Chacao Channel to Guamblín Island IMMA

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

The South American sea lion (Otaria byronia) has a wide distribution in South America, from northern Perú to Tierra del Fuego in the Pacific and from southern Brazil to Tierra del Fuego in the Atlantic Ocean (Dans et al., 2012). The species has an estimated global abundance of about 500,000 individuals, 130,000 of which inhabit the Chilean Coast (between 17º30’S and 55º58’S). Populations in Chile are divided among northern (40,000), central (23,000), southern (65,000) Chile and Magallanes (2,000) (Oliva, 2020). Using genetic data Feijoo et al. (2012) proposed the existence of three metapopulations; northern, central, and southern-Magallanes stocks. There is also a genetic discontinuity at 40°S (Chacao Channel) that can be explained by glacial-interglacial dynamics (Weinberger et al., 2021). In southern Chile, 90% of the Chilean South American sea lion new born pups are concentrated in five rookeries (between 39°15’S – 49°16’S) (Oliva et al., 2008, 2020). These areas include: two islets (Isla Doña Sebastiana and Isla Metalqui), two rocky islands (Isla Guafo and Isla Guamblín) and one continental rookery (Punta Chaiguaco) within the boundaries of this IMMA. Isla Metalqui, located in the Chiloé National Park, is the largest South American sea lion breeding ground in throughout the species’ range, with 56% of the southern population observed in 2013, including 14,331±68 newborn pups (Oliva, 2020). Guafo Island is located in the Guafo Channel southwest of Chiloé Island. The island has extended areas with rocky platforms and beaches, and in the summer of 2019, 4000 SASL were registered. Guamblín Island has an area of 156 km2 where South American sea lions inhabit rocky platforms with a summer 2019 population estimate of 8000 individuals with 3200 pups (Oliva et al., 2020).

The IMMA also hosts a significant aggregation of South American fur seals (Arctocephalus australis). Guafo represents the northernmost distribution of the southern population of South American fur seals in Chile (Seguel and Pavés, 2018, Cárcamo et al., 2021). During a 2019 survey a total of 2000 South American fur seals were recorded in this island and another and larger South American fur seals colony on Isla Quilán was documented for the first time with a population of 7000 individuals, of which 2700 were pups (Oliva, 2020).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

The abundance of the South American sea lion in the five colonies within this IMMA during the years 1998, 2007 and 2012 (with available abundance data for the entire Chilean territory) accounted for 90%, 91%, 90% and 41%, 31%, 34% of the total pups born in southern Chile and in the entire country, respectively (Cárcamo, 2019).

In the case of the South American fur seals – the number of breeding colonies in southern Chile has increased from two in 1996 to 17 in 2019, with a subsequent increase in total and pup populations (Oliva et al., 2020). The total population for South American fur seal in northern, central, and southern Chile is 32,700. The IMMA hosts 37% of the southern population and 22% of the national population. However, the pup production in 2019 represents 65% of the southern population and 43% of the total Chilean population  (Oliva et al., 2020).

Sub-criterion C2: Feeding Areas

Sepúlveda et al (2015) attached instruments to 8 South American sea lions in the inner sea of Chiloé Island. Documented feeding trips (n=160) had a mean duration of 2.5 ± 1.4 days, whereas haul-outs ranged between 0.48 and 1.67 days (N = 142 haul-out periods). Most foraging trips were concentrated between La Sebastiana breeding colony (41°45’S; 73°48’W) and the inner waters of Chiloe Island. The maximum distance travelled from La Sebastiana ranged between 74.6 and 127.1 km, with a mean value of 100 km (Sepúlveda et al., 2015). The diet of South American sea lions in southern Chile is principally composed of demersal fish species such as Merluccius australis, Mustelus mento, Genypterus spp., Callorhinchus callorhynchus, farmed salmon and pelagic preys like Sprattus fueguensis (Muñoz et al., 2013; Sepúlveda et al., 2017).