Savu Sea and Surrounding Areas IMMA

Criterion A – Species or Population Vulnerability

Blue whales (Balaenoptera musculus) were confirmed to be found across the Savu and Timor Seas (Kahn 2007; Dethmers et al. 2009). The species has been assessed by the IUCN Red List as Endangered. In addition, the presence of the pygmy blue whale (Balaenoptera musculus brevicauda) has also been confirmed to use this region as a migration corridor (Kahn 2007, 2009; Double et al. 2014). However, the current global status of pygmy blue whale is very uncertain. Nevertheless, it is possible that commercial and small scale whaling has caused a decrease in the number of pygmy blue whales, with their recovery being slower than the Antarctic blue whale (Branch et al. 2007, 2009). From 2001-2008, 10-day boat-based surveys were conducted in the Solor-Area, with blue whales sighted frequently (i.e. Kahn, 2002, 2005). Initial satellite tagging efforts on blue whales identified the Banda Sea as the migratory destination, with the tagged whale spending over 60 days in this area. Furthermore, detailed diving data was consistent with diurnal foraging behaviour (Kahn 2007). In 2013 during an 18-day boat-based survey of a much broader area, blue whales were recorded in 5 separate sightings from the Savu Islands to northwest Timor (Kahn, 2013).  In 2008 aerial and boat based surveys of Timor Leste waters observed blue whales, with two adults sighted in September and a group of two adults with a calf sighted in November in the north-western coastal waters offshore from the Dili and Liquisa districts (Dethmers et al. 2009). Field surveys in Solor waters during May-October 2017 also recorded 5 sightings of pygmy blue whale, including 7 individuals.  Pygmy blue whales were further reported in October 2017 in Waihenga Bay-Lembata (Putra et al. 2017). Double and colleagues further tracked 11 pygmy blue whales from Australia in April 2011, and 5 individual were successfully tracked and entered Savu Sea waters in June 2011 and spent several days in this area before they moved into the Banda Sea and the Moluccas Sea (Double et al. 2014). Sperm whales (Physeter macrocephalus) have been assessed by the IUCN as a Vulnerable species. However, in Indonesia the hunters of Lamalera in the Savu Sea region have hunted sperm whales for more than 500 years, and there has been an 80% decline in catch rates of sperm whale in Solor waters of the Savu Sea, that indicates a potential wider decrease of their population in this region (Mustika, 2006).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

The Alor Strait (Between Lembata and Pantar), in particular the area near Marisa Island which is located in the middle of a main migratory corridor (and shipping lane), is inhabited by residential pods of spinner dolphin (Kahn and Hennicke, 2017). Survey results indicate several areas with resident small cetaceans i.e. hundreds of spinner dolphin in Barate bay which can be observed every morning and afternoon (Kahn and Fajariyanto, 2014). Pantar Strait (between Pantar and Alor), in particular the area around Pura Island, is inhabited by a residential pod of mixed cetaceans including melon-headed whales,  Fraser’s dolphins, and  spinner dolphins. This mixed pod has been stable in group-composition and has been consistently sighted in this area for at least 4 years (Kahn, 2005; Kahn and Fajariyanto, 2014). Indo-pacific bottlenose dolphin Tursiops aduncus have been assessed as Near Threatened for the IUCN Red List. A small pod of only 3-6 individual Indo-pacific bottlenose dolphins can be consistently observed in Kalabahi Bay, while a further 6 individuals were also observed in the straits between Pantar and Lembata Island (Kahn and Hennicke, 2017). Furthermore, the spinner dolphin is the most frequently observed species in Solor waters of the Savu Sea (Putra and Topan, Forthcoming). While, long-term rapid ecological assessment (REA) of the oceanic cetacean program in 2001-2005, also recorded that the spinner dolphin is relatively consistent as the most abundant species in this region (Kahn 2002, 2004a, 2004b, 2005). The spinner dolphin that can be found year-round in this region and is likely to be a resident species.

Sub-criterion B2: Aggregations

Based upon the year-round monitoring program in Solor waters of the Savu Sea, the seasonal aggregations of cceanic dolphins peak in relative abundance during June to November, although they also can be found throughout the year (Putra and Topan, forthcoming). The seasonal aggregation of these species is strongly related to oceanographic features (i.e. upwelling current, mesoscale eddies, and thermal and chlorophyll-a front) that provide high primary productivity (Adriani, 2010). The upwelling current associated with eddies and internal waves in this region has increased the local productivity. The pygmy blue whale annually migrates through the area from western Australia to the Banda Sea through the Savu Sea, and is strongly-associated with the upwelling period in eastern Indonesia (Kahn 2007, Double et al. 2014). One bull sperm whale (estimated length 18m) was sighted in 2013 from a survey north of Timor Island (Kahn and Fajariyanto, 2014). Male sperm whales were seen on two occasions on the 2015 boat-based survey, as well as identified acoustically at several listening stations (Kahn and Hennicke, 2017).

A recent study from Putra and Topan (Forthcoming) found the inter-annual variation on their aggregations was influenced by ENSO, where the oceanic dolphin relative abundance increased during positive El Niño, while the relative abundance of whales was decreased.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Young oceanic dolphins and calves (i.e. spinner dolphin, pan-tropical spotted dolphin, Fraser’s dolphin etc.) have been recorded frequently in Solor waters, where they were seen together in big pods with adult dolphins (Putra et al. 2017). Solor waters are potentially used as a nursery ground for these dolphin species. Furthermore, Kahn and colleagues also observed a 3 meter humpback whale mother and calf pair in the south of Sabu Island, and calves of spinner dolphins in southwest of Tuakau Cape, Timor Island (Kahn 2013). While, in 2015 they also recorded both young spinner dolphins and sperm whales in the south of east Pantar Island, south of Lembata, and to the west of Pantar Island (Kahn and Hennicke 2017).

Sub-criterion C2: Feeding Areas

The presence of important oceanographic features in this region (e.g. upwelling current, bathymetry slope, thermal front and meso-scale eddies) support high-densities of prey species. Studies have found that cetaceans aggregate close to frontal zones and eddies, which provide a high-density of prey. Their distribution is described the productivity hotspots (Putra et al., 2016), as well close to the transition zone of fronts and eddies that indicate their foraging (Adriani, 2010). In Solor waters, local fishermen also report that the spinner dolphins often interact with their fishing activity (e.g. gillnet and purse seine) during night hours, and they swim actively to access meso-pelagic prey, sometimes becoming trapped in the fisher’s nets (Putra et al. 2017). During some sightings, pods of dolphins were associated with seabird aggregations, indicating further feeding/foraging behaviour in this area (MIH Putra personal observation). Furthermore, the several studies of pygmy blue whale describe that the movement pattern of this species is strongly associated with the dynamics of local productivity that occurs in the Savu Sea, where the pygmy blue whale is likely utilizing this region for feeding (Kahn, 2005, 2007; Double et al. 2014).

Sub-criterion C3: Migration Areas

The Savu Sea appears to provide a critical migratory habitat for certain marine mammal species. Tagging of a blue whale off Alor in 2007
identified the Banda Sea as the migratory destination for blue whales passing through the Savu SEA (Kahn, 2007). Based on the tagging studies of Double and colleagues (2014), the Ombai Strait and Timor Sea has been observed to function as a migration corridor for pygmy blue whales, which migrate from western Australia to the eastern Indonesia Sea (Sunda-Banda-Halmahera ecoregion). This species was recorded arriving in the Savu Sea in the end of May, continuing their migration to the Banda Seram Sea through Solor-Alor waters, the Timor Sea, and Ombai Strait. More recently, a series of dedicated cetacean surveys have been conducted throughout the Banda Sea (2016-2018), to further investigate the cetacean habitat and possible development of MPAs (Kahn et al., 2019).

Criterion D: Special Attributes

Sub-criterion D2: Diversity

The Savu Sea and Surrounding Areas IMMA provides a habitat for at least 24 recorded species of marine mammal, which includes beaked whales, blue whale, Bryde’s whale, common bottlenose dolphin, Cuvier’s beaked whale, dugong, dwarf sperm whale, false killer whale, Fraser’s dolphin, humpback whale, Indo-Pacific bottlenose dolphin, melon-headed whale, orca, pantropical spotted dolphin, pygmy blue whale, pygmy killer whale, pygmy sperm whale, Risso’s dolphin, rough-toothed dolphin, short-finned pilot whale, sperm whale, and spinner dolphin (Kahn, 2002, 2005, 2013; Kahn and Fajariyanto, 2014; Kahn and Hennicke, 2017; Putra et al. 2017).