Humboldt Archipelago IMMA

Criterion A – Species or Population Vulnerability

Blue whales (Balaenoptera musculus) and sperm whales (Physter macrocephalus) are listed as EN and VU on the IUCN Red List, respectively (Cooke, 2018, Taylor et al., 2019), and both listed as VU by the Chilean Regulation for the classification of the wild species in Conservation categories (clasificacionespecies.mma.gob.cl). Fin whales (Balaenoptera physalus) are listed as VU on the IUCN Red List (Cooke, 2018) although they are listed as CR by the Chilean Regulation. For these species, the area is recognized as an important feeding area, particularly for fin and blue whales (Sepúlveda et al., 2020; Buchan et al., 2021). Marine otters (Lontra felina) are classified as Endangered according to both listing systems (Valqui and Rheingantz, 2021), and are resident within this IMMA.

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

A single resident population of common bottlenose dolphins (Tursiops truncatus) has been reported in a small area between the Isla Chañaral Marine Reserve and the Choros-Damas Marine Reserve (29º02’-29º14’S) (Pérez-Alvarez et al., 2018). The population is estimated to contain approximately 45 individuals, although numbers seem to have been drastically reduced according to recent studies (Sepúlveda et al., 2020). Trophic (Santos-Carvallo et al., 2015), genetic (Pérez-Alvarez et al., 2018) and behavioural (Pérez-Alvarez et al., 2018) studies demonstrated that this population is different from the transient or non-resident population of bottlenose dolphins. Group sizes are usually15-20 individuals, and some resident individuals show long residence (15 years) and strong site fidelity, using the area for feeding, nursing and calving with in a home range of 2-40 km (Gibbons, 1992; Thomas, 2005).

Marine otters are present on Isla Chañaral and Isla Choros, with a density of 6 and 3.7 ind/km2, respectively (Sepúlveda et al., 2020). Densities of marine otters estimated for these islands are among the highest documented on the Chilean coast, and the highest of northern Chile (Guido Pavez, unpublished data). With the species’ home range calculated to be less than 4.5 km, the populations are wholly resident within the IMMA, which is critical for the conservation of the species in Central Chile (Medina et al., 2007).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Four of the six colonies of the South American sea lions (Otaria byronia) in the area are classified as breeding colonies (Oliva et al., 2020). In 2019 a total of 808 newborn pups were documented in these colonies, which represents 31.4% of the total pup production in north-central Chile (Oliva et al., 2020). One of the breeding colonies for this species (Isla Chañaral) has been extensively studied, demonstrating a rapid increase in the number of pups born in this colony, from 109 in 2007 to 760 in 2019 (Sepúlveda et al., 2009; Oliva et al., 2020).

A breeding colony of the South American fur seal (Arctocephalus australis) is found in the Isla Chañaral, with an abundance of 1,237 individuals in 2019, of which 269 were classified as pups (Oliva et al., 2020). Interestingly, the abundance of this species in this colony has rapidly increased, from a few individuals in 2009 (Guido Pavez, unpublished data) to more than one thousand in 2019 (Guido Pavez, unpublished data). Pups were first registered in 2018, with a total of three individuals (Guido Pavez, unpublished data). Isla Chañaral is now the southernmost breeding colony of the Peruvian/Chilean population of the South American fur seal in the Pacific coast.

Sub-criterion C2: Feeding Areas

This area is recognized as an important feeding area for baleen whales, particularly fin, blue and humpback (Megaptera novaeangliae) whales (Sepúlveda et al., 2020; Buchan et al., 2021). Diet composition studies (Pérez et al., 2006; Buchan et al., 2021), observational studies (Toro et al., 2016) and tracking studies (Sepúlveda et al., 2018) demonstrate that fin whales feed in the area, particularly preying on krill (Euphasia mucronate) (Pérez et al., 2006; Toro et al., 2016; Buchan et al., 2021). For blue and humpback whales, observational studies and diet studies have demonstrated these species also feed on the krill species, E. superba in the area (Sepúlveda et al., 2020; Buchan et al., 2021). This keystone euphausiid is the most abundant and endemic krill species of the Humboldt Current System and is associated with coastal upwelling zones (Antezana, 2010; Riquelme et al., 2016), which in turn explain the relevance of the area as a feeding hot spot for these baleen whales (Brediñana-Romano et al., 2022).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

A total of 12 marine mammal species are regularly seen in the Humboldt Archipelago. Four species or populations are found year-round in the area (South American sea lions, South American fur seals, marine otters, and the resident population of bottlenose dolphins) (Sepúlveda et al., 2016, 2017, 2020). Baleen whales (fin, blue and humpback whales), as well as the Southern elephant seals (Mirounga leonina) are regularly seen in austral summer months (Sepúlveda et al., 2007, 2020; Cárcamo et al., 2017). Fin whales remain in the area for several months after the summer with some documented sightings even in winter months. Other species are seasonally unpredictable, but also regularly seen in the area, such as Risso’s (Grampus griseus), dusky (Lagenorhynchus obscurus) and common (Delphinus delphis) dolphins, sperm whales, and non-resident common bottlenose dolphins (Sepúlveda et al., 2016, 2017, 2020).