|Scientific Name:||Mesoplodon densirostris (Blainville, 1817)|
|Red List Category & Criteria:||Data Deficient (Regional assessment) ver 3.1|
|Assessor(s):||Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team|
The range of this species does not qualify as threatened under criterion B. It cannot be ruled out that the regional population of this species is small enough to warrant listing under criteria C-D. Population trend or abundance data for this species are unavailable. As with other beaked whales, threats that could cause widespread declines include high levels of anthropogenic sound, especially military sonar and seismic surveys, and bycatch.
The combination of possible declines driven by vulnerability to high-level anthropogenic sound sources and bycatch is believed sufficient that a 30% reduction over three generations could not be ruled out. Therefore, the species is currently considered to be Data Deficient.
|Range Description:||Blainville's beaked whales occur in temperate and tropical waters of all oceans (Mead 1989). This species has the most extensive distribution of any species of the genus Mesoplodon, and is also the most tropical of the genus (Pitman 2002, MacLeod et al. 2006). Like other beaked whales, they are found mostly offshore in deep waters, but they may sometimes occur reasonably close to shore (MacLeod and Zuur 2005). Sightings are also common around some oceanic archipelagos, like the Hawaiian (USA) and Society Islands (French Polynesia). They occur in many enclosed seas with deep water, such as the Gulf of Mexico, Caribbean Sea, and the Sea of Japan. However, there are only rare records of this species occurring in the Mediterranean, and therefore the species is considered to be a vagrant there.|
Native:Portugal (Azores); Spain; United Kingdom
|FAO Marine Fishing Areas:|
Atlantic – northeast; Atlantic – eastern central; Atlantic – southwest; Atlantic – southeast; Atlantic – northwest; Atlantic – western central; Indian Ocean – eastern; Indian Ocean – western; Mediterranean and Black Sea; Pacific – western central; Pacific – eastern central; Pacific – northwest; Pacific – southwest; Pacific – southeast
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Overall, the species appears to be fairly common in most tropical seas, and it is one of the most common of all the species of Mesoplodon (Reeves et al. 2003). Estimates of abundance are generally not available for most areas, but there are estimated to be 2,138 (CV=77%) in Hawaiian waters (Carretta et al. 2006). Abundance is often underestimated using visual survey methods because they dive for long periods and are inconspicuous when they surface (Barlow 1999).|
|Current Population Trend:||Unknown|
|Habitat and Ecology:||There is more information available on the behavior and ecology of Blainville’s beaked whale than for any other species of Mesoplodon (Reeves et al. 2003). There is a subpopulation of this species that is being studied in detail in the Bahamas (Balcomb 1981, MacLeod and Zuur 2005). Individual whales have been identified, based on natural marks. This represents only the second case that a beaked whale subpopulation has undergone long-term behavioral and ecological study (the other case is northern bottlenose whales in the Gully). Groups of 3-7 Blainville's beaked whales have most often been recorded, although singles or pairs are most common. In the Bahamas, adults are generally grouped into what appear to be ‘harems’, with a single adult male accompanying several adult females. Subadults appear to stay in separate groups. The harems tend of occur in more productive waters over the continental shelf canyon walls, while subadults tend to occur in less productive waters inshore and offshore of these areas.|
Although there is not a great deal know of habitat preferences for beaked whales, there is more known for this species than for any other in the genus. A detailed analysis of habitat preferences in the Bahamas, where this species is commonly encountered, indicated that Blainville’s beaked whales were found preferentially in waters of intermediate depth gradients and depths between 200 and 1,000 m (continental slope waters). These may be areas of increased prey availability caused by interactions of currents and local topography (MacLeod and Zuur 2005). Observations around Hawaii seem to indicate that animals prefer water depths of 700 - 1000m (Baird et al. 2006). Dives of up to 1,400 m and over 54 minutes have been recorded in Hawaiian waters (Baird et al. 2006). Squid are apparently the main food items, but some deepwater fish may be taken as well. Like most other ziphiids, they are thought to be suction feeders (Heyning and Mead 1996) .
No incidental or directed catches of this species have been recorded in European waters, although they have been recorded elsewhere in the species' global range.
Like other beaked whales, this species appears to be highly vulnerable to mortality associated with naval sonar exercises (Cox et al. 2006). Subadult whales, found in more offshore waters, may be more susceptible (Anonymous 2001). At least one animal died in September 2002 during a naval exercise conducted around Gran Canaria, Canary Islands (Vidal Martin pers. comm.). Another two specimens live stranded during a naval exercise off the Bahamas in March 2000 (Rowles et al. 2000). High intensity Low Frequency Active Sonar (LFAS) was used by US and NATO vessels in both these areas, respectively, which apparently led to a multi-species mass stranding in the Bahamas, including both M. densirostris and Ziphius cavirostris (Balcomb and Claridge 2001).
Concerns regarding the impact of man-made debris in the marine environment are increasing. Pollution in the form of plastic debris has been recently recognised as a major threat to marine wildlife, in terms of ingestion and entanglement. On 27 February 1993, a 419 cm adult female Blainville's beaked whale was found washed ashore in an advanced state of decomposition at Mar Grosso Beach (32°07'S, 52°02'W), Sao Jose do Norte, southern Brazil (Secchi and Zarzur 1999). Stomach analysis revealed the presence of a blueish bundle of plastic threads occupying a large part of the main stomach chamber. Both stomach and intestines were completely free of parasites, as well as food remains and faeces, indicating that the whale had not fed for some time.
|Conservation Actions:||The species is poorly known with respect to abundance, migratory patterns, by-catch and direct catch rates. Range states should be encouraged to conduct more coordinated research efforts.|
|Citation:||Species account by IUCN SSC Cetacean Specialist Group; regional assessment by European Mammal Assessment team. 2007. Mesoplodon densirostris. The IUCN Red List of Threatened Species 2007: e.T13244A3426293.Downloaded on 22 May 2018.|
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