Carnegie Ridge, Galapagos to Mainland IMMA
Size in Square Kilometres
459 869 km2
Qualifying Species and Criteria
Blue whale – Balaenoptera musculus
Criterion A; C (2, 3)
Sperm Whale – Physeter macrocephalus
Criterion A; C (2, 3)
Marine Mammal Diversity
Balaenoptera edeni, Delphinus delphis, Megaptera novaeangliae, Mesoplodon peruvianus, Orcinus orca, Pseudorca crassidens, Stenella attenuata
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Summary
The Carnegie Ridge forms a natural seaway between the eastern Galapagos Archipelago and the coasts of Ecuador (0°) and Peru (5°S), including the Gulf of Guayaquil. Geologically, the Carnegie Ridge structure comprises an area approximately 1,350 km long and 300 km wide. It was created by the passage of the Nazca Continental Plate over the Galapagos hotspot subducted beneath the Ecuador Andes. This area is permanently influenced by the Equatorial Front between the equator and 5°S, a shallow oceanographic feature that further fluctuates seasonally, probably controlled by winds, that increases regional productivity between the Galapagos and the mainland. The Carnegie Ridge serves as a migratory route between feeding and calving areas for various species of large whales. Most notably by Endangered blue whales (Balaenoptera musculus) and Vulnerable sperm whales (Physeter macrocephalus). The IMMA encompasses highly productive coastal and oceanic upwelling areas adjacent to the Galapagos archipelago and the Gulf of Guayaquil. These productive waters comprise important feeding habitat for blue, sperm, Bryde’s (Balaenoptera edeni), and humpback whales (Megaptera novaeangliae), as well as the pygmy beaked whale (Mesoplodon peruvianus).
Description of Qualifying Criteria
Criterion A – Species or Population Vulnerability
Blue whales are currently listed as Endangered on the IUCN Red List of Threatened Species (Cooke, 2018). Blue whales were once abundant in the Southern Hemisphere but were intensely exploited by industrial whaling that began in 1904 (Branch et al., 2004). In the South Pacific there were widespread catches along the west coast of South America north of 44°S off Chile, Peru, and Ecuador, and from Peru to the Galapagos Islands but no other catches north of 59°S in the waters stretching west to 180° (Branch et al., 2007). Pre-whaling abundance of southeast Pacific blue whales has been estimated at 1,500-5,000 individuals but the abundance in 1998 was estimated to be just above 12% of pre-whaling levels, based on minimum abundance estimates (Williams et al., 2011, 2017). Recent abundance estimates for Chilean blue whales in Chile and for the northern Chilean Patagonia feeding ground, provide remarkably similar results: 303 whales (95% CI 176–625) (Williams et al., 2011) and 373 whales (95% CI 191–652) (Bedriñana‐Romano et al., 2018), respectively. A third study based on different photo-id data sets yielded higher estimates, ranging between 569 (95% CI = 455-683), and 761 (95% CI = 614-908) (Galletti-Vernazzani et al., 2017). Uncertainty envelopes overlap across all recent studies and are indicative of a population ranging from low to mid hundreds. Due to the low population size of this blue whale subspecies/population, for which estimated potential biological removal (PBR) should not exceed 0.548 individuals per year, or one human-caused death in every 1.8 years (Bedriñana-Romano et al., 2018).
Sperm whales are currently listed as Vulnerable on the IUCN Red List of Threatened Species (Taylor et al., 2019).The current global estimated abundance of 360,000 individual whales represents an estimated 67% reduction from the initial pre-whaling population size (Whitehead, 2002). Historic whaling in the 19th century in the southeast Pacific including within the coastal waters of Peru and Ecuador caused severe declines of sperm whales in the region (Eguiguren et al., 2020). The eastern Pacific population was estimated to include 22,666-26,053 individuals (Wade and Gerrodette, 1993; Whitehead, 2002). There is no evidence that population has increased in recent years (Taylor et al., 2019). Sperm whales have been regularly documented in the Carnegie Ridge area, and from the Galapagos Archipelago to the Gulf of Guayaquil (Whitehead et al., 1997; Hamilton et al., 2008; Whitehead, 2011).
Criterion C: Key Life Cycle Activities
Sub-criterion C2: Feeding Areas
Although blue whales typically migrate between tropical breeding grounds and high latitude feeding grounds, some individuals may reside year-round in habitats of high productivity feeding on zooplankton, while others may stop to feed in areas of high productivity on route (Cooke, 2018). Multiple sightings of blue whales in this IMMA (Hamilton et al., 2008; CPPS/PNUD, 2012; Guzman pers. obser.) indicate that the area is used by blue whales, and data on productivity and whale behaviour during the time of observations indicate that the Carnegie Ridge encompasses feeding areas off the coast of mainland Ecuador (Gulf of Guayaquil) as well around the eastern Galapagos islands (CPPS/PNUD, 2012). In particular, Southern Hemisphere blue whales that occur off Ecuador and the Galapagos Islands, mostly during the austral winter, seem to be foraging in the area (Palacios, 1999; Busquete-Vass et al., 2021). Similarly to blue whales, Sperm whales have been reported feeding along the Carnegie Ridge, from the Galapagos Islands and mainland Ecuador (Whitehead, 1989; Whitehead, 2011; CPPS/PNUD, 2012; Eguiguren et al., 2021).
Sub-criterion C3: Migration Routes
At the global level there is evidence that most blue whales migrate between separate wintering and summering areas (Hucke-Gaete et al., 2004; Cooke, 2018; Torres et al., 2015). Blue whale populations in the northeast Pacific and the eastern tropical pacific seem to be largely spatially and temporally separated (Reilly and Thayer, 1990; Ballance et al., 2006; Hamilton et al., 2009; Busquets-Vass et al., 2021). There is evidence that blue whales that use the eastern tropical pacific further migrate north from Chile to the Galapagos and close to the mainland in and around the Gulf of Guayaquil (CPPS/PNUD, 2012; Hucke-Gaete et al., 2018). Recent data on sperm whale distribution and habitat use around the Galapagos suggest that whales use the Carnegie Ridge as migratory corridor from offshore areas to mainland areas between Northern Peru to Panama (CPPS/PNUD, 2012; Whitehead et al., 2008; Eguiguren et al., 2021). Movements determined by focal follows and re-sightings of photo-identified individuals indicate that movement patterns vary with gender and age, ranging from 2,000 to 5,000 km, with no reports of transoceanic movements between the eastern and western Pacific (Whitehead et al., 2008).
Supporting Information
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