Sub-contract proposal ADVANCING REMOTE MARINE MAMMAL STOCK ASSESSMENT WITH PASSIVE ACOUSTIC GLIDERS Submitted to Pacific Islands Fisheries Science Center National Oceanic and Atmospheric Administration Funding Opportunity Number NOAA-NMFS-PIFSC-2010-2002304 19 March 2010 by Bruce M. Howe University of Hawai’i at Manoa, School of Ocean and Earth Science and Technology 2540 Dole St., Holmes Hall #402, Honolulu, HI 96822 (808) 956-0466 email@example.com Project Duration: 1 May 2010 – 30 April 2012 Amount Requested: Year 1: $64,000 Year 2: $96,000 Project Summary Traditional methods of cetacean stock assessment often require resources beyond those available in most regions and institutions. As such, stock assessments are inadequate for many species and have not been completed at all in many regions. We propose an alternative platform for cetacean assessments. The acoustic Seaglider is an autonomous vehicle capable of carrying acoustic instrumentation as well as oceanographic sensors for periods of up to 200 days. In the first year of our proposed project we will test the cetacean detection capabilities of the Seaglider relative to visual methods during a planned cetacean assessment around Hawaii. In response to the outcome of the test mission, we will also begin developing new hardware and software aboard the glider for detection, classification, and localization of vocal animals. In the second project year we will implement the acoustic design changes and again test the effectiveness of the glider versus a traditional visual survey. Although the experimental design of a glider-based survey must be modified from that of visual line-transect surveys, we are confident that established statistical methods can be used to evaluate cetacean distribution and abundance based on acoustic detections and localizations from the glider. Alternatives to traditional methods are sorely needed, particularly in the Pacific Islands Region where the requirements across the survey area vastly exceed the resources available to conduct robust assessments. The project will be a joint effort of investigators at the PIFSC (E. Oleson and J. Polovina) and the University of Hawaii (B. Howe). The UH component of the work, proposed herein, will consist primarily of preparing and operating the acoustic Seagliders, providing acoustic, temperature and salinity data for colleagues at PIFSC for analysis. Project Description Problem Statement Under the Marine Mammal Protection Act, NMFS is required to assess the status of cetacean stocks occurring within US waters every three years. Cetacean stock assessments must include description of the stocks geographic range, minimum population estimate, the population trend and maximum productivity rate, Potential Biological Removal (PBR) rates, the status of the stock relative to the PBR, and estimates of human-caused mortality. Existing assessments have been classified into two tiers, Tier I and Tier II, based on the accuracy of stock identification, abundance, and mortality estimates, and on the assessment frequency and data quality (Merrick et al. 2004). As of the last Tier I and Tier II status update, only 18% of identified cetacean stocks were classified as Tier II. New requirements for more advanced ecosystem-based assessments (Tier III- Merrick et al. 2007) are now being considered. Cetacean stock assessment surveys require a very large investment of resources. Regions with significant annual allocations of ship time and ample personnel often struggle to maintain up-to- date assessments for all species, with many of those assessments including only the most basic biological and distributional information (Merrick et al. 2004). The NMFS Pacific Islands Region (PIR) encompasses the U.S. Exclusive Economic Zone (EEZ) around the Hawaiian archipelago, Johnston Atoll, Kingman Reef and Palmyra Atoll, Baker and Howland Islands, Jarvis Island, American Samoa, Wake Island, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI), the largest region under NMFS management and representing approximately 1.8 million nmi2 of ocean. Stock assessments for marine mammals in this region are currently available only for the Hawaiian EEZ (Carretta et al. 2009), and with the exception of single survey in the Palmyra and Johnston EEZs (Barlow et al. 2008), cetacean stocks in the remaining PIR have never been surveyed. Known cetacean stocks in the PIR are all at the Tier I stage. Over 500 days of ship time are required to conduct one line-transect survey of each PIR EEZ. With limited ship time and resources, this represents a significant challenge to using traditional ship-based methods, thus requiring new approaches and new technology in order to meet our assessment mandates. As NMFS moves toward next generation assessments of protected species (Tier III assessments), the PIR is in a unique position to design and implement a more advanced, mobile, and flexible system for cetacean assessment, even during the first surveys of many of the region’s EEZs. Scope and Objectives Distribution and abundance of cetacean stocks is typically surveyed using visual line transect techniques (Buckland et al. 2001), where density of animals is a function of the number of animals seen along systematically placed track lines and the probability of detecting the target animal at various distances from the track line. Successful execution of this technique often requires months of continuous ship time and the support of dozens of personnel, particularly when used to assess cetacean abundance over broad geographic areas. In some regions, surveys include the collection of oceanographic datasets that may be used to place the occurrence of each cetacean species into an ecosystem context, thereby improving stock assessments with habitat information. The field of passive acoustic sensing for marine mammals has grown immensely over the past 10 years. Towed hydrophones have become a regular addition to the traditional line transect visual survey design as they provide an alternative method for detecting vocal animals that are not available to the visual observers – because they are submerged, difficult to see, or further from the survey vessel – therefore producing more precise abundance estimates. The addition of towed hydrophone arrays has provided correction factors for the number of animals missed by the visual team, increasing the accuracy of the abundance estimate (Barlow & Rankin 2007), and for some species, has provided independent estimates of species abundance (Barlow and Taylor 2005). Stationary acoustic sensors have provided opportunity for year-round assessment of the occurrence of several cetacean species (partially reviewed by Mellinger et al. 2007). Under certain environmental conditions or when placed in the appropriate configuration, stationary sensors may also provide the capability to assess abundance of cetaceans over time (e.g. McDonald & Fox 1999, Marques et al. 2009). However, both towed and fixed acoustic methods are limited in their capabilities; towed surveys by ship time allocation and the timing of ship surveys, stationary surveys by the small geographic range of the assessment. The success of passive acoustics in detecting cetaceans suggests that deployment of acoustic sensors on alternative platforms may provide a robust, cost-effective, and flexible means of surveying for many species. Gliders are autonomous, re-usable, underwater vehicles designed to glide along a saw tooth trajectory from the ocean surface to a programmed depth, measuring a suite of oceanographic quantities along their path. Gliders can be deployed from a pier or from a small boat requiring far less logistical support than a large-scale ship survey. In addition, the sensor suite of a glider provides the capability to collect the oceanographic measurements that allow for assessment of cetaceans within an ecosystem-based context. Incorporation of oceanographic variables into models of cetacean occurrence has already proven useful in reducing the uncertainty of cetacean density estimates (Ferguson et al. 2006b, Forney 2000). We propose an experiment to assess the current acoustic sensing capabilities of existing gliders to provide an alternative means of measuring cetacean occurrence, and development of more advanced acoustic sensing and processing methods to allow for estimation of distance to vocal animals, a key component when using distance sampling statistical methods. By project year, our goals are the following: Year 1 1) assess the detection capability of the acoustically-capable Seaglider versus a visual line- transect survey 2) assess oceanographic correlates of cetacean occurrence based on glider detections and evaluate further development of glider-based oceanographic sensors 3) initiate development of advanced acoustic detection and localization capabilities on the glider to provide the data sets necessary to compute abundance estimates from glider detections Year 2 1) implement new acoustic-sensing technology into the glider and test the new system versus a visual and acoustic survey 2) evaluate new or enhanced existing statistical methods for estimating abundance from glider-based acoustic detections. Technical Approach Our proposal seeks to advance the capabilities of an existing platform to increase opportunity and reduce cost for stock assessment surveys for cetaceans, particularly when use of traditional methods is limited by available resources. We will use Seaglider (Eriksen et al. 2001), a commercially-available (http://www.irobot.com/sp.cfm?pageid=393) unmanned underwater vehicle whose capabilities have been expanded to provide duty-cycled continuous acoustic sampling over the course of the deployment. Although Seaglider’s ability to detect cetacean vocalizations has already been proven (Moore et al. 2007- Figure 1.), the comparison of those capabilities to existing assessment methods has not been evaluated. Our goal will be to evaluate the use of autonomous gliders, and by extension, other autonomous vehicles, for providing the type and quality of data needed to carry out a quantitative assessment of cetacean populations. This will be achieved through comparison of temporally concurrent glider and shipbased cetacean surveys off the Kona coast during each of the project years. The Seaglider: Seagliders are currently capable of travel at roughly ½ knot using ½ W of power. With basic temperature and salinity sensors, glider missions can last over 200 days, including 600 dives to 1000 m, and cover distances up to 3500 km. The Seaglider has been designed to make CTD and other measurements as it yo-yo’s through the water column, navigating along a prescribed route (Eriksen et al., 2001; Davis et al., 2001). On a steady glide slope, the Seaglider travels at a nominal speed of 0.25 m/s through the ocean, propelled by buoyancy. Buoyancy and internal mass control, combined with body and wing hydrodynamics, cause Seaglider to alternately dive and climb along slanting glide paths. The Seaglider dead reckons underwater between sea surface GPS navigation fixes to glide through a sequence of programmed waypoints. Via Iridium satellite data telemetry, Seaglider transmits collected environmental (high resolution profiles of physical, chemical, and bio-optical) variables and internal system data and receives command files. The antenna is exposed above the sea surface for a few minutes between dive cycles. This ability to receive data and change mission goals in near real-time provides tremendous operational flexibility. Gliders can be readily launched and recovered from a small boat with a crew of two, avoiding costly reliance on ships. Figure 1. From Moore et al. 2007. Example of (a) blue A and B calls, (b) humpback upsweeps and (c) sperm whale echolocation clicks recorded on acoustic Seagliders deployed in Monterey Bay. An acoustic recording system (ARS), recently added to the basic Seaglider, uses a CF2 processor combined with a 4 GB flash memory and a 60 GB hard disc. With each surfacing, the Seascan clock in the ARS is synchronized to GPS providing absolute timing accuracy of about 1 ms over a dive. The current Seaglider uses a single hydrophone and can maintain sampling at 4 kHz with the low pass filter set at 30 kHz. The 64 kHz bandwidth is adequate for detection of the sounds produced by mysticetes and many odontocetes. Software parameters (both acoustic recording system and glider parameters such as waypoints) can be changed on the fly each time the glider surfaces and communicates with the pilot on shore. The current Seaglider configuration is limited to recording data just over 50% of the time due to the requirement to write data to disk from flash when sampling is not occurring. This limitation is not expected to impact our results and can be accounted for during data analysis. Figure 2. The acoustic Seaglider. In the current configuration, the hydrophone is in the top of the tail of the glider. The second project year will include the incorporation of new acoustic technology (DMON) capable of continuous broadband (up to 300kHz) acoustic sampling of three hydrophone channels. The hydrophones can be placed at different points along the glider, or on the wings, providing the capability for 2-dimensional localization of a vocalizing animal. Experimental Design: The first phase of this project will include a multi-day field assessment of the detection capabilities of Seaglider relative to a visual survey off the Kona coast of the Island of Hawai’i. The leeward coast of Hawaii is surveyed several times per year for a few weeks each survey. The glider will be preprogrammed to travel a series of transect lines that fall within the visual survey area. Attempts will be made each day to conduct visual survey within the immediate vicinity of the glider track in order to provide direct comparison of the two methods. Because the glider travels at only ½ kt, while vessels generally survey at much higher speeds (8- 10+ kts), vessel and glider surveys will not occur in parallel, but will provide independent measures of cetacean occurrence within the defined survey area. At the end of the survey, we will compare local and regional detection rates between the visual survey and the glider providing a measure of the ability of the glider to provide a representative sample of cetaceans in the study area. Echosounders aboard the visual survey vessel will also be used to calibrate the acoustic detection capabilities of the glider at various frequencies and distances. Recent dualmode visual and acoustic surveys near the Hawaiian Islands and around Palmyra suggest that the acoustic detection rate for most cetacean species will exceed visual detections for a large number of species (Rankin et al. 2008), though some species, particularly those with vocalizations higher than 30kHz, may not be detected as frequently or at all with the current glider (Figure 3). During the survey effort the glider will also collect high resolution temperature and salinity measurements. The glider’s vertical temperature profile data will be analyzed to map the depth of the top of the thermocline and any eddy or frontal features in the survey area. The detection of cetaceans based on the glider acoustics will be compared to the vertical and horizontal distribution of measured oceanographic variables to provide the basic data required to assess the environmental context of cetacean occurrence within the study area. We anticipate that it will be necessary to upgrade the current acoustic capabilities of the glider to allow for higher bandwidth sampling in order to assess the occurrence of most cetacean species. The DMON hydrophone system being developed by the Woods Hole Oceanographic Institution is well suited to this goal and will be available for commercial purchase and incorporation into other oceanographic systems by late-2010. The DMON system also has multiple hydrophone channels providing the capability to obtain bearing estimates to vocal cetaceans. The DMON processor is low power, but powerful enough to support sophisticated cetacean detection and classification algorithms. As the DMON is integrated into the glider, we will begin testing sensor placement to determine the optimal configuration to detect signals for distance and bearing estimation, while minimizing interference with glider operation or other glider sampling capabilities. We will aim for a 3-D hydrophone arrangement so that location of vocal cetacean groups can be estimates based on the time of arrival of the sounds at each hydrophone. In the second year of the project we will implement the glider improvements and repeat field tests versus visual techniques. Analysis of the second year of field test data will focus on the accuracy of bearing estimates generated from the glider hydrophones versus known animals or test source locations and will include detailed model-based analysis of oceanographic correlates to cetacean occurrence within the study area using a combination of methods outlined by Redfern et al. (2006), including flexible generalized models (Hastie & Tibshirani 1990). We will also compare of the detection function between the glider and a traditional ship survey. Detection of cetacean vocalizations on a multi-hydrophone platform provides the capability to estimate location, and therefore distance to the vocal group. This is the primary measure needed to apply traditional distance sampling techniques to estimate density and abundance. Figure 3. From Mellinger et al. (2007): Known frequency ranges of cetacean sounds. Large whales are listed by species and toothed whales by family. The range of the most common vocalizations (blue bar) and the recorded extremes (thin line) are shown. The proposed project focuses primarily on the hardware and software improvements needed to implement cetacean assessments using alterative glider technology. We are fully aware that significant challenges remain for acoustic-only assessment of cetaceans, primarily including the ability to classify detected sounds to specific species with a measured degree of certainty, and the ability to estimate the size of detected groups based on the acoustic characters alone. Acoustic detection methods contribute the greatest amount to visual surveys when species-specific calls can be identified. The calls of many baleen whales are highly stereotyped and well-described (Edds-Walton 1997) and a rapidly increasing number of tropical and subtropical delphinids can be identified by the characteristics of their clicks and whistles (e.g. Oswald et al. 2003, Oswald et al. 2007, Baumann-Pickering 2009). However, significant gaps still remain in our ability to acoustically classify sounds to species. There are a great number of researchers and institutions contributing data and techniques to address this short-coming, and we feel that once the glider technology is proven capable of detecting and localizing cetaceans, new processing algorithms can be integrated as they become available, either into the acoustic acquisition system onboard the glider or during post-processing of the collected data. Acoustic estimates of group size are currently not possible for most species. General trends indicate that larger groups are more frequently detected acoustically than small groups (Rankin et al. 2008); however, this may vary based on animal behavior. The oceanographic data collected with the glider may provide some insight into the range of expected group sizes (Ferguson et al. 2006a); however, much more data on acoustic behavior and the relationship between acoustic characters and group size is needed before we will be able to estimate this important parameter based on acoustics alone. Ongoing studies should eventually provide this data, and the appropriate correction factors can them be applied to newly advanced glider technology. The Cetacean Research Program at PIFSC actively contributes to these efforts. Our primary goal is to develop a new tool that will contribute to existing (Tier I and II) and advanced (Tier III) cetacean stock assessments. We feel the increased detection capabilities and continuous environmental sampling will provide powerful new methods for conducting initial assessments in the PIR and for augmenting ongoing assessment efforts in regions with established assessment resources and protocols. Scientific Merit and ASTWG Mission The proposed research addresses the mission of the ASTWG by advancing current glider technology to provide a promising alternative means of conducting cetacean stock assessments. Acoustic sensing is a very effective way to detect the occurrence of cetaceans, providing a higher rate of detection than standard visual surveys for many species (Rankin et al. 2007). Incorporating passive acoustic sensors into autonomous underwater vehicles, such as gliders, provide the capability to effectively survey a broad region, a cost-effective alternative to the current visual line-transect standard. The glider also provides the capability to continuously collect oceanographic data that can be incorporated into models of cetacean distribution and abundance, increasing the accuracy and precision of stock assessments. Gliders equipped with acoustic sensors and software capable of classifying and localizing cetacean groups while collecting environmental data may be used in any NMFS region. We propose developing this technology in the PIR where this type of technology can not only fill basic assessment gaps, but can rapidly increase the quality of assessments. A broad range of species can be reliably found in the protected waters off the Kona coast of Hawaii providing an excellent test location for evaluating design changes and sampling schemes. Once the hardware and software capabilities are stable and proven robust, this technology may be easily deployed elsewhere in the PIR and in other regions. Qualifications of the Principle Investigator Glider technical expertise and the gliders themselves will be provided by co-PI Bruce Howe at the University of Hawaii. Howe has had over 30 years of experience in ocean acoustics, most notably in ocean observing technology (please see CV). While at the University of Washington Applied Physics Lab, he initiated the Acoustic Seaglider program in 2003 with ONR support and in 2005-2006 deployed Seagliders carrying a broadband hydrophone (10 Hz – 30 kHz). The acoustic Seaglider proved its capability in marine mammal detection under Howe’s direction during the 2006 Monterey Bay PLUSNet experiment (Moore et al., 2008). The University of Hawaii is currently operating 8 Seagliders: one as part of the Hawaii Integrated Ocean Observing System (HIOOS), operating south of Oahu and in the channel between Oahu and Molokai; four as part of the Center for Microbial Oceanography Research and Education (CMORE) at Station ALOHA 100 km north of Oahu; and three for the ONR-funded Philippine Sea 2010 experiment (to be deployed there November 2010-April 2011). One or more of the latter gliders will be used for this work. Work Plan, Schedule & Milestones A general timeline is provided for this project in Table 1 below. Exact dates cannot be provided as the timing of some phases will be dependant on ship time allocations. The year 1 objective is to deploy one acoustic Seaglider on the leeward coast of Hawaii to record marine mammal vocalizations, and to compare these with visual observations. The acoustic Seaglider work will be carried out under the direction of Howe, with Oleson (NOAA) being responsible for the overall experiment, including the visual observations. In year 1, we will prepare one acoustic Seaglider that includes a 1-day test dive off Honolulu. From a NOAA supplied vessel, we will deploy the glider off the west coast of Hawaii and pilot it for up to one month while it collects data. The track and acoustic recording schedule will be determined in collaboration with Oleson. The tentative time for deployment is in the April-June 2010 timeframe. Upon completion of the mission, the glider will be recovered by UH personnel, again, using a NOAA-supplied vessel. The glider acoustic and engineering data will be processed and made available to all collaborators. This will include glider position and depth as a function of time, temperature and salinity as a function of depth/time, and acoustic data files appropriately time-stamped. A brief data report will be delivered that provides a summary of the engineering data and initial acoustic results (e.g., time traces and spectra from representative files). Oleson and colleagues will process the acoustic data for marine mammal vocalizations. In year 2 – an option, essentially the same will be repeated, but this time, with a more capable acoustic recording unit (based on DMON, made by WHOI (Mark Johnson), and integrated into gliders by iRobot). This system will support up to three hydrophones, from which we will be able to determine bearing to a vocalizing animal. The standard system comes with one hydrophone; part of year 2 work will be to add the second and third hydrophones and test. Howe will manage and direct the UH portion of the project. Karynne Morgan will provide administrative assistance. Jennie Mowatt is the resident glider technician. Table 1. Work Schedule Time Activity Milestones Frame 2010 – Project Year 1 Spring – Acoustic Seaglider deployed during 1. Report to ASTWG on detection Summer visual surveys of the Kona coast of capability of existing acoustic Seaglider 2010 Hawaii and anticipated capability of upgraded system Fall 2010 – Comparision of Seaglider and visual Winter survey performance 2011 Spring Integration of new acoustic system and 2011 optimal sensor placement for multi- channel sensing Summer Acoustic Seaglider deployed with new 1. Produce Final Report to 2011 acoustic system during planned visual ASTWG survey off Hawaii 2. Report on new glider capabilities and future directions to clleagues at national workshops and meetings Fall 2011 – Work with survey design colleagues to Winter modify existing statistical methods for 2012 use with acoustic Seaglider detections Spring Comparison of Seaglider and visual 2012 survey performance and evaluate habitat-associations based on oceanographic sampling onboard the glider Budget Justification The total requested University of Hawaii (UH) budget for year 1 is $64,000. The budget includes the costs necessary to provide engineering support and glider expertise for the proposed project. These costs include partial salary support for UH PI Bruce Howe, as well as a Project Engineer and Assistant. The SOEST Ocean Gliders (SOG) Facility has set a nominal per mission cost of $36,000, which includes batteries, sensor calibration, insurance, Iridium communication charges, and piloting. Also included are travel costs for field deployment of the glider of the Kona coast and the costs of materials and supplies. The total budget for year 2 is $96,000. The cost largely mirrors that of year 1, with the addition of the purchase of the acoustic recorder DMON for incorporation into the glider ($10,000), and increases due to inflation and merit-based personnel salary increases. The current average benefit rate for UH faculty and staff is 37.13% of salaries. Composite fringe rates varies for UH and RCUH employees, but benefits are similar for both and consist of vacation reserve, sick leave, medical/dental insurance, retirement/pension, group life insurance, long-term disability and care, FICA, unemployment insurance, workers compensation, and flex spending. The DMON acoustic recorder is a component to be added to the glider (non stand alone item without a lease-to-purchase option).
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