Commerson’s Dolphin Habitat Network IMMA

Size in Square Kilometres

10 917 km2

Qualifying Species and Criteria

Commerson’s dolphin – Cephalorhynchus commersonii

Criterion B (1); D (1)

Lahille’s bottlenose dolphin – Tursiops truncatus gephyreus

Criterion A; B (1)

Download fact sheet


This IMMA is a network of coastal habitats along the coast of Argentina, that are important for small resident populations of Commerson’s dolphins.  The Commerson’s dolphins are patchily distributed and there is a high genetic distinctiveness among groups along the coast.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

Lahille’s bottlenose dolphin (Tursiops truncatus gephyreus): This subspecies has been recorded in the IMMA often in mixed groups, feeding and traveling together with common bottlenose dolphins (Tursiops truncatus truncatus) especially in the area of Bahía Engaño in the mouth of Chubut river (Vermeulen et al., 2017).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Commerson’s dolphin: At Bahía Engaño in the mouth of the Chubut River, the population is estimated to be around 350 individuals, most of which remain in the area all year round.  There is  a decrease in abundance of the species in that area that has been linked to an increase of Sea Surface Temperature during summer months (Coscarella, 2005; Coscarella el al 2010). In the area of Camarones, the estimate of Commerson’s dolphins is 239 individuals (Coscarella, 2005). At Bahía San Julián although there is no population estimation, there have been 95 Commerson’s dolphins photo-identified since 1996 (Iñíguez Bessega, unpublished data). For the rest of the areas in this network there are reports on the presence of dolphins, but no estimates of abundance are available.

In all the areas calves have been observed. In Bahía Engaño in the mouth of the Chubut river and in Bahía Camarones calves have been reported from September until March (Coscarella, 2005) and in Comodoro Rivadavia/ Rada Tilly from November until May (Coscarella unpublished information). The breeding season takes place during the austral spring and summer, between September and February (Iñíguez, 1991; Iñíguez & Tossenberger, 2007, Righi et al., 2014). Bahía San Julián is also a reproductive area for Commerson’s with at least 4 newborn Commerson’s every year (Iñíguez Bessega, unpublished data).

In every area Commmerson’s were observed chasing and hunting silversides (smelt or whitebait). Commerson’s dolphins are opportunistic feeders, exhibiting pelagic feeding strategies in northern Patagonia, at the northern end of its range. This species can change its foraging tactics by adapting to different habitats, including those with extreme tidal ranges (Koen-Alonso, 1999). They deploy different hunting techniques in each area. In Bahía Engaño and Camarones, dolphins use not only individual feeding but cooperative feeding (Coscarella et al., 2010).  In Bahía San Julián, Commerson’s dolphins prey on silversides fish and squid (Iñíguez et al., 2000). At Ría Santa Cruz, diving showed a high frequency during the ebb tide, and could therefore be potentially related to a benthic foraging strategy (Loizaga de Castro et al., 2013). A diet study of Commerson’s dolphins at Tierra del Fuego (53º20’S, 68º30’W), showed the presence of benthic preys, indicating that this species feeds at or near the bottom (Bastida et al., 1988).

Lahilles Bottlenose dolphins –  An abundance estimate for both subspecies of bottlenose dolphins combined, created a joint estimate from aerial surveys indicating a very small population of 34 individuals in the the area of Bahía Engaño in the mouth of Chubut river (CI 95% 22-51) (Coscarella et al. (2012).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

Commerson’s dolphins: There is evidence for reduced gene flow (at least of females as shown by mitochondrial DNA analysis) between all of the sampling locations and the suggestions for isolation and divergence of Commerson’s dolphin groups over relatively small geographic distances (Cipriano et al., 2011; Kraft et al., 2021).   Therefore, the precautionary approach suggests that each discrete location within this IMMA network be considered as a candidate for separate management, with efforts made to identify and reduce potential threats even in the absence of evidence for existing threats  (Cipriano et al., 2011; Kraft et al., 2021).

Supporting Information

Brownell R.L. Jr and Praderi R. (1985) Taxonomy and distribution of Commerson’s dolphin, Cephalorhynchus commersonii. The Scientific Reports of the Whales Research Institute, Tokyo 36, 153–164. 

Capella J.J. and Gibbons J.E. (1991) Commerson’s dolphin, Cephalorhynchus commersonii (Lace ́pe`de, 1804), sighted at continental Chile waters. Estudios Oceanolo ́gicos, Facultad de Recursos del Mar, Universidad de Antofogasta 10, 127–130. 

Cipriano, F., Hevia, M. and Iñíguez, M. 2011. Genetic divergence over small geographic scales and conservation implications for Commerson’s dolphins (Cephalorhynchus commersonii) in southern Argentina. Marine Mammal Science 27: 701–718.

Coscarella, M. A. (2005). Ecología, comportamiento y evaluación del impacto de embarcaciones sobre manadas de tonina overa Cephalorhynchus commersonii en Bahía Engaño, Chubut. (Ph.D.). Universidad de Buenos Aires, Buenos Aires. 

Coscarella, M. A., Pedraza, S. N.,  Crespo, E. A. 2010. Behavior and seasonal variation in the relative abundance of Commerson’s dolphin Cephalorhynchus commersonii in northern Patagonia, Argentina. The Journal of Ethology, 28, 463–470. doi:10.1007/s10164-010-0206-4

Coscarella, M. A., Dans, S. L. D., Mariana, Garaffo, G., & Crespo, E. A. (2012). Bottlenose dolphins at the southern extreme of the south-western Atlantic: local population decline? Journal of the Marine Biological Association of the United Kingdom, 92(Special Issue 8), 1843-1849. doi:10.1017/S0025315411001901

Coscarella, Mariano A.; Dellabianca, Natalia A.; Cáceres-Saez, Iris; Hevia, Marta; Morgenthaler, Annick; Failla, Mauricio; Iñíguez Bessega, Miguel A.; Loizaga de Castro, Rocío (2019). Cephalorhynchus commersonii. En: SAyDS–SAREM (eds.) Categorización 2019 de los mamíferos de Argentina según su riesgo de extinción. Lista Roja de los mamíferos de Argentina. Versión digital:

 Crespo, E. A., Schiavini, A. C., García, N. A., Franco‐Trecu, V., Goodall, R. N. P., Rodríguez, D., . . . de Oliveira, L. R. (2015). Status, population trend and genetic structure of South American fur seals, Arctocephalus australis, in southwestern Atlantic waters. Marine Mammal Science, 31(3), 866-890. 

Crespo E., Olavarria C., Dellabianca N., Iñíguez M., Ridoux, V. & R. Reeves, 2017. Cephalorhynchus commersonii (errata version published in 2018). The IUCN Red List of Threatened Species 2017: e.T4159A128963283.

De Bruyn, P.J.N., Hofmeyr, G.J.G., and de Villiers, M.S. 2006. First record of a vagrant Commerson’s dolphin, Cephalorhynchus commersonii, at the southern African continental shelf. African Zoology, 41(1), 131-133.

Goodall R.N.P., Galeazzi A.R., Leatherwood S., Miller K.W., Cameron I.S., Kastelein R.K. and Sobral A.P. (1988) Studies of Commerson’s dolphins, Cephalorhynchus commersonii, off Tierra del Fuego, 1976– 1984, with a review of information on the species in the South Atlantic. Reports of the International Whaling Commission (Special Issue no. 9), 3–70. 

Goodall, R.N.P., de Haro,J.C., Iñíguez,M.A. and Norris, K.S. 1997.Sightings and behaviour of Peale´s dolphins, Lagenorhynchus australis, with notes on dusky dolphins, L. Obscurus, off southernmost South America. Rep. Int. Whal. Commn. 47: 757-776.

Grandi, F., Dans, S. & Crespo E.A. (2015) The recovery process of a population is not always the same: The case of Otaria flavescens, Marine Biology Research, 11:3, 225-235, DOI: 10.1080/17451000.2014.932912

Hevia M., Dellabianca N.A., Reyes L.M., Loizaga de Castro R., Gribaudo C.A. & N.A. García. Lagenorhynchus australis. En: SAyDS–SAREM (eds.) Categorización 2019 de los mamíferos de Argentina según su riesgo de extinción. Lista Roja de los mamíferos de Argentina. Versión digital:

Hevia, M, Iñíguez Bessega, M.A., Reyes Reyes, M.V., Zuazquita, E.P. (2022). A review of marine protected areas in Argentina and their overlap with current cetacean distribution. A Report prepared for OceanCare. May 2022. 83p.

Iñíguez, M.A. 1991. Tonina overa. En H.L.Capozzo y M.Junín(Eds)  Estado de Conservación de los Mam. Marinos del Atlántico Sudoccidental. Informes y Estudios del Programa de Mares Regionales del PNUMA Nº138: 78-82.

Iñíguez, M.A. 1991. Delfín austral. En H.L.Capozzo y M.Junín (Eds.). Estado de Conservación de los Mam. Marinos del Atlántico Sudoccidental. Informes y Estudios del Programa de Mares Regionales del PNUMA Nº138: 48-51.

Iñíguez, M. A. (1997). Toninas overas: Los delfines del fin del mundo. Buenos Aires: Zagier & Urruty Publications. 127 pp.

Iñíguez, M. A., Tossenberger, V.P. and Tomsin, A.L.. 2000. Comportamiento y Biologıa de toninas overas (Cephalorhynchus commersonii) en la bahía San Julián, Pcia. Santa Cruz, Argentina [Behavior and biology of Commerson’s dolphins (Cephalorhynchus commersonii) in San Julian bay, Santa Cruz province, Argentina]. X Reunion de Trabajo de Especialistas en Mamıferos Marinos—III Congreso de SOLAMAC [Proceedings of the X Conferences on Specialists on Aquatic Mammals from South America and III SOLAMAC Congress], Buenos Aires, Argentina.

Iñiguez, M.A.; Belgrano, J.; Tomsin, A.; de Haro, C.; Gribaudo, C. and Tossenberger, V. 2003. Sighting and stranding of southern right whales (Eubalaena australis) off Santa Cruz, Patagonia Argentina (1986-2003). Submitted to the International Whaling Commission. SC/55/BRG8. 6pp.

Iñíguez, M., M. Hevia, F. Cipriano, J. Sarradell and R Doumecq Millieu. 2010. Stranding of a Commerson’s dolphin, Cephalorhynchus commersonii, in Buenos Aires province, Argentina. Marine Biodiversity Records Vol 3, May 2010, e2.

Kraft, S., Pérez-Alvarez, M., Olavarría, C., Moraga, R., Baker, C. S., Steel, D., Brickle, P. (2021). From Settlers to Subspecies: Genetic Differentiation in Commerson’s Dolphins Between South America and the Kerguelen Islands. Frontiers in Marine Science, 8(782512). 

Loizaga de Castro, R., Dans, S. L., Coscarella, M. A., & Crespo, E. A. (2013). Living in an estuary: Commerson´s dolphin (Cephalorhynchus commersonii (Lacépède, 1804)), habitat use and behavioural pattern. Latin American Journal of Aquatic Research, 41(5), 985-991. doi:103856/vol41-issue5-fulltext-17

Perillo, G. M., Piccolo, M. C., Scapini, M. d. C., & Orfila, J. (1989). Hydrography and circulation of the Chubut river estuary (Argentina). Estuaries, 12(3), 186-194. 

Piccolo, M. C., & Perillo, G. M. E. (1997). Geomorfología e hidrografía de los estuarios. In E. Boschi (Ed.), El Mar Argentino y sus recursos pesqueros: Tomo 1- Antecedentes históricos de las explotaciones en el mar y las características ambientales (Vol. 1, pp. 133-161). Mar del Plata: INIDEP.

Pinedo M.C., Barreto A.S., Lammardo M.P., Andrade A.L.V. and Geracitano L. (2002) Northernmost records of the spectacled por- poise, Layard’s beaked whale, Commerson’s dolphin, and Peale’s dolphin in the southwestern Atlantic Ocean. Aquatic Mammals 28, 32–37. 

Reyes Reyes, M. V., Tossenberger, V. P., Iñíguez, M. A., Hildebrand, J. A. and Melcón, M. L. 2016. Communication sounds of Commerson’s dolphins (Cephalorhynchus commersonii) and contextual use of vocalizations. Mar. Mam. Sci. 32, 1219–1233.

Rice D.W. (1998) Marine mammals of the world, systematics and distri- bution. The Society for Marine Mammalogy, Special Publication no. 4, 231 pp. 

Vermeulen, E., Bastida, R., Berninsone, L. G., Bordino, P., Failla, M., Fruet, P., Harris, G., Iñíguez, M., Marchesi, M. C. y Petracci, P., (2017). A review on the distribution, abundance, residency, survival and population structure of coastal bottlenose dolphins in Argentina. Latin American Journal of Aquatic Mammals 12(1-2):2-16.


Download the full account of the Commerson’s Dolphin Habitat Network IMMA using the Fact Sheet button below:

To make a request to download the GIS Layer (shapefile) for the Commerson’s Dolphin Habitat Network IMMA please complete the following Contact Form:

    * Required fields

    Please read the User Licence Agreement and IMMA Layer Metadata Description