Bryde’s whale calls recorded in the Gulf of Mexico

Bryde’s whales (Balaenoptera edeni) inhabit tropical and subtropical waters worldwide and, unlike most other mysticetes, they are not thought to make long seasonal migrations (Jefferson et al. 2008). They are the only balaenopterid regularly found in the U.S. waters of the Gulf of Mexico (GOM), with their range likely constrained to the shallow, northeastern part of the GOM around DeSoto Canyon (Maze-Foley and Mullin, 2006). Bryde’s whales are likely the smallest population of cetaceans in the region (Maze-Foley and Mullin, 2006). While it is possible Bryde’s whales are present in this area year-round as four reported strandings have been recorded across seasons (Mead 1977, Jefferson and Schiro 1997, W€ursig et al. 2000), visual surveys have been conducted only during the spring (Waring et al. 2009). National Oceanographic and Atmospheric Administration (NOAA) Fisheries has been conducting regular marine mammal surveys in the GOM since the 1990s. The number of Bryde’s whales in the U.S. Exclusive Economic Zone (EEZ) was estimated at 35 (CV = 1.10) between 1991 and 1994 (Hansen et al. 1995), and 40 (CV = 0.61) between 1996 and 2001 (Mullin and Fulling 2004). Based on the most recent surveys conducted in 2003 and 2004, Bryde’s whale population in the US EEZ in the GOM is estimated at 15 (CV = 1.98) individuals (Mullin 2007). It has been suggested that the GOM population is a distinct stock, but no evidence exists to confirm their separation from the nearby southern Caribbean or Atlantic stocks (Waring et al. 2009). Bryde’s whales produce a variety of call types in different geographic regions and it has been suggested calls may delineate different stocks (Oleson et al. 2003). Distinct low frequency (60–950 Hz) pulses, tonals, and moans have been described for freeranging Bryde’s whale adults and calves in the Eastern Tropical Pacific (ETP), the Gulf of California, southern Caribbean, and the North Pacific (Cummings et al. 1986, Edds et al. 1993, Oleson et al. 2003, Heimlich et al. 2005, Kerosky et al. 2012).