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Cephalorhynchus eutropia 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Cetartiodactyla Delphinidae

Scientific Name: Cephalorhynchus eutropia Gray, 1846
Common Name(s):
English Chilean Dolphin
French Dauphin du Chili
Spanish Delfín Chileno

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2017
Date Assessed: 2017-07-25
Assessor(s): Heinrich, S. & Reeves, R.
Reviewer(s): Brownell, R., Hammond, P.S. & Secchi, E.
Facilitator/Compiler(s): Lowry, L.
Justification:

The best available information indicates that the total population size of Chilean Dolphins is in the low thousands, meaning that the number of mature individuals is likely to be fewer than 10,000 and therefore it is likely that the population size threshold for Vulnerable under criterion C is met. Subcriterion C1 requires an estimated continuing decline of at least 10% within the next three generations, or 42 years (14 years per generation for this species according to Taylor et al. 2007). As summarized by Dawson (2009), “Impacts over the last three decades have been severe and the population [of Chilean Dolphins] is substantially reduced.” Although there is reason to suspect that subcriterion C1 would be met, no estimate of decline rate is yet available. Therefore, the species continues to be best considered Near Threatened, pending better information on both population size and rate of decline.

Bycatch is known to occur but the magnitude is unknown. Several additional threats have been identified, and the species has a restricted range with at least two genetically distinct subpopulations (Pérez-Alvarez et al. 2015). Therefore, it is urgent that range-wide research be conducted on the current status of this species. Re-assessment of Red List category should be a high priority once better information becomes available.
Previously published Red List assessments:

Geographic Range [top]

Range Description:The Chilean Dolphin is found only along the Chilean coast (and possibly in southern Argentina) from about 30°S to Cape Horn (56°S) at the southern tip of South America. As is common for other members of the genus, it is found in shallow coastal waters, in particular close to estuaries and river mouths. It inhabits two different marine biogeographic regions: north of Isla Chiloé (42°S) it occurs along the exposed Pacific coast, and to the south it is seen in the sheltered waters of the archipelagos, channels and fjords of southern Chile (Goodall et al. 1988). Few recent sightings exist south or east of Punta Arenas (53°S). Its distribution appears to be continuous but substantial genetic differences have been found between northern (open coast) and southern (fjord) subpopulations (Pérez-Alvarez et al. 2015). Unusual extralimital sightings of some individual Chilean Dolphins in groups of Commerson’s Dolphins (Cephalorhynchus commersonii) have been recorded in southern Argentina (Morgenthaler et al. 2014).
Countries occurrence:
Native:
Chile
Vagrant:
Argentina
FAO Marine Fishing Areas:
Native:
Pacific – southeast
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The only reliable local abundance estimate is of 60 Chilean Dolphins in an area of approximately 270 km² off south-eastern Isla Grande de Chiloé (Heinrich 2006). The total population appears to be small (low thousands at most) although the perceived rarity of these dolphins may be due, to some extent, to the lack of observation effort and trained observers, and to the animals’ shyness and evasive behaviour. Chilean Dolphins are regularly seen and thought to be more abundant off Constitución (Maule River), south of Concepción (Golfo de Arauco), south-west of Puerto Montt, in the south-eastern Chiloé archipelago, in Laguna San Rafael, near Puerto Eden, near Puerto Natales, and west of Punta Arenas (Goodall et al. 1988, Gibbons et al. 2002, Heinrich 2006, Pérez-Alvarez et al. 2007, Viddi et al. 2010). They are not often seen in Chile's vast southern fjords (Gibbons et al. 2002, Dawson and Slooten 2008, Zamorano-Abramson et al. 2010).
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:UnknownPopulation severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:

The Chilean Dolphin is restricted to cold, shallow, coastal waters. According to Goodall (1994) it inhabits two distinct marine regions: (1) the channels from Cape Horn to Isla Grande de Chiloé and (2) open coasts, bays and river mouths north of Isla Chiloé. It seems to prefer areas with freshwater influence, rapid tidal flow, and shallow waters over banks at the entrance to fjords. The dolphins readily enter estuaries and river mouths.

Most sightings have been near shore and therefore the Chilean Dolphin is considered a coastal species, although there has been little survey effort in adjacent offshore waters. Movements appear quite limited, with most dolphins resident in small areas. Individuals identified from natural markings on their dorsal fins have been shown to concentrate their activities in specific bays and channels (Heinrich, 2006). Where year-round studies have been conducted, Chilean Dolphins reside in the same inshore waters throughout all seasons (Heinrich 2006, Pérez-Alvarez et al. 2007). Groups tend to be small (between 2 and 15), but aggregations of 50-60 dolphins, likely representing temporary associations of smaller groups, have been seen along the open coast near the northern limit of the species’ range (Goodall 1994, Pérez-Alvarez et al. 2007). Although mixed groups of Chilean Dolphins and Peale’s Dolphins (Lagenorhynchus australis) have been observed, a clear pattern of habitat partitioning by the two species has been documented based on fine-scale environmental features, with Chilean Dolphins having a notable preference for proximity to rivers and areas of higher tidal flow (Heinrich 2006, Genov, 2012, Viddi et al. 2010, 2015)

Recent genetic studies (Pérez-Alvarez et al. 2015, 2016) have shown that two distinct sub-populations exist: north of Isla Grande de Chiloé (northern coast) and south of Laguna San Rafael (southern fjords). This pattern is thought to be a result of post-glacial range expansion from a northern coastal refuge during glaciation into the southern fjords after the last glacial maximum ~11,000 years ago (Pérez-Alvarez et al. 2016). Fine-scale genetic population structure remains unknown, but it is suspected that substantial structuring might exist between localised sub-populations in the southern fjords where the species seems to be more patchily distributed.

No systematic studies of diet have been made, but anecdotal evidence suggests that Chilean Dolphins feed on shallow-water fishes (e.g., Sardines, Anchovies, Rock Cod), cephalopods, and possibly crustaceans (Goodall 1994).

Systems:Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat:No
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade:

This species was hunted mainly as bait for use in fisheries. This practice declined as alternative bait became available and there is no recent evidence to suggest that it continues. However, dolphins killed accidentally in fishing gear might still be used for bait.

Threats [top]

Major Threat(s):

Chilean Dolphins were hunted for many years for food and crab bait in southern Chile (Lescrauwaet and Gibbons 1994). Historically, fishermen in coastal areas north of Isla Grande de Chiloé harpooned dolphins or used those taken incidentally in their nets as bait for longlines targeting Róbalo (Eleginops maclovinus), individual hooks targeting Swordfish (Xiphias gladius), and ring nets for crabs (Cancer sp.) (Goodall et al. 1988). From Isla Chiloé south, dolphins were used along with sheep, seals, sea lions, penguins, other marine birds, and fish for bait for the lucrative King Crab (Lithodes santolla and Paralomis granulosa) fisheries. In the early 1980s it was estimated that two Chilean Dolphins could be taken per week per boat at one cannery in Magellan Strait (Goodall et al. 1988), and in 1992 up to 600 dolphins (including the more numerous and approachable Peale’s Dolphins) were harpooned per year in the area near the western Strait of Magellan (Lescrauwaet and Gibbons 1994). Since then, alternative sources of bait (such as offal from the fishing and fish-farming industries) have become more readily available. The killing of dolphins for bait might continue to some extent but there is no reliable recent information on this issue. Although hunting of dolphins is illegal in Chile, enforcement of the law in remote areas is difficult and usually lacking.

Incidental mortality in fishing gear is known to occur throughout the range, and particularly coastal gillnet fisheries pose potentially serious threats to local subpopulations. Unfortunately, no estimate exists of total incidental mortality in Chile. Historical data from one port south of Valdivia (Queule) showed that Chilean Dolphins comprised nearly half of the dolphins taken in gillnets set from some 30 boats (Reyes and Oporto 1994). This would imply a catch of some 65-70 Chilean Dolphins per year occurred at this one port (Goodall 1994). An unknown number of Chilean Dolphins are caught in intertidal gillnets set by local people from Isla Grande de Chiloé to capture small native fish and introduced farmed salmon that have escaped from their cages (Heinrich 2006). Such bycatch events are rarely reported, but for small resident subpopulations even a small number of incidental deaths could have substantial population-level consequences.

Aquaculture farms for salmon and shellfish also may have negative effects on Chilean Dolphins, for example by restricting their movements and eliminating important habitat where farm densities are high, such as in the eastern Chiloé archipelago. Exclusion of Chilean Dolphins from bays and fjords is mainly a result of large-scale shellfish farming operations but also of salmon farms (Kemper et al. 2003, Heinrich 2006, Ribeiro et al. 2007). It has been shown that boat traffic, mainly related to aquaculture, affects the behaviour of Chilean Dolphins (Ribeiro et al. 2005). There is evidence that Chilean Dolphins are sometimes caught incidentally in nets set up around salmon farms to exclude sea lions in the southern fjords and channels (Francisco Viddi pers. comm., April 2007; Marjorie Fuentes pers. comm., March 2013).

Conservation Actions [top]

Conservation Actions:

The Chilean Dolphin is listed in Appendix II of the Convention on International Trade in Endangered Species.

Better information on the status of Chilean Dolphins is needed, especially at the subpopulation level. The species may be declining because of bycatch and the consequences of extensive modification of its limited habitat in southern Chile. Specifically, it is important to obtain abundance estimates, quantitative information on incidental (and possibly direct) mortality, and better information on habitat use in relation to aquaculture and other human activities that may degrade or eliminate these dolphins’ habitat. The rapid expansion of salmon (and shellfish) farming southward in southern Chile is of particular concern. It is also important to evaluate possible gaps in the distribution of Chilean Dolphins to determine the conservation status of various subpopulations.


Citation: Heinrich, S. & Reeves, R. 2017. Cephalorhynchus eutropia. The IUCN Red List of Threatened Species 2017: e.T4160A50351955. . Downloaded on 14 December 2017.
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