Gulf of Arauco IMMA

Size in Square Kilometres

1 648 km2

Qualifying Species and Criteria

Chilean dolphin – Cephalorhynchus eutropia

Criterion A; B (1, 2)

Marine otter – Lontra felina 

Criterion A; B (1)

South American sea lion – Otaria byronia 

Criterion B (2)

South American fur seal – Arctocephalus australis 

Criterion B (2)

Marine Mammal Diversity 

Eubalaena australis, Phocoena spinipinnis, Mirounga leonina, Balaenoptera borealis

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This area represents one of the strongest upwelling zones located along the central Humboldt current system. Seasonal coastal upwelling, mainly during the austral spring and summer months, supports the survival of four marine mammal species that are frequently observed in this area, including two species of cetaceans, two species of sea lions, and the marine otter. Two of these four species are presently subject to grave conservation concern: the Chilean dolphin (Cephalorhynchus eutropia), and the marine otter (Lontra felina). This area hosts one of the largest known populations of Chilean dolphins as well as the highest density of marine otters in Chile, and supports a breeding colony of the South American fur seal (Arctocephalus australis) in an area. Sei whales (Balaenoptera borealis) are also regularly observed in the Gulf of Arauco IMMA but more studies are required to understand their status in the area.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The Chilean dolphin (Cephalorhynchus eutropia) is listed as Near Threatened (NT) on the IUCN Red List of Endangered Species (Heinrich & Reeves, 2017) but it is listed as Vulnerable (VUc1) in the northern part of the species distribution under the Chilean Regulation for the Classification of Wild Species. The species’ restricted geographical range, obligatory nearshore habitat, and the existence of two separate genetic lineages off the coast of Chile all give rise to conservation concern for this species (Pérez-Alvarez et al., 2015, Viddi et al., 2016). The marine otter (Lontra felina) is resident in this area, with its activities confined to an area not wider than 50 m on land and 150 m offshore (Medina et al., 2007). The marine otter is classified as Endangered (EN) on the IUCN Red List (Valqui and Rheingantz, 2021), and also by the Chilean Regulation for the Classification of Wild Species. These designations are based on inferred future population decline due to habitat loss and other threats (Valqui and Rheingantz, 2021). In Chile, this species is subject to habitat loss, bycatch in artisanal fisheries, and lethal attacks from dogs. Habitat loss has led to increased fragmentation of the otters’ population (Medina-Vogel et al. 2008, Vianna et al. 2010). Despite official legal protections, there is very poor law enforcement in relation to activities threatening the marine otter´s conservation.

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

A population of Chilean dolphins has been documented in Bahia Llico, in the Gulf of Arauco. Based on photo-identification of dorsal fins, Sepúlveda et al. (2020) and Valenzuela (2022) estimated that approximately 134 individuals dolphin utilise the area. Some individuals were documented to be present in the area year-round, which suggests that at least some individuals are resident (Sepúlveda et al., 2020, Valenzuela, 2022). Adults accompanied by calves have been also observed, which suggests the area is also used as a reproductive area. The home range of marine otters has been estimated to be less than 4.5 linear km of the marine littoral zone, which is heavily affected by human use (Medina et al., 2007). In the Gulf of Arauco, marine otters are present in three main areas, with Caicura hosting the highest density of marine otters reported for any single area in Chile (Sepúlveda et al., 2020; Guido Pavez, pers.comm). This Gulf of Arauco IMMA is therefore important for the conservation of marine otters in Chile.

Sub-criterion B2: Aggregations

Within the Gulf of Arauco IMMA, Isla Santa Maria constitutes an important site for the congregation of South American sea lions (Otaria byronia) in central Chile. In the summer of 2019, Oliva et al. (2020) estimated that 3,500 individuals were using the island as a haul-out. However, a year-round study in 2019-2020 found that abundance varied through the year, being particularly high in the austral autumn months when almost 10,000 individuals were counted (Sepúlveda et al., 2020). Traditionally, two different evolutionary significant units (or even subspecies) of South American fur seals have been recognized including the Peru/northern Chile and the southern Chile/Atlantic populations (Oliveira and Brownell, 2014), with a distribution gap in central Chile. Recently, Cárcamo et al. (2021) demonstrated the presence of South American fur seals in three colonies off central Chile within that supposed gap in distribution. One of these three colonies is Isla Santa Maria, with an estimated abundance of 246 ± 6 individuals (Cárcamo et al., 2021). A year-round study by Sepúlveda et al. (2020) in 2019-2020 found that the abundance of this species varies through the year, with an increase in the number of individuals in austral autumn months to about 250 individuals. However, the evolutionary significant units to which these individuals belong has not yet been determined. Based on mark-recapture and photo-identification, Sepúlveda et al. (2020) and Valenzuela (2022) estimated an abundance of 134 Chilean dolphins in the Bahía Llico, in the Gulf of Arauco. This is one of the highest abundance estimates observed for a population of this species (Pérez-Alvarez et al., 2020).

Supporting Information

Cárcamo, D., Pizarro, M., Orellana, M., Canto, A., Herrera, P., Muñoz, L., Vásquez, P., Guerrero, A., Sepúlveda, M., Durán, L.R. and Oliva, D. 2021. ‘Long-term monitoring for conservation: closing the distribution gap of Arctocephalus australis in central Chile’. BMC Research Notes, 14:1-6.

Cooke, J.G. 2018. Balaenoptera borealis. The IUCN Red List of Threatened Species 2018: e.T2475A130482064.

Daneri, G., Dellarossa, V., Quiñones, R., Jacob, B., Montero, P. and Ulloa, O. 2000. ‘Primary production and community respiration in the Humboldt Current System off Chile and associated oceanic areas’. Marine Ecology Progress Series, 197, 41-49.

Goodall, R. N. P., K. Norris, A. Galeazzi, J. Oporto and I. Cameron. 1988. On the Chilean dolphin Cephalorhynchus eutropia Gray, 1846. Report of the International Whaling
Commission (Special Issue 9):197–257.

Goodall, R. N. P. 1994. Chilean dolphin Cephalorhynchus eutropia (Gray 1846). Pages 269–287 in S. H. Ridgway and R. Harrison, eds. Handbook of marine mammals. Academic
Press, San Diego, CA.

Heinrich, S. & Reeves, R. 2017. Cephalorhynchus eutropia. The IUCN Red List of Threatened Species 2017: e.T4160A50351955.

Iriarte, J. L., Vargas, C. A., Tapia, F. J., Bermúdez, R., & Urrutia, R. E. (2012). Primary production and plankton carbon biomass in a river-influenced upwelling area off Concepción, Chile. Progress in Oceanography, 92, 97-109.

Medina-Vogel, G., Boher, F., Flores, G., Santibañez, A., and Soto-Azat, C. 2007. ‘Spacing behavior of marine otters (Lontra felina) in relation to land refuges and fishery waste in central Chile’. Journal of Mammalogy, 88(2), 487-494.

Medina-Vogel, G., Merino, L., Monsalve, R. and Vianna, J. 2008. ‘Coastal-marine discontinuities, critical patch size and isolation: implications for marine otter conservation’. Animal Conservation, 11 57-64.

Oliveira LR, Brownell RL Jr. ‘Taxonomic status of two subspecies of South American fur seals: Arctocephalus australis australis vs. A. a. gracilis’. Marine Mammal Science 30(3), 1258–1263.

Pérez-Alvarez MJ, Olavarría C, Moraga R, Baker CS, Hamner RM, et al. 2015. Microsatellite Markers Reveal Strong Genetic Structure in the Endemic Chilean Dolphin. PLOS ONE 10(4): e0123956.

Pérez-Alvarez, M.J., Estevez, R., Gelcich, S., Heinrich, S., Olavarría, C., Santos-Carvallo, M., Sepúlveda, M., Medrano, C., Rodríguez, C. and Espinosa-Miranda, C. 2020. Evaluación de la interacción del delfín chileno (Cephalorhynchus eutropia) y actividades de pesca costera y acuicultura a lo largo de su distribución. Fase 1. Informe Final Proyecto FIPA 2018-43, 262 pp + Anexos.

Sepúlveda, M., Santos-Carvallo, M., Gutiérrez, L., Vargas, F. and Pavez, G. 2020. ‘Línea base y monitoreo de las poblaciones de cetáceos, chungungos y lobos marinos en el Golfo de Arauco, Región del Bio-Bio’.

Valenzuela, D. 2022. Patrones de residencia y permanencia del delfín chileno Cephalorhynchus eutropia (Gray, 1846) en el golfo de Arauco (VIII Región, Chile) y sus interacciones antropogénicas. Tesis de Biología Marina, Universidad de Valparaíso, 68 pp.

Valle‐Levinson, A., Atkinson, L. P., Figueroa, D., & Castro, L. 2003. Flow induced by upwelling winds in an equatorward facing bay: Gulf of Arauco, Chile. Journal of Geophysical Research: Oceans, 108(C2).

Valqui, J. & Rheingantz, M.L. 2021. Lontra felina. The IUCN Red List of Threatened Species 2021: e.T12303A95970132.

Vianna, J.A., Ayerdi, P., Medina-Vogel, G., Mangel, J.C., Zeballos, H., Apaza, M. and Faugeron, S. 2010. ‘Phylogeography of the marine otter (Lontra felina): historical and contemporary factors determining its distribution’. Journal of Heredity, 101(6), 676-689.

Viddi, Francisco A., Robert G. Harcourt, and Rodrigo Hucke‐Gaete. 2016. Identifying key habitats for the conservation of Chilean dolphins in the fjords of southern Chile. Aquatic Conservation: Marine and Freshwater Ecosystems 26.3: 506-516.


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