Chiloé Interior IMMA

Criterion A – Species or Population Vulnerability

Chilean dolphins (Cephalorhynchus eutropia) are endemic to south-central and southern Chile and are listed as Near Threatened (NT) on the IUCN Red List (Heinrich and Reeves, 2017). The range-wide abundance is not known but the species is thought to number in the low thousands which, if confirmed, would meet the criteria for Vulnerable (VU) status (Heinrich and Reeves, 2017). An up-listing of the species’ conservation status to Vulnerable would reflect the ongoing concerns about bycatch affecting the dolphins along the open coast as well as in the Tenth (Xth) Region which includes Chiloé (Pérez-Alvarez et al., 2021). Chilean dolphins along the open coast to the north of Chiloé are considered genetically distinct from those of the southern fjord region (Pérez-Alvarez et al., 2015). The exact genetic boundary is not clear as samples have not been analysed from Chiloé but this area most likely constitutes the transition zone between northern and southern populations.

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Chilean dolphins inhabit discrete nearshore habitat that is characterised by shallow depth (less than 30m), very near to shore (within 1 km), often with estuarine conditions and areas of strong tidal flow (Heinrich et al., 2019). Mother-calf pairs including neonates are observed during the spring to autumn period with dolphins breeding and feeding across the area they occupy (Heinrich, 2006; Heinrich et al., 2019). The populations of Quellón and Castro/Dalcahue have been studied since 2001 (Heinrich, 2006) and habitat preference has remained stable for decades with the same channels and bay occupied over years (Heinrich et al., 2019). Passive acoustic monitoring also indicates that Chilean dolphins also occupy the same channels and bays year-round (Filun, 2015, Hack et al., in prep) as do photo-identification studies (Heinrich, 2006, Heinrich and Espinosa-Miranda, 2019, Heinrich et al., in prep). In the Quellón area, where photo-ID effort spans 20 years, individuals show clear small-scale site fidelity (Heinrich, 2006) with one individual resighted in 2019 within 1,000 m of the 2001 sighting location (Heinrich, unpublished data). Chilean dolphins seem to form discrete local populations along the coast with no confirmed individual movement even between adjacent study areas (Heinrich et al., in prep). Local population size in Quellón seems to have remained stable at around 60 adult individuals (Heinrich, 2006, Heinrich and Espinosa-Miranda, 2019; Heinrich et al., in prep). For other areas within the IMMA population size estimates range from 40 to 120 individuals (Inio: 40; Quellón: 60, Queilen: 123, Castro/Dalcahue: 30-40, Quemchi: 44) giving a combined total of around 300 Chilean dolphins in the inner seas of Chiloé (Heinrich, 2021; Heinrich and Espinosa-Miranda, 2019; Heinrich et al., in prep). A compilation of sighting data from all other available sources further supports the discrete distribution patterns of Chilean dolphins in the inner seas of Chiloé with no sightings to the east into the Corcovado Gulf or in waters deeper than 100 m ( Hucke-Gaete et al., 2022).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Peale’s dolphins and Burmeister’s porpoises share the inshore waters of Chiloé with Chilean dolphins, and although all three species overlap, their preferred habitat differs. Peale’s dolphins are more widely distributed, and use more exposed coastline with less reliance on estuarine characteristics than Chilean dolphins (Heinrich et al., 2019). Burmeister’s porpoises are usually seen in slightly deeper waters from 30 to 100m depth (Heinrich, 2006; Genov, 2012). In all areas both Peale’s dolphins and Burmeister’s porpoises are observed regularly with neonates and calves. There is no evidence for specific nursing areas but mother-neonate pairs of both species tend to be sighted along more sheltered coastline and closer to shore than groups without neonates. Both species also feed and socialise in the same area that they occupy regularly (Heinrich, 2006; Heinrich, unpublished data).
Population size estimates are not available for Peale’s dolphins or Burmeister’s porpoises. Both species are more frequently encountered in the central part of Chiloé. Photo-ID data indicated that Peale’s dolphins tended to be more abundant than Chilean dolphins in the long-term study areas of Quellón and Castro respectively (Heinrich, 2006). Individually identified Peale’s dolphins were resighted between months and years in the same areas indicating at least some degree of site fidelity (Heinrich, 2006). Peale’s dolphins and Burmeister’s porpoises seem to extend further into the deeper waters of Golfo Corcovado than Chilean dolphins. There are no data available on the year-round presence of either species as systematic surveys in winter are lacking. However, both species are seen regularly in the same species-specific areas indicating that their use of those areas has been stable over time (Heinrich et al., 2019).