San Jorge Gulf IMMA

Size in Square Kilometres

28 617 km2

Qualifying Species and Criteria

Commerson’s dolphin – Cephalorhynchus commersonii

Criterion B (1)

Peale’s dolphin – Lagenorhynchus australis

Criterion B (2)

Dusky dolphin – Lagenorhynchus obscurus

Criterion B (2)

Bottlenose Dolphin – Tursiops truncatus truncatus

Criterion B (2)

Lahille´s Bottlenose Dolphin – Tursiops truncatus gephyreus

Criterion A; B (2)

Southern right whales – Eubalaena australis

Criterion C (3)

Sei whales – Balaenoptera borealis

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

Humpback whale – Megaptera novaeangliae

Criterion C (2, 3)

South American sea lion – Otaria byronia

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

Marine Mammal Diversity 

Criterion D (2)

Cephalorhynchus commersonii, Lagenorhynchus australis, Lagenorhynchus obscurus, Orcinus orca, Grampus griseus, Tursiops truncatus truncatus, Tursiops truncatus gephyreus, Eubalaena australis, Balaenoptera borealis, Megaptera novaeangliae, Arctocephalus australis, Otaria byronia

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This IMMMA includes a significant proportion of a highly productive ecosystem, which hosts an important diversity of marine mammals from Patagonia. The IMMA encompasses five coastal protected areas from two provincial states and partially overlaps with a Biosphere reserve. These include Rocas Coloradas, Punta Marqués, Costa Norte de Santa Cruz, Caleta Olivia, Barco Hundido and Monte Loayza. The area includes significant pupping, nursing and haul-out areas for South American sea lions (Otaria byronia), and provides feeding grounds and calving areas for several species of dolphins and whales, including, but not limited to Commerson’s (Cephalorynchus commersonii), Risso’s (Grampus griseus), dusky (Lagenorhynchus obscurus), Peale’s (Lagenorhyncus australis), Lahille’s (Tursiops truncatus gephyreus) and common bottlenose (Tursiops truncatus truncatus) dolphins, and the endangered sei whale (Balaenoptera borealis). It is also used as a migration corridor for humpback whales (Megaptera novaeangliae) and southern right whales (Eubalaena australis).

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

There are populations of both common bottlenose dolphins (Tursiops truncatus truncatus), and Lahille’s bottlenose dolphins (T. t. gephyreus) in the San Jorge Gulf (Golfo San Jorge), and it is probably the southern border for the later sub-species’ distributions (Fruet et al., 2014). Small groups of both subspecies are sighted regularly within the IMMA, and sporadically large groups of approximately 50 individuals (putative common bottlenose dolphins) are sighted with calves (Coscarella et al., 2021a). Lahille’s bottlenose dolphins are listed as Vulnerable by the IUCN (Vermeulen et al. 2019), but are not assigned to a category at the national level in Argentina. Although the common bottlenose at the international level is listed as Least Concern, at the national level in Argentina it is listed as Vulnerable.

The sei whale (Balaenoptera borealis) is listed as EN both by the IUCN (Cooke, 2018) and the Red List of Argentina (Hevia et al. 2019). These whales have increased their presence in the last ten years in the area, and still increase according to the sighting per unit effort presented in Coscarella et al. (2023). Their main activity in the IMMA is feeding, so it may be a previously unknown feeding ground for the species, particularly important since these behaviours are performed very close to the shore (Coscarella et al., 2022).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

There is a small population of Commerson’s dolphins (Cephalorhynchus commersonii) that are regularly sighted in the IMMA (Coscarella et al., 2021a; Mermoz, 1980). There is no abundance estimation available, but in recent aerial surveys more than 50 individuals were sighted (Coscarella, unpublished information). Commerson’s dolphins are sighted during the whole year from a land station in Punta Marqués, with highest sighting rates during the summer months (Coscarella, 2021a).

Sub-criterion B2: Aggregations

There are two rookeries of South American sea lions (Otaria byronia) (also known as Otaria flavescens in Argentina) present in the IMMA at Monte Loayza and Punta Marqués, with more than 12,000 individuals in total (Grandi et al. 2014; Páez et al. 2017).

There is a population of sei whales regularly present in the coastal zone of the area from October until July. A preliminary abundance estimation from aerial surveys conducted during the 2021-2022 season, estimated  706 sei whales were present in the area in November 2021,  and a total of 2776 in May 2022 (Coscarella et al., 2023).

The San Jorge Gulf IMMA also provides breeding habitat for dusky (Lagenorhynchus obscurus), Peale’s (Lagenorhynchus australis), Risso’s (Grampus griseus) and both bottlenose subspecies all of which have been sighted in groups including calves during the summer months (Coscarella et al., 2021).  The productive waters in this IMMA provide abundant food resources on which these species depend.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The IMMA hosts two South American sea lion rookeries, where pups are regularly documented. The main area of reproduction is Monte Loayza within the IMMA where 245 pups were recorded in 1995 and 1415 recorded in 2012 making this one of the biggest breeding areas for this species in southern Patagonia (Crespo et al., 2021; Grandi et al., 2014).

Sub-criterion C2: Feeding Areas

The San Jorge Gulf is a very rich area that provides prey for sea lions and all dolphin species.  It is likely to be the productive habitat and abundant food resources that attract such large numbers of marine mammals.

Coscarella & Riera (2022) reported that Sei whales devote 30% of their time budget to feeding, mainly on squat lobsters (Munida gregaria) in the area, very often near the coast. The estimate is obtained from the frequency this behavior is observed from a vantage point in the top of a cliff in the center of the area, particularly in Punta Marquès, where they can be observed very close to the shore (Coscarella et al. 2023)..

Humpback whales frequently feed on silversides near the coast (Riera et al. 2022).

Sub-criterion C3: Migration Routes

Several species of balaenopterids use the area for transit between feeding grounds in the Antarctic / sub-Antarctic and breeding grounds in the tropics, and many can be observed very close to the shore in Punta Marquès (Coscarella et al. 2023). The San Jorge Gulf is an important stop off point for the southern right whale during its migration (IWC, 2013, Coscarella et al., 2021; Iñíguez et al., 2010).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

Recently humpback whales have been reported feeding in the Punta Marqués Protected Area. The whales swim very close to the shore, and the feeding technique named natural barrier feeding, presented as a cultural trait, consists of the whale forcing prey against a barrier (a wave-cut platform) and then accelerating towards the prey using, generally, a lateral lunge-feeding approach to capture small fishes (Riera et al., 2022).

Sub-criterion D2: Diversity

This IMMA includes habitat that supports an important diversity of marine mammal species, both pinnipeds and cetaceans. Nineteen marine mammal species are sighted in the area, with 12 that are sighted more frequently, some during the whole year and others during a specific season every year. The rest of the species are sighted once or twice a year (Hevia et al. 2022; Coscarella et al. 2021a; Retana & Lewis, 2017; Iñíguez et al, 2010; Reyes, 2006).

Supporting Information

Cooke, J.G. ( 2018). Balaenoptera borealis. The IUCN Red List of Threatened Species 2018: e.T2475A130482064. Accessed on 01 February 2023.

Coscarella, M. A. & Riera, M. G. (2022). Seasonal occurrence and abundance estimation of sei (Balaenoptera borealis)  and other species in Golfo San Jorge (Chubut Province, Argentina). Paper presented at the SC/68D, Cambridge – Uk.

Coscarella, M. A., Riera, M. G., Dans, S. L., Degrati, M., Sueyro, N., Chalcobsky, B. A., & Fernández, S. (2021a). Cetáceos en el área natural protegida punta marqués, zona central del Golfo San Jorge. In (pp. 33): UNPSJB.

Coscarella, M. A., Riera, M. G., Dans, S. L., & Lucchetti, D. D. (2021b). Cetáceos del Golfo San Jorge: Guía de Identificación. Buenos Aires: Fundación Félix de Azara.

Coscarella, M.A ., Riera M.G.,  Galaz, J.,  Yakimovicz, F.,  Asenié, K., Fernàndez, S. & Sueyro, N.(2023). Seasonal occurrence and abundance estimation of sei (Balaenoptera borealis) and other cetacean species in Golfo San Jorge (Chubut Province, Argentina) to be regarded as a new whale watching site in Patagonia. Paper presented at the SC/69A, Bled- Eslovenia.

Crespo, E., Oliveira, L., & Sepulveda, M. (2021). South American Sea Lion (Otaria flavescens, Shaw 1800). In (pp. 93-118).

Dans, S. L., Cefarelli, A. O., Galvan, D. E., Góngora, M. E., Martos, P., Varisco, M. A., . . . Bovcon, N. D. (2021). El golfo san jorge como área prioritaria de investigación, manejo y conservación en el marco de la iniciativa pampa azul.

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., Dans, S., & Crespo, E. (2015). The recovery process of a population is not always the same: The case of Otaria flavescens. Marine Biology Research. doi:10.1080/17451000.2014.932912

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.

Hevia, Marta; Gribaudo, César A.; Dellabianca, Natalia A.; Mandiola, Agustina (2019). Balaenoptera borealis. 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:

Iñíguez, M., J.F.Masello, C.Gribaudo, D.Arcucci, F.Krohling & J. Belgrano. (2010) On the occurrence of sei whales, Balaenoptera borealis, in the south-western Atlantic. Marine Biodiversity Records Vol 3, May 2010, e2.

IWC. 2013. Report of the IWC Workshop on the Assessment of Southern Right Whales. J. Cetacean Res. Manage. (Suppl.) 14: 437-62.

Mermoz, J. F. (1980). A brief report on the behavior of Commerson´s dolphin, Cephalorhynchus commersonii, in patagonian shores. The Scientific Reports of the Whales Research Institute, 32, 149-153.

Páez, M., Luchetti, D., Vilardo, G., Riera, M., & Gribaudo, C. V. (2017). Dinámica estacional de Otaria flavescens en el Área Natural Protegida Punta Marques, Patagonia Argentina. Paper presented at the V Congreso Nacional de Conservación de la Biodiversidad, Las Grutas, Río Negro.

Palma, E. D., Matano, R. P., Tonini, M. H., Martos, P., & Combes, V. (2020). Dynamical analysis of the oceanic circulation in the Gulf of San Jorge, Argentina. Journal of Marine Systems, 203, 103261. doi:

Retana, M. V., & Lewis, M. N. (2017). Suitable habitat for marine mammals during austral summer in San Jorge Gulf, Argentina. Revista de Biología Marina y Oceanografía, 52(2), 275-288.

Reyes, L. M. (2006). Cetaceans of central Patagonia, Argentina. Aquatic Mammals, 32(1), 20-30.

Riera, M. G., Luccchetti, D., & Coscarella, M. A. (2022). Natural barrier feeding technique in Megaptera novaeangliae in central coastal area of Golfo San Jorge, Patagonia Argentina. Aquatic Mammals.

Vermeulen, E., Fruet, P., Borges De Camargo Costa, A., Coscarella, M. y Laporta, P., (2019). Tursiops truncatus ssp. gephyreus, Lahille’s bottlenose dolphin. IUCN Red List of Threatened Species 2019


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