Acoustic detection of mesopelagic fishes in scattering layers of the Balearic Sea (western Mediterranean)

Peña, Marian; Olivar, M. Pilar; Balbín, Rosa; López-Jurado, José Luís; Iglesias, M.; Miquel, Joan

doi:10.1139/cjfas-2013-0331

Cited by 59 publications

(40 citation statements)

References 51 publications

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“…Mid-and deep-water (400-800 m) catches were largely dominated by Cyclothone spp., a group of non-migratory mesopelagic fish very abundant worldwide (Nelson, 2006). Most Cyclothone species are strong scatterers at the 38 kHz frequency (Peña et al, 2014;Ariza et al, 2016) and this group likely was the major source of the day and nighttime backscatter over seamount slopes and in open-waters. Another important contributor to the backscatter outside the summits may be A. hemigymnus, also known to reside at depth all day long (Peña et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…Most Cyclothone species are strong scatterers at the 38 kHz frequency (Peña et al, 2014;Ariza et al, 2016) and this group likely was the major source of the day and nighttime backscatter over seamount slopes and in open-waters. Another important contributor to the backscatter outside the summits may be A. hemigymnus, also known to reside at depth all day long (Peña et al, 2014). Myctophids (especially Lobianchia dofleini, Diaphus rafinesquei, and Lampanyctus pusillus) were the second most abundant group overall but the first in shallow waters at night (Porteiro et al, 2011), consistent with their well-known DVM (Sutton, 2013).…”

Section: Discussionmentioning

confidence: 99%

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Persistent Enhancement of Micronekton Backscatter at the Summits of Seamounts in the Azores

et al. 2017

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Knowledge of the dynamics of micronekton at seamounts is critical to understanding the ecological role of these ecosystems. Active acoustic techniques are an effective tool to monitor the distribution and movements of pelagic organisms. We carried out several day-and nighttime active acoustic surveys over a 3-year period (2009)(2010)(2011) to characterize the spatial and temporal distribution of micronekton backscatter on two seamounts (Condor and Gigante) in the Azores and in the surrounding open-waters. The highest mean volume backscattering strength (MVBS) was consistently found in the water column over the seamount summits, regardless of the season and diel period. MVBS over the summits was 14-26 times higher than over the slopes, and 10 times higher than in open-waters. Diel variations in backscatter intensity were more pronounced in open-waters and in Gigante seamount, with higher values during the day in open-waters, and at night over the summits and slopes of Gigante. Over Condor seamount, diel changes in backscatter intensity were small, but MVBS was generally higher at night than during the day, as in Gigante. Persistence of strong acoustic backscatter over the summits of Condor and Gigante seamounts is a key finding of this study and may be explained by the presence of a seamount-associated micronekton community and by the retention of vertically migrating micronekton. The latter hypothesis is consistent with observed day-night differences in backscatter, suggesting that nocturnal migrants may be passively transported or actively swim above seamount summits and slopes. Possible physical mechanisms leading to the observed patterns in micronekton distribution are discussed. This study contributes to a better understanding of how seamounts may influence the spatial and temporal dynamics of micronekton assemblages.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Persistent Enhancement of Micronekton Backscatter at the Summits of Seamounts in the Azores

et al. 2017

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“…We acknowledge that our assumption of equal catchability, based on the use of a consistent gear and assuming that the species' behavior and vertical distribution are unlikely to have changed between voyages, is a great simplification. Small and/or gelatinous organisms may not be retained by trawls (e.g., Gartner et al, 1989;Peña et al, 2014), and larger fish may avoid nets (Davison et al, 2015). This is one reason why our training dataset was small.…”

Section: Mark Classificationmentioning

confidence: 99%

“…Lanternfishes (Myctophidae) and the sternoptychid Maurolicus australis (Sternoptychidae) are commonly collected in the mid-water trawls and dominate the biomass of mesopelagic fish on the Chatham Rise (Robertson et al, 1978;McClatchie and Dunford, 2003;O'Driscoll et al, 2009;Gauthier et al, 2014;Escobar-Flores et al, 2018). Usually underrepresented in trawl catches due to their small size (i.e., Peña et al, 2014), the bristlemouth Cyclothone spp. (Gonostomatidae), regarded as the most numerically abundant oceanic vertebrate globally (Gjøsaeter and Kawaguchi, 1980), is also likely to be an important component of the micronekton on the Chatham Rise.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Assessment of the Micronekton Community on the Chatham Rise, New Zealand, Using a Semi-Automated Approach

2019

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Micronekton are a key component of the pelagic food web of the Chatham Rise east of New Zealand. The Chatham Rise is an important fishing area for hoki (Macruronus novaezelandiae), New Zealand's largest finfish fishery, and a predator on mesopelagic fish. Four fisheries oceanographic voyages provided multi-frequency acoustic data (18, 38, 70, 120, and 200 kHz) and midwater trawls, which were used to define a classification tree to separate micronektonic organisms. We carried out validation and sensitivity analyses that showed that we were able to classify pearlside (Maurolicus australis) and euphausiids. Other mesopelagic targets (mainly myctophids) were classified together based on their acoustic frequency response. Using scripting in the open-source software ESP3, we applied our classification tree to an independent time series of acoustic data from trawl surveys on the Chatham Rise between 2009 and 2018, that was not used for model development or validation. Our methodology allowed us to study temporal and spatial patterns of M. australis, euphausiids, and total backscatter in the water column. Total backscatter associated with micronekton has varied over the last 10 years, with no clear trend. The abundance of euphausiids showed a significant decreasing trend over the last 10 years. Abundance of M. australis also decreased since 2012, though this was not significant. This work contributes to ongoing efforts to monitor and detect changes in the pelagic ecosystems.

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“…The importance of these factors in structuring sound scattering layers can vary and is dependent on the location, community dynamics, and physical setup of the oceanic system. For example, the processes that structure high-latitude systems may vary in scale relative to mid-latitude or tropical systems (Godø et al, 2012;Peña et al, 2014;Røstad et al, 2016;Aksnes et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Oceanographic Structure and Light Levels Drive Patterns of Sound Scattering Layers in a Low-Latitude Oceanic System

et al. 2020

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Several factors have been reported to structure the spatial and temporal patterns of sound scattering layers, including temperature, oxygen, salinity, light, and physical oceanographic conditions. In this study, we examined the spatiotemporal variability of acoustically detected sound scattering layers in the northern Gulf of Mexico to investigate the drivers of this variability, including mesoscale oceanographic features [e.g., Loop Current-origin water (LCOW), frontal boundaries, and Gulf Common Water]. Results indicate correlations in the vertical position and acoustic backscatter intensity of sound scattering layers with oceanographic conditions and light intensity. LCOW regions displayed consistent decreases, by a factor of two and four, in acoustic backscatter intensity in the upper 200 m relative to frontal boundaries and Gulf Common Water, respectively. Sound scattering layers had greater backscatter intensity at night in comparison to daytime (25x for frontal boundaries, 17x for LCOW, and 12x for Gulf Common Water). The importance of biotic (primary productivity) and abiotic (sea surface temperature, salinity) factors varied across oceanographic conditions and depth intervals, suggesting that the patterns in distribution and behavior of mesopelagic assemblages in low-latitude, oligotrophic ecosystems can be highly dynamic.

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Acoustic detection of mesopelagic fishes in scattering layers of the Balearic Sea (western Mediterranean)

Cited by 59 publications

References 51 publications

Persistent Enhancement of Micronekton Backscatter at the Summits of Seamounts in the Azores

Persistent Enhancement of Micronekton Backscatter at the Summits of Seamounts in the Azores

Acoustic Assessment of the Micronekton Community on the Chatham Rise, New Zealand, Using a Semi-Automated Approach

Oceanographic Structure and Light Levels Drive Patterns of Sound Scattering Layers in a Low-Latitude Oceanic System

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