A Wave Glider Approach to Fisheries Acoustics: Transforming How We Monitor the Nation’S Commercial Fisheries in the 21St Century

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CITATION Greene, C.H., E.L. Meyer-Gutbrod, L.P. McGarry, L.C. Hufnagle Jr., D. Chu, S. McClatchie, A. Packer, J.-B. Jung, T. Acker, H. Dorn, and C. Pelkie. 2014. A wave glider approach to fisheries acoustics: Transforming how we monitor the nation’s commercial fisheries in the 21st century. Oceanography 27(4):168–174, http://dx.doi.org/10.5670/oceanog.2014.82.

DOI http://dx.doi.org/10.5670/oceanog.2014.82

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A Wave Glider Approach to Fisheries Acoustics Transforming How We Monitor the Nation’s Commercial Fisheries in the 21st Century

By Charles H. Greene, Erin L. Meyer-Gutbrod, Louise P. McGarry, Lawrence C. Hufnagle Jr., Dezhang Chu, Sam McClatchie, Asa Packer, Jae-Byung Jung, Timothy Acker, Huck Dorn, and Chris Pelkie

168 OceanographyOceanography | Vol | .Vol27, .No27,. 4No.4 ABSTRACT. Possessing the world’s largest Exclusive Economic Zone (EEZ), the biennial basis due to the expense and United States enjoys the benefits of a multi-billion dollar commercial fishing industry. limited availability of ship time. In addi- Along with these benefits comes the enormous task of assessing the status of the tion, such surveys often are conducted nation’s commercial fish stocks. At present, many of the most valuable commercial fish by a single ship over a time span of one stocks are assessed using acoustic surveys conducted from manned survey vessels. The or two months with no repetition of expense and limited availability of ship time often compromise the quantity and quality spatial coverage. Thus, the data cannot of the acoustic stock assessment data being collected. be assumed as synoptic in any realistic Here, we describe our vision for how an unmanned mobile platform, the Liquid sense, and there is no way to determine Robotics Wave Glider, can be used in large numbers to supplement manned survey if the results are repeatable. These oper- vessels and transform fisheries acoustics into a science more consistent with the new ational compromises have become stan- ocean-observing paradigm. Wave Gliders harness wave energy for propulsion and dard practice in many stock assessments, solar energy to power their communications, control, navigation, and environmental- but such data-collection methods greatly sensing systems. This unique utilization of wave and solar energy allows Wave Gliders limit the accuracy and precision of abun- to collect ocean environmental data sets for extended periods of time. dance estimates, blur our understand- Recently, we developed new technology for Wave Gliders that enable them to col- ing of temporal changes in spatial distri- lect multifrequency, split-beam acoustic data sets comparable to those collected with bution patterns, and diminish our ability manned survey vessels. A fleet of Wave Gliders collecting such data would dramatically to detect ecosystem regime shifts, over - improve the synoptic nature as well as the spatial and temporal coverage of acoustic fishing, and other factors influencing the stock assessment surveys. With improved stock assessments, fisheries managers would abundances and distributions of com- have better information to set quotas that maximize yields to fishermen and reduce the mercially important fish stocks. likelihood of overfishing. Improved observational capabilities also would enable fisher- Given the importance of commer- ies scientists and oceanographers to more closely monitor the responses of different fish cial fisheries to the US economy and stocks to climate variability and change as well as ocean acidification. the challenges society faces in monitoring and managing them properly, now is INTRODUCTION greater success—the amount of avail- the time to reassess our strategy for fish- Commercial marine fisheries in the able ship time. As currently practiced, eries acoustics in the future. Fortunately, United States Exclusive Economic Zone acoustic stock assessments are conducted we find ourselves contemplating this (US EEZ) produce annual landings val- from manned survey vessels, ships that strategic reassessment right in the mid- ued at $5 billion (NOAA NMFS, 2012). In are expensive to both build and operate. dle of what has been described as an addition, they directly or indirectly sup- Therefore, even as the demand for acous- “ocean-observing revolution” (Perry and port more than one million jobs, yielding tic stock assessment data has steadily Rudnick, 2003). Since the beginning of an additional $32 billion to the US econ- increased, budgetary constraints have the twenty-first century, marine scien- omy. Since the middle of the twenti- often limited the ability of fisheries scientists have witnessed a large increase in the eth century, ship-based acoustic surveys tists to keep up with this demand. Such variety of unmanned mobile platforms have been adopted by fisheries agen- budgetary constraints typically manifest (e.g., autonomous underwater vehicles, cies throughout the world as a standard themselves through the reduced avail- drifters, floats, and gliders) available for method for assessing the status of many ability of ship time. The high cost of observing the ocean environment and its commercial fish stocks (Fernandes et al., building and operating a fleet of ships has processes. These unmanned mobile plat- 2002; Simmonds and MacLennan, 2006). resulted in fewer federally funded ves- forms are rapidly advancing the abilities In the United States, responsibility for sels being built and a steady decline in of oceanographers to quantify ocean cir- acoustically assessing and managing the the numbers of operational days available culation and biogeochemical dynam- nation’s commercial fish stocks resides for stock assessment surveys (National ics (Perry and Rudnick, 2003; Rudnick with the National Marine Fisheries Ocean Council, 2013). Because these et al., 2004; Davis et al., 2008). They also Service (NMFS) regional science centers budgetary constraints will likely continue have the potential to transform the way (NOAA Fisheries Science Centers, 2004). to limit the availability of ship time into fisheries scientists and oceanographers While there have been many signifi- the foreseeable future, fisheries scien- study marine population and ecosystem cant advances in fisheries acoustics over tists must find a new way to stretch their dynamics (Fernandes et al., 2003; Ohman the past 50 years (Fernandes et al., 2002; budgets without compromising the quan- et al., 2013). Here, we describe our vision Simmonds and MacLennan, 2006; Chu, tity and quality of the stock assessment for how one of these unmanned mobile 2011; Alaska Fisheries Science Center, data being collected. platforms, the Liquid Robotics Wave 2013), one major impediment has pre- Currently, many stock assessment sur- Glider, can be used in large numbers vented the field from achieving even veys are conducted only on a yearly or to transform fisheries acoustics from a

Oceanography | December 2014 169 A Weather Station B & Marker Light Solar Panels Solar Panel

Dry Box Radar Re ector Command & Control Unit Auxiliary Power Unit Foam Insert Foam Insert

Recovery Buoy

Payload Bay Payload Bay

FIGURE 1. (A) The Wave Glider SV3. (B) Components of the Wave Glider SV3’s surface float. science severely constrained by the lim- power systems, and a modular payload interface transmits control system and ited availability of ship time to a science unit for user-specified environmental- sensor data from the Wave Glider to consistent with the new ocean-observing sensing systems (Figure 1B). The sub- shore and commands back from shore to paradigm, one based on near-synoptic, mersible glider has a series of paired the Wave Glider during a mission. Two- continuous monitoring of the nation’s wings that generate propulsive forces way transmission via cellular network or commercial fisheries. and a rudder to provide steering. The key Iridium satellite provides real-time nav- innovation of the Wave Glider is its ability igational, operational, and sensor con- THE WAVE GLIDER APPROACH to harness wave energy for propulsion. It trol as well as real- or near-real-time The Liquid Robotics Wave Glider is a does this with each passing wave by tak- data reporting. self-propelled, unmanned mobile plat- ing advantage of the differential motion The Wave Glider’s performance and form designed for long-term deploy- between the surface float and the sub- versatility at sea make it a consistent and ments to collect oceanographic and other mersible glider (Figure 2). Solar panels reliable platform for collecting ocean environmental data (Manley et al., 2009; on the deck of the surface float recharge a environmental data. Its speed through Willcox et al., 2009). It consists of a surface lithium ion battery pack inside the Wave water is proportional to sea state, with float tethered with an umbilical cable to a Glider’s hold. This battery pack supplies higher waves increasing the differential submersible glider (Figure 1A). The sur- power to systems inside the Wave Glider’s motion between the surface float and sub- face float houses a command and control command and control unit and modu- mersible glider and thus propelling the unit for communications, navigation, and lar payload unit. A simple, Web-based glider more rapidly. During rigorous test- ing, the Wave Glider has been found to cruise at speeds between 0.5 and 1.5 knots Charles H. Greene ([email protected]) is Director, Ocean Resources and Ecosystems in Beaufort Sea State 1 conditions and at Program, and Professor, Department of Earth and Atmospheric Sciences, Cornell speeds greater than 1.5 knots in Beaufort University, Ithaca, NY, USA. Erin L. Meyer-Gutbrod is PhD Candidate, Ocean Resources and Ecosystems Program, Department of Earth and Atmospheric Sciences, Cornell University, Sea State 3 conditions or higher. Over Ithaca, NY, USA. Louise P. McGarry is Postdoctoral Associate, Ocean Resources and longer-duration missions, speeds tend Ecosystems Program, Department of Earth and Atmospheric Sciences, Cornell University, to average ~ 1.5 knots or higher, even Ithaca, NY, USA. Lawrence C. Hufnagle Jr. is Supervisory Physical Scientist, National while weathering storms with sustained Oceanic and Atmospheric Administration (NOAA), Northwest Fisheries Science Center, Seattle, WA, USA. Dezhang Chu is Research Physical Scientist, NOAA Northwest Fisheries winds of 30 knots, gusts up to 80 knots, Science Center, Seattle, WA, USA. Sam McClatchie is Supervisory Oceanographer, NOAA and wave heights exceeding 8 m (Manley Southwest Fisheries Science Center, La Jolla, CA, USA. Asa Packer is Lead Systems et al., 2009; Willcox et al., 2009). In terms Engineer, BioSonics Incorporated, Seattle, WA, USA. Jae-Byung Jung is Lead Electrical of endurance, the Wave Glider’s unique Engineer, BioSonics Incorporated, Seattle, WA, USA. Timothy Acker is President and Chief utilization of wave and solar energy for Executive Officer, BioSonics Incorporated, Seattle, WA, USA.Huck Dorn is Senior Project Engineer, Liquid Robotics Incorporated, Sunnyvale, CA, USA. Chris Pelkie is Information/ propulsion and systems power, respec- Data Manager, Lab of Ornithology, Cornell University, Ithaca, NY, USA. tively, enables it to collect data for extended periods of time. The effects of

170 Oceanography | Vol.27, No.4 biological fouling on Wave Glider per- ship powered by diesel engines can match Bingham et al. (2012) demonstrated that formance after months at sea typically set the quiet operations of a Wave Glider. In a the Wave Glider operates at low noise the limits on mission duration. study assessing performance during both levels, especially when data are collected For applications in fisheries acous- passive and active acoustics research, from near the submersible glider. tics, several technologies were developed for deploying a multifrequency, split- beam acoustic system from the Wave Glider (Munday et al., 2014; Online Supplement). The acoustic system itself is a modified version of the commercially available BioSonics DT-X Submersible (SUB) echosounder (Munday et al., 2014). This version of the DT-X SUB echosounder can operate at all four fre- quencies typically used by the NMFS for its acoustic stock assessment surveys: 38 kHz, 70 kHz, 120 kHz, and 200 kHz. It is fully programmable, allow- ing the user to set a variety of system and data-processing parameters either prior to deployment or during the mission via cellular network or satellite-relayed Wave Glider propulsion from the differential motion of the surface float and the submers- commands. Raw multifrequency, split- FIGURE 2. ible glider. With the passing of a wave crest, the larger wave amplitude at the surface relative to beam data are stored internally for post- that at depth causes the surface float to pull upward on the submersible glider, placing the umbilical mission processing, while real-time pro- cable under tension. Specially designed wings on the submersible glider shift their angles of attack cessing for echo integration is conducted, (as shown by the small red curved arrows) to convert this upward tension into a forward directed with reports transmitted to shore at regu- propulsive force (as shown by large white straight arrows). With the passing of a wave trough, the umbilical cable slackens, and the submersible glider begins to descend in response to gravity. The lar intervals, typically 10 minutes. wings on the submersible glider shift their angles of attack by 90o to convert this gravity-driven This version of the DT-X SUB echo- downward force once again into a forward directed propulsive force. Equipped with a rudder, the sounder was modified for packaging in submersible glider acts like a tug for the surface float, propelling and steering the Wave Glider in the pressure case of a custom-built tow accordance with commands relayed to the vehicle. body (Figure 3A). Constructed of acetal plastic (DelrinTM) and polyvinyl chlo- ride, the neutrally buoyant tow body is A B deployed directly behind the submersible glider with a sinusoidal-shaped tow cable Surface Float (Figure 3B). The shape of the tow cable is the result of adding slack-tensioning elements, which greatly reduce pitch, Acoustic Transducers roll, and yaw of the tow body relative to its performance with a conventional tow Umbilical cable (Figure 3B; Online Supplement Cable Videos S1 and S2). No description of a new platform for fisheries acoustics, manned or unmanned, Submersible Glider would be complete without some discus- sion of noise considerations. The fisher- Tow Body ies research community has worked dil- Tow Cable igently to reduce the noise of vessels FIGURE 3. (A) Four-frequency version of the BioSonics DT-X SUB echosounder packaged in the used for acoustic stock assessment sur- pressure case of a custom-built tow body. Isometric and side views of the tow body are shown, with veys (Mitson, 1995). Although dramatic the four transducers of the echosounder labeled. (B) Side view of the tow body deployed from the noise reductions have been achieved, no Wave Glider’s submersible glider with a sinusoidal-shaped tow cable.

Oceanography | December 2014 171 FIGURE 4. Transect lines from the SWFSC) cooperated with the Canadian 2012 SaKe Joint-Pacific Hake and Department of Fisheries and Oceans to Sardine Survey. Survey lines were spaced 10 nautical miles apart and conduct the SaKe integrated acoustic and run by FSV Belle M. Shimada and trawl survey of sardine and hake stocks R/V Ricker from central California along the US West Coast EEZ and into to northern British Columbia. Canadian waters (Figure 4) (CalCOFI, 2013). With this stock assessment survey requiring over two months to complete, the expense of ship time alone exceeded $1 million. These surveys are conducted THE WAVE GLIDER during the summer months when hake FLEET: POWER IN behavior (viz. reduced migration and the NUMBERS presence of feeding aggregations) and With the recent commission- weather conditions are more favorable for ing of its newest fishery survey improving the accuracy and precision of vessel (FSV) Reuben Lasker, stock assessments. the National Oceanic and For comparison, we explore the poten- Atmospheric Administration tial for conducting an acoustic stock (NOAA) has upgraded its assessment of the US West Coast EEZ, fleet to include five state- with approximately the same spatial res- of-the-art, low-noise ships olution as the SaKe survey, using a fleet designed for conducting fish- of Wave Gliders running the same sur- eries acoustics studies. These vey lines (Figure 5, Videos 1 and 2). The five FSVs—Reuben Lasker, NMFS low-noise FSVs have an opera- Belle M. Shimada, Oscar tional cruising speed between 10 and Dyson, Henry B. Bigelow, and Pisces— valuable investment by the federal gov- 12 knots in calm seas, but that speed can are the only ships operated on behalf of ernment in enhancing NMFS’s ability to be reduced by half when encountering the NMFS regional science centers that assess and manage the nation’s commer- rougher sea states, like those more com- comply with the International Council cial fisheries. mon during other seasons. For illustra- for the Exploration of the Sea (ICES)- Valuable as they are, however, these tion purposes, we will assume an average recommended standards for noise reduc- low-noise FSVs are too few and too operational cruising speed of 7.5 knots. tion in ships used for fisheries acous- expensive to meet the full scientific needs The cruising speed of a Wave Glider is tics research and surveys (Mitson, 1995; of the NMFS by themselves. With the wave-height dependent and actually Alaska Fisheries Science Center, 2013). world’s largest EEZ, at 11,351,000 km2, increases asymptotically with increas- Construction to meet the ICES standards the United States faces an enormous task ing sea state conditions. We will assume is expensive, but ships compliant with in monitoring the health of its marine an average cruising speed of 1.5 knots, these standards have been demonstrated ecosystems and the status of its living a value consistent with many sea trials to reduce fish avoidance and poten- marine resources, including its com- under a variety of conditions (Willcox tially improve the accuracy of acoustic mercial fisheries. While satellites pro- et al., 2009). Cruising at 7.5 knots, an stock assessment surveys (DeRobertis vide synoptic coverage on large scales, FSV can complete one survey line five et al., 2008). In addition to their low- which can be useful for some applica- times faster than a Wave Glider cruising noise characteristics, these five FSVs tions, unmanned mobile platforms oper- at 1.5 knots, and it can complete approxi- are capable of collecting acoustic data ating on or below the ocean’s surface will mately five lines in the time it would take while simultaneously trawling for bio- be essential for filling in the huge gaps in a Wave Glider to complete just one line logical samples. These samples are criti- coverage that cannot be monitored by a (Figure 5A,B; Video 1). cal for ground truthing the acoustic data relatively small fleet of FSVs. However, the power of the Wave Glider and determining other important infor- To illustrate the potential of Wave approach to fisheries acoustics comes in mation about the age and size structure, Gliders for filling in this coverage gap, we numbers. With a fleet of Wave Gliders, health, and reproductive condition of the will look at an example from the west coast each one running a survey line, an acous- fish stocks being assessed. In a period of of continental North America. During tic stock assessment of the West Coast tightened science budgets, acquisition of 2012, the Northwest and Southwest EEZ could be completed in one week, the these highly capable FSVs represents a Fisheries Science Centers (NWFSC and same time that an FSV would complete

172 Oceanography | Vol.27, No.4 just ~ 12.5% of the survey (Figure 5C; spatial coverage in a week also reduces and trawl survey of the West Coast EEZ’s Video 2). During the eight weeks that it concerns about aliasing and other sam- hake and small pelagic fish stocks. would take an FSV to complete an acoustic pling issues that are especially rele- However, fulfilling this demand comes stock assessment survey of the West Coast vant when the assessed fish stocks are at the expense of ship time that could EEZ, a fleet of Wave Gliders would com- highly migratory and/or sparsely distrib- otherwise be used for additional efforts plete the equivalent of eight near-synoptic uted in schools. to sample the ecosystem, operations surveys (Figure 5D; Video 2). Remarkably, these significant improve- also critical to ecosystem-based fisher- For the purpose of stock assessment, ments in the quality of acoustic stock ies management (Rose, 2014). A techno- acoustic data derived from a Wave Glider assessment data need not come at great economic analysis, which takes into con- fleet would offer significant advantages expense, especially when the costs are sideration data-quality issues and costs over those derived from conventional spread over a sufficiently long time per unit area surveyed, would be valu- ship-based surveys. Most importantly, period. While it is true that the capital able in determining the most effective spatial and temporal coverage would be expense associated with acquiring a fleet mix of assets and protocols necessary improved dramatically, with each real- of fully equipped Wave Gliders to mon- for the NMFS regional science centers to ization of fish stock distribution more itor the West Coast EEZ would be com- meet their scientific objectives at present closely achieving the synoptic ideal. In parable to the expense of adding another and in the future. With ship-time costs comparison to the eight weeks required FSV, the ongoing operational and main- between $25 thousand and $30 thousand to complete one conventional, ship-based tenance costs would be reduced consid- per day, including fuel, FSVs like Reuben survey, the one week required to achieve erably. Currently, the SWFSC’s Reuben Lasker and Belle M. Shimada are too valu- full spatial coverage with a Wave Glider Lasker and NWFSC’s Belle M. Shimada able to be used for collecting only acous- fleet makes concerns about replication are capable of fulfilling the ship-time tic survey data, an activity often referred and repeatability largely disappear. Full demand for a combined annual acoustic to by fisheries scientists as mowing the

A B

C D

FIGURE 5. (A) Assuming an average cruising speed of 7.5 knots, an FSV covers five times the distance along a single survey line as a Wave Glider cruising at 1.5 knots for the same length of time. (B) Five Wave Gliders, each running its survey line at 1.5 knots, can complete five lines in the same amount of time that a single FSV completes the same five lines Video 1( ). (C) With a fleet of Wave Gliders, each one running a survey line, a full acoustic stock assessment of the West Coast Exclusive Economic Zone (EEZ) can be completed in one week, the same amount of time that an FSV would need to complete ~ 12.5% of the survey. (D) A fleet of Wave Gliders can complete the equivalent of eight near-synoptic surveys of the West Coast EEZ during the eight weeks that it takes an FSV to complete one full acoustic stock assessment survey of the West Coast EEZ (Video 2). Each color corresponds to the survey lines completed during a given week.

Oceanography | December 2014 173 lawn. Such routine tasks should be left fisheries scientists and oceanographers Fernandes, P.G., F. Gerlotto, D.V. Holliday, O. Nakken, and E.J. Simmonds. 2002. Acoustic applications to unmanned mobile platforms, while to more closely monitor the responses of in fisheries science: The ICES contribution. ICES FSVs conduct integrated acoustic and different fish stocks to climate variabil- Marine Science Symposia 215:483–492. Fernandes, P.G., P. Stevenson, A.S. Brierley, trawling operations as well as other sam- ity and change as well as ocean acidifica- F. Armstrong, and E.J. Simmonds. 2003. pling activities that are only possible at tion. The global demand for food from a Autonomous underwater vehicles: Future platforms for fisheries acoustics. ICES Journal of Marine present using ships. rapidly changing ocean will be staggering Science 60:684–691, http://dx.doi.org/10.1016/ when the world population reaches 9 bil- S1054-3139(03)00038-9. Manley, J., S. Willcox, and R. Westwood. 2009. The CONCLUDING REMARKS lion in 2050. Fisheries science and man- Wave Glider: An energy harvesting unmanned Viewing the Wave Glider approach to agement will need the best observational surface vehicle. Marine Technology Reporter, http://legacy.digitalwavepublishing.com/pubs/nwm/ fisheries acoustics as only an incremental and analytical tools available to help soci- MT/200911/index.asp?pgno=30. improvement to the way we collect stock ety meet this demand. By supplement- Mitson, R. 1995. Underwater noise of research vessels: Review and recommendations. ICES assessment data fails to appreciate its full ing its relatively small fleet of FSVs with Cooperative Research Report No. 209. ICES, potential. This approach offers an oppor- a large fleet of Wave Gliders, the NMFS Copenhagen, Denmark. 61 pp. Munday, E., T. Acker, and J. Dawson. 2014. Tools tunity to transform fisheries science and can begin to position itself for the chal- for biological assessment using split beam management in a truly fundamental way. lenges ahead. hydroacoustics. Sea Technology 55(2):17–24, http://www.sea-technology.com/features/2014/ At present, ship-based assessment sur- 0214/2.php. veys provide fisheries scientists and man- ACKNOWLEDGEMENTS. This paper is based on National Ocean Council. 2013. Federal an exhibit prepared for the US State Department’s Our Oceanographic Fleet Status Report. Executive agers with what can be thought of as Ocean Conference. We wish to express our appre- Office of the President, Washington, DC, 42 pp, static snapshots of fish stocks, often col- ciation to the State Department for an invitation to http://www.whitehouse.gov/sites/default/files/ participate in the conference. The first author also federal_oceanographic_fleet_status_report.pdf. lected at relatively infrequent intervals of acknowledges the Whiteley Center at the University of NOAA NMFS. 2012. Annual commercial land- a year or more. In addition, because these Washington’s Friday Harbor Laboratories for providing ing statistics. http://www.st.nmfs.noaa.gov/ an inspiring setting within which to prepare this paper. commercial-fisheries/commercial-landings/ surveys take so long to complete, the cor- The research described here was supported by the annual-landings/index. responding assessments are in fact highly National Science Foundation Ocean Technology and NOAA Fisheries Science Centers. 2004. NOAA pro- Interdisciplinary Studies Program, the National Marine tocols for fisheries acoustics surveys and related blurred snapshots, far from the synop- Fisheries Service Advanced Survey Technologies sampling. US Department of Commerce National tic ideal typically assumed when the Program, and the Office of Naval Research Biological Oceanic and Atmospheric Administration National Oceanography Program. Marine Fisheries Service. data are analyzed. Ohman, M.D., D.L. Rudnick, A. Chekalyuk, R.E. Davis, In contrast, because of much lower R.A. Feely, M. Kahru, H.-J. Kim, M.R. Landry, ONLINE SUPPLEMENTARY MATERIALS. T.R. Martz, C.L. Sabine, and U. Send. 2013. Autono- operational costs, a fleet of Wave Gliders Videos 1 and 2 and the supplemental materi- mous ocean measurements in the California would not face the same logistical con- als, Field Performance of a Prototype System Current Ecosystem. Oceanography 26(3):18–25, and Videos S1 and S2, are available online at: http://dx.doi.org/10.5670/oceanog.2013.41. straints that compromise the stock assess- http://dx.doi.org/10.5670/oceanog.2014.82. Perry, M.J., and D.L. Rudnick. 2003. Observing ment data collected by FSVs. 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