Almirante Montt Gulf IMMA

Size in Square Kilometres

2 174 km2

Qualifying Species and Criteria

Chilean dolphin – Cephalorhynchus eutropia

Criterion B (1); D (1)

Southern elephant seal – Mirounga leonina

Criterion B (1); C (1)

Marine Mammal Diversity 

Arctocephalus australis, Cephalorhynchus commersonii, Hydrurga leptonyx, Lagenorhynchus australis, Lagenorhynchus obscurus, Otaria byronia, Megaptera novaeangliae 

Download fact sheet


The Almirante Montt Gulf system is part of the southern Patagonian Fjords in Chile. The area is of great importance to various marine mammal species. The area hosts the northernmost southern elephant seal (Mirounga leonina) reproductive colony in the southeast Pacific region. The species was almost extirpated in the region and this breeding colony represents an important site to support the possible recovery of the species in the southeast Pacific. This area also sustains one of the two largest populations of Chilean dolphins (Cephalorhynchus eutropia) in the southern Patagonia Fjords.

Description of Qualifying Criteria

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

The Almirante Montt Gulf is considered the only area of continental Chile that hosts reproductive colonies of elephant seals, Mirounga leonina (Acevedo et al., 2014, Capella & Gibbons, 2016, Capella et al., 2017). The species has been recorded consistently in the area since 2014 with a maximum number of 61 animals in 2018-2019 (Capella & Gibbons, 2021). Capella et al., (2017) documented year-round elephant seal presence, with a peak in abundance observed between November and March (average 27.1; range 12-46 animals) (Capella et al., 2017). Although the species was historically relatively common, and the population large, after extensive hunting the last elephant seal in Chile was killed in 1840 (Philippi, 1892 – in Torres et al., 1997). This breeding colony represents one of the few colonies that appear to be recovering after it was practically extinct in Chile (Torres et al., 1997). There is no information about the genetic identity of this recently discovered colony, and whether or not it represents a newly colonised haul-out site or a newly discovered but previously used haul-out site. Although elephant seals fitted with Rototags in breeding colonies in Peninsula Valdes and Falkland/Malvinas have been observed other elephant seal colonies in Chile (e.g. Almirantazgo Sound), none of these animals have ever been documented within the Almirante Montt Gulf. This breeding colony represents one of the only three elephant seal breeding colonies in Chile (Acevedo et al., 2016), and could indicate a new incipient colonization of the historical breeding grounds.

The Chilean dolphin, Cephalorhynchus eutropia, has been mostly studied in the northern portions of its’ range. The population located south of the Gulf of Penas differs genetically and constitutes an independent management unit from populations in the north (Pérez-Alvarez et al., 2015). Documented records and abundance estimates seem very low in the Patagonian and Fuegian fjords (Gibbons et al., 2000, Gibbons et al., 2001, Lescrauwaet & Gibbons, 2008). The Almirante Montt Gulf, which has been systematically surveyed, is considered one of the two most important sites in the Southern Patagonia for the species (Capella & Vilina, 2010, Capella & Gibbons, 2013). Relatively large groups (~15 individuals) have been recorded in the area (Gibbons & Capella, 2021). Based on photo-identification and mark-recapture studies Capella and Gibbons (2021) estimated that at least 120 individuals are present in the Almirante Montt Gulf area. However, low interannual re-sighting rates (~2%) suggest that the Almirante Montt Gulf could sustain a larger population than these 120 individuals. Capella and Gibbons (2021) suggest that this low interannual re-sighting rate could be explained either by an open population with frequent immigration and emigration, or a resident population confined to the Almirante Montt Gulf but widely distributed with only a small proportion of individuals sampled. Suggests that this population size is probably much larger than this estimate. In either scenario, a local population size of over a hundred animals is significant for the Chilean dolphin and emphasizes the importance of the Almirante Montt Gulf for the species.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The presence of elephant seal pups was confirmed in three consecutive reproductive seasons with a maximum of 4 pups/season. Several of the pup records were neonates (Capella et al., 2017). This area corresponds to one of only three breeding colonies in Chile (Acevedo et al 2016). Although the pup production is still low in comparison with other colonies in other areas of the Southern Hemisphere (e.g. Peninsula Valdes in Argentina) its contribution to the total pup production in Chile, after the extirpation of the population, represents more than 17% of the total pup production annually in Chile, estimated at only ~23 individuals (Acevedo et al., 2016, Capella & Gibbons, 2021). This highlights the importance of the area for the recovery of the extirpated population. Moreover, the elephant seal assemblage of the Almirante Montt Gulf is the northernmost established colony within the South Eastern Pacific, 325 km north of those known in the Almirantazgo sound (Capella et al., 2017).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness 

The population of Chilean dolphins located south of the Gulf of Penas differs genetically and constitutes an independent management unit from Cephalorhynchus eutropia populations in the north of -42⁰ latitude (Pérez-Alvarez et al., 2015).

Supporting Information

Acevedo, J., Aguayo-Lobo, A., Brito, J.L., Torres, D., Cáceres, B., Vila, A., Cardeña, M. and Acuña, P. 2016. ‘Review of the current distribution of southern elephant seals in the eastern South Pacific’, New Zealand Journal of Marine and Freshwater Research, 50,240-258.

Capella, J. and Vilina, Y. 2010. ‘Mamíferos marinos y aves marinas de Ensenada Ponsonby, Seno Skyring, XII Región, Chile: prospección Mayo 2010’. Informe final para Acuícola Riverfish Ltda, Junio 2010, 18 pp.

Capella, J., Toro, F., Kush, A. and Gibbons, J. 2017. ‘Primera colonia reproductiva de Foca Elefante del Sur Mirounga leonina (Linnaus 1758) en Chile continental, fiordo Poca Esperanza, región de Magallanes’. Anales Instituto de la Patagonia 45(3),87-92.

Capella, J. and Gibbons, J. 2016. ‘Monitoreo de biodiversidad de mamíferos y aves marinas en el estero Poca Esperanza, seno Obstrucción y oeste de Almirante Montt, provincia de Ultima Esperanza, Chile. Monitoreo primaveral 2015’. Informe final para Salmones Magallanes SA, Junio 2016. 20 pp.

Capella, J. and Gibbons, J. 2021. ‘Monitoreo de biodiversidad de mamíferos y aves marinas en el estero Poca Esperanza, seno Obstrucción y oeste de Almirante Montt, provincia de Ultima Esperanza, Chile. Monitoreo estival 2020’. Informe final para Salmones Magallanes SA.

Gibbons, J., Gazitua, F. Venegas, C. 2000. ‘Cetáceos del Estrecho de Magallanes y senos Otway, Skyring y Almirantazgo’. Anales Instituto Patagonia, Serie Cs.Nat.(Chile) 28,107 – 118.

Gibbons, J., Venegas, C., Guzmán, L., Pizarro, G. and Boree, D. 2001. ‘Programa de monitoreo de pequeños cetáceos en la XII región’. Informe Final FIP No 99 – 28. 94 páginas.

Hucke-Gaete, R., Bedriñana-Romano, L., Acevedo, J., Viddi, F., Buchan, S., Sielfeld, W., Aguayo-Lobo, A., Zárate, P., Cari, I., Zerbini, A. and Redfern, J. 2022. ‘Diseño para la estimación poblacional de cetáceos en aguas jurisdiccionales de Chile, FIPA 2021-18’. Pre-Informe final. Fondo de Investigación Pesquera y de Acuicultura, Subsecretaría de Pesca y de Acuicultura. Unpublished report. 229 pp.

Lescrauwaet, A.K. and Gibbons, J. 2008. ‘A review of the crab bait related exploitation of small cetaceans in Magallanes and Tierra del fuego with an update on the current situation’. Paper SC/60/SM5 presented to the IWC Scientific Committee, June 2008, Santiago, Chile (unpublished). 14 pp.

Mujica, A. and Medina, M. 2000. ‘Distribución y abundancia de larvas de crustáceos decápodos en el zooplancton de los canales australes’. Proyecto Cimar-Fiordo 2. Cienc. Tecnol. Mar, 23: 49-68

Pérez-Alvarez, M.J., Olavarría, C., Moraga, R., Baker, C.S., Hamner, R.M. and Poulin, E. 2015. ‘Microsatellite markers reveal strong genetic structure in the endemic Chilean dolphin’. PLoS One, 10(4), e0123956.


Download the full account of the Almirante Montt Gulf IMMA using the Fact Sheet button below:

To make a request to download the GIS Layer (shapefile) for the Almirante Montt Gulf IMMA please complete the following Contact Form:

    * Required fields

    Please read the User Licence Agreement and IMMA Layer Metadata Description