Northern Patagonian Gulfs and Valdes Front IMMA

Size in Square Kilometres

44 582 km2

Qualifying Species and Criteria

South American sea lion – Otaria byronia

Criterion B (1); C (1)

Southern elephant seal – Mirounga leonina

Criterion B (1); C (1, 2)

Southern right whale – Eubalaena australis

Criterion B (1); C (1)

Dusky dolphin – Lagenorhynchus obscurus

Criterion C (2)

Common dolphin – Delphinus delphis

Criterion C (2)

Killer whale – Orcinus orca

Criterion B (1); C (2)

Common bottlenose dolphin – Tursiops truncatus truncatus

Criterion B (1); C (2)

Lahille´s Bottlenose dolphin – Tursiops truncatus gephyreus

Criterion A; B (1); C (2)

South American fur seal – Arctocephalus australis

Criterion C (2)

Marine Mammal Diversity 

Criterion D (2)

Otaria byronia, Mirounga leonina, Eubalaena australis, Lagenorhynchus obscurus, Delphinus delphis, Orcinus orca, Tursiops truncatus truncatus, Tursiops truncatus gephyreus, Arctocephalus australis

Download fact sheet


This IMMA includes habitat that supports at least 11 marine mammal species, including both pinnipeds and cetaceans. In the austral winter and spring, it serves as an important area for mating, calving and nursing for southern right whales (Eubalaena australis). The IMMA is also home to resident populations of fewer than 250 Lahille´s bottlenose dolphins (Tursiops truncatus gephyreus) and 30 Killer whales (Orcinus orca). Northern Patagonian coastal areas host over 20 South American sea lion (Otaria byronia) colonies, with an estimated population of 63,000 and pupping occurring between mid-December and February each year. The IMMA also contains important rookeries for Southern elephant seals (Mirounga leonina), with around 15-16,000 pups born every year.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The IMMA hosts a resident population of Lahille’s bottlenose dolphins (Tursiops truncatus gephyreus), which are classified as Vulnerable on the IUCN Red List (Vermeulen et al. 2019).  Fewer than 250 are thought to be present in the IMMA based on average numbers of sightings since the 1970’s (Coscarella et al. 2012).  The estimated abundance of Lahille’s bottlenose dolphins in Argentine waters is less than 1000 mature individuals, across at least two genetically distinct subpopulations (Vermeulen et al. 2017, Vermeulen et al. 2019, Loizaga et al. 2020). The cause of this decline is unknown (Coscarella et al. 2012).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

There are small and resident populations of both common bottlenose dolphins (Tursiops truncatus truncatus)  and Lahille’s dolphins (T.t. gephyreus) in Golfo San Matías, with the latter proven to be genetically isolated from other neighbouring populations (Fruet et al. 2014). 

Approximately, 30 killer whales (Orcinus orca) inhabit this IMMA year-round, and the matrilineal lines of the different pods had been identified by means of photo identification (for more information see Punta Norte Research), as well as the individuals that perform the intentional stranding while hunting for southern sea lions. (López and López 1985, Iñíguez 1990, 2001; Hoelzel 1991, Reyes and García-Borboroglu 2004, Sironi et al. 2008, Vila et al. 2008, Coscarella et al. 2015).

Sub-criterion B2: Aggregations

The IMMA harbours temporal aggregations of multiple different marine mammal species. These include at least 21 permanent rookeries and haul-out colonies of South American sea lions (Otaria byronia), representing about 120,700 individuals in breeding and non-breeding colonies (Cardenas Alayza et al. 2015). Southern elephant seals (Mirounga leonina) occupy all of the coast of Península Valdés and the area to the south of the mouth of Golfo Nuevo for their breeding and moulting seasons (Crespo et al., 2007). Over the past 10 years, this species has increased at a rate that appears to be reaching carrying capacity (Ferrari et al. 2013). An estimated, 2,200 southern right whales (Eubalaena australis) congregate in the IMMA between April and December to mate, calve and nurse their young (Crespo et al., 2019).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The area is a significant breeding ground for Southern right whales, who use the nearshore waters of all three bays of this IMMA between April and December each year to mate, calve and nurse young. These waters are especially important for mothers and calves seeking protection and rest in shallow water (Arias et al. 2018, Crespo et al. 2019, Rowntree et al. 2020). When research on this population first began in 1999, roughly 150 calves were documented per year (Crespo et al. 2018).  Between 2005 and 2011, recorded calves peaked at an average of 500 (Crespo et al. 2019). However, the number of calves born each year is variable. In 2018 the number of calves recorded in one season increased to 710, while in 2019 the number was 448 and in 2022 the number was 390 (Crespo et al. 2023).

South American sea lions inhabit northern Patagonia where they are concentrated in 21 colonies (Crespo et al. 2021) that hold an estimated 63,000 individuals. Males and females arrive to the breeding colonies in mid-December, with a maximum number of individuals on land during the second half of January. Females give birth to a single pup 2-3 days after their arrival at the rookeries and remain onshore to breed for approximately 7 days. Pups are born from mid-December to early February, with a peak in mid-January (Crespo et al. 2021).

A large proportion of the Península Valdés coastline is also occupied by approximately 20,000 southern elephant seals that give birth to 15-16,000 pups between September and October every year (Ferrari et al. 2013; Campagna et al. 2021, Lewis and Eder, 2021). They return back to moult between December and May (Crespo et al. 2007).

Sub-criterion C2: Feeding Areas

The Patagonian gulfs provide abundant prey for South American fur seals, Southern elephant seals and common (Delphinus delphis), dusky (Lagenorhynchus obscurus) and Bottlenose dolphins (Koen Alonso et al. 1998, 2000).  The most important  fish prey species for sea lions, fur seals and dolphins are southern anchovy (Engraulis anchoita), hake (Merluccius hubbs), ‘pampanito’ (Stromateus brasiliensis), and southern cod (Nothotenia sp.).  Cephalopods also make up important elements in these marine mammals’ diets, and include the shortfin squid (Illex argentinus), the Patagonian squid (Loligo gahi), sepiolid Semirossia tenera, and octopus (Octopus tehuelchus). Elephant seals feed on deeper waters squid and fish (Daneri & Carlini  2002).

Killer whales also prey in this area on pinnipeds, cetaceans, sea birds and sharks (López and López 1985, Iñíguez 1990, 2001; Hoelzel 1991, Reyes and García-Borboroglu 2004, Sironi et al. 2008, Vila et al. 2008, Coscarella et al. 2015).The pods usually encountered in the area feed on sea lion and elephant seal pups by beaching themselves and returning into the sea during specific periods of the year (Lopez and Lopez, 1985; Hoelzel, 1991, Iñiguez 2001, Vila et al., 2008). Killer whales have been observed hunting dusky (Lagenorhynchus obscurus) and common dolphins (Delphinus delphis) in coordinated attacks where killer whales herd small groups of dolphins towards a ‘catcher’ placed in the path of the dolphins (Coscarella et al 2015). The same killer whales have also been reported training juveniles in these hunting techniques and successfully attacking Southern right whales (Sironi et al., 2008).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

The area includes habitat that supports an important diversity of marine mammal species.  At least 11 species, both pinnipeds and cetaceans are regularly documented in the area (Foro para la Conservación del Mar Patagónico y Áreas de Influencia 2013, Falabella 2014). Each year the Northern Patagonian Gulfs (Golfo Nuevo, Golfo San José and Golfo San Matías) are visited by 1000 to 2000 southern right whales (all age classes), out of a total estimated population of 5000 to 6000 individuals. This area is a key breeding and nursery ground for southern right whales, southern elephant seals and South American sea lions. In these waters the resident killer whales have developed intentional stranding, a hunting technique that has cultural transmission. The IMMA hosts a resident population of Lahille’s bottlenose dolphins, which are classified as Vulnerable on the IUCN Red List.

Supporting Information

Amaral, A. R., Sequeira, M., Martínez-Cedeira, J., & Coelho, M. M. (2007). New insights on population genetic structure of Delphinus delphis from the northeast Atlantic and phylogenetic relationships within the genus inferred from two mitochondrial markers. Marine Biology, 151(5), 1967-1976.

Arias, M., Coscarella, M. A., Romero, M. A., Sueyro, N., Svendsen, G. M., Crespo, E. A., & González, R. A. (2018). Southern right whale Eubalaena australis in Golfo San Matías (Patagonia, Argentina): evidence of recolonisation. Plos one, 13(12), e0207524.

Beade, M., Loureiro, J.D. and Mendez de Cabrera, G. A. 1988. Avistaje de Orcinus orca en Bahía Samborombón – Argentina y un caso de ataque sobre Tursiops gephyreus. III Reunión de trabajo de especialistas en mamíferos acuáticos de América del Sur. 25-30 de Julio.Montevideo, Uruguay. P.12..

Campagna, C., & Le Boeuf, B. J. (1988). Reproductive behaviour of southern sea lions. Behaviour, 104(3-4), 233-261.

Campagna, C., Boeuf, B. L., & Bisioli, C. (2021). Mating Games and Raiding Parties in Southern Sea Lions. In Ethology and Behavioral Ecology of Otariids and the Odobenid (pp. 183-203). Springer, Cham.

Cardenas Alayza, S., Crespo, E. A., & Oliveira, L. (2016). Otaria byronia, South American sea lion.

Coscarella, M.A., S.L. Dans, M. Degrati, G.V. Garaffo & E.A. Crespo. 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, 92:1843-1849.

Coscarella, M. A., Bellazzi, G., Gaffet, L., Berzano, M., & Degrati, M. (2015). Technique used by killer whales (Orcinus orca) when hunting for dolphins in Patagonia, Argentina. Aquatic Mammals, 41(2), 192-197. doi:10.1578/AM.41.2.2015.192

Coscarella, M.A., Cáceres-Saez, I., Loizaga de Castro, R. y García, N.A. (2019a). Orcinus orca. 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., Pedraza, S.N. & Coscarella, M.A. (2008) Estudio de las amenazas para la conservación de mamíferos marinos de Patagonia. Informe Final.  II CONVOCATORIA DE AYUDAS A LA INVESTIGACIÓN EN BIOLOGÍA DE LA  CONSERVACIÓN DE LA FUNDACIÓN BBVA. 2005-2008.

Crespo,  E.A., A. Schiavini, N. García, V. Franco-Trecu, N. Goodall, D. Rodríguez, J. Morgante & L.R. Oliveira. (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. A., Oliveira, L. R. D., & Sepúlveda, M. (2021). South American sea lion (Otaria flavescens, Shaw 1800). In Ecology and conservation of pinnipeds in Latin America (pp. 93-118). Springer, Cham.

Crespo, E.A. & Oliveira, L.R. (2021). South American fur seal (Arctocephalus australis, Zimmermann 1783). Chapter 2. pp 13-27. In: Ecology and Conservation of Pinnipeds in Latin America. Heckel, G., Schramm, Y. (eds) Springer, Cham.

Crespo, E. A., Pedraza, S. N., Dans, S. L., Svendsen, G. M., Degrati, M., & Coscarella, M. A. (2019). The southwestern Atlantic southern right whale, Eubalaena australis, population is growing but at a decelerated rate. Marine Mammal Science, 35(1), 93-107.

Crespo, E.A., S.N. Pedraza, S.L. Dans, G.M. Svendsen, M. Degrati and M.A. Coscarella. 2018. Southwestern Atlantic Southern Right Whales Eubalaena australis still growing but at a decelerated speed. Marine Mammal Science. DOI:10.1111/mms.12526

Crespo, E.A., M.A. Coscarella and N. Sueyro. (2023). The Southwestern Atlantic Southern Right Whale, Eubalaena australis: updated population rate of increase. International Whaling Commissionn SC/69A/CMP/01.

Crespo, E.A. & García, N.A. (2016). Síntesis del estado actual de los mamíferos marinos del Mar Argentino: tasas de incremento y factores denso–dependientes. XI Congreso de la Sociedad Latinoamericana de Especialistas en Mamíferos Acuáticos (SOLAMAC) – RT17. Libro de Resúmenes. Valparaíso, Chile. 28 noviembre – 1 diciembre.

Crespo, E.A., M.N.Lewis & C. Campagna. 2007. Mamiferos marinos: pinnipedios y cetáceos. En: El Mar Argentino y sus recursos pesqueros, Tomo 5 El Ecosistema Marino. INIDEP. Pp 127-150.

Daneri G.A. and A.H. Carlini. 2002. Fish prey of southern elephant seal, Mirounga leonina, at King George Island. Polar Biology 25:739-743.

Degrati, M., S.L. Dans, S.N. Pedraza, E.A. Crespo & G.V. Garaffo. 2008. Diurnal behavior of dusky dolphins, Lagenorhynchus obscurus, in Golfo Nuevo, Argentina. Journal of Mammalogy, 89(5):1241–1247.

Degrati, M., Coscarella, M. A., Crespo, E. A., & Dans, S. L. (2019). Dusky dolphin group dynamics and association patterns in Península Valdés, Argentina. Marine Mammal Science, 35(2), 416-433.

Degrati, M., Loizaga, R., Coscarella, M. A., Sueyro, N., Crespo, E. A., & Dans, S. L. (2020). Integrating Multiple Techniques to Estimate Population Size of an Impacted Dusky Dolphin’s Population in Patagonia, Argentina. Frontiers in Marine Science, 7, 289.

Dellabianca, N.A., Mandiola, A. y Denuncio, P.E. (2019). Phocoena spinipinnis. 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:

Falabella, V. 2014. Identificación de áreas de alto valor de conservación como potenciales áreas marinas protegidas.Informe elaborado durante la fase preparatoria del Proyecto GEF 5112-FAO-Secretaria de Ambiente y Desarrollo Sustentable. Conservation Society y Fundación Vida Silvestre Argentina.

Félix, F., Alfaro, J., Reyes, J., Mangel, J., Dellabianca, N., Heinrich, S. and Crespo, E. (2018). Phocoena spinipinnis. The IUCN Red List of Threatened Species 2018: e.T17029A50370481.

Ferrari, M., C. Campagna, R. Condit & M. Lewis. (2013). The founding of a southern elephant seal colony. Mar. Mamm. Sci. 29(3): 407–423)

Foro para la Conservación del Mar Patagónico y Áreas de Influencia (2013). Faros del Mar Patagónico. Áreas relevantes para la  Conservación de la biodiversidad marina. Resumen ejecutivo. Buenos Aires, Argentina, Wildlife

Fruet, P. F., Secchi, E. R., Daura-Jorge, F., Vermeulen, E., Flores, P. C., Simões-Lopes, P. C., . . . Möller, L. M. (2014). Remarkably low genetic diversity and strong population structure in common bottlenose dolphins (Tursiops truncatus) from coastal waters of the Southwestern Atlantic Ocean. Conservation Genetics, 15(4), 879-895. doi:10.1007/s10592-014-0586-z

Grandi M.F., Dans S.L. & Crespo E.A. 2016. Improvement in survivorship: the key for population recovery? Zoological Studies. 55: 9. doi:10.6620/ZS.2016.55-09.

Grandi, M. F., de Castro, R. L., & Crespo, E. A. (2012). Killer whales attack on South American sea lion associated with a fishing vessel: predator and prey tactics. Latin American Journal of Aquatic Research, 40(4), 1072-1076.

Hoelzel, A. R. (1991). Killer whale predation on marine mammals at Punta Norte, Argentina; food sharing, provisioning and foraging strategy. Behavioral Ecology and Sociobiology, 29(3), 197-204.

Iñíguez, M. A. 1990. Interacción entre orcas (Orcinus orca) y otras especies en el Atlántico Sudoccidental. 4ª Reunión de trabajo de especialistas en mamíferos Acuáticos de América del Sur, 12-15 Nov, Valdivia, Chile. p.31.

Iñiguez, M. (2001). Seasonal distribution of killer whales (Orcinus orca) in Northern Patagonia, Argentina. Aquatic Mammals, 27(2), 154-161.

Koen  Alonso M., Crespo, E.A., Garcia, N.A., Pedraza,  S.N.  & Coscarella, M. 1998. Diet  of Dusky Dolphins (Lagenorhynchus Obscurus), In Waters Of Patagonia, Argentina. Fishery Bulletin 96(2):366-374.

Koen Alonso, M., E.A. Crespo,  S.N. Pedraza, N.A. Garcia & M. Coscarella. 2000. Feeding habits of the southern sea lion Otaria flavescens of Patagonia. Fishery Bulletin. 97(2):250-263.

Lewis, M., & Eder, E. (2021). Southern elephant seal (Mirounga leonina, Linnaeus 1758). In Ecology and conservation of pinnipeds in Latin America (pp. 165-190). Springer, Cham.

Loizaga de Castro, R., Dans, S. L., & Crespo, E. A. (2016). Spatial genetic structure of dusky dolphin, Lagenorhynchus obscurus, along the argentine coast: preserve what scale? Aquatic Conservation: Marine and Freshwater Ecosystems, 26(1), 173-183.

Loizaga, R., Vales, D.G., García, N.A. and Crespo, E.A. (2018). Isotopic evidence of structuring killer whale groups along the Southwestern South Atlantic Ocean. IsoEcol, Libro de Resúmenes.

Loizaga, R., M.F. Grandi, H. Cunha & E.A. Crespo. 2020. New genetic diversity for endangered bottlenose dolphin subspecies along Argentina coast. Mammalia.

Lopez, J. C., & Lopez, D. (1985). Killer whales (Orcinus orca) of Patagonia, and their behavior of intentional stranding while hunting nearshore. Journal of Mammalogy, 66(1), 181-183.

Machovsky-Capuska, G. E., von Haeften, G., Romero, M. A., Rodríguez, D. H., & Gerpe, M. S. (2020). Linking cadmium and mercury accumulation to nutritional intake in common dolphins (Delphinus delphis) from Patagonia, Argentina. Environmental pollution, 263, 114480.

Reyes, L. M., & García-Borboroglu, P. (2004). Killer whale (Orcinus orca) predation on sharks in Patagonia, Argentina: a first report. Aquatic Mammals, 30(3), 376-379.

Romero, M. A., Svendsen, G., Arias, M., & González, R. (2021). Varamiento masivo de delfines comunes Delphinus delphis en la Bahía de San Antonio.

Romero, M.A., M.A. Coscarella, J.C. Pedraza, R. González & E.A. Crespo. 2022. Historical reconstruction of the population dynamics of Southern Right whales in the western South Atlantic Ocean. Scientific Reports 12:3324.

Rowntree, V. J., Payne, R. S., & Schell, D. M. (2020). Changing patterns of habitat use by southern right whales (Eubalaena australis) on their nursery ground at Península Valdés, Argentina, and in their long-range movements. J. Cetacean Res. Manage., 133-143.

Schiavini, A.C.M., Pedraza, S.N., Crespo, E.A., Gonzalez, R. & Dans, S.L. 1999. The abundance of dusky dolphins (Lagenorhynchus obscurus) off north and central  Patagonia,  Argentina, in spring and a comparison with incidental catch in fisheries Results from a pilot  survey  in spring 1995. Marine Mammal Science 15(3):828-840.

Sironi, M., López, J. C., Bubas, R., Carribero, A., García, C., Harris, G.,Intrieri, E, Iñíguez, M & Payne, R. (2008). Predation by killer whales (Orcinus orca) on southern right whales (Eubalaena australis) off Patagonia, Argentina: effects on behavior and habitat choice. Journal of Cetacean Research and Management, 29, 1-18.

Vaz-Ferreira, R. (1982). Otaria flavescens (SHAW), South American sea lion. Mammals in the seas, 4, 477-495.

Vila, A. R., Campagna, C., Iñíguez, M., & Falabella, V. (2008). South American sea lions (Otaria flavescens) avoid killer whale (Orcinus orca) predation. Aquatic Mammals, 34(3), 317-330.


Download the full account of the Northern Patagonian Gulfs and Valdes Front IMMA using the Fact Sheet button below:

To make a request to download the GIS Layer (shapefile) for the Northern Patagonian Gulfs and Valdes Front IMMA please complete the following Contact Form:

    * Required fields

    Please read the User Licence Agreement and IMMA Layer Metadata Description