A scientific echosounder is a device which uses
sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigation, navigate, measure distances (ranging), communicate with or detect o ...
technology for the measurement of underwater physical and biological components—this device is also known as ''scientific sonar''. Applications include
bathymetry
Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...
,
substrate classification, studies of
aquatic vegetation
Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...
,
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
, and
plankton
Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...
, and differentation of
water mass
An oceanographic water mass is an identifiable body of water with a common formation history which has physical properties distinct from surrounding water. Properties include temperature, salinity, chemical - isotopic ratios, and other physical ...
es.
Technology
Scientific echosounder equipment is built to exacting standards and tested to be stable and reliable in the transmission and receiving of sound energy under the water. Recent advances have led to the development of the
digital scientific echosounder, further enhancing the reliability and precision with which these systems operate. Modern scientific echosounders are reliable, portable, and relatively easy to use.
Collected acoustic data is "stamped" with geographic information for precise positional information (coordinates and time). This enables analysis and incorporation of the results into a
Geographic Information System
A geographic information system (GIS) is a type of database containing Geographic data and information, geographic data (that is, descriptions of phenomena for which location is relevant), combined with Geographic information system software, sof ...
(GIS) for further analysis, correlation with other variables, mapping, and display.
Currently, the only three manufacturers of scientific-quality digital echsounders commonly used for resource assessment are BioSonics, HTI (Hydroacoustic Technology, Inc.) and Simrad. Other specialty manufacturers of scientific quality echosounders exist.
Features of modern digital scientific echosounder technology include:
* Low side-lobe transducers
* Simple data collection
* Low system noise
* Wide dynamic range
* High system stability
* High accuracy
* Easy system expansion
* Multiplexing systems (multiple transducers can operate simultaneously on the same system)
Scientific software for analysis of hydroacoustic data
Specially written software is available for analysis of hydroacoustic data for assessment of underwater physical and biological characteristics. "Fish" here can apply to any "target" in the water column, e.g., fish, plankton, squid, mammal. All results can be imported into a GIS for additional analysis, correlation with other variables, mapping, and display.
;
Bathymetry
Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...
: the depth (range) of the bottom of the river, lake, or ocean below the transducer.
; Range : the distance between the
transducer
A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another.
Transducers are often employed at the boundaries of automation, measurement, and contr ...
and the "target" (fish, zooplankton, vegetation, bottom). This is determined by precise timing from sound generation to sound reception (by the transducer).
;Bottom type;
Seabed
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'.
The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...
type; Substrate type; or
Sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
type : can be assessed and classified (''e.g.'', sand, rock, soft mud, hard mud).
;Fish quantity : can be estimated and reported as numbers of fish or
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
.
;Fish size : can be determined in a relative manner, based on acoustic "target size".
;Fish behavior : can be assessed through a combination of instantaneous and temporal measures and observations. Spatial distribution, size distributions, diurnal activity, predator-prey relationships, migration rates, temporal activity, etc. can be observed and quantified.
;Submersed aquatic vegetation; Submerged aquatic vegetation; or SAV : can be detected and assessed for location, density, and height.
;Fish passage : can be quantified for fish movement past a fixed-location hydroacoustic monitoring system. Examples include: Migrating salmon or fish entrained by water intakes.
Data collected with a scientific echosounder can be analyzed for the presence, abundance, distribution and acoustic characteristics of such variables as: depth (bathymetry), bottom substrate class (e.g., sand, mud, rock),
submersed aquatic vegetation
Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that g ...
(SAV), and water column scattering (fish and plankton). Resulting analysis can be used to generate
GIS
A geographic information system (GIS) is a type of database containing Geographic data and information, geographic data (that is, descriptions of phenomena for which location is relevant), combined with Geographic information system software, sof ...
data layers for these variables.
Applications
Scientific echosounders are commonly used by International, Federal, State and Local government and management agencies, as well as private-sector consultants working for these public agencies. Academic institutions have realized and are teaching the value of sampling non-invasively with sound to enhance both the spatial coverage and objectivity of fisheries sampling.
Fisheries management
The goal of fisheries management is to produce sustainable biological, environmental and socioeconomic benefits from renewable aquatic resources. Wild fisheries are classified as renewable when the organisms of interest (e.g., fish, shellfish, am ...
agencies such as the membership of
ICES and the United States
National Marine Fisheries Service
The National Marine Fisheries Service (NMFS), informally known as NOAA Fisheries, is a United States federal agency within the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) that is responsible for the stew ...
(NMFS) commonly use scientific sonar for stock assessment purposes, such as herring biomass assessment for resource management purposes.
More recently, the acoustic data collected has been valuable in underwater habitat assessment and classification for the variables; seabed type (e.g. rock, mud, sand) and submersed aquatic vegetation and algae - with the appropriate software.
See also
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External links
''Overview of Acoustic Methods and Technology''Hardware
BioSonics, Inc.Hydroacoustic Technology, Inc. (HTI)Simrad
Software
*Echoview
Sonar4 and Sonar5-ProL-trippel-S
*BioSonic
Visual Analyzer
("fish")
EcoSAV
(vegetation), an
VBT
(substrate classification)
QTC Impact
(substrate classification)
{{hydroacoustics
Sonar