Model-based localization of deep-diving cetaceans using towed line array acoustic data

Passive acoustic monitoring using a towed line array of hydrophones is a standard method for localizing cetaceans during line-transect cetacean abundance surveys. Perpendicular distances estimated between localized whales and the trackline are essential for abundance estimation using acoustic data. Uncertainties in the acoustic data from hydrophone movement, sound propagation effects, errors in the time of arrival differences, and whale depth are not accounted for by most two-dimensional localization methods. Consequently, location and distance estimates for deep-diving cetaceans may be biased, creating uncertainty in abundance estimates. Here, a model-based localization approach is applied to towed line array acoustic data that incorporates sound propagation effects, accounts for sources of error, and localizes in three dimensions. The whale’s true distance, ship trajectory, and whale movement greatly affected localization results in simulations. The localization method was applied to real acoustic data from two separate sperm whales, resulting in three-dimensional distance and depth estimates with position bounds for each whale. By incorporating sources of error, this three-dimensional model-based approach provides a method to address and integrate the inherent uncertainties in towed array acoustic data for more robust localization

Examining distribution patterns of foraging and non-foraging sperm whales in Hawaiian waters using visual and passive acoustic data

Following the end of over a century of intensive commercial whaling in 1986, the monitoring and assessment of sperm whale populations is essential for guiding management and conservation decisions for their recovery. Species distribution models (SDMs) are a useful tool for examining and predicting cetacean distribution patterns and typically incorporate visual, ship-based observations. However, understanding sperm whale distribution and habitat use based solely on surface visual observations is challenging due to the significant amount of time sperm whales spend foraging at depth. For the endangered sperm whale population occurring in Hawaiian waters, we used visual and passive acoustic data collected during four annual NOAA marine mammal line-transect surveys and a suite of biologically relevant environmental variables to develop SDMs within a generalized additive modeling framework to study the distribution of sperm whale groups throughout the island chain. Additionally, the passive acoustic data allowed us to differentiate sperm whale groups as foraging or non-foraging based on their click types to account for differences in distribution and behavior within the archipelago. Foraging groups were predicted primarily in the northwestern region of the archipelago between Laysan Island and Pearl and Hermes Reef as well as north of Maui and Hawaiʻi in the main Hawaiian Islands. Non-foraging groups were predicted to be more uniformly distributed throughout the archipelago. Foraging whale models selected temperature at 584 m depth, surface chlorophyll, and location, while the only significant variables for non-foraging whale models included the standard deviation of sea surface height and location. Each variable provides insight into the oceanographic processes influencing prey abundance and, thus, sperm whale foraging behavior. This study furthers our understanding of the distribution patterns for the sperm whale population in Hawaiʻi and contributes methods for building SDMs with visual and passive acoustic data that may be applied to other cetacean species

Idaho Forestry Best Management Practices Field Guide: Using BMPs to Protect Water Quality

This practical guide will help forest landowners, managers, and operators apply Idaho's mandatory forestry BMPs. Contents include (1) the science related to forests, forest hydrology, aquatic ecology, and related biology; (2) Idaho Forest Practices Act rules; and (3) highly recommended voluntary management practices. 156 pages

Characterizing patterns in endangered cetacean populations of the Hawaiian Archipelago using passive acoustic data

Ph.D

Differences in oscillatory whistles produced by spinner (Stenella longirostris) and pantropical spotted (Stenella attenuata) dolphins

Acoustic recordings of two closely related species, spinner dolphin (Stenella longirostris) and pantropical spotted dolphin (Stenella attenuata), were investigated from four different geographic locations: two in the Central Tropical Pacific, one in the Eastern Tropical Pacific and one in the Indian Ocean. The two delphinid species occur in tropical and warm temperate waters, with overlapping ranges. They produce very similar vocalizations, but at the same time their calls exhibit a certain degree of intraspecific variation among different geographic locations as has been observed in other delphinid species. Oscillatory whistles (whistles with at least two oscillations in their frequency contours) were identified and manually extracted from the recordings. Whistles with four or more maxima (oscillations) occurred only in spinner dolphins and they were present in all geographic regions investigated. In addition, the oscillatory whistles with two and three maxima were significantly more frequent in spinner than in spotted dolphins. The differences in oscillatory whistles for these two species seem to be consistent across study areas and therefore, could be used in addition to other whistle features to help distinguish between the

Vocal behavior of false killer whale (Pseudorca crassidens) acoustic subgroups

Understanding the vocal behavior of cetaceans is an important component of many passive acoustic applications. This study quantifies the vocal behavior of acoustic subgroups of false killer whales (Pseudorca crassidens) from the Hawaiian Archipelago. The acoustic subgroups (N = 523) exhibit diverse vocal behavior that varies between encounters. Overall, 29% of acoustic subgroups only echolocate, 16% only whistle, and 55% emit both types of vocalizations. These results contribute important information for developing automated passive acoustic cetacean tracking, localization, and classification techniques, and thus, support future cetacean monitoring and assessment efforts

Click detection rate variability of central North Pacific sperm whales from passive acoustic towed arrays

Passive acoustic monitoring (PAM) is an optimal method for detecting and monitoring cetaceans as they frequently produce sound while underwater. Cue counting, counting acoustic cues of deep-diving cetaceans instead of animals, is an alternative method for density estimation, but requires an average cue production rate to convert cue density to animal density. Limited information about click rates exists for sperm whales in the central North Pacific Ocean. In the absence of acoustic tag data, we used towed hydrophone array data to calculate the first sperm whale click rates from this region and examined their variability based on click type, location, distance of whales from the array, and group size estimated by visual observers. Our findings show click type to be the most important variable, with groups that include codas yielding the highest click rates. We also found a positive relationship between group size and click detection rates that may be useful for acoustic predictions of group size in future studies. Echolocation clicks detected using PAM methods are often the only indicator of deep-diving cetacean presence. Understanding the factors affecting their click rates provides important information for acoustic density estimation.</p

A Seaglider-Integrated Digital Monitor for Bioacoustic Sensing

An acoustic Digital MONitor (DMON) has been integrated into a Seaglider autonomous underwater vehicle to serve as a general-use tool for passive acoustic sensing of marine mammal vocalizations. The system is being developed as a complement to conventional ship-based cetacean survey methods. The acoustic system includes three omnidirectional hydrophones, one located on centerline of the aft payload hatch and one on each wingtip. An onboard real-time detector has been implemented to record an audio sample if ambient noise has risen above a user-prescribed signal-to-noise ratio (SNR) threshold level. The data size and the number of detections are available in semi-real time, and the acoustic data are retrieved upon recovery of the instrument. Because the DMON system interfaces with the Seaglider firmware, the glider pilot has the capability to modify several operational parameters governing the collection of acoustic data while the glider is deployed to tailor the data recording to the desired mission objectives. This implementation is referred to as the Seaglider Customizable Sampling Configuration (SCSC) DMON and has recorded a wide variety of cetacean vocal activity offshore the Hawaiian Islands