SWFSC's Advanced Survey Technologies Program (AST)
AST's charter is to expand the scope of bioacoustical oceanographic research, and expedite the development and implementation of new survey methods and tools at SWFSC. In addition to the long-term project of improving and implementing tools for ecosystem assessments of the Antarctic Peninsular region with Rennie Holt (SWFSC), the Program has recently been involved in: 1) an analysis of measurement uncertainty in the multi-national, multi-ship acoustical assessment of krill in the FAO statistical area 48 with the Commission for the Conservation of Antarctic Marine Living Resources; 2) a multi-year assessment of the Ligurian Sea ecosystem (meteorological and physical oceanographic investigations coupled with acoustical, net, and video assessments of zooplankton, fish, and squid) in cooperation with Angela D'Amico (NATO's SACLANT Center), Duncan McGehee (BAE SYSTEMS), and Joe Warren (SWFSC/WHOI), and funded by Bob Gisiner (ONR); 3) an exploratory Lidar/acoustical survey of fisheries resources off Tampa Bay, Florida with Jim Churnside (ETL) and Behzad Mahmoudi (FWC); 4) studies of radiated ship noise and associated fish behavior with Chris Wilson (AFSC); and 5) improvements to the multiple-frequency target strength method with Mike Soule (RSA).
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| Figure 1. AST's multi-instrumented small-craft for surveying the near-shore dispersion and abundance of krill around the Antarctic Peninsula. Instrumentation includes a GPS, weather station, multi-frequency echosounder, radar, VHF, CTD, underwater audio-video probe, and small net. |
Primary research projects now include: 1) broad-bandwidth acoustical characterization of fish and zooplankton from reverberation measurements in an echoic tank with Stephane Conti (SWFSC); 2) feasibility studies of broad-bandwidth and multibeam sounders for quantitative investigations of fish stocks and behaviors; and 3) the development and utility of small, multi-functional research platforms (boats (Fig. 1) and autonomous buoys), for economically addressing ecosystem-based fisheries management issues and studying predator-prey interactions (e.g. whale-krill, penguin-fish/krill, and seal-fish/squid/krill).
The following is an example of one of AST's current projects that combines both passive- and active-acoustical instrumentation and methods:
Tuna industry cooperative to reduce by-catch in fishing on fish aggregating devices
A research cooperative has been established between the SWFSC and the U.S. Tuna Foundation to minimize by-catch when fishing on fish aggregating devices (FADs). Instrumentation will be further developed and deployed to characterize the spatial, temporal, and size distributions of tuna and other fish beneath and surrounding FADs used by the U.S. tuna fishing fleet in the eastern tropical Pacific (ETP). These distributions will be related to concurrent observations of environmental conditions and predator-prey interactions. Ultimately, results from this research could be used to help fishers develop strategies that minimize by-catch of under-size tuna and other undesirable fish species. These actions will help to ensure the long-term sustainability of FAD-based tuna fisheries in the ETP and central and western Pacific. Shipboard, we will use multiple-frequency echosounders, in-situ target strength measurements, and echo-integration processing methods to quantify the abundance, dispersion, and temporal variability of tuna and other fish surrounding fish aggregating devices (FADs). Additionally, a cast-deployable underwater-audio-video system will be used to validate the acoustical discrimination of scatterers and passive-acoustically monitor the sounds associated with the fish. The passive acoustical system may also be used for target tracking.
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| Figure 2. Multi-instrumented, remotely- monitored buoys will be attached to standard FADs. |
Information from beneath FADs will be collected using autonomous and remotely monitored multi-instrumented buoys. The buoys will include a multi-frequency split-beam scientific echosounder (side-looking and down-looking), an underwater video system, two preamplified hydrophones, a data logging and control computer, GPS, 900 MHz spread-spectrum radio modem with antenna, radar transponder, strobe light, AGM battery, and power control circuitry. The buoy design is a variant of one that has been successfully deployed in the Southern Ocean to describe krill abundance and dispersion, environmental conditions, and predator activities in an area around Cape Shirreff, Livingston Island, Antarctica (Fig. 2). Volume backscattering strengths and in-situ target strengths will be recorded over multiple-hour periods. The spectral characteristics of sound scatter will be used for taxa discrimination and delineation [Demer et al., 1999, J. Acoust. Soc. Am. 105(4): 2359-2376]. The position of the buoy will be monitored with GPS. The data set will be stored in its entirety inside the package while a subset is telemetered to the supporting fishing vessel via a VHF modem link.
The real-time echograms will be used to direct timing of net sampling and underwater video deployments for validation of acoustical species discrimination algorithms and possibly allow in-situ observations of predator-prey interactions. The acoustical analysis will be linked to the concurrently collected biological, oceanographic, and meteorological sampling collected shipboard. The aim is to collectively use these observations to delineate tuna from other co-existent species, estimate tuna sizes, explore associations between biotic and abiotic conditions, and observe tuna behavior and dispersion.
David A. Demer, NOAA/NMFS/SWFSC/Fisheries Resources Division, 8604 La Jolla Shores Drive, La Jolla, CA 92037 (david.demer@noaa.gov)
Selected recent publication and works in progress:
D.A. Demer, M. Barange and A. Boyd, "Measuring fish school velocities with an acoustic Doppler current profiler," Fisheries Research 47:201-214 (2000).
D. A. Demer, S. Conti, J. De Rosny and P. Roux, "Absolute measurements of total target strength from reverberation in a cavity," J. Acoust. Soc. Am., submitted — 2001, MS=25p
S. Allen and D.A. Demer, "Detection and characterization of yellowfin and bluefin tuna using passive acoustical techniques," Fisheries Research, submitted - 2001, MS=24p
D.E. McGehee, D.A. Demer, and Joseph Warren, "Acoustically Measured Zooplankton Distributions in the Ligurian Sea in August 1999 and Their Relation to Physical and Biological Oceanographic Features," J. Plankton Res., submitted - 2002, MS~24p
J. H. Churnside, D.A. Demer and B. Mahmoudi, "A comparison of lidar and echosounder measurements of fish schools in the Gulf of Mexico," ICES Jour. Mar. Sci., submitted - 2002, MS=26p
D.A. Demer, "An Estimate of Error for the CCAMLR 2000 Estimate of Krill Biomass," Deep Sea Res. Sp. CCAMLR 2000 Iss. in-press, 2002, MS=50p
D.A. Demer and S. Conti, "Reconciling theoretical versus empirical target strengths of krill; effects of phase variability on the distorted wave Born approximation," ICES J. Mar. Sci.., submitted — 2002, MS=16p
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