Estimates of density of mesopelagic fish in the Southern Ocean derived from bulk acoustic data collected by ships of opportunity

Escobar-Flores, Pablo C.; O’Driscoll, Richard L.; Montgomery, John C.; Ladroit, Yoann; Jendersie, Stefan

doi:10.1007/s00300-019-02611-3

Cited by 28 publications

(24 citation statements)

References 55 publications

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“…Our results highlight a general different pattern among these tools, not only in the absolute biomass estimates but also in the temporal and spatial distribution. These two models are commonly used to assess species distributions in both marine and terrestrial realms (e.g., Moisen et al, 2006;Rooper et al, 2017;Kosicki, 2020), however RF models have been seen to have substantially more performance power and control over the model overfitting compared to GAM approaches (Elith et al, 2006;Rooper et al, 2017), as it is also shown in this study. This is likely because of the RF algorithm, which is an ensemble of models (regression trees), each built on a random selection of relatively few predictors (Breiman, 2001).…”

Section: Data Quality and Model Performancementioning

confidence: 60%

Spatial Distribution and Abundance of Mesopelagic Fish Biomass in the Mediterranean Sea

et al. 2020

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Mesopelagic fish, being in the middle of the trophic web, are important key species for the marine environment; yet limited knowledge exists about their biology and abundance. This is particularly true in the Mediterranean Sea where no regional assessment is currently undertaken regarding their biomass and/or distribution. This study evaluates spatial and temporal patterns of mesopelagic fish biomass in the 1994–2011 period. We do that for the whole Mediterranean Sea using two well-established statistical models, the Generalized Additive Model (GAM) and Random Forest (RF). Results indicate that the bathymetry played an important role in the estimation of mesopelagic fish biomass and in its temporal and spatial distribution. The average biomass over the whole time period reached 1.08 and 0.10 t/km2, depending on the model considered. The Western Mediterranean and Ionian Seas were the sub-regions with the highest biomass, while the Adriatic was the area with the lowest. Temporal trends showed different trajectories with steep decrease and a fluctuation, using respectively RF and GAM. This study constitutes the first attempt to estimate the biomass and the spatial temporal patterns of mesopelagic fish using environmental variables as predictors. Given the growing interest in mesopelagic fish, our study sets a baseline to further develop mesopelagic fish biomass assessments in the region. Our results stress the need to improve data collection and quality in the region while identifying appropriate tools to better understand and assess the processes behind mesopelagic fish dynamics in the basin.

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Section: Data Quality and Model Performancementioning

confidence: 60%

Spatial Distribution and Abundance of Mesopelagic Fish Biomass in the Mediterranean Sea

et al. 2020

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“…At mesopelagic depths, echosounders operating at 38 kHz are well-suited to detect larger organisms in the 2-20 cm size range that bear air inclusions, such as swim-bladders 30 and pneumatophores 31 . Previous studies have also reported low overall backscatter in poleward mesopelagic ecosystems 22,24,32,33 , however the use of strictly low-frequency measurements can be biased by changes in scattering properties of fish 33 . Therefore, to detect weakly scattering organisms, we compiled backscatter profiles at higher frequency and closer range using 150 kHz and 300 kHz lowered acoustic Doppler current profilers (LADCP) (Figure 2).…”

Section: Main Textmentioning

confidence: 95%

“…As a first order approximation, biomass of mesopelagic organisms should scale with energy input to the mesopelagic zone. However, research on mesopelagic macrozooplankton and micronekton has mainly focused on low-or mid-latitude systems 19,20 and knowledge of their vertical structure and effect on carbon fluxes at high latitudes remains scarce [21][22][23][24][25] . Scientific echosounders are frequently used to map mesopelagic deep-scattering layers (DSL).…”

Section: Main Textmentioning

confidence: 99%

The transformation of mesopelagic structure across polar fronts

Chawarski¹,

Klevjer²,

Côté³

et al. 2021

Preprint

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The oceans sequester 31% of atmospheric carbon annually 1, but the magnitude of biologically enhanced sequestration is not evenly distributed across the globe 2. Measuring surface primary productivity offers a reasonable proxy for estimating carbon flux into the ocean 3 but entirely misses the processes that affect carbon export to sequestration depths. A high proportion of carbon flux is broken up 4 or respired 5 by organisms at mesopelagic depths (200-1000 m). At low and mid-latitudes, daytime biomass peaks of mesopelagic organisms are clearly present and detectable as sound-scattering layers, and up to 40% of oceanic carbon passes through these layers 6,7. Here we demonstrate that acoustic backscatter, a proxy for abundance of mesopelagic fish and zooplankton decreases by up to 97% across polar fronts, revealing a distinct pelagic structure in high latitude systems. As mesopelagic fish and macrozooplankton comprise a large component of active carbon transport in the upper ocean, this latitudinal reduction in mesopelagic biomass across thermal fronts, in both the Arctic and Antarctic, suggests different carbon flux attenuation schemes exists in ocean twilight zones of polar ecosystem compared to low latitude systems. Rapid ocean warming projected at mesopelagic depths8 will likely disrupt vertical connectivity and alter biogeochemical cycles at high latitudes.

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“…To define the size range of mesopelagic fish, we used the minimum and maximum recorded sizes from three datasets of mesopelagic fish length-weight measurements (85)(86)(87). The combined datasets contained samples from the trophic and equatorial Atlantic as well as the Southern Ocean and gave a body size range of 0.01-500gm for mesopelagic fish.…”

Section: Mesopelagicsmentioning

confidence: 99%

The global ocean size-spectrum from bacteria to whales

Hatton

Heneghan

Bar-On

et al. 2021

Preprint

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It has long been hypothesized that aquatic biomass is evenly distributed among logarithmic body mass size-classes. Although this community structure has been observed locally among plankton groups, its generality has never been formally tested across all marine life, nor have its impacts by humans been broadly assessed. Here, we bring together data at the global scale to test the hypothesis from bacteria to whales. We find that biomass within most order of magnitude size-classes is indeed remarkably constant, near 1 Gt wet weight (10^15 grams), but that bacteria and whales are markedly above and below this value, respectively. Furthermore, human impacts have significantly truncated the upper one-third of the spectrum. Size-spectrum theory has yet to provide an explanation for what is possibly life's largest scale regularity.

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Estimates of density of mesopelagic fish in the Southern Ocean derived from bulk acoustic data collected by ships of opportunity

Cited by 28 publications

References 55 publications

Spatial Distribution and Abundance of Mesopelagic Fish Biomass in the Mediterranean Sea

Spatial Distribution and Abundance of Mesopelagic Fish Biomass in the Mediterranean Sea

The transformation of mesopelagic structure across polar fronts

The global ocean size-spectrum from bacteria to whales

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