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Fisheries and plankton acoustics: Past, present, and future
... We brie y highlight only two from among many promising areas of active research. Even though we do not include it explicitly, much of the progress we will discuss is relevant to attacks on the Grand Challenge in bioacousticsremote species identification [5]. These developments in research also bear on a Grand Challenge in fisheries science and biological oceanography an accurate. ...
... Although McNaught did not fully quantify his work, the ideas behind today s multi-frequen cy methods were clearly outlined. By the mid-90's, the dependencies of acoustical volume scattering on the size of small crustaceans was sufficiently well described that it could be used as a practical tool in marine ecosystems work with plankton [5,15,16]. Spatial distributions of plankton and micronekton biomass. with size discrimination , could be resolved at vertical distributions of ca 2 m with casts to nominally 100 m [17]. ...
... Sound of low to moderate frequency (1-100 s kHz), travels much farther in water than light, enabling acoustics to detect objects significantly beyond visual range, providing greater spatial coverage than optics and permitting effective detection of objects independent of light (Cook et al., 2019;Mueller et al., 2006). However, this comes at the expense of resolution, and although fish size, distribution and density can be readily quantified using acoustics , species identification is challenging (Bollinger and Kline, 2017;Egg et al., 2018;MacLennan and Holliday, 1996), including for multibeam sonar (Mueller et al., 2006;Becker et al., 2013). Where light is not limiting, optics can be used to provide information to identify acoustic targets, sometimes known as "groundtruthing" (Bolser et al., 2020;Wilson, 2000, 1997), but more accurately termed "additional evidence" (Fernandes et al., 2016). ...
... In addition to the general, extensively described drawbacks of acoustics (e.g., limited resolution for species identification -Bollinger and Kline, 2017; Egg et al., 2018;MacLennan and Holliday, 1996), this study has identified several key limitations of imaging sonar that compromise its effectiveness for surveying fishes around complex, hard substrate habitat (Table 3). Preliminary inspection of the imaging sonar footage revealed that imaging sonar consistently failed to distinguish fishes from soft benthic growth of medium and high complexity (e.g., sponges, and soft corals, respectively; as determined using simultaneous optical footage), even when inspecting consecutive sequences of footage. ...
... Sound of low to moderate frequency (1-100 s kHz), travels much farther in water than light, enabling acoustics to detect objects significantly beyond visual range, providing greater spatial coverage than optics and permitting effective detection of objects independent of light (Cook et al., 2019;Mueller et al., 2006). However, this comes at the expense of resolution, and although fish size, distribution and density can be readily quantified using acoustics , species identification is challenging (Bollinger and Kline, 2017;Egg et al., 2018;MacLennan and Holliday, 1996), including for multibeam sonar (Mueller et al., 2006;Becker et al., 2013). Where light is not limiting, optics can be used to provide information to identify acoustic targets, sometimes known as "groundtruthing" (Bolser et al., 2020;Wilson, 2000, 1997), but more accurately termed "additional evidence" (Fernandes et al., 2016). ...
... In addition to the general, extensively described drawbacks of acoustics (e.g., limited resolution for species identification -Bollinger and Kline, 2017; Egg et al., 2018;MacLennan and Holliday, 1996), this study has identified several key limitations of imaging sonar that compromise its effectiveness for surveying fishes around complex, hard substrate habitat (Table 3). Preliminary inspection of the imaging sonar footage revealed that imaging sonar consistently failed to distinguish fishes from soft benthic growth of medium and high complexity (e.g., sponges, and soft corals, respectively; as determined using simultaneous optical footage), even when inspecting consecutive sequences of footage. ...
... As the years progressed, there was a steady shift from adapting military and navigational hardware to the needs of fisheries biology to the development of acoustic hardware and methodologies specifically for the research needs of this field. These research SONARs included multibeam SONAR, side scan SONAR, parametric SONAR, synthetic aperture SONAR, and conventional low-frequency SONAR [53][54][55][56]. These different types of SONARs may be combined to facilitate specific research interests. ...
... Interesting results of high-resolution population density imaging were obtained through ultrasonic echo sounders; another valuable result was obtained by applying several independent acoustic systems aimed to measure the low-frequency target strength and population density of the Atlantic herring: the lowfrequency falloff in the response of schools of hundreds of millions of animals was confirmed by the response of an individual and interpreted as being caused by the subresonance scattering of the fish swim bladder [66,67]. The largest sources of error in fisheries acoustic surveys are incomplete coverage of the entire population, inaccuracy in proportioning backscatter to taxa, and error in estimating target strengths of individual organism [54]. ...
The development of acoustic methods for measuring depths and ranges in the ocean environment began in the second decade of the twentieth century. The two world wars and the “Cold War” produced three eras of rapid technological development in the field of acoustic oceanography. By the mid-1920s, researchers had identified echoes from fish,
Gadus morhua
, in the traces from their echo sounders. The first tank experiments establishing the basics for detection of fish were performed in 1928. Through the 1930s, the use of SONAR as a means of locating schools of fish was developed. The end of World War II was quickly followed by the advent of using SONAR to track and hunt whales in the Southern Ocean and the marketing of commercial fish finding SONARs for use by commercial fisherman. The “deep scattering layer” composed of invertebrates and fish was discovered in the late 1940s on the echo sounder records. SONARs employing high frequencies, broadband, split beam, and multiple frequencies were developed as methods for the detection, quantification and identification of fish and invertebrates. The study of fish behavior has seen some use of passive acoustic techniques. Advancements in computer technology have been important throughout the last four decades of the twentieth century.
... Research on zooplankton distribution and abundance patterns in marine ecosystems has advanced considerably since the first application of hydroacoustics (Flagg and Smith, 1989;Batchelder et al., 1995;MacLennan and Holliday, 1996;Zimmerman and Biggs, 1999;Lavery et al., 2002;Cabreira et al., 2006). As a noninvasive technique, hydroacoustics provides real-time high-resolution, both quantitative and qualitative, data that cannot be obtained with traditional sampling methods. ...
... Moreover, the net-ADCP combination allowed a better indication of the zooplankton distribution than that provided individually by either nets or ADCP. Despite these encouraging results, caution is still needed when interpreting Sv from a single frequency instrument such as the ADCP (MacLennan and Holliday, 1996;Fielding et al., 2004), especially in estuaries like the Tamar where several noise sources may affect backscatter strength. In addition, while backscatter strength could potentially be used as a proxy of zooplankton abundance, there are important limitations in the use of singlefrequency acoustic systems (Holliday, 1992). ...
We examined the spatio-temporal synchronicity between zooplankton biomass and larval fish concentrations within a highly flushed
system in northern Tasmania, Australia, combining the data from nets and acoustic methods obtained between October 2001 and
November 2002. Zooplankton and larval fish data from nets were analysed in terms of water temperature, salinity and freshwater
flow, while backscatter strength from an Acoustic Doppler Current Profiler (ADCP) was employed to complement zooplankton–net
data and identify the likely areas of high secondary productivity. Zooplankton and fishes varied significantly across months,
peaking simultaneously during late spring (November) at an average temperature of ∼15°C. Maximum zooplankton (20.5 mgC/m3) and fishes (874 larvae/100 m3) were recorded within mesohaline (5–17) and polyhaline (18–29) zones, respectively, also in spring. Peaks in zooplankton
and larval fish occurred a month after peak freshwater flow, with temperature explaining variability better than did flow
or salinity. The coupling of spring peaks in zooplankton biomass and larval fish implies that estuary-spawning fishes may
have a fixed spawning period timed to increasing temperatures to ensure a match with abundant microplankton food supply. Backscatter
strength complemented zooplankton biomass from nets, and could arguably be used as a proxy for zooplankton abundance even
within “noisy” estuarine systems.
... While the Escore algorithm does not solve "the grand challenge" of identification of organisms to the species level using multifrequency acoustic data [54], it may provide substantial insight into the vertical distribution of scatterers in the water column, especially when combined with other multifrequency acoustic visualization tools (such as RGB echograms), statistical techniques and theoretical scattering models fine-tuned with trawl observations if available. Furthermore, this approach can be applied using different frequencies, for varied scientific objectives and/or in various oceanographic environments. ...
The impact of a cyclonic (C), an anticyclonic (AC) eddy and transition zone (TZ), which is the area between the two eddies, on acoustic groups representing various mesopelagic organisms, was investigated using a semi-supervised multifrequency classification approach (hereafter, Escore algorithm). The Escore algorithm involved selecting regions of interest (ROIs) within multifrequency (18, 38, 70, and 120 kHz) echograms and classifying into four clusters or echo-classes using Sv differences (Sv18-38, Sv70-38, and Sv120-38). Acoustic densities and diel vertical migration strength varied between the AC, C, and TZ according to the frequency. The vertical stratification of temperature, salinity and fluorescence within the oceanographic structures had varied influences on the vertical structure of each echo-class which represent zooplankton-like organisms, small and large fish with swimbladders, and small and large siphonophores with pneumatophores. The echo-classes within the C were influenced by surface fluorescence, whereas in the AC and TZ, the echo-classes were influenced by deeper fluorescence and strong EKE. Our study provides new insights into the environmental variables within mesoscale and sub-mesoscale features impacting different groups of mesopelagic communities in the Indian Ocean.
... Therefore, a cut-off angle or threshold of beam compensation has been applied to filter inappropriate data [4,6,7]. Discrimination between species by means of acoustic data is a challenge in this field [8]. The frequency response is an important characteristic of the backscattering utilized for acoustic discrimination. ...
... Recently the need for use of un-invasive means of research has been emphasised. The advances in non-destructive methods in fish survey began with the acoustic monitoring but they lack the species determination possibility (Maclennan and Holliday 1996) and can be biased since fish echoes might be mistaken with bubbles (Ostrovsky 2009). Acoustic survey is also used for observations of fish schools (e.g. ...
The research presented in this thesis contributes to broadening of the knowledge on
free-living adult fish schools and behavioural patterns in a temperate freshwater
reservoir. The behaviour of fish in the pelagic zone is rather poorly studied. Naturally,
schooling tendency varied between species mostly due to increasing vulnerability to
predation. Heterospecificity in schools was not a rare phenomenon, mainly for
vulnerable species that shared the same space and food niche with a predatory less
attractive species. The individual needs fluctuate as factors might be reconsidered in
short time periods and most probably are reflected in behavioural responses.
Individual responses are also reflected in the distribution of the fish in the reservoir
and density in particular habitat. There is a “critical density” that triggers the
formation of fish schools, followed by a slowing increase in density of fish clusters
(observed units). This corresponds to increasing proportion of fish in a school and
declining proportion of singletons. The trend of count of clusters tended to have an
upper limit that should result in constant count of fish clusters after reaching a
particular fish density. In other words, fish in the habitat maintain maximal distances
even when the density increases. During high density periods the distances are kept
by school formation. Overall the usage of the visual census as presented, proved to
be a convenient tool for observation and assessment of freshwater fish. It has been
demonstrated that the method can obtain comparable results to hydroacoustic survey
amounts as well as purse seining.
... D'autres études ont été menées pour identifier les espèces de poissons commerciaux à partir de leur fréquence de résonance (Stanton et al., 2010 (MacLennan and Holliday, 1996). L'acoustique large bande a notamment permis d'affiner les modèles acoustiques utilisés sur le plancton (Martin Traykovski, 1998;Stanton et al., 1998a;Foote et al., 2005), ou in situ de résoudre des mélanges d'organismes (Lavery et al., 2010;Ross et al., 2013). ...
Intermediate trophic components of pelagic ecosystem (from mesozooplakton to micronekton) funnel energy and organic matters from primary producers to many commercial species (anchovy, sardines…). Some of these organisms are supposed to be important contributors to the ubiquitous Sound Scattering Layers (SSLs) observed over a broad range of spatio-temporal scales and geographical areas. Yet, the SSLs taxonomic composition remains largely unknown. The aim of this PhD was to describe the composition and repartition of dense SSLs observed in the Bay of Biscay (France) in spring at several spatial scales, using broadband acoustics, nets and videos. In the first chapter, we showed that the echo sounder beam widths had few effect on the SSLs backscatter, suggesting those SSLs could be composed of unidentified small gaseous scatterers. In the second chapter we applied a forward approach to characterize the composition of SSLs sampled in spring 2016 at small scale, by comparing in situ frequency responses to predictions of scatterer models parameterized with biological sampling data. We determined that these SSLs were probably composed of gas-bearing siphonophores, who, together with mesopelagic fish, dominated the frequency spectra at low frequencies (18-150 kHz). The acoustic backscatter at higher frequencies was dominated by a mix of mesozooplankton organisms, including high densities of pteropods. In the third chapter we applied unsupervised classification methods and a supervised discriminant analysis to delineate the spatial distribution of a peculiar surface SSL composed of centimetric gas-bearing siphonophores. We showed that those small siphonophores were distributed over a meso-scale area (~100 km) in spring 2016 in the northern Bay of Biscay. Our results suggest that siphonophores might be more abundant, and then might play a larger ecological role in eutrophic ecosystems than suspected so far.
... Increase in damaging impact of fishing activities (Cooke and Cowx, 2004) and the need for protection of the bottom structures (Turner et al., 1999) enhance the importance of the use of non-invasive methods. Hydroacoustics is frequently used in research surveys, but species identification using this gear is rather challenging (Maclennan and Holliday, 1996), particularly when fish in freshwater do not always form conspecific schools (Krause et al., 2000). ...
Fishing survey gear often causes damage to the ecosystem and can be size or species selective. Use of an underwater video camera (UVC) omits these flaws, and can bring accurate information on species composition and density of daytime assemblages, moreover it can discover unknown details about behavioural patterns. This study presents a model situation and proposes the use of the UVC as a valid sampling method even in the systems with higher trophies. No significant difference in species composition was found between traditionally used survey gear – purse seining and camera; nor was there a difference in the standardised fish abundance between hydroacoustics and camera when surveying an open water habitat of a temperate freshwater reservoir.
... D'autres études ont été menées pour identifier les espèces de poissons commerciaux à partir de leur fréquence de résonance (Stanton et al., 2010 (MacLennan and Holliday, 1996). L'acoustique large bande a notamment permis d'affiner les modèles acoustiques utilisés sur le plancton (Martin Traykovski, 1998;Stanton et al., 1998a;Foote et al., 2005), ou in situ de résoudre des mélanges d'organismes (Lavery et al., 2010;Ross et al., 2013). ...
Intermediate trophic components of pelagic ecosystem (from mesozooplakton to micronekton) funnel energy and organic matters from primary producers to many commercial species (anchovy, sardines…). Some of these organisms are supposed to be important contributors to the ubiquitous Sound Scattering Layers (SSLs) observed over a broad range of spatio-temporal scales and geographical areas. Yet, the SSLs taxonomic composition remains largely unknown. The aim of this PhD was to describe the composition and repartition of dense SSLs observed in the Bay of Biscay (France) in spring at several spatial scales, using broadband acoustics, nets and videos. In the first chapter, we showed that the echo sounder beam widths had few effect on the SSLs backscatter, suggesting those SSLs could be composed of unidentified small gaseous scatterers. In the second chapter we applied a forward approach to characterize the composition of SSLs sampled in spring 2016 at small scale, by comparing in situ frequency responses to predictions of scatterer models parameterized with biological sampling data. We determined that these SSLs were probably composed of gas-bearing siphonophores, who, together with mesopelagic fish, dominated the frequency spectra at low frequencies (18-150 kHz). The acoustic backscatter at higher frequencies was dominated by a mix of mesozooplankton organisms, including high densities of pteropods. In the third chapter we applied unsupervised classification methods and a supervised discriminant analysis to delineate the spatial distribution of a peculiar surface SSL composed of centimetric gas-bearing siphonophores. We showed that those small siphonophores were distributed over a meso-scale area (~100 km) in spring 2016 in the northern Bay of Biscay. Our results suggest that siphonophores might be more abundant, and then might play a larger ecological role in eutrophic ecosystems than suspected so far.
... Acoustic techniques used in the field of fishery resources assessment can overcome some of the special geographical and visual limitations of traditional sampling methods, and provide much more information on fish density, behavior, size composition, and spatial distribution (MacLennan and Simmonds 1992;Simmonds and MacLennan 2005). Furthermore, hydroacoustic methods can decrease the sampling biases of the traditional trawl surveys by detecting a much larger water column, thus allowing wider application of statistical sampling theory to stock assessment surveys (MacLennan and Holliday 1996). With these advantages, acoustic surveys are specially recommended to be used as the primary nondestructive method to perform ecological fishery assessments and management in the marine ranching ecosystem based on artificial reefs. ...
Various techniques have been used in marine fishery resources assessment. Among those, acoustic techniques have high efficiency and wide adaptability, and are environment friendly. Therefore, acoustic techniques played a key/indispensable role in the field of ecosystem-based fishery management. Acoustic surveys were conducted during the wet (May) and dry (November) seasons in 2016 in the artificial reefs ecological reserve of Bohai Gulf and a nearby control region to understand the current situation of fishery resources and explore the effectiveness of underwater artificial constructions by a dual-frequency identification sonar (DIDSON) and a scientific split-beam echosounder (120 KHz, Simrad EY60). Fish densities in various seasons and regions showed significant differences and interaction, with a maximum value of 358020.34 ind/n.mile² in the artificial reefs’ region and a minimum value of 71898.35 ind/n.mile² in the control region during the wet season. Fish densities in defined parallel transects revealed a roughly southward migration trend of small-size individuals from wet season to dry season. Single echo detections in the artificial reefs region demonstrated a wider target strength (TS) range (− 60 ~ − 30 dB vs − 60 ~ − 51 dB) and higher mean TS values (− 55.87 dB vs − 58.31 dB) than the control region both in the wet and dry seasons, which indicated a more complicated and stable fish community structure in the artificial reefs area. The vertical distribution of single echo detections tracked by the echoview post-processing system showed an apparent downward gathering effect. A positive correlation between TS and water depth was discovered from Pearson correlation analysis in the artificial reefs region during the dry season.
... When these trawls were removed contribution dropped to <0.2% Table 3. Fish species that contributed on average > 2% by number across trawl catch and were present in at least 2 trawls (Occurrence) changes acoustic target strength (TS) (Johnson 1977, Huse & Ona 1996, Godø et al. 2009). DVM may influence fish tilt angle (but see Janssen et al. 1986), which also changes TS (Maclennan & Holliday 1996, Godø et al. 2006. Higher backscatter observed at night in the mesopelagic zone could also relate to resonance scattering (e.g. ...
Mid-trophic level organisms (MTLO) of open-ocean marine ecosystems play a key role linking primary and tertiary consumers. Despite their importance, characterisation of MTLO is limited due to sampling difficulty, and is largely obtained through active acoustics. Acoustic data collected from vessels of opportunity transiting across the Southern Ocean between New Zealand and the Ross Sea provided the opportunity to study distribution and abundance of MTLO over 7 yr. Analyses were performed to identify spatial (vertical and horizontal) and temporal (annual, seasonal and diel) patterns in 28 acoustic transects collected between 2008 and 2014. Mean acoustic backscatter (sa) at 38 kHz varied between years, but overall was reasonably stable, being in the same order of magnitude across all transects. Backscatter consistently and significantly decreased from north to south. Although this latitudinal pattern could be related to MTLO abundance, trawl samples collected in 3 research voyages suggest that it may also reflect differences in species composition and size distribution; consequently, indices based on bulk backscatter must be interpreted with caution. Vertical distribution of backscatter showed clear diel vertical migration patterns and 4 distinct vertical bands (i.e. epipelagic, transition, mesopelagic and deep mesopelagic), with seasonal differences in concentration and behaviour. Deep mesopelagic layers stopped north of the Ross Sea, which may relate to the temperature limitation of contributing organisms. Predicted climate change effects in the Southern Ocean could modify the spatial distribution of MTLO and have impacts on top predators relying upon the mid-trophic level as their main food source.
... Biomass is commonly estimated as an integration of acoustic energy scattered from discrete targets per unit volume of water, where each discrete target's acoustic intensity is its target strength (TS). Fish length has been estimated with TS in several studies Foote, 1987;Love, 1977;MacLennan and Holliday, 1996) using an equation originally presented by Love (1969). Fish length is then converted to weight using known length-to-weight relationships for commonly sampled fish species within the survey area (Boswell, Wilson, and Wilson, 2007). ...
Visual observation methods via SCUBA are commonly used to survey artificial reef fish, although conditions in the Gulf of Mexico often make surveys difficult or even dangerous for divers. In this study, sidescan sonar was used to quantify water-column fish abundance and was compared to the established visual observation methods on SCUBA over four reef sites. Calibrated intensity values measured from sidescan sonar echo returns were used to estimate fish body length and to calculate scaled biomass (g/m2 reef) from a pooled fish length–weight relationship of commonly observed reef fish in the area. Sidescan sonar methods were equivalent to SCUBA surveys for measuring fish abundance over the same reef areas; however, overall reef-associated abundances measured with sidescan were significantly higher because the sidescan could measure a larger water-column area and furthermore allowed for a rapid assessment of abundance on a greater number of reefs in a single sampling day. Scaled abundance and biomass differed significantly between structural types, with the reefed oil-jacket structures in deeper, federally managed waters showing the highest scaled abundance and biomass. With sidescan methods, five reef sites could be surveyed in one day, demonstrating the capability for macroscale comparisons of fish abundance, biomass, and structural preference among sites.
... Fisheries researchers often rely on hydroacoustic estimates of fish size and abundance (MacLennan, 1990;MacLennan and Holiday, 1996;Rose, 2003;Simmonds and MacLennan, 2005); however, this technique's effectiveness can be limited when sampling low-density fish in shallow-water, resulting in a small sample size (Kubecka and Wittingerova, 1998;Knudsen and Saegrov, 2002). In addition, TS estimates are highly variable (McClatchie et al., 1996), therefore, at times estimates may be based on both sparse and variable data. ...
Hydroacoustic sampling of low-density fish in shallow water can lead to low sample sizes of naturally variable target strength (TS) estimates, resulting in both sparse and variable data. Increasing maximum beam compensation (BC) beyond conventional values (i.e., 3 dB beam width) can recover more targets during data analysis; however, data quality decreases near the acoustic beam edges. We identified the optimal balance between data quantity and quality with increasing BC using a standard sphere calibration, and we quantified the effect of BC on fish track variability, size structure, and density estimates of Lake Erie walleye (Sander vitreus). Standard sphere mean TS estimates were consistent with theoretical values (−39.6 dB) up to 18-dB BC, while estimates decreased at greater BC values. Natural sources (i.e., residual and mean TS) dominated total fish track variation, while contributions from measurement related error (i.e., number of single echo detections (SEDs) and BC) were proportionally low. Increasing BC led to more fish encounters and SEDs per fish, while stability in size structure and density were observed at intermediate values (e.g., 18 dB). Detection of medium to large fish (i.e., age-2+ walleye) benefited most from increasing BC, as proportional changes in size structure and density were greatest in these size categories. Therefore, when TS data are sparse and variable, increasing BC to an optimal value (here 18 dB) will maximize the TS data quantity while limiting lower-quality data near the beam edges.
... A key procedure in acoustic biomass estimation is the correct assigning of backscatter to species or species-group level (MacLennan and Holliday, 1996;Horne, 2000), a process typically called scrutinizing or categorization. Categorization, supported by biological sampling and human experience is time-consuming and subjective and there is a need to make the process more objective so as to reduce human-generated bias and uncertainty in acoustic abundance estimates. ...
Sonars and echosounders are widely used for remote sensing of life in the marine environment. There is an ongoing need to make the acoustic identification of marine species more correct and objective and thereby reduce the uncertainty of acoustic abundance estimates. In our work, data from multi-frequency echosounders working simultaneously with nearly identical and overlapping acoustic beams are processed stepwise in a modular sequence to improve data, detect schools and categorize acoustic targets by means of the Large Scale Survey System software (LSSS). Categorization is based on the use of an acoustic feature library whose main components are the relative frequency responses. The results of the categorization are translated into acoustic abundance of species. The method is tested on acoustic data from the Barents Sea, the Norwegian Sea and the North Sea, where the target species were capelin (Mallotus villosus L.), Atlantic mackerel (Scomber scombrus L.) and sandeel (Ammodytes marinus L.), respectively. Manual categorization showed a high conformity with automatic categorization for all surveys, especially for schools.
... The fifth acoustic symposium took place in Aberdeen, Scotland, in 1995 (Simmonds, 1996). One notable feature of this meeting was the movement away from dealing with instrumentation problems and the greater emphasis on extracting information on aquatic animals and their environment (MacLennan and Holliday, 1996). ...
... Alternatively, sound in the ocean travels fast and efficiently with detection possible over relatively great distances. As a result, active acoustic techniques, those that use sounds that are both transmitted and received (e.g., sonars), are widely applied to fish, zooplankton, and other animals in the ocean for both fisheries and ecological studies (MacLennan and Holliday 1996). One of the key challenges for utilizing acoustics to study biology is the difficulty in identifying the source of the scattering (McClatchie et al. 2000 ). ...
Acoustic echo sounders designed to map and discriminate organisms in the water column have primarily been deployed on ships. Because of acoustic attenuation of higher frequencies used to detect and discriminate micronekton and nekton, this has effectively restricted the range of this information to the upper water column. In an effort to overcome these range limitations by reducing the distance between the transducer and the targets of interest, dual-frequency (38 and 120 kHz) split-beam echo sounders were integrated into a Remote Environmental Monitoring Units (REMUS) 600 autonomous underwater vehicle (AUV), effectively doubling the range of quantitative acoustic data into the mesopelagic zone (600-1200 m). Data from the first set of missions in a range of conditions revealed that the AUV provided a stable platform for the echo sounders and improved vertical and horizontal positional accuracy over echo sounders towed by ships. In comparison to hull-mounted echo sounders, elimination of ship noise and surface bubbles provided a 17- and 19-dBW decrease in the noise floor for the 38- and 120-kHz echo sounders, respectively, effectively increasing the sampling range by 30%-40%. The extended depth range also increased the resolution of the acoustic horizontal footprint from 37-40 to 0.6-3.7 m, enabling discrimination of individual targets at depth. Also developed here is novel onboard echo sounder data processing and autonomy to allow sampling not feasible in a surface ship or towed configuration. Taken together, these data demonstrate an effective new tool for examining the biology of animals in the mesopelagic zone (600-1200 m) in ways previously only possible in the upper ocean.
... Active acoustics is increasingly used to study the abundance, distribution, and behavior of fish and zooplankton communities (e.g., Greenlaw, 1979;MacLennan and Holliday, 1996;Sato et al., 2013). Using ships, moorings, or cabled observatories, acoustics provides continuous measurements of organism densities at high spatial and temporal resolutions. ...
... Ancillary, nonacoustic information on factors external to the shoals themselves (e.g. environmental conditions, bottom depth, or geographic position) may contribute additional species-discriminating ability (as suggested by MacLennan and Holliday, 1996;Scalabrin et al., 1996), although very little work to date has attempted to integrate such data with descriptors of shoal features. ...
Stock assessment of exploited pelagic species often relies on hydroacoustic surveys, but a major limitation of this approach stems from an inability to distinguish between the echoes of co-occurring species. We make acoustic measurements of morphometric, energetic, and bathymetric features of anchovy (Engraulis capensis), sardine (Sardinops sagax), and round herring (Etrumeus whiteheadi) schools, to test the hypothesis that schools of each species can be distinguished on the basis of such acoustic descriptors. School measurements were extracted using commercially available software from acoustic data collected by a vertical echosounder during trawling operations of pelagic stock surveys of the South African continental shelf, November 1997, 1998 and 1999. Principal components analysis of 18 school descriptors of the 214 schools for which the species composition was satisfactorily determined by trawl samples suggested that schools of the three species differed in energetic features and position in the water column, but not in morphometrics. Discriminant function analysis indicated that schools could be correctly identified to species in 88.3% of all cases (94.9% for anchovy, 82.6% sardine, 82.6% round herring). Sardine were distinguished from anchovy and round herring primarily on the basis of school depth and energy, and anchovy from the two other species based on an index of school altitude. Correct classification was not improved by including the ratios of measurements of school features made at a 65 dB processing threshold relative to measurements made at 60 dB. Inclusion of ancillary information (latitude, longitude, sea surface temperature, bottom depth, and time of day) improved the accuracy of school identification to 94.9%, since such variables allowed discrimination on the basis of inter-specific differences in habitat use, as well as in schooling behaviour. 2001 International Council for the Exploration of the Sea
... We used acoustic measures sorted into rough multispecies groupings based on similarities in backscattering characteristics to provide an index of variation in potential prey density. Species identification is seen as a great challenge in fisheries acoustics and is nearly impossible without trawl samples (MacLennan & Holliday 1996, Korneliussen & Ona 2002. Despite this, acoustics data even in the absence of trawls can provide a relative measure of multispecies prey distributions that can help to inform models of top predator distributions (Hazan et al. 2011), as is evident here. ...
To gain further insight into the foraging behaviour of predator species, it is essential that interactions between predators, their prey and the surrounding environment are better understood. The primary purpose of this study was to determine the underlying processes, both physical and biological, driving variation in the times and locations of seabird foraging events. Using fine-scale simultaneous measurements of seabird abundance, prey density and oceanographic variability collected during an at-sea survey in the Firth of Forth region of the North Sea, zero-inflated negative binomial models were applied to identify the underlying processes driving foraging behaviour in 2 seabird species: the common guillemot Uria aalge and the black-legged kittiwake Rissa tridactyla. Both guillemot and kittiwake models showed consistency in their results; specific tidal states and thermal stratification levels explained observed increases in abundance. The secondary purpose of this study was to identify key oceanographic processes driving variability in prey density and determine if these were comparable to those underlying the behaviour of foraging seabirds. Log-transformations of 2 measures of prey density, NASC-40-50(MAX) and NASC-50-70(MAX), were modelled using generalised least squares. Similar tidal conditions and thermal stratification levels explained distributional patterns, suggesting that these processes act to increase prey availability, creating profitable foraging opportunities for predators to exploit. This has been termed the tidal coupling hypothesis and identifies that critical marine habitats occur not only at limited spatial locations but also within specific temporal intervals relating to the tidal cycle. Further more, by incorporating this oceanographic influence on foraging habitat, fine-scale predator-prey relationships were also identified. Foraging guillemots and kittiwakes displayed a Type II functional response to increasing values of NASC-40-50(MAX).
... Ancillary, nonacoustic information on factors external to the shoals themselves (e.g. environmental conditions, bottom depth, or geographic position) may contribute additional species-discriminating ability (as suggested by MacLennan and Holliday, 1996;Scalabrin et al., 1996), although very little work to date has attempted to integrate such data with descriptors of shoal features. ...
It is shown that schools of similarly sized and behaving pelagic fish species can be accurately identified to species over a large spatial area, on the order of the broad spatial‐scales typical of standard assessment surveys, and over a time‐span of three years. Acoustic measurements of morphometric, energetic, and bathymetric features of anchovy, sardine, and round herring schools were extracted using commercially available software from acoustic data collected by a conventional single‐frequency narrow‐band echosounder during trawling operations of pelagic stock surveys of the South African continental shelf (November 1997, 1998 and 1999). Discriminant function analysis of 18 descriptors of the 214 schools for which the species composition was satisfactorily determined by trawl samples indicated that schools could be correctly identified to species in 88.3% of all cases (94.9% for anchovy, 82.6% sardine, 82.6% round herring). The three species were differentiated primarily on the basis of school bathymetric position and backscattered energy. Including ancillary information (latitude, longitude, sea surface temperature, bottom depth, and time of day) in analysis improved the accuracy of school identification to 94.9%, since such variables allowed discrimination on the basis of interspecific differences in habitat use, as well as in schooling behavior. a)Currently at MIT/Woods Hole Joint Program.
... Fisheries acoustics is a branch of applied biological oceanography aimed at developing and using active hydroacoustic systems for the detection, quantification and qualification of aquatic life. Its application in the assessment of fish stocks and for broader ecosystem studies is well established (MacLennan and Holliday 1996) and becoming ever more significant (Fernandes et al. 2002). In the case of many pelagic fish stocks, acoustic survey data are used in assessment models in order to determine population size (Patterson and Melvin 1996). ...
2002). AUVs as research vessels: the pros and cons. ICES CM2002/J:02, 11 pp. Traditional ocean going research vessels have advanced considerably over the last century. However, as marine sampling platforms they suffer from some major shortcomings related to their large size and surface restriction. Autonomous underwater vehicles (AUVs) are small unmanned submarines which have emerged over the past ten years as alternative platforms. Currently, there are over 75 AUVs either under development or in operation in the offshore industries of mineral exploration, in the military, and in applied and academic oceanographic science. This paper reviews the application of AUVs to marine research. Compared to traditional research vessel platforms, AUVs are able to sample previously impenetrable environments such as the sea surface, the deep sea and under sea ice. Furthermore, AUVs are typically small, very quiet, and have the potential to operate at low cost and be unconstrained by the vagaries of weather. Examples of how these traits may be utilised in marine science are given with reference to previous work and to potential future applications. However, before many of the more prospective applications can be accomplished, advances in AUV power source technology are required to increase the range of operation. The paper reviews current power sources for AUVs and examines other developments which will overcome many of the limitations currently inhibiting the wider application of AUVs for gathering data in marine science.
... There is, therefore, not only a need for acoustic surveys to be more accurate and precise, but also to direct efforts toward an increasing array of targets. In such a context it is clear why MacLennan and Holliday (1996) proclaimed that species identification is "the grand challenge of fisheries and plankton acoustics". ...
M. (2004). Determining the quality of a multifrequency acoustic identification algorithm. ICES CM2004/R:11, 11 pp. The identification of species using multifrequency acoustic data has become a popular method which has the potential to enhance the precision of acoustic surveys and enable them to be used for wider ecosystem studies. Many techniques are still focussed on the development of algorithms for any one single species. These algorithms may incorporate image analysis techniques to isolate echotraces, and, or, mathematical operators on the coincident (in space and time) mean volume backscattering strengths from different frequencies. There is, however, no agreed method of determining just how good any one algorithm may be relative to another for identifying the same species. Moreover, there are no objective means of altering the various components of any one algorithm to improve it. This study aims to assess how the quality of a species identification algorithm can be evaluated and improved. Using a multifrequency algorithm developed to distinguish North Sea mackerel from herring, a method is proposed which renders a similarity of identification index (s id) for the algorithm. The method is based on comparing the algorithm output to a set of ground-truthed echograms collected during a survey in the North Sea in 2003. Enhancements to s id as a result of modifications to the algorithm are directly linked to an improvement in performance. Other algorithms could be evaluated in the same framework and a comparison with a similar algorithm used to detect sandeels is also made.
... Within acoustic surveying methodology there is an incessant call for improvement, in order to reduce ambiguity in the interpretation of acoustic data and thereby reduce the uncertainty of acoustic abundance estimates. Species identification was addressed by MacLennan and Holliday (1996) as "the grand challenge of fisheries and plankton acoustics". Considerable potential for improvement may be derived from the echogram interpretation process as shown by Mathisen et al., 1974;Korsbrekke and Misund, 1993;Misund, 1997. ...
Acoustic methods are widely used for estimating fish abundance. Currently the Institute of Marine Research (IMR) uses the Bergen Echo Integrator (BEI) to analyse the acoustic data. Development of BEI started in 1987, and although it still fills its purpose it has become increasingly difficult to maintain and expand. An evaluation of existing post-processing systems for acoustic data concluded that present software systems do not meet the future demands of IMR. Therefore IMR decided to develop a new post-processing system, the Large Scale Survey System (LSSS). LSSS is described here.
... The use of hydroacoustic technologies on fishing research showed a substantial development in the 1970s, when the echo-integration technique was introduced. This technique allowed estimates of schools density, unlike the echo-counting technique that had been employed (MacLennan and Holliday, 1996). Since then, the use of the method for assessment and management of fisheries, species identification and acoustic characterization, behavioral and trophic relationships studies have been widely described in literature (Gerlotto, 1993;Paramo et al., 2003;Vehanen et al., 2005). ...
AIM: To study the distribution, structure, size and density of fish in the karst lake: Lagoa Central (Lagoa Santa, MG - surface area: 1.7 km2; mean depth: 4.0 m; and maximum depth: 7.3 m). METHODS: The hydroacoustic method with vertical beaming was applied, using the echosounder Biosonics DT-X with a split-beam transducer of 200 kHz. The analysis of the acoustic data was performed with the software Visual Analyzer (Biosonics Inc.). Thematic maps of density echoes associated with fish, estimated by the technique of echo-integration, were made using the kriging interpolation. The density and vertical distribution of insonified fish were estimated using the technique of echo-counting. RESULTS: The lake had a mean density of 0.89 echoes associated with fish per m2, showing large spatial variations in the density of fish. The size estimated for the echoes associated with fish range from 2.7 to 15.9 cm (mean = 5.3 cm). CONCLUSIONS: The use of hydroacoustic to obtain rapid and realistic estimates of fish abundance and vertical distribution of the fish stock was successful.
... The evolution of acoustic technologies fits within a movement towards an information-rich research of the oceans, which has generated a converging interdisciplinary approach (MacLennan and Holliday, 1996) incorporating large sensor arrays, data fusion and various ground-truthing techniques (McClatchie et al., 2000). Currently, ambitious global-scale enterprises aim to revolutionize oceanographic research by providing interactive technological platforms for sampling and monitoring the world's waters, relying on state-of-the-art connectivity and vast communication networks (Delaney and Barga, 2009). ...
This thesis investigates the incorporation of target phase into sonar signal processing, for enhanced information in the context of fisheries and acoustical oceanography. A sonar system phase calibration method, which includes both the amplitude and phase response is proposed. The technique is an extension of the widespread standard-target sonar calibration method, based on the use of solid metallic spheres as standard targets. Frequency domain data processing is used, with target phase measured as a phase angle difference between two frequency components. This approach minimizes the impact of range uncertainties in the calibration process. Acoustic scattering from target spheres is predicted with full-wave modal solutions. Calibration accuracy is examined by comparison to theoretical results. Sources of ambiguity are examined in terms of system, medium and target uncertainties. While the error analysis is mainly aimed at phase response, the limits of the classical amplitude-only standard-target calibration are also revisited. The system complex response is obtained for an operating frequency of 50 to 150 kHz. Distortion issues associated with resonant systems, examined in terms of network theory, are seen to be caused by the non-minimum phase components deviating from a linear response. The calibrated broadband sonar system is then used to study the complex scattering of objects important for the modelling of marine organism echoes, such as elastic spheres, fluid-filled shells, cylinders and prolate spheroids. Underlying echo formation mechanisms and their interaction are explored. Phase-sensitive sonar systems could be important for the acquisition of increased levels of information. This is crucial for the development of improved oceanographical acoustics methods that could lead, for example, to automated species identification. Studies of sonar system phase calibration and complex scattering from fundamental shapes are necessary in order to incorporate this type of fully-coherent processing into scientific acoustic instruments.
... Thus, phytoplankton cells displaced by the internal waves we observed would not have been exposed to increased light levels 4.4. Across-shore variability in sources of acoustic backscatter A major benefit to using acoustic backscatter as a proxy for organism abundance is that acoustic sensors are capable of sampling large swaths of the coastal ocean in short periods of time (MacLennan and Holliday, 1996;Pieper et al., 2001). However, only limited information regarding the sources of observed backscatter can be gleaned using these instruments alone. ...
The purpose of this study was to further our understanding of the role of the coastal physical environment as a dynamic and constantly evolving habitat for plankton. Over a 3-wk period in the summer of 2010, an array of moorings were deployed and shipboard and autonomous underwater vehicle (AUV) surveys were conducted in order to investigate the association between physical processes and plankton distributions over the Monterey Bay, California inner shelf. Acoustic backscatter, chlorophyll-a fluorescence, and high-resolution zooplankton imagery data collected during the shipboard surveys were used to map the distributions of phytoplankton and zooplankton; and profiles of temperature, salinity, oxygen, and nitrate from the AUV were used to characterize the physical and chemical environment. A synthesis of underway and moored time series data provided insight into the histories of water masses in the area, and facilitated tracking of internal wave groups as they propagated towards shore. A near-bottom intrusion of recently-upwelled water was found to be strongly influenced by the diurnal tide, resulting in daily across-shelf excursions past our mooring array at the 20-m isobath. Behind the leading edge of the intrusion, the water column was highly stratified in temperature, salinity, oxygen, and nitrate; and thin layers of phytoplankton and zooplankton persisted at the upper boundary of the intrusion. In ambient waters shoreward of the intrusion, stratification was weak; copepod, appendicularian, and gelatinous zooplankton abundances were relatively low; and phytoplankton and acoustic backscatter were broadly distributed throughout the lower half of the water column. The arrival of two shoreward-propagating internal wave groups observed during the shipboard survey corresponded with disparate responses in plankton distribution. In the wake of the first wave group, phytoplankton and zooplankton layers thinned or converged; in the wake of the second wave group, an eight-fold increase in gelatinous zooplankton was observed. These findings reveal a strong coupling between physical processes and plankton abundance and vertical distributions. It is necessary to understand the underlying physical environment in order to understand the complex distribution of organisms in the sea.
... In this study we examine the age characteristics of echoes of walleye pollock (Theragra chalcogramma) schools to identify the representative ages of the schools. When more information of this type has been collected and the results verified, it will be easier to identify the species of marine organisms acoustically (MacLennan and Holliday, 1996;Horne, 2000); this is just a first step. For age identification, a wealth of information is created by combining the frequency characteristics approach (DMVBS characteristics) and the distribution characteristics method (morphological and bathymetric characteristics). ...
The purpose of this study was to investigate the possibility of identifying the age of walleye pollock (Theragra chalcogramma) using acoustic information. Acoustic data targeting walleye pollock were collected at 38 and 120 kHz from 16 June to 12 July 2000 in the Pacific, off Hokkaido, Japan. To complement these data 33 trawl hauls were made and the species and age of the sample fish were accurately examined. The echoes of walleye pollock schools according to age were used to determine the morphological and bathymetric characteristics such as mean height, maximum length, centre depth, seabed depth, and distance from the seabed, as well as the frequency characteristics, this latter being the difference of mean volume backscattering strengths at 38 and 120 kHz, respectively (ΔMVBS). The ΔMVBS method is elaborated using MVBS (mean volume backscattering strength) from an integration cell of optimal size, the cell being examined by means of various integration periods to highlight the characteristics of the walleye pollock schools resulting in 20 pings (120 m), and by applying this method only in a common observation range for two frequencies. The ages of the schools are identified by a combination of morphological and bathymetric characteristics, and ΔMVBS characteristics. Age-0 groups are easy to distinguish from other age groups because they exist in distinct, small schools, are close to the coast, and have a narrow range of ΔMVBS regardless of time of day. Age-1 schools are low in height and very long, are distributed close to the sea floor, and have an ΔMVBS range of -1 to 8 dB, with most between 3 and 5 dB. These characteristics of age-1 schools are distinct from other age groups. As age-2 and age-5 schools have similar maximum length and distribution depth, it is almost impossible to identify these two by just morphological and bathymetric characteristics. However, the ΔMVBS of age-2 and age-5 schools show characteristic patterns that can be used as a means of identification. The pattern of ΔMVBS, which reflects an internal structure (swimming angles) of a school, is different for each age class, and is essential in the identification of the age of a walleye pollock school.
... These techniques have made significant progress in recent decades with the development of more rapid computers, new transducers and microelectronics. Despite the technological advances in acoustic devices with improvements in detection capacity and computer processing, there is still the challenge of species identification directly by acoustics (MacLennan and Holliday, 1996;Horne, 2000;Fernandes et al., 2006;Trenkel et al., 2008). Echograms provide information about size, location and echo intensity of fish schools, however the species composition is not directly known (Fernandes, 2009). ...
The purpose of this study was to compare the results of the multi-class support vector machines (SVM) classification method to those of the classification tree (CART) method for automatic classification of fish schools. The discrimination study was done using descriptors of morphology, bathymetry, energy, and space positions for schools of three species; anchovy (Engraulis ringens), common sardine (Strangomera bentincki), and jack mackerel (Trachurus murphyi) from acoustic data in southern-central Chile. The classification rate averages were 86.8% with classification trees and 89.5% with SVM. The levels of importance of the descriptors presented by the two methods are not fully concordant (Kendall's rank coefficient of concordance is 0.77). However, the two methods agree on the groups of descriptors considered as effective for classification. The bottom depth descriptor was the most important for classification trees, while the school-altitude index was the most important for SVM. This highlights the importance of the bathymetric and positional descriptors in the classification of species compared to energetic and morphometric descriptors. Advantages and disadvantage of the methods are presented. Classification trees have the advantages over SVM of being easier to implement and interpret, but have a lesser performance. One major problem with trees is their high degree of variance. Because each classification method has its own performance, limitations and advantages, a good practice is to use two or more classifiers.
... Within acoustic-surveying methodology there is an incessant call for improvement in order to reduce ambiguity in the interpretation of acoustic data and thereby reduce the uncertainty of acoustic abundance estimates. ''Species identification'' was seen by MacLennan and Holliday (1996) as ''The grand challenge of fisheries and plankton acoustics''. Considerable potential for improvement may be derived from the echogram interpretation process of Mathisen et al., 1974;Korsbrekke and Misund, 1993;Misund, 1997. ...
Calibrated and digitized data from two or more discrete echosounder frequencies can be combined for the purpose of separating
and extracting the acoustic scattering from zooplankton and fish in mixed recordings. This method is also useful for quantifying
the relative contribution of each frequency to the total acoustic-backscattering when scrutinizing records in large-scale,
acoustic surveys. Echosounder hardware requirements are defined which would permit the ideal extraction of such information.
These include calibration, transducer specification, pulse resolution and digital representation of the signals. During this
initial study a special version of the Simrad EK500 multi-frequency, split-beam echosounder and the Bergen Echo Integrator
(BEI) post-processing system were used. The echosounder transmitted pulses simultaneously at four frequencies, 18, 38, 120
and 200 kHz and transferred the received signals to the post-processing system in calibrated, raw, digitized format. Methods
are described for echogram manipulation and for the construction of new, synthetic, combined-frequency [c(f)] echograms. Examples
of extracted scattering information from mixed layers of fish and small scattering-organisms, such as copepods and euphausiids,
are shown, and the potential of the method is discussed.
... Therefore, they were unable to assess how resource selection might change as the species composition and availability of food resources changed. Advances in hydroacoustic hardware technology, data processing, and the availability of classification statistical methods have facilitated limited identification of fish schools (MacLennan & Holliday 1996), allowing us to add forage species to the suite of variables considered by the previous studies. By collecting data over three years we were able to examine how selection of fish schools by seabirds changed among years. ...
We sought to determine how fish school selection by Marbled Murrelets Brachyramphus marmoratus changed as the availability of forage fish fluctuated among years within Prince William Sound, Alaska. Hydroacoustic and bird-location data were collected simultaneously while traveling systematically arranged transects during the summers of 1997, 1998 and 1999. We determined the number, location, species composition and general characteristics of all fish schools within the hydroacoustic data set. We determined which schools were associated with murrelets and compared their characteristics to the non-associated schools through multivariate logistic regression modeling. During 1997 when lipid-rich Pacific Herring Clupea pallasi were abundant, murrelets selected smaller schools near the surface. In 1998 the schools detected by hydroacoustics were bigger schools of large herring, located in deeper water, and further from the surface than those observed in 1997 and 1999, and murrelets were not associated with those schools. Gadids (predominantly Walleye Pollock Theragra chalcogramma, but also Pacific Cod Gadus macrocephalus and Saffron Cod Microgadus proximus, all low-lipid species, were the most abundant school type in 1999, and herring were less numerous than in the previous years. Murrelets responded to the 1999 changes in availability by selecting for herring, while school size and depth to schools were less important in choosing food resources. We suggest that murrelets responded to changes in the availability of food by making choices that maximize their net energy intake, as predicted by foraging theory. We further observe that resource selection studies that utilize data from one point in time may not demonstrate the full range of possible models.
... Acoustic methods have developed gradually and are used increasingly to quantify zooplankton abundance (MacLennan and Holliday, 1996). A few previous applications also relate to gelatinous zooplankton (Mutlu, 1996;Monger et al., 1998;Brierley et al., 2001). ...
Four non-invasive methods (three acoustic and one video) were compared to estimate the abundance and vertical distribution of scyphomedusae, using the locally abundant coronate species Periphylla periphylla in Lurefjorden, north of Bergen, Norway, as the test organism. The acoustic methods included single-target quantification by, respectively, a hull-mounted 38 kHz split-beam echo sounder and a 675 kHz scanning sonar mounted on a remotely operated vehicle (ROV). Data from acoustic backscattering provided estimates of abundance and changes in the vertical position of scattering (¼ aggregation) layers. Vertical migration was also studied by acoustic target tracking, following single individuals as they ascended in the afternoon. The ROV-mounted scanning sonar missed an unidentified part in the lower size distribution of the target population. Vertical video profiles, conducted during ROV dives, provided the most detailed information on abundance and distribution, although uncertainties remained regarding the size distribution in the population.
... Identification of acoustic backscatter to taxa is one of the grand challenges of fisheries acoustics (MacLennan and Holliday 1996). In this paper, identification is defined as the objective determination of acoustic backscatter to genus or species, whereas classification is defined as the less rigorous product of objectively categorizing acoustic backscatter to some anatomical feature or lower-level taxon. ...
Acoustic surveys have been conducted on Georges Bank from 1998 to present to estimate Atlantic herring (Clupea harengus) population abundance. Acoustic data were collected with a 12 or 18, 38, and 120 kHz Simrad EK500 scientific echo sounder. A pelagic trawl and underwater video images were used to collect biological information and to verify the species composition of acoustic backscatter. A multifrequency classification method was developed to improve the efficiency and accuracy of classifying species from acoustic echograms. In this method, a volume backscatter (Sv) threshold was applied equivalently to all echograms, and then a composite echogram was created based on which frequencies had Sv greater than or less than the Sv threshold. The results of this method were compared with the standard method of visually scrutinizing regions, and metrics were developed to evaluate the accuracy of classification algorithms relative to current methods, as well as to assess the effects of classification methods on population abundance estimates. In general, this method matched visually scrutinized Atlantic herring regions, but with consistent biases in classifying 38 kHz backscatter. The metrics highlighted spatial and temporal changes in the acoustic landscape, which may be indicative of intra- and inter-annual biological changes.
... This is consequential not only from an ecological point of view but also for sampling. Mysids have traditionally been collected with vertical hauls, but because of their often very patchy distribution, hydroacoustic techniques are becoming more common (MacLennan and Holliday 1996, Holbrook et al. 2006, Rudstam et al. 2008, since acoustics allow for extensive coverage at a reasonably low cost. Interpretation of hydroacoustic information is however not trivial and good knowledge of the behavior and position of the studied organisms is crucial for correct abundance and biomass estimations (Simmonds and MacLennan 2005). ...
We report on abundance, biomass, trophic position and vertical size distribution of pelagic mysids (Mysis mixta, Mysis relicta/salemaai, Neomysis integer) in a coastal Baltic Proper area. As compared with the situation in this area in the 1980s, the formerly dominating M. mixta has declined and the total mysid biomass decreased by 50%. Neomysis integer now constitutes the bulk of the mysids. Stable isotopes indicate that they feed on a lower trophic level than Mysis spp., and M. relicta appears more carnivorous than M. mixta. For N. integer, size increases with depth and decreases with in situ light. This was not found for Mysis spp., probably due to their narrow size span and smaller sample size than for N. integer. In N. integer, in situ light explained the size variation with depth better than temperature, indicating that this variation is a response to predation rather than size-related thermal preference.
... Rudstam et al. (1986) found that Mysis mixta could consume 23-51% of net annual zooplankton production in a coastal area of the Baltic proper. Mathematical models on intra guild predation (IGP) further suggest that intermediate predators like mysids must be superior competitors for a shared resource in order to persist in the system (MacLennan and Holliday 1996). ...
Mysid shrimps (Mysidacea, Crustacea) are efficient zooplanktivores in both marine and freshwater systems as well as lipid rich prey for many species of fish. Although some efforts have been made to study the role of mysids in the Baltic Sea, very few studies have been carried out in recent time and there are still knowledge gaps regarding various aspects of mysid ecology. This thesis aims to explore some of these gaps by covering a mixture of topics. Using multifrequency hydroacoustics we explored the possibility to separate mysids from fish echoes and successfully established a promising and effective method for obtaining mysid abundance/biomass estimates (paper I). An investigation of the current mysid community in a coastal area of the northern Baltic proper (paper II) demonstrated that the formerly dominant, pelagic mysid Mysis mixta had decreased substantially (textasciitilde50%) in favor for phytoplanktivorous, juvenile Neomysis integer and Mysis relicta sp. By examining different aspects of mysid behavior, we studied the vertical size distribution of mysids in the field and found that size increased with depth/declining light, irrespective of temperature; indicating that their vertical size distribution primarily is a response to predation (paper II). In paper III, a combination of ecological and genetic markers was used to investigate intraspecific differences in migratory tendency. Both marker types indicated that some part of the Mysis salemaai population is sedentary on the bottom and that this strategy is a phenotypically plastic but persistent trait, analogous to the partial migrations seen in many birds and fishes. In paper IV a temperature and weight specific respiration model was developed for the littoral Praunus flexuosus. Routine respiration was moreover elevated by post-prandial effects (specific dynamic action) for longer times than previously suggested. Consequently, ignoring such effects could significantly bias respiration measurements.
... The methodology for quantifying acoustic backscatter from echosounders is well developed (reviewed in Simmonds and MacLennan 2005). One of the major challenges in the use of acoustics in this context is the conversion of acoustic backscatter to biologically relevant information such as species composition and body size (Holliday and Pieper 1995; MacLennan and Holliday 1996; Horne 2000). The traditional approach to species identification (hereafter referred to as the traditional identification method) has been to combine acoustic measurements with information from trawls or optical instruments and visual interpretation of echograms to interpret acoustic backscatter (e.g., McClatchie et al. 2000; Jech and Michaels 2006). ...
We evaluated the feasibility of identifying major acoustic scatters in North Pacific ecosystems based on empirical measurements of relative frequency response. Acoustic measurements in areas where trawl catches were dominated by single taxa indicated that it might be possible to discern among key groups of scatterers such as fish with gas-filled swimbladders, euphausiids, myctophids, and jellyfish. To establish if walleye pollock (Theragra chalcogramma), a key species in the ecosystem, can be separated reliably from other groups under prevailing conditions, we developed a method based on the normal deviate (or Z score) to identify backscatter consistent with the pollock relative frequency response. We evaluated the performance of the method by comparing it with the traditional method of species identification (i.e., directed trawl catches and subjective interpretation of echograms) during five large-scale acoustic surveys of the eastern Bering Sea. Pollock abundance estimates employing the multifrequency method were highly correlated with those using the traditional method, which indicates that the multifrequency method performs well in this situation. In this environment, multifrequency methods will allow more inferences to be drawn when direct sampling of organisms is limited and will also complement existing abundance surveys by improving species classification and providing information about key nontarget species.
... Lawson et al. (2001) combined the SHAPES system with discriminant function analysis to classify and assign morphometric attributes of fish schools, such as school height, depth, or width, which differed between schools of different species. Although these methods can obtain a classification success of up to 96% in monospecific situations, it is generally thought that the information available at a single frequency is rarely sufficient to deal with more complex situations (MacLennan and Holliday 1996). The use of more than one frequency in an acoustic survey can give more acoustic information, which may improve the accuracy of the scrutinizing process, especially if the acoustic properties of individual species vary with the frequency in use (Madureira et al. 1993). ...
The multifrequency backscattering characteristics of echotraces of Atlantic herring (Clupea harengus) and Norway pout (Trisopterus esmarkii) are described. These fish cohabit similar areas of the North Sea in summer and echotraces of their schools are difficult to distinguish. Mean volume backscattering strengths at 18, 38, 120, and 200 kHz were taken from the International North Sea Herring Acoustic Surveys along with coincident pelagic trawl samples. The results indicate that echotraces of these fish species cannot be distinguished on the basis of differences in backscattering at discrete frequencies typically used in fish surveys and on fishing vessels. However, some discrimination between herring size-classes was evident. The empirical data for herring were then compared with a backscattering model for herring combining fish flesh, the swimbladder, and the effect of increased pressure at depth. Both the empirical data and model data indicate that, compared with large herring, progressively smaller herring generally have higher backscattering at the lowest frequency (18 kHz), although variability was high. According to the model, this frequency-specific signature is due to the progressively more significant contribution made by the fish body compared with the swimbladder, as the latter diminishes owing to an increase in ambient pressure in deeper water.
... Identification of targets is a major source of bias in estimating fish abundance acoustically (Maclennan and Simmonds 1992, Maclennan and Holliday 1996, Reid 2000. The problem can be acute in areas with great species diversity and much mixing, such as Angola. ...
Pelagic fish off Angola constitute about 80% of the total fish landed and some 75% of the animal protein in the diet of the coastal population. The primary means of estimating stock abundance is through acoustic surveys, a method that is sensitive to identification of echo traces. This paper describes commonly encountered pelagic fish aggregations in terms of acoustic properties, and morphological and spatio-temporal descriptors. A knowledge base of reference observations validated by an experienced team of regional operators was used in a stepwise General Discriminant Analysis (GDA) that sought to identify traits characteristic to common species groups. A range of descriptors provided significant discriminant power (p < 0.01), and these were used to construct a classification algorithm. The resulting overall classification success emanating from the GDA was 46% when only considering the greatest posterior probability of group membership. This success rate increased to 62% and 71% respectively when including the second and third highest group membership probabilities. For Cape horse mackerel Trachurus trachurus capensis and Sardinella spp., success rates of 80% and 75% were obtained when including classifications that fell into groups with probabilities ranging from greatest to third greatest respectively.
... The application of fisheries acoustics in the assessment of fish stocks and for broader ecosystem studies is well established (MacLennan and Holliday, 1996). In the case of many pelagic fish stocks, acoustic-survey data are essential inputs to assessment models that determine population size (e.g. ...
2003. Autonomous underwater vehicles: future platforms for fisheries acoustics – ICES Journal of Marine Science, 60: 684–691. Autonomous underwater vehicles (AUVs) are unmanned submersibles that can be pre-programmed to navigate in three dimensions under water. The technological advances required for reliable deployment, mission control, performance, and recovery of AUVs have developed considerably over the past 10 years. Currently, there are several vehicles operating successfully in the offshore industries as well as in the applied and academic oceanographic sciences. This article reviews the application of AUVs to fisheries-and plankton-acoustics research. Specifications of the main AUVs currently in operation are given. Compared to traditional platforms for acoustic instruments, AUVs can sample previously impenetrable environments such as the sea surface, the deep sea, and under-sea ice. Furthermore, AUVs are typically small, quiet, and have the potential to operate at low cost and be unconstrained by the vagaries of weather. Examples of how these traits may be utilized in fisheries-acoustics science are given with reference to previous work in the North Sea and Southern Ocean and to potential future applications. Concurrent advances in multi-beam sonar technology and species identification, using multi-frequency and broadband sonars, will further enhance the utility of AUVs for fisheries acoustics. However, before many of the more prospective applications can be accomplished, advances in power-source technology are required to increase the range of operation. The paper ends by considering developments that may turn AUVs from objects sometimes perceived as science fiction into instruments used routinely to gather scientific facts.
In its controversy with older geotectonic theories, plate tectonics in the first phase of its formulation gathered its most conclusive arguments through a double shift in its foundations: instead of the complicated, billion-year-old geological history of the continents, the theorists of plate tectonics rely on marine geology and favor a geophysical style of reasoning. Strong economic interests have promoted this style of thinking. But it earned its formative power through the geopolitical interests of the USA in the times of the Second World War and the Cold War within the framework of the established military-industrial complex. The study describes the development of geophysical techniques and methods within this historical, geopolitical and structural setting. The theory of plate tectonics can be understood without this background, but not the research infrastructure, the established research methods and research equipment, which continue to the present day. They all bear the signature of war.
In fishery acoustics, surveys using sensor systems such as sonars and echosounders have been widely considered to be accurate tools for acquiring fish species data, fish species biomass, and abundance estimations. During acoustic surveys, research vessels are equipped with echosounders that produce sound waves and then record all echoes coming from objects and targets in the water column. The preprocessing and scrutinizing of acoustic fish species data have always been manually conducted and have been considered time-consuming. Meanwhile, deep learning and machine learning-based approaches have also been adopted to automate or partially automate the acoustic echo scrutinizing process and build an objective process with which the species echo classification uncertainty is expected to be lower than the uncertainty of scrutinizing experts. A review of the state-of-the-art of different deep learning and machine learning applications in acoustic fish species echo classification has been highly requested. Therefore, the present paper is conceived to identify and scan the studies conducted on acoustic fish echo identification using deep learning and machine learning approaches. This document can be extended to include other marine organisms rather than just fish species. To search for related papers, we used a systematic approach to search the most known electronic databases over the last five years. We were able to identify 13 related works, which have been processed to give a summary of multiple deep and machine learning approaches used in acoustic fish species identification, and then compare their architectures, performances, and the challenges encountered in their applications.
Gas bubbles in the oceans can be detected by acoustic remote devices exploring the water column between the water‐atmosphere interface and the seafloor. It is admitted that natural seepage can be observed in most of sedimentary basins and continental shelves around the world. However, under certain temperature and pressure conditions, only a fraction of gas seepage areas can be directly associated with the presence of gas hydrate‐bearing sediments. Hence, the relationship between gas hydrates and the acoustic detection of gas bubbles in the water column may be mostly divided into several categories. Calibrated acoustic systems for amplitude associated with knowledge about the acoustic wave propagation environment enable quantitative measurements of the backscattered signals. Acoustic remote sensing has been used for almost a century for the detection of biological and non‐biological targets in the oceans.
The multi-frequency characteristics of anchovy schools were investigated using six acoustic lines collected at 38 and 120 kHz while a primary trawl survey was conducted from 14 April and 18 April of 2014 in off the coast of Tongyeong and Geo–je. Here, the frequency characteristics mean ΔMVBS that is the difference of Mean Volume Backscattering Strength at two frequencies. To use the characteristics effectively, the optimal cell size (10×2 m) was determined by examining several different cell sizes in consideration with the shapes of fish schools and the ΔMVBS pattern. By examining 6 histograms of ΔMVBS, afternoon groups were occupied more in the ΔMVBS range of –6~–4 dB than that of –4~–2 dB, comparing to morning groups. The ΔMVBS range of the morning groups was between –16.9 dB and 11.6 dB, and that of the afternoon groups –16.7 dB and 13.0 dB. The average and standard deviation were –3.9±3.6 dB in the morning and –4.1±3.4 dB in the afternoon, suggesting that morning groups were 2 dB higher than afternoon groups. The ΔMVBS range of all anchovy schools regardless of morning and afternoon was between –16.9 dB and 13.0 dB, their average ΔMVBS was –4.1±3.5 dB. The characteristics can support to identify anchovy species in the waters where multiple fish species are distributed. It is hoped that this study presents the availability and benefit of acoustic data from a primary trawl survey.
Acoustic survey methods are now widely used for stock assessments of finfish, both those with and without swimbladders, but their application to squid stocks has been limited in the past, probably because squid are not particularly strong targets for detection with echosounders. Experience with acoustic stock assessment of krill (Euphausia superba) has revealed that it is possible to survey effectively for a species that is a weaker target than squid; this is partly due to the tendency for krill to form dense aggregations. This paper discusses examples of acoustic studies on different squid species from the South Atlantic (Loligo gahi, Martialia hyadesi) and demonstrates that squid detection is possible in widely differing locations. L. gahi observed during a survey on the Falkland Shelf were shown to have acoustic characteristics in common with smaller organisms which may enable them to be distinguished acoustically from finfish encountered in these waters. When a species has been characterised acoustically, the technique permits rapid surveys of large areas to determine the geographic range of a population, both outside the usual area that can be surveyed using fishing methods and within areas that are inaccessible to nets for some reason.
Harmful algal blooms (HABs), commonly known as red tides, are aquatic phenomena caused by the rapid growth and accumulation of certain microalgae, which can lead to marked discoloration of surface waters, and severe impacts on public health, commerce, and the environment. In South Korea, the red tides have been a serious and recurrent problem, especially along the south coast. Plenty of yellow loess was used to control an outbreak of the red tides for 15 years from 1996 until now. Yellow loess was almost sprayed in the vicinity of a large fish farming industry. In this research, the distribution characteristics and density distribution of zooplankton were investigated in autumn (Oct. 2008) and spring (Apr. 2009) using volume backscattering strength (SV) calculated by the zooplankton collected with north pacific standard (NORPAC) net and the echo intensity measured with ADCP at stations on the study area in the spraying ocean of yellow loess (SOYL), and the non-spraying ocean of yellow ocean (NOYL) by the red tide generating every year. The species number and the individuals per unit volume of the zooplankton collected in NOYL was high and it which was collected in SOYL was low. As a result of comparing the volume backscattering strength (SVc) calculated by species and length of the zooplankton collected with NORPAC net with the volume backscattering strength (SVm) calculated by the echo intensity measured with ADCP at stations on the study area, although SVc and SVm of NOYL were generally in agreement, SVm of SOYL was higher than SVc 4. 3dB, i. e. ADCP is greatly influenced by suspended solid in SOYL. The horizontal distribution map of SVm at the study area in autumn (Oct. 2008) and spring (Apr. 2009) was drawn. SVm of SOYL is higher than NOYL and autumn is higher than spring. SVm can suppress the overestimate or underestimate of SVc.
The eastern Bering Sea shelf is a productive ecosystem with extensive commercial fisheries. Although the area is well-studied during summer months, little is known about the abundance and distribution of fish and macrozooplankton during periods of seasonal ice cover. The use of an icebreaker during the Bering Sea Ecosystem Study (BEST) provided a platform for spring acoustic surveys of fish and zooplankton in ice-covered areas for the first time. Icebreaker measurements were complemented with observations from conventional vessels during spring and summer. In spring, very little backscatter from fish (dominated by walleye pollock, Theragra chalcogramma) was observed in the ice-covered northern areas where near-bottom waters were cold (<∼0.5 °C), including areas where walleye pollock are abundant in summer. The majority of fish were observed within 40 km (and often slightly inside) the ice edge over similar seafloor depths as in summer. Together, these observations suggest that pollock, a dominant component of the ecosystem, shift their distribution to a more restricted geographic area in spring, following the ice edge southeast along the bathymetry, away from areas of cold water and extensive ice cover, then reoccupying these areas in summer. In contrast, acoustic backscatter attributed to zooplankton (likely dominated by euphausiids) was more evenly distributed, and less restricted by water temperature and ice cover. The implications of this seasonal shift in fish distribution are uncertain, but this may affect predator–prey interactions by reducing overlap of pollock with euphausiids, an important prey source, while increasing overlap of adult and juvenile pollock and potentially increasing cannibalism.
OBJETIVOS: O presente estudo tem como objetivo demonstrar as potencialidades da hidroacústica no estudo do comportamento do predador invertebrado Chaoborus e de peixes em ambientes aquáticos tropicais; MÉTODOS: Foram realizadas campanhas diurnas e noturnas em maio e junho/2008 nas lagoas Dom Helvécio e Carioca, no Parque Estadual do Rio Doce e no reservatório do Nado em Belo Horizonte (MG). O espalhamento acústico dos alvos foi estudado utilizando-se uma ecossonda com transdutor digital "split-beam" de 200 kHz direcionado verticalmente para o fundo do lago; RESULTADOS: A ecossondagem nos permitiu detectar eco-sinais claros provenientes de peixes e das larvas de Chaoborus, que estavam presentes grande densidade em todos os ambientes estudados. O comportamento migratório normal das larvas de Chaoborus pôde ser acompanhado facilmente na Lagoa Dom Helvécio e no reservatório do Nado. Entretanto, tal comportamento não foi visualizado na Lagoa Carioca. CONCLUSÕES: Os resultados mostrados neste estudo revelaram o potencial de aplicação da abordagem acústica no estudo do comportamento de peixes e organismos zooplanctônicos em sistemas aquáticos de água doce.
Reliable data on reef fishes inhabiting the southeastern United States (North Carolina to Florida) continental shelf large marine ecosystem are difficult to obtain; catch quotas and time and area closures limit the collection of fishery-dependent samples. Further, unbiased fishery-independent samples are expensive to collect with conventional fishing gear. Consequently, stock assessments are often data-limited, especially for deepwater reef species. We estimated the relative abundance of deepwater reef fish with a double sampling approach using fisheries acoustics and conventional fishing gear (hook and line and chevron traps). Double sampling occurred within the newly-created Snowy Wreck Marine Protected Area and a nearby control site. Reef fish concentrations were identified by a single-beam Simrad ES60 transceiver with a transducer operating at 38kHz. Hook and line samples were collected at 73 acoustic events, and chevron trap samples were collected at 20 acoustic events. The relationship between fisheries acoustic data and catch-per-unit-effort (CPUE) data was examined to develop a model to predict species-generic CPUE at unfished locations. Akaike's Information Criteria (AIC) found equal support for linear, exponential, and power relationships between acoustic backscatter and CPUE for each conventional fishing gear. Further model development would be aided by refining acoustic target information and applying complimentary fish sampling gears (i.e., split-beam fisheries acoustics gear, underwater video). Given further development, a double sampling design should be useful to estimate the relative abundance of important deepwater reef species over a wide area of the shelf break off the southeastern United States, utilizing either survey vessels or vessels-of-opportunity to rapidly collect acoustic samples.
The field of nekton and plankton acoustics is expanding with the development of new hardware and software and their applications. A symposium on nekton and plankton acoustics was held at the American Fisheries Society Annual Meeting in Monterey, CA, 1997. New and standardized measurement techniques to identify and classify nekton and plankton aggregations, and to estimate density, swimming speed and other target characteristics were presented. As the conservation community and the general public becomes more aware of the need to improve nekton and plankton measurement capability in fisheries science, there will be a growing demand for interdisciplinary research, development and education between the fields of physics and biology.
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