Attraction of gray whales, Eschrichtius robustus, to underwater outboard engine noise in Laguna San Ignacio, Baja California Sur, Mexico

Abstract

off-shore drilling, human movements, unidentified machinery, tugs, and other marine service craft. The recordings, made in winter, spring, and fall, were obtained from under the ice, or from leads, polynyas, or open water at distances from a.few meters to about 185 km from the source. Estimated overall source levels varied from 40 to over 200 dB re 1 /xPa at 1 m, in the effective bandwidths. Principal acoustic energy occurred in bands falling between 10 Hz and 13 kHz. Among the lowest levels encountered were those from the sounds of oil exploration drilling. The highest were from seismic profiling. Durations of man-made sounds varied from msec (metallic impulses) to continuous (line spectra from engines). In terms of frequency (Hz) The presence and behavior of bowhead whales near offshore oil and gas exploration activities in the eastern Beaufort Sea were studied during August 1980.'Numerous bowheads were within 5 km of an artificial island construction site where a large dredge, a barge camp, and several boats were operating. In a different situation, the physical presence of a 16.1-m boat had no apparent effect on the behavior of bowheads at a distance of 3.7 km. Subtle changes in behavior were noted when the vessel' s engines were idling with propellers disengaged. Bowheads within 1 km of vessels responded by spending briefer periods at the surface, by respiring fewer times per surfacing, and by moving away from the disturbance. Surfacing and breathing patterns returned to normal following the disturbance, while interanimal distances remained greater. Whales 13 km from an underwater seismic exploration operation did not behave differently from animals in the same area on days preceding and following the seismic work. In 1969 an underwater test facility was constructed specifically to study the biological effects produced by underwater blast. Investigations were conducted to determine the ranges from explosive charges, up to 3.6 kg, that were safe, damaging, or lethal to selected species of fish, birds, and mammals. It was established that the impulse (integral pdt) in the underwater blast wave was the parameter that governed biological damage and not peak pressure or energy. There was good correlation between the impulse and body weight in fish that ranged from 12 pKa.ms for 0.02-g guppy fry to 341 kPa-ms for 744-g carp. The blast response of fish with ducted swim bladders was the same as fish having nonducted swim bladders. Mallard ducks were selected as a model to represent birds on and beneath the water surface. Impulse levels-that were safe, injurious, or lethal to birds were determined and presented as a function of range and charge weight. The tolerance of six mammalian species, that ranged in body weight from 0.2-45 kg, was investigated. A tentative interspecies extrapolation, relating impulse to body weight, was illustrated as a method that may be pursued to predict the response of large marine mammals to underwater blast. A safe-impulse criterion of 14 pKa.ms for personnel was evaluated by an unprot...

Response of southern right whales to simulated swim‐with‐whale tourism at Península Valdés, Argentina

“…These whales voluntarily approach stationary vessels and remain nearby for hours, resulting in elevated risks to participants due to the close proximity of large animals, and to the focal whales due to boat strikes and/or entanglement with ropes used by swimmers (Mangott et al 2011). These results bear similarities to the “boat‐positive” behavior of gray whales ( Eschrichtius robustus ) in Mexico (Dalheim et al 1981), but are starkly different from other descriptions of large whale reactions to vessel traffic. The Scientific Committee of the International Whaling Commission noted that the impact of tourism activity may vary by species or site, and each situation should be evaluated on its individual merits (IWC 2000).…”

Gray whale (Eschrichtius robustus) at calving sites in the Gulf of California, México

“…Since acoustical communication is almost certainly necessary to maintain contact between gray whale mothers and their newborn calves (Dahlheim, 1987), human-induced underwater noise may interfere with this and other important social behaviours. Dahlheim (1983) and Dahlheim et al (1984) reported that gray whales in Laguna San Ignacio (evidently necessarily) became more vocal when exposed to man-made noises, and Jones et al (1994) and Dahlheim et al (1995) found that most gray whales, especially cow/calf pairs, abandoned Laguna San Ignacio for a year in response to a month of underwater playback experiments of noises from outboard motors of boats, industrial activities and other sources, including killer whale vocalisations. As mentioned previously, the only records of gray whales inside Bahía de Yavaros were at a time when killer whales were sighted in the area outside this coastal lagoon.…”