.LAJAM 8(1-2): **-**, December 2010
UPDATE ON THE FRESHWATER DISTRIBUTION OF SOTALIA IN COLOMBIA, ECUADOR, PERU, VENEZUELA AND SURINAME 5Amazon River basin - S. fluviatilis is distributed throughoutthe Ucayali River in Peru, considered the main headwaterof the Amazon River, and its confluence with theMarañón River, where the Amazon River begins. S.fluviatilis is also distributed through the Pacaya-SamiriaNational Reserve, including the Samiria and Pacaya riversand lakes such as Tipishca del Samiria and San Pablo deTipishca. There are also records of Sotalia from theMarañon River and from its major tributaries that flowsoutheasterly from Ecuador: the Pastaza, Morona, Tigreand Napo rivers. The Pastaza River and its tributary, theBobonaza River, are located in the southern EcuadorianAmazon. There are some records in the Morona River,parallel to the Pastaza, and several of its tributaries (theMangosiza, Cushuimi, Cangaime, Makuma and Wichimirivers). Finally, fewer records of S. fluviatilis occur in theNapo River in northern Ecuador, and some of itstributaries such as the Panayacu, the Tiputini, the Yasuníand the Aguarico (which receives the Cuyabeno andLagarto Cocha Rivers). S. fluviatilis is distributed widelythroughout the Amazon River as it flows through thesouthernmost region of Colombia, receiving the LoretoYacu (El Correo and Tarapoto Lakes), Atacuari, andAmacayacu tributaries and the Caballo Cocha Lake onthe border with Peru and the Javari River on the borderof Peru and Brazil. In addition, S. fluviatilis is distributedin southwest Colombia in the Putumayo and Caquetárivers along the border of Ecuador and Peru. ThePutumayo and Caquetá Rivers are main tributariesflowing southeast into the Amazon River in Brazil, wheretheir names change to Içá and Japurá, respectively. Themost northwestern records of S. fluviatilis in the AmazonRiver basin are from the Apaporis River, a tributary ofthe Caquetá River in Colombia.Orinoco river basin - Sotalia sp. is distributed across theOrinoco River (middle and lower Orinoco basin) inVenezuela, beginning 20km from the border ofColombia where the Parguaza rapids are formed,~815km away from the river mouth. In the middleOrinoco basin, Sotalia is distributed 1-3km upriver fromthe Parguaza and Cinaruco Rivers (major tributaries ofthe Orinoco River). In the lower Orinoco basin, Sotalia(possibly S. guianensis) is found in the river mouth wherethe Orinoco River forms a wide delta that createshundreds of tributaries and channels that flow northeastinto the North Atlantic Ocean.In Colombia, Sotalia dolphins are not present in the upperand middle Orinoco basin south of the confluence withthe Meta River in waters shared by Colombia andVenezuela. Therefore, the closest Sotalia population isfrom coastal areas of the Atlantic Ocean (S. guianensis)(Caballero et al., 2007). Sotalia in the Orinoco River werepreviously thought to be S. guianensis making incursionsof up to 800km upriver (Borobia et al., 1991; Boher et al.,1995; Trujillo et al., 2000; Caballero et al., 2007; Bolaños-Jiménez et al., 2008). However, S. guianensis is significantlylarger than S. fluviatilis (Flores and da Silva, 2009) andindividuals from the middle Orinoco appear to be smallerthan individuals in the delta of the Orinoco. In terms ofmorphology, individuals observed in the middle Orinocoin Venezuela have a dorsal fin that has a more slenderbase, more similar to their counterparts in the Amazonbasin, than to S. guianensis in the lower Orinoco. Sotaliaobserved in the lower Orinoco (at about 12-15km upriverfrom the Atlantic Ocean) have a wider dorsal fin base,do not have pink coloration patterns in their flanks, andtheir eyes appear to be bigger than S. fluviatilis, and moresimilar to S. guianensis (Figure 4). We suggest that Sotaliadolphins in the Orinoco delta in Venezuela are in fact S.guianensis making incursions into the river. Genetic andmorphological studies are urgently needed to clarifywhether populations in the middle Orinoco of Venezuelaare coastal transients making incursions into the river orpart of a population that entered via the Amazon to theOrinoco (Borobia et al., 1991; Boher et al., 1995; Cunha etal., 2005; Caballero et al., 2007) or perhaps anothersubspecies or species altogether.Differences in the colouration patterns between Sotaliaspecies are interesting and worth investigating. S.fluviatilis in the Amazon River basin are light grey andtheir flanks vary from white to pink that continuesthrough their abdomen (da Silva and Best, 1996; Figure4). S. guianensis in Suriname are light grayish-blue todark grey and also have flanks that vary from pink tolight pink and white. However, the colour in their flanksappears to continue through to their abdomen. This isin contrast to S. fluviatilis in the Amazon, which have agrey streak in between the light coloration of their flanks(Figure 4). Sotalia dolphins in the lower Orinoco do notappear to have any pink in their flanks, and Sotaliadolphins in the middle Orinoco have some pink colourin their flanks.Suriname - Currently, S. guianensis in the Suriname Riverhas only been recorded up to ~23km up from the rivermouth (Paramaribo city), much less than the ~58kmupriver previously recorded by Husson (1978) in daSilva and Best (1996). It is of serious concern thatpollution from Paramaribo city may be one of the factorscausing this restriction in their movements (M. Pool,pers. comm.). S. guianensis is also recorded in theCommewijne River (~38km from the Suriname Rivermouth) and they are occasionally seen up to the localityof Bakkie during the long dry season. In addition, thereare reports of S. guianensis in the Corantijn River, theMarowijne and the Coppename Rivers. Overall, S.guianensis only swim upriver during the dry seasonwhen the saltwater incursion is further upriver and thesalinity of the water is high enough.As final remarks, we think that the results of thiscompilation of available information on the distributionof Sotalia in freshwater of Ecuador, Peru, Colombia,Venezuela and Suriname are useful for identificationof some of the major natural barriers for this species,and provide a baseline for monitoring future changesin their geographic range. The current distribution ofS. fluviatilis in the Colombian and Peruvian AmazonLAJAM 8(1-2): **-**, December 2010
Page 1: LAJAM 8(1-2): **-**, December 2010
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18 Gomez Salazar et al.pmd

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