Southern Caribbean Upwelling System IMMA

Criterion A: Species or Population Vulnerability

This IMMA hosts the regular presence of sperm whales (Physeter macrocephalus), which are globally assessed as ‘Vulnerable’ according to the IUCN Red List (Taylor et al., 2019), with data indicating a concerning decline in populations over time (Whitehead and Shin, 2022).  Concerns persist in the neighboring community of sperm whales in the Lesser Antilles which continue to decline (Gero and Whitehead, 2016). This is exacerbated by the species’ complex social organization. Culture appears to structure communities of females into clans based on coda vocalizations (Gero et al., 2016; Rendell and Whitehead, 2003), indicating cultural ecological specialization and habitat partitioning on flexible spatial scales according to local conditions (Vachon et al., 2022).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

There are resident and semi-resident populations of bottlenose dolphins (Tursiops truncatus) and Atlantic spotted dolphins (Stenella frontalis) off the central coast of Venezuela, specifically along the Aragua State coast (Bolaños-Jiménez et al., 1998; Bolaños-Jiménez, 2017; Sifontes, 2013). At least 25% of the bottlenose dolphins recorded (14 individuals) are considered resident (4-8 individuals with resightings over periods of between 198-344 days; Cobarrubia-Russo et al., 2021). One individual of Atlantic spotted dolphin has been resighted over a period of at least 15 years (1996-2009) (Bolaños-Jiménez et al., 1998; Bolaños-Jiménez unpublished data; González-Fernández, 2000).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Humpback whales (Megaptera novaeangliae) are the second most encountered baleen whale species in the IMMA (Acevedo et al., 2007, 2008, Bolaños-Jiménez et al., 2021; Silva et al., 2006). Mother and calf groups have been recorded along the eastern coast of Venezuela, specifically in Los Frailes Archipelago (Acevedo et al., 2007, 2008; Swartz et al., 2003), corresponding with the boreal winter season (January–March). Additionally, a few reports of humpback whales have been documented in Venezuela during the austral winter and spring (June–November), suggesting that the whales are coming from the Southern Hemisphere (Bolaños-Jiménez et al., 2015, 2021).

Sub-criterion C2: Feeding Areas

The main environmental feature of the Southern Caribbean Upwelling System IMMA is the wind-driven coastal upwelling that results in remarkable productivity, supporting extensive foraging habitat for local species of marine mammals (Andrade et al., 2003; Andrade and Barton, 2005; Arévalo-Martínez and Franco-Herrera, 2008; Criales-Hernández et al., 2006; Lonin et al., 2010; Müller-Karger et al., 1989; Paramo et al., 2011).  Atlantic spotted dolphins (Stenella frontalis), common bottlenose dolphins (Tursiops truncatus), pantropical spotted dolphins (Stenella attenuata), and rough-toothed dolphins (Steno bredanensis) have been regularly observed feeding across the IMMA, including in coastal waters along the mouth of the Magdalena River and La Guajira Peninsula in Colombia (Barragán-Barrera et al., 2019a; Combatt and González, 2007; Farías-Curtidor and Ayala, 2015; Farías-Curtidor and Barragán-Barrera, 2017).  Feeding habitats in La Guajira Peninsula have been confirmed through isotopic analyses, which suggest delphinids share the same isotopic niche, consuming the same prey along this region (Barragán-Barrera et al., 2019a; Farías-Curtidor et al., In Prep.). Around the (A) Aruba – (B) Bonaire – (C) Curaçao (ABC) Islands, foraging behavior has also been observed for the previously mentioned delphinids as well as Gray’s spinner dolphins (Stenella longirostris longirostris) (CCS, 2024; Luksenburg, 2013). In the state of Aragua, central Venezuela, Atlantic spotted dolphins and resident common bottlenose dolphins are regularly observed preying upon unknown prey species (Bolaños-Jiménez et al., 1998, 2007).

Common dolphins (Delphinus delphis) are associated with upwelling-modified habitats (Au and Perryman, 1985). They are distributed along the extension of the Southern Caribbean Upwelling System from Colombia along the coast of La Guajira Peninsula (Farías-Curtidor et al., 2017), through the Venezuelan Gulf (Bolaños-Jiménez et al., 2013; Ramírez-Carroz and Gonzalez-Hernandez, 2004), the Aruba-Bonaire-Curaçao Islands (Luksenburg, 2013), the Central Caribbean Coast of Venezuela (Bolaños-Jimenez et al., 2013), the Cariaco Basin off eastern Venezuela (Oviedo, 2008, Oviedo et al., 2010; Oviedo, 2012; Molero Lizarraga et al., 2021) and to the north of the island of Trinidad. Their distribution overlaps with the upwelling foci located off the eastern coast of Venezuela, where the Spanish sardine (Sardinella aurita), which is the main prey of common dolphins, is found (Naveira, 1996; Oviedo, 2009, 2011, 2012). Behavioral observations corresponding to foraging and travel have been documented by direct observation in the eastern portion of this IMMA (Oviedo, 2008; Oviedo et al., 2010; Oviedo, 2012; Molero-Lizarraga et al., 2021).

Bryde’s whales  (Balaenoptera edeni) in the Southern Caribbean Upwelling System, appear to be closely associated with the most active upwelling in this area, from Colombia (Pardo and Palacios, 2006), the Aruba-Bonaire-Curaçao Islands (Barros and Debrot, 2006; CCS, 2024; Luksenburg, 2013, 2015; Scheidat et al., 2015), off La Guaira Bank in Central Venezuela (Briceño and Sanchez, unpublished data) and overlapping with areas of high concentration of common dolphins in eastern Venezuela (Acevedo, 2007, Acevedo et al., 2007, Silva-Schwarzberg et al., 2010, Notarbartolo di Sciara, 2013). As the most frequently observed whale in this IMMA (Acevedo, 2007; Acevedo et al., 2007), the majority of these records report foraging in shelf waters within the 200 m isobath, frequently in multi-predator aggregations preying on bait balls of small pelagic fish (Acevedo, 2007; Acevedo et al., 2007; Naveira, 1996). The relative abundance of Bryde’s whales in the eastern portion of this IMMA appears to increase in the northern hemisphere autumn months (Notarbartolo di Sciara, 1983), possibly in response to the availability of small pelagic fish within the first 10 km of upwelling foci during the weakest upwelling season in September–October (Rueda-Roa et al., 2013, 2018).

The upwellings associated with this IMMA provide suitable feeding habitat for sperm whales (Physeter macrocephalus) (Rueda-Díaz et al., 2023). Sperm whales are regularly sighted near the edges of the shelves and canyon system within the IMMA (Avila et al., 2022; CCS, 2024; Smultea et al., 2013). Acoustic data from the Caribbean Cetacean Society (CCS, 2024) and Heenehan et al. (2019) reported feeding behavior (echolocation clicks) of sperm whales north of Bonaire and Curaçao.

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

Common dolphins along this IMMA appear to be a distinctive morphotype associated with the upwelling habitat of the area. Genetic analysis using skin biopsies gathered from wild dolphins sighted off La Guajira Peninsula (Colombian waters) suggest that they are genetically closer to short beaked common dolphin, even though morphologically there is a resemblance with the long beak form (Farías-Curtidor et al., 2017). Skull morphometric analysis using samples from Margarita Island in the eastern portion of the Southern Caribbean Upwelling Area, also found important intermediate features between the short and long beak form, suggesting again a different morphotype (Esteves and Oviedo, 2007). Additionally, genetic findings based on mitochondrial DNA (mtDNA) shows common dolphins sampled in Colombia and Venezuela form a population unit highly differentiated from individuals in Brazil and Northeast Atlantic Ocean (Chávez, 2015).

Sub-criterion D2: Diversity

A total of 22 species of cetaceans (20 odontocetes and 2 mysticetes), approaching 25% of the world’s total number of cetacean species (Committee on Taxonomy, 2021), have been confirmed to occur in the IMMA. Among these species, 11 have been regularly observed throughout the year across the area and are associated with the productive and diverse seascape and the many critical habitats in this IMMA. These species include: 1) Common dolphin (Acevedo, 2001, 2007; Molero-Lizarraga et al., 2021; Oviedo, 2008, 2009, 2011; Oviedo et al., 2010), 2) Guiana dolphin, (Sotalia guianensis) (Acevedo, 2001, 2007; Oviedo, 2008, 2009, 2011, 2012), 3) common bottlenose dolphin (Acevedo, 2001, 2007; Bolaños-Jiménez et al., 2007; Combatt and González, 2007;  CCS 2024; Debrot et al., 2011; Oviedo and Silva, 2005; Oviedo et al., 2005), 4) Atlantic spotted dolphin (Acevedo, 2001, 2007; CCS, 2024; Debrot et al., 2011; Oviedo, 2009), 5) Bryde’s whale (Acevedo, 2001, 2007; Acevedo et al., 2007, Debrot et al., 2011; Silva-Schwarzberg et al., 2010), 6) killer whale (Orcinus orca) (Bolaños‐Jiménez et al., 2014, 2023a; Luksenburg, 2013), 7) sperm whale (Avila et al., 2022; CCS, 2024; Heenehan, 2019; Smultea et al., 2013), 8) pantropical spotted dolphins (Barragán-Barrera et al., 2019b; CCS, 2024; Debrot et al., 2011), 9) Gray’s spinner dolphins (Barragán-Barrera et al.. 2019b; CCS, 2024; Debrot et al., 2011), 10) short-finned pilot whales (Globicephala macrorhynchus) (CCS 2024; Debrot et al., 2011; Luksenburg, 2013),  11) rough-toothed dolphins (Debrot et al., 2011; Luksenburg, 2013); and humpback whales (Acevedo et al., 2007, 2008, Bolaños-Jiménez et al., 2021; Silva et al., 2006).

Around Aruba stranded neonates have been recorded for Atlantic spotted dolphins, Gray’s spinner dolphins, common bottlenose dolphins, pantropical spotted, striped dolphins, and rough-toothed dolphins and calving, sheltering and nursing behavior have been observed there (Henriquez, 2024; Luksenburg, 2013). Several species of small-sized delphinids (e.g., Atlantic spotted dolphin, common bottlenose dolphin, and pantropical spotted dolphin) have been observed with calves and juveniles around Aruba-Bonaire-Curaçao Islands (Barros and Debrot, 2006; CCS, 2024), the coast of Aragua in Venezuela (Bolaños-Jiménez et al., 1998), and along La Guajira Peninsula in Colombia (Farías-Curtidor and Ayala, 2015; Farías-Curtidor and Barragán-Barrera, 2017).

An additional 11 aquatic mammal species, which include Risso’ dolphins (Grampus griseus), dwarf sperm whales (Kogia sima), Gervais’ beaked whales (Mesoplodon europaeus), melon headed whales (Peponocephala electra), pigmy killer whales (Feresa attenuata), false killer whales (Pseudorca crassidens), Antillean manatees (Trichechus manatus manatus), Clymene dolphins (Stenella clymene), Striped dolphins (Stenella coeruleoalba), and Cuvier’s beaked whales (Ziphius cavirostris) have been included as Supporting Species within the IMMA. These species have been  less well studied. Beaked whales have mostly been reported as strandings, they likely also occur but are hard to detect  (Acevedo et al., 2008; Bolaños-Jiménez et al., 2023b; Caicedo-Herrera et al., 2005; Chávez-Andrade et al., 2023; Debrot, 1998; Debrot et al., 1998; Debrot et al., 2011; Fraija et al., 2009; Geelhoed et al., 2014; Mutis-Martinezguerra and Polanco, 2019; Palacios et al., 2013; Pardo and Palacios, 2006; Scheidat et al., 2015; Smultea et al., 2013).