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Define and Critique Data and Methods for Seascape Ecology: Active and Passive Acoustics

Define and Critique Data and Methods for Seascape Ecology: Active and Passive Acoustics. Mike Jech NOAA/NEFSC Woods Hole, MA 02543 Michael.Jech@noaa.gov. “Water column” data Active acoustic data are acquired, processed, and archived within the same organization

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Define and Critique Data and Methods for Seascape Ecology: Active and Passive Acoustics

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  1. Define and Critique Data and Methods for Seascape Ecology: Active and Passive Acoustics Mike Jech NOAA/NEFSC Woods Hole, MA 02543 Michael.Jech@noaa.gov

  2. “Water column” data • Active acoustic data are acquired, processed, and archived within the same organization • Hence, there is no clearing house for these data – yet. • Hurdles to creating this warehouse: • Meta-data. There is an international effort to create a standard for water column data. Should have a 1st generation standard within the next 1-2 years. • Data formats are manufacturer dependent. There has been an effort to standardize data format, but no consensus. • Data are processed for very specific purposes, e.g., single species stock assessments, academic projects. • NOAA National Geophysical Data Center has offered to archive and serve water column data – stay tuned.

  3. Sound is used A LOT in water!!By both animals and humans For navigation To find food Listen to sounds Sharing resources! To find food To communicate

  4. Sound is an effective and efficient way of sampling the underwater environment: Sound travels about 1500 m s-1 in water Sound can travel nearly around the planet 106 10,000 1,000 100 10 1 104 Range 102 100 Sample Volume Typical Sample Volume [m3 ] Maximum Range [m] 10-2 Schools 10-4 Fish 10-6 Plankton 10-8 1 10 100 1,000 10,000 Echosounder Frequency [kHz] (Figure from MacLennan and Simmonds, Fisheries Acoustics, 1992)

  5. Fig. 1. Spatio-temporal scope of a single observation by various sampling devices and sensors. Resolution of the measurement is indicated by the lower-left side of the polygon and its range by the upper-right side. These represent the spatial extent of a single observation, not a time series. (Trenkel et al., MEPS, 2011)

  6. Trenkel et al. (MEPS 442: 285-301, 2011) Proposals for Ecosystem Indicators Using Active Acoustics

  7. Data • Start with voltage & time, everything else is derived • Remote sensing technology – information from a distance, i.e., beyond direct sensory detection of the target (sight and hearing) • Goal is to not affect targets • Calibrated instrumentation – any changes in signal are not due to electronics • Most common application is to learn about the “target” – source of sound or echo – which means you need to know about the propagating medium. • The less you know about the medium, the more uncertainty you add to interpretation. • Issues with near-boundary regions (e.g., sea bed and surface) • Grand challenge is identification using acoustics alone • Verification is necessary

  8. Acoustic Data Sources • “Scientific” (calibrated, linear) systems • In the past, only expensive systems on government vessels had these. Now, many commercial systems conform to this. • In mid-Atlantic to Gulf of Maine, multi-frequency acoustic data are collected during fall and spring bottom trawl surveys, and dedicated herring surveys from 1998 to present. • “Commercial” systems • May or may not be useful. • Gain values must be recorded • Data must be collected over areas larger than the scale of an aggregation • Processing effort goes up considerably for data collected from systems that are not calibrated and have “dynamic” parameters (e.g., gains, depth, frequency)

  9. Passive Acoustic Systems: • Uses: • Detect animals that vocalize • a. Whales, dolphins, fish • Detect human-made objects • Vessels • Tags & telemetry (fish, mammal, turtle, …) • Remote platforms (AUV, ROV, glider) • Systems (selected list): • Marine Autonomous Recording Units (MARUs) • Used on Stellwagon Bank • http://www.birds.cornell.edu/brp/hardware • DTAG • a. Attach to whales; records orientation of animal and sounds • http://www.whoi.edu/page.do?pid=39337

  10. Active acoustic methods transmit sound (aka, ‘ping’) and listen for echoes • Echoes contain information about the target(s): • DTime: distance to targets • Duration: 1 target = 1 echo length, so longer echoes = more targets • Amplitude: Echo strength dependent on target properties, such as size, type, numbers • Frequency: possibly most important characteristic; all echoes have very strong dependence on frequency • Bandwidth: frequency content • narrow band systems are simple but limited interpretation potential • wider bands (i.e., more frequencies) have more potential information, but at increased ‘cost’

  11. Atlantic herring surveys in 2000

  12. Herring Aggregations on the Northern Edge of Georges Bank (2001) 12 kHz Atlantic herring 38 kHz 120 kHz

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