There is good evidence of large-scale reductions in many predatory fish populations (e.g., Baum
et al. 2003, 2005; Sibert
et al. 2006; Polacheck 2006) and over-fishing and collapse of several important “prey” fish stocks world-wide (e.g., Jackson
et al. 2001). The effects of such fish population reductions and subsequent ecosystem changes on world-wide populations these whales are unknown but could result in population declines.
Never the main target of commercial whalers, Cuvier’s beaked whales have sometimes been taken as bycatch in other direct fisheries, such as those in the Caribbean islands, Indonesia, Taiwan, Peru, and Chile (Heyning 1989; Jefferson et al. 1993). In the Japanese Berardius fishery, Z. cavirostris have been taken on an opportunistic basis, with catches varying from 3 to 35 animals taken yearly (Omura and Kimura 1955). Although the Berardius fishery still continues, there have been no direct takes of Z. cavirostris in recent years (Nishiwaki and Oguro 1972).
Mignucci-Giannoni et al. (1999) conducted an assessment of cetacean strandings in waters off Puerto Rico, the United States and the British Virgin Islands to identify the factors associated with reported mortality events between 1867 and 1995. The most common human-related cause categories observed were entanglement and accidental captures, followed by animals being shot or speared.
Bycatch of Cuvier’s beaked whales has been reported in several fisheries. Julian and Beeson (1998) report a mortality of 22-44 individuals per year in the California/Oregon drift gillnet fishery from 1992 to 1995. Mora Pinto et al. (1995) report on bycatches from Colombian fisheries. Notarbartolo di Sciara (1990) reported on bycatch in the Italian swordfish fishery. Bycatch in the western North Atlantic is very low, with one animal reported between 1994 and 1998 (Waring et al. 2001).
Evidence from stranded individuals of several similar species indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.
In recent years, there has been increasing concern that loud underwater sounds, such as active sonar and seismic operations, may be harmful to beaked whales (Malakoff 2002). The use of active sonar from military vessels has been implicated in a number of mass strandings of Cuvier’s beaked whales, including in the Mediterranean Sea during 1996 (Frantzis 1998), the Bahamas during 2000 (Balcomb and Claridge 2001), the Madeira Islands in 2000 (Frietas 2004) and the Canary Islands in 2002 (Jepson et al. 2003). Mass strandings of Cuvier’s beaked whales in Japan also appear to be correlated with locations of naval exercises (Brownell et al. 2006). A stranding of two Cuvier’s beaked whales in the Gulf of California was closely correlated with a seismic survey (Malakoff 2002).
Predicted impacts of global climate change on the marine environment may affect this species of whale, although the nature of impacts is unclear (Learmonth et al. 2006).
