On acoustic estimates of zooplankton biomass

Stanton, Timothy K.; Wiebe, Peter H.; Chu, Dezhang; Benfield, Mark C.; Scanlon, Lori; Martin, Linda V.; Eastwood, Robert L.

doi:10.1006/jmsc.1994.1051

Cited by 178 publications

(160 citation statements)

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“…Although volume backscattering was lower in the north, echo energy at 200 kHz per unit biomass has been shown to be comparable for certain sizes of siphonophores and euphausiids (Stanton et al, 1994), and this volume backscattering decrease is more likely related to a difference in biomass than to spatial patterns in community composition.…”

Section: Potential Limitations Of the Acoustic Techniquementioning

confidence: 92%

“…Measurements of the intensity of echoes returned from sonic pulses emitted into the water column therefore can be used to make estimates of more biologically-meaningful quantities such as animal abundance and size. This process of inferring the abundance and distribution of zooplankton in a quantitative sense from acoustic measurements, however, is not straightforward (Stanton et al, 1994;Wiebe et al, 1996). Scattering in the water column can result from both physical oceanic processes (e.g., microstructure; Warren et al, 2003) and the biota, where scattering from the latter is a complex function of the taxonomic composition of animals present, and the associated variability in their size, shape, physical properties, and behavior.…”

Section: History Of Krill Research and The Krill Fisherymentioning

confidence: 99%

“…Expected echo intensities, or backscattering cross-sections (abs), were estimated based on the length of each individual determined by silhouette analysis and models of acoustic scattering appropriate to the individual's taxonomic group. These models were developed by Stanton et al (1994Stanton et al ( , 1998, are reviewed in Stanton and Chu (2000), and are sensitive to numerous parameters in addition to animal length, including animal orientation and material properties (Chu et al, 2000a; …”

Section: Taxonomic Composition Of Zooplankton and Micronektonmentioning

confidence: 99%

“…The echo energy scattered per unit biomass of a pteropod, for example, can be 70 times greater than that from a decapod or pneumatophore-bearing siphonophore (Stanton et al, 1994). An observed increase in volume backscattering therefore could result either from an increase in the biomass of a given taxon of zooplankton, or from a shift in taxonomic composition towards stronger scatterers such as pteropods; such a shift could even be accompanied by a decrease in biomass.…”

Section: Potential Limitations Of the Acoustic Techniquementioning

confidence: 99%

“…Large copepods were an important predicted constituent at many stations, particularly below a depth of 100 m. Despite their never contributing more than 11% of net-sampled biomass , pteropods were occasionally responsible for the majority of predicted volume backscattering levels (up to 69%). This is due to the hard shell and associated strong scattering intensity of pteropods in comparison to the weakly-scattering taxa such as euphausiids or copepods (Stanton et al, 1994). Similarly, at certain depths and locations, a majority of total volume backscattering was predicted to arise from pneumatophore-bearing siphonophores.…”

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Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

Lawson¹

2006

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The physical and biological forces that drive zooplankton distribution and patchiness in an antarctic continental shelf region were examined, with particular emphasis on the Antarctic krill, Euphausia superba. This was accomplished by the application of acoustic, video, and environmental sensors during surveys of the region in and around Marguerite Bay, west of the Antarctic Peninsula, in the falls and winters of 2001 and 2002. An important component of the research involved the development and verification of methods for extracting estimates of ecologically-meaningful quantities from measurements of scattered sound. The distribution of acoustic volume backscattering at the single frequency of 120 kHz was first examined as an index of the overall biomass of zooplankton. Distinct spatial and seasonal patterns were observed that coincided with advective features. Improved parameterization was then achieved for a theoretical model of Antarctic krill target strength, the quantity necessary in scaling measurements of scattered sound to estimates of abundance, through direct measurement of all necessary model parameters for krill sampled in the study region and survey period. Methods were developed for identifying and delineating krill aggregations, allowing the distribution of krill to be distinguished from that of the overall zooplankton community. Additional methods were developed and verified for estimating the length, abundance, and biomass of krill in each acoustically-identified aggregation. These methods were applied to multifrequency acoustic survey data, demonstrating strong seasonal, inter-annual, and spatial variability in the distribution of krill biomass. Highest biomass was consistently associated with regions close to land where temperatures at depth were cool. Finally, the morphology, internal structure, and vertical position of individual krill aggregations were examined. The observed patterns of variability in aggregation characteristics between day and night, regions of high versus low food availability, and in the presence or absence of predators, together reinforced the conclusion that aggregation and diel vertical migration represent strategies to avoid visual predators, while also allowing the krill access to shallowly-distributed food resources. The various findings of this work have important implications to the fields of zooplankton acoustics and Antarctic krill ecology, especially in relation to the interactions of the krill with its predators.

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Section: Potential Limitations Of the Acoustic Techniquementioning

confidence: 92%

Section: History Of Krill Research and The Krill Fisherymentioning

confidence: 99%

Section: Taxonomic Composition Of Zooplankton and Micronektonmentioning

confidence: 99%

Section: Potential Limitations Of the Acoustic Techniquementioning

confidence: 99%

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confidence: 99%

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Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

Lawson¹

2006

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Spatial and temporal variability of zooplankton off New Caledonia (Southwestern Pacific) from acoustics and net measurements

et al. 2015

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Spatial and temporal distribution of zooplankton off New Caledonia in the eastern Coral Sea was studied during two multidisciplinary cruises in 2011, during the cool and the hot seasons. Acoustic measurements of zooplankton were made using a shipborne acoustic Doppler current profiler (S-ADCP), a scientific echosounder and a Tracor acoustic profiling system (TAPS). Relative backscatter from ADCP was converted to biomass estimates using zooplankton weights from net-samples collected during the cruises. Zooplankton biomass was estimated using four methods: weighing, digital imaging (ZooScan), ADCP and TAPS. Significant correlations were found between the different biomass estimators and between the backscatters of the ADCP and the echosounder. There was a consistent diel pattern in ADCP derived biomass and echosounder backscatter resulting from the diel vertical migration (DVM) of zooplankton. Higher DVM amplitudes were associated with higher abundance of small zooplankton and cold waters to the south of the study area, while lower DVM amplitudes in the north were associated with warmer waters and higher abundance of large organisms. Zooplankton was largely dominated by copepods (71-73%) among which calanoids prevailed (40-42%), with Paracalanus spp. as the dominant species (16-17%). Overall, zooplankton exhibited low abundance and biomass (mean night dry biomass of 4.7 6 2.2 mg m 3 during the cool season and 2.4 6 0.4 mg m 3 during the hot season) but high richness and diversity (Shannon index $4). Substantially enhanced biomass and abundance appeared to be episodically associated with mesoscale features contributing to shape a rather patchy zooplankton distribution.

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Diel vertical migration of zooplankton at the S1 biogeochemical mooring revealed from acoustic backscattering strength

2016

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We examined the diel vertical migration of zooplankton by using the backscatter strength obtained from moored acoustic Doppler current profilers at mooring site S1 in the North Pacific subtropical gyre. There was seasonal variability in the vertical distribution and migration of the high‐backscatter layers in that they became deeper than the euphotic zone (<100 m) in winter and were confined above this depth in other seasons. Seasonal changes in daylight hours also affected the timing of the diel migration. We found that lunar cycles affected vertical distributions of zooplankton near the surface by changing the light intensity. Physical events, such as mixed‐layer deepening and restratification and the passage of a mesoscale eddy, also affected zooplankton behavior possibly by changing food environment in the euphotic zone. Since the comparison with net samples indicated that the backscatter likely represents the bulk biomass, the accuracy of biomass estimates based on net samples could be influenced by the high temporal variability of zooplankton distributions.

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On acoustic estimates of zooplankton biomass

Cited by 178 publications

References 0 publications

Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

Spatial and temporal variability of zooplankton off New Caledonia (Southwestern Pacific) from acoustics and net measurements

Diel vertical migration of zooplankton at the S1 biogeochemical mooring revealed from acoustic backscattering strength

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