BLAINVILLE’S BEAKED WHALE (Mesoplodon densirostris): Northern Gulf of Mexico Stock

• Main Authors: Stock Definition, Geographic Range
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: POPULATION SIZE; Reeves; North Atlantic; Sowerby's beaked whale
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.298.9418; http://www.nefsc.noaa.gov/nefsc/publications/tm/tm194/pdfs/194.pdf

Three species of Mesoplodon are known to occur in the Gulf of Mexico, based on stranding or sighting data (Hansen et al. 1995; Würsig et al. 2000). These are Blainville's beaked whale (M. densirostris), Gervais ' beaked whale (M. europaeus) and Sowerby's beaked whale (M. bidens). Sowerby’s beaked whale in the Gulf of Mexico is considered extralimital because there is only 1 known stranding of this species (Bonde and O’Shea 1989) and because it normally occurs in northern temperate waters of the North Atlantic (Mead 1989). Identification of Mesoplodon to species in the Gulf of Mexico is very difficult, and in many cases, Mesoplodon and Cuvier’s beaked whale (Ziphius cavirostris) cannot be distinguished; therefore, sightings of beaked whales (Family Ziphiidae) are identified as Mesoplodon sp., Cuvier’s beaked whale, or unidentified Ziphiidae. Blainville’s beaked whales appear to be widely but sparsely distributed in temperate and tropical waters of the world’s oceans (Leatherwood et al. 1976; Leatherwood and Reeves 1983). Strandings have occurred along the northwestern Atlantic coast from Florida to Nova Scotia (Schmidly 1981), and there have been 4 documented strandings and 2 sightings of this species in the northern Gulf of Mexico (Hansen et al. 1995; Würsig et al. 2000). Beaked whales were seen in all seasons during GulfCet aerial surveys of the northern Gulf of Mexico from 1992 to 1998 (Hansen et al. 1996; Mullin and Hoggard 2000). The Gulf of Mexico population is provisionally being considered a separate stock for management purposes, although there is currently no information to differentiate this stock from the Atlantic Ocean stock(s). Additional morphological, genetic and/or behavioral data are needed to provide further information on stock delineation.