Guadalupe Island IMMA

Criterion A – Species or Population Vulnerability

The Guadalupe fur seal (Arctocephalus philippii townsendi) was severely exploited in the late 18th and early 19th centuries, being declared as commercially extinct in 1897 (Hubbs, 1956). Its pre-exploitation population size reached 100,000-200,000 individuals (Hubbs, 1979) with a distribution from the Revillagigedo Islands, Mexico, to areas offshore from Washington State, USA (Etnier, 2002). Currently its only remaining well-established breeding site is Guadalupe Island, mainly along the east side of the island, and especially on the southern portion, called Punta Sur, where the largest aggregation of fur seals is located within the area. There are also non-breeding sites on San Benito and in the Gulf of California (García-Aguilar et al., 2018a; Elorriaga-Verplancken et al., 2021; Gutiérrez-Ozuna et al., 2021; Gálvez et al., 2022). The species’ current abundance is 57,199-72,631 individuals (Juárez-Ruiz et al., 2022), still under recovery and impacted by an unusual mortality event from 2015 to 2021 along the California, Washington, and Oregon coastlines (NOAA-Fisheries, 2021) as well as a 2015-2016 El Nino associated decline at San Benito (Elorriaga-Verplancken et al., 2016). These warm anomalies can change Guadalupe fur seal movement patterns due to changes in the availability of prey in the food web (Amador-Capitanachi et al., 2020). Although this fur seal species is currently classified as Least Concern (LC) on the IUCN Red List, it is ‘Endangered’ under Mexican Law (Norma-Oficial-Mexicana-NOM-059-SEMARNAT-2010) and ‘Threatened’ under the U.S. Endangered Species Act of 1973.

The northern elephant seal (Mirounga angustirostris) colony on Guadalupe Island is one of the three main breeding locations (Guadalupe, San Benito Archipelago, and Cedros Island) off the Baja California Peninsula (Arias del Razo et al., 2017). The abundance of northern elephant seals in Baja California colonies, including Guadalupe Island, has decreased during the last three decades, probably as a probable consequence of increased local air temperatures. An indicator of this decline is that the contribution of the Baja California (Mexico) colonies in terms of number of births for the entire species decreased from 25% in the early 1990s to 11% in 2009 (García-Aguilar et al., 2018b). This species is classified as ‘Threatened’ under Mexican Law (Norma-Oficial-Mexicana-NOM-059-SEMARNAT-2010).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Northern elephant seals have a small resident colony on the island, which has been estimated to contain around 12,000 individuals (García-Aguilar et al., 2018b ; Arias-del-Razo et al., 2017) concentrated on the northern portion of Guadalupe. This represents a significant number in relation to the population of around 201,000 in California (Lowry et al., 2014) and around 22,000 on the Baja California Peninsula, Mexico (García-Aguilar et al., 2018b). Even though they are mainly present in winter and spring-summer for breeding and moulting, respectively, they are present on the island year-round (Programa de Manejo- Reserva de la Biosfera Isla Guadalupe, 2013). Adult female and male northern elephant seals perform two annual migrations off Guadalupe Island to the northern Pacific, where their main foraging grounds are located; one is accomplished after the breeding season in winter and another one after the moulting season in spring-autumn (Robinson et al., 2012).

Preliminary photo-identification studies combined with the data collected by Cárdenas-Hinojosa et al. (2015), indicated a total of 87 individual Cuvier’s beaked whales (Ziphius cavirostris) are likely resident in the waters around the island. More than half of these photo-identified individuals were seen more than once (n= 57) (Cárdenas-Hinojosa et al., 2022). Furthermore, long-term acoustic monitoring using a High-frequency Acoustic Recording Package (HARP) deployed from November 2018 to October 2020 in Bahía Norte, revealed year-round presence of Cuvier’s beaked whales around Guadalupe Island (Cárdenas-Hinojosa et al., 2015; 2022).

Sub-criterion B2: Aggregations

The largest aggregation of Guadalupe fur seals anywhere in the species’ range is on the east coast of Guadalupe Island. This represents almost the entire extant population for the species. More than 99% of all births take place on this island. Hence, even though there are non-breeding Guadalupe fur seal sites elsewhere (Elorriaga-Verplancken et al., 2021; Gutiérrez-Osuna et al., 2021; Gálvez et al., 2022), all individuals are part of the Guadalupe Island population, since they were born on this island (García-Aguilar et al., 2018a). Most of the colony remains on the island year-round, although male Guadalupe fur seals seem to perform migrations off Guadalupe Island once the breeding season is over (Pierson, 1987; Gallo-Reynoso, 1994). Additionally, juvenile, subadult, and adult males also perform seasonal migrations to the San Benito Archipelago (Aurioles et al., 2010; Elorriaga-Verplancken et al., 2016) and to the Gulf of California (Elorriaga-Verplancken et al., 2021; Gálvez et al., 2022).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Guadalupe Island is the only known reproductive site for the Guadalupe fur seals, with reproductive areas located along the entire east coast (Gallo-Reynoso, 1994; García-Aguilar et al., 2018 ; Juárez-Ruiz et al., 2022). The number of Guadalupe fur seal pups born on this island is related to annual shifts in sea surface temperature. Numbers ranged between ~12,500 and 15,400 in 2018-2019 (Juárez-Ruiz et al., 2022). Northern elephant seals also breed on Guadalupe Island and this colony on the island represents around 60% of the births (around 3,000 in 2009) in the Baja California (Mexico) population (García-Aguilar et al., 2018b). Resident Cuvier’s beaked whales also reproduce in the area (Cárdenas-Hinojosa et al., 2016). Surveys conducted from October 2016 to February 2021 documented a total of 384 sightings, of which 93 were of mother and calf pairs (Cárdenas-Hinojosa et al., 2022).

Sub-criterion C2: Feeding Areas

Guadalupe fur seals undertake foraging trips around Guadalupe Island. Preliminary data suggest that a foraging area around Guadalupe Island is occupied in around 40% of the time by this species (Amador-Capitanachi, 2018). Like other otariids (Boness and Bowen, 1996), adult females that give birth every summer, must alternate maternal care with localised foraging trips during the 8–9-month lactation period until pups are weaned (Gallo-Reynoso, 1994; Amador-Capitanachi, 2018). The Guadalupe fur seal diet is primarily teutophagous in this region, mostly comprising jumbo squid (Dosidicus gigas) and opalescent squid (Doryteuthis opalescens), as well as other squid species and members of the lantern fish (Myctophidae) family (Amador-Capitanachi et al., 2020).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

High levels of productivity and a wide range of habitats from beaches to deep near-shore canyons support a wide range of marine mammal species off Guadalupe Island. Perhaps the most notable species is the Guadalupe fur seal, which resides in the IMMA year-round and breeds on the island. Cuvier’s beaked whales and northern elephant seals are also present throughout most of the year, as are California sea lions. Other cetacean species that are regularly observed in the Guadalupe Island IMMA include fin whales (Balaenoptera physalus), blue whales (Balaenoptera musculus), Bryde’s whales (Balaenoptera edeni), humpback whales (Megaptera novaeangliae), common bottlenose dolphins (Tursiops truncatus), common dolphins (Delphinus delphis), short-finned pilot whales (Globicephala macrorhynchus), Risso’s dolphins (Grampus griseus), Pacific white-sided dolphins (Lagenorhynchus obliquidens), killer whales (Orcinus orca), sperm whales (Physeter macrocephalus), as well as dwarf and pygmy sperm whales (Kogia spp) (Gallo-Reynoso and Figueroa-Carranza, 2005 ; Programa de Manejo- Reserva de la Biosfera Isla Guadalupe, 2013; Cárdenas-Hinojosa, unpublished data).