Methods are developed for estimating the size/density of cetacean populations using data from a set of fixed passive acoustic sensors The methods convert the number of detected acoustic cues into animal density by accounting for (i) the probability of detecting cues, (ii) the rate at which animals produce cues, and (iii) the proportion of false positive detections Additional information is often required for estimation of these quantities, for example, from an acoustic tag applied to a sample of animals Methods are illustrated with a case study: estimation of Blainville’s beaked whale density over a 6day period in spring 2005, using an 82 hydrophone wide-baseline array located in the Tongue of the Ocean, Bahamas To estimate the required quantities, additional data are used from digital acoustic tags, attached to five whales over 21 deep dives, where cues recorded on some of the dives are associated with those received on the fixed hydrophones Estimated density was 253 or 225 animals/1000km2, depend

/pdf/estimating-cetacean-population-density-using-fixed-passive-2qhtevjdmh.pdf

Estimating cetacean population density using fixed passive acoustic sensors: an example with Blainville's beaked whales.

Fixed autonomous acoustic recording devices (autonomous recorders [ARs]) are defined as any electronic recording system that acquires and stores acoustic data internally (i.e., without a cable or radio link to transmit data to a receiving station), is deployed semi-permanently underwater (via a mooring, buoy, or attached to the sea floor), and must be retrieved to access the data. More than 30 ARs were reviewed. They varied greatly in capabilities and costs, from small, hand-deployable units for detecting dolphin and porpoise clicks in shallow water to larger units that can be deployed in deep water and can record at high-frequency bandwidths for over a year, but must be deployed from a large vessel. The capabilities and limitations of the systems reviewed herein are discussed in terms of their effectiveness in monitoring and studying marine mammals.

A Review and Inventory of Fixed Autonomous Recorders for Passive Acoustic Monitoring of Marine Mammals

The North Atlantic right whale Eubalaena glacialis is endangered, in part, due to vessel- strike mortality. We use vessel traffic and right whale survey data (~3 nautical miles (n miles), ~5.6 km resolution) for the Bay of Fundy and on the Scotian Shelf (northwest Atlantic) to determine the relative risk of lethal vessel encounters by using 2 estimates: (1) the event — the relative proba- bility of a vessel encountering a right whale, and (2) the consequence — the probability of a lethal injury arising from an encounter. For the Bay of Fundy region our estimates demonstrate that the rel- ative risk of lethal collision could be reduced by 62% by means of an amendment to the traffic sepa- ration scheme (TSS) that intersects a Right Whale Conservation Area. In the Roseway Basin region of the Scotian Shelf, the majority of vessels navigate outside of a Right Whale Conservation Area, although the highest relative risk is concentrated within the Conservation Area where fewer vessels navigate at greater speed. Here, our estimates demonstrate that a seasonal recommendatory area to be avoided (ATBA) could be designed to reduce the risk imposed by vessels upon right whales in the region. Our estimates contributed to the International Maritime Organisation (IMO) adoption of a TSS amendment in the Bay of Fundy and an ATBA on the Scotian Shelf. Thus, the goal of achieving the greatest reduction in the risk of lethal vessel-encounters with whales, balanced by some minimal disruption to vessel operations while maintaining safe navigation, can be achieved.

/pdf/reducing-the-risk-of-lethal-encounters-vessels-and-right-4ah09czys1.pdf

Reducing the risk of lethal encounters: vessels and right whales in the Bay of Fundy and on the Scotian Shelf

Passive acoustic methods are increasingly being used to estimate animal population density. Most density estimation methods are based on estimates of the probability of detecting calls as functions of distance. Typically these are obtained using receivers capable of localizing calls or from studies of tagged animals. However, both approaches are expensive to implement. The approach described here uses a MonteCarlo model to estimate the probability of detecting calls from single sensors. The passive sonar equation is used to predict signal-to-noise ratios (SNRs) of received clicks, which are then combined with a detector characterization that predicts probability of detection as a function of SNR. Input distributions for source level, beam pattern, and whale depth are obtained from the literature. Acoustic propagation modeling is used to estimate transmission loss. Other inputs for density estimation are call rate, obtained from the literature, and false positive rate, obtained from manual analysis of a data sample. The method is applied to estimate density of Blainville's beaked whales over a 6-day period around a single hydrophone located in the Tongue of the Ocean, Bahamas. Results are consistent with those from previous analyses, which use additional tag data.

http://lenthomas.org/papers/KuselJASA2011.pdf

Cetacean population density estimation from single fixed sensors using passive acoustics.

We present a method for estimating animal density from fixed passive acoustic detec- tors, and illustrate it by estimating the density of North Pacific right whales Eubalaena japonica in the areas surrounding 3 hydrophones deployed in the southeastern Bering Sea in 2001 to 2002 and 2005 to 2006. Input data were the distances to detected right whale calls, estimated using a normal mode sound propagation model, and call production rate, estimated from encounters by survey vessels with right whale groups. Given the scarcity of information about this highly endangered species, we also extrapolate our results to provide a tentative estimate of the total population size in shelf waters of the eastern Bering Sea. This gives a point estimate of 25 animals (CV 29.1%; 95% confidence interval 13-47), which agrees well with what little is known for this species. We discuss the assumptions underlying the method. Obtaining more reliable values requires a larger sample of randomly located hydrophones, together with improved estimates of call rate.

/pdf/estimating-north-pacific-right-whale-eubalaena-japonica-12ku920pln.pdf

Estimating North Pacific right whale Eubalaena japonica density using passive acoustic cue counting

A year-long acoustic survey for critically endangered North Atlantic right whales was conducted at two sites on the central and western Scotian Shelf Autonomous hydrophones recorded sound continuously from July 2004 to August 2005 Right whale contact calls (upcalls) were identified using automatic recognition software, and the resulting detections were checked manually Substantial numbers of hours with upcalls were observed at both sites, with approximately four times as many hours with calls at the western site as the central one Calls occurred mainly from August through October, with the earliest calls in late June and the latest at the end of December at both sites In addition to this seasonal trend, there was a significant diel pattern in calling at the central site but not at the more westerly site Results are analyzed in light of feeding ecology and broad-scale movements of right whales

Seasonal occurrence of north atlantic right whale (Eubalaena Glacialis) vocalizations at two sites on the scotian shelf

An accurate, single-user beach-elevation profile device that relies on lightweight, inexpensive materials is described The device is used to rapidly survey beach topographic profiles and is appropriate for scientific data collection The profiler consists of two vertical legs and two horizontal spacer bars in the shape of the pound (#) symbol with a freely rotating arm to determine the horizontal level The light weight and ease of operation of the apparatus permit profiles to be surveyed in 1-m increments at roughly 2 m/min Standard deviations of the profiler reading at specific points along a single profile varied between 0003 and 0014 m as recorded by four different users Root-mean-square errors on data along five different cross-shore profiles collected at Rehoboth Beach, Delaware, by the four users were 001–013 m when compared to standard rod and sighting scope and ground-based light detecting and ranging Several potential causes for the differences, including intrinsic profiler bias

A Single-User Subaerial Beach Profiler

[1] The seismicity of the North Atlantic was monitored from May 2002 to September 2003 by the ‘SIRENA array’ of autonomous hydrophones. The hydroacoustic signals provide a unique data set documenting numerous low-magnitude earthquakes along the section of the Mid-Atlantic Ridge (MAR) located in a ridge-hot spot interaction context. During the experiment, 1696 events were detected along the MAR axis between 40°N and 51°N, with a magnitude of completeness level ofmb≈ 2.4. Inside the array, location errors are in the order of 2 km, and errors in the origin time are less than 1 s. From this catalog, 15 clusters were detected. The distribution of source level (SL) versus time within each cluster is used to discriminate clusters occurring in a tectonic context from those attributed to non-tectonic (i.e. volcanic or hydrothermal) processes. The location of tectonic and non-tectonic sequences correlates well with regions with positive and negative Mantle Bouguer Anomalies (MBAs), indicating the presence of thinner/colder and thicker/warmer crust respectively. At the scale of the entire array, both the complete and declustered catalogs derived from the hydroacoustic signals show an increase of the seismicity rate from the Azores up to 43°30′N suggesting a diminishing influence of the Azores hot spot on the ridge-axis temperature, and well correlated with a similar increase in the along-axis MBAs. The comparison of the MAR seismicity with the Residual MBA (RMBA) at different scales leads us to think that the low-magnitude seismicity rates are directly related to along-axis variations in lithosphere rheology and temperatures.

/pdf/spatiotemporal-distribution-of-the-seismicity-along-the-mid-1ncdmxn085.pdf

Spatiotemporal distribution of the seismicity along the Mid-Atlantic Ridge north of the Azores from hydroacoustic data: Insights into seismogenic processes in a ridge-hot spot context

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Seasonal occurrence of north atlantic right whale (Eubalaena Glacialis) vocalizations at two sites on the scotian shelf

A Single-User Subaerial Beach Profiler

Spatiotemporal distribution of the seismicity along the Mid-Atlantic Ridge north of the Azores from hydroacoustic data: Insights into seismogenic processes in a ridge-hot spot context