A new context-based approach to assess marine mammal behavioral responses to anthropogenic sounds.

Acute effects of anthropogenic sounds on marine mammals, such as from military sonars, energy development, and offshore construction, have received considerable international attention from scientists, regulators, and industry. Moreover, there has been increasing recognition and concern about the potential chronic effects of human activities (e.g., shipping). It has been demonstrated that increases in human activity and background noise can alter habitats of marine animals and potentially mask communications for species that rely on sound to mate, feed, avoid predators, and navigate. Without exception, regulatory agencies required to assess and manage the effects of noise on marine mammals have addressed only the acute effects of noise on hearing and behavior. Furthermore, they have relied on a single exposure metric to assess acute effects: the absolute sound level received by the animal. There is compelling evidence that factors other than received sound level, including the activity state of animals exposed to different sounds, the nature and novelty of a sound, and spatial relations between sound source and receiving animals (i.e., the exposure context) strongly affect the probability of a behavioral response. A more comprehensive assessment method is needed that accounts for the fact that multiple contextual factors can affect how animals respond to both acute and chronic noise. We propose a three-part approach. The first includes measurement and evaluation of context-based behavioral responses of marine mammals exposed to various sounds. The second includes new assessment metrics that emphasize relative sound levels (i.e., ratio of signal to background noise and level above hearing threshold). The third considers the effects of chronic and acute noise exposure. All three aspects of sound exposure (context, relative sound level, and chronic noise) mediate behavioral response, and we suggest they be integrated into ecosystem-level management and the spatial planning of human offshore activities.

Calibration and comparison of the acoustic location methods used during the spring migration of the bowhead whale, Balaena mysticetus, off Pt. Barrow, Alaska, 1984-1993.

Between 1984 and 1993, visual and acoustic methods were combined to census the Bering-Chukchi-Beaufort bowhead whale, Balaena mysticetus, population. Passive acoustic location was based on arrival-time differences of transient bowhead sounds detected on sparse arrays of three to five hydrophones distributed over distances of 1.5-4.5 km along the ice edge. Arrival-time differences were calculated from either digital cross correlation of spectrograms (old method), or digital cross correlation of time waveforms (new method). Acoustic calibration was conducted in situ in 1985 at five sites with visual site position determined by triangulation using two theodolites. The discrepancy between visual and acoustic locations was <1%-5% of visual range and less than 0.7 degrees of visual bearing for either method. Comparison of calibration results indicates that the new method yielded slightly more precise and accurate positions than the old method. Comparison of 217 bowhead whale call locations from both acoustic methods showed that the new method was more precise, with location errors 3-4 times smaller than the old method. Overall, low-frequency bowhead transients were reliably located out to ranges of 3-4 times array size. At these ranges in shallow water, signal propagation appears to be dominated by the fundamental mode and is not corrupted by multipath.

Safety and efficacy of lomefloxacin versus cefaclor in the treatment of acute exacerbations of chronic bronchitis.

In two multicenter trials, lomefloxacin and cefaclor were compared as treatments for acute bacterial exacerbations of chronic bronchitis. In total, 522 adult outpatients were enrolled at 50 centers in the United States. Patients were randomized to treatment groups receiving either 400 mg lomefloxacin orally once daily (n = 259) or 250 mg cefaclor every 8 hours (n = 263) for 7-10 days. Both groups were comparable in terms of age, severity of exacerbation, smoking history, theophylline use, and baseline pathogens. The most common baseline pathogens were Haemophilus influenzae, found in 32% of patients in the lomefloxacin group and in 29% in the cefaclor group, Pseudomonas aeruginosa (13% and 16%, respectively), Moraxella (Branhamella) catarrhalis (12% and 13%), and Streptococcus pneumoniae (10% in both groups). Bacterial eradication rates 1-4 days after the completion of treatment for all patients with baseline pathogens were 81.8% in the lomefloxacin group and 62.7% in the cefaclor group (p less than 0.001). Clinical success (disappearance or improvement of presenting signs and symptoms) was noted in 80.0% of patients in the lomefloxacin group and 64.7% in the cefaclor group (p = 0.002). Eradication rates for the subgroup of patients who had pathogens susceptible in vitro to both study drugs and who completed treatment were 97.1% for lomefloxacin and 84.6% for cefaclor (p = 0.002). Clinical success rates in this subgroup were 92.4% for lomefloxacin and 90.1 for cefaclor (p = 0.585). Treatment-related adverse events were reported for 7% of patients in the lomefloxacin group and 5% in the cefaclor group. The most common adverse events in both groups were nausea and diarrhea. Six patients were withdrawn from treatment with lomefloxacin and four from the cefaclor group because of adverse events. There was no clinical or laboratory evidence of theophylline interaction with either treatment. Once-daily oral administration of 400 mg lomefloxacin was an effective, well-tolerated alternative to 250 mg of cefaclor three times daily in the treatment of acute exacerbations of chronic bronchitis.