http://www.mesopp.eu/
Title
Name (affiliation)Name (affiliation)
Linking the mesopelagic components of ecosystem models
to acoustic vertical echosounder observations
Roland Proud1*, Martin J. Cox2, Rudy Kloser3, Nils Olav Handegard4, & Andrew S. Brierley1
1Pelagic Ecology Research Group, Scottish Oceans Institute, Gatty Marine Laboratory, University of St Andrews, UK, 2Australian Antarctic Division, Kingston, Tasmania, Australia, 3CSIRO Oceans and Atmosphere Flagship, GPO Box 1538, Hobart, TAS
7001, Australia, 4Institute of Marine Research, PO Box 1870, Nordnes, 5817 Bergen, Norway.
©MESOPP consortium
Modelling Ecosystems
• Food-web models e.g. Size-based models (figure; Blanchard et al. 2009, 2011, 2012).• End-to-end models e.g. Atlantis.• Habitat models.
Framework for open ocean ecosystem monitoring with acoustics – integrated with ecosystem models
Fish and Fisheries 2012
©MESOPP consortium
Mesopelagic component
• Formed of nekton and zooplankton.• Resides between 200 and 1000m during the daytime.• Migrates daily to feed at the surface at night (Diel Vertical Migration; DVM).• DVM facilitates the biological carbon pump.
©MESOPP consortium
Uncertainty
Estimates of global (open-ocean) mesopelagic fish biomass1 Gt Gjoseter and Kawaguchi (1980) Ocean trawl data14.3 to 19.5 Gt Irigoien et al. (2014) Acoustics< 1.4 Gt Jennings and Collingridge (2015) Macroecological model2.4 Gt Anderson et al. (2018) Food-web model1.8 to 16 Gt Proud et al. (2018) Acoustics
• Tropic efficiency may vary between 5 and 20% per trophic level.• Most ecosystem models do not account for this variability.• We need to use observations to validate mesopelagic component of
ecosystem models…Picture from Acoustic Laboratory for Ecological Studies (http://aleslab.blogspot.co.uk/2012/08/)
©MESOPP consortium
Acoustic Observations (IMOS)
Public data since 2010
16 vessels monitored
8 produce >80% of data
6 of these fishing vessels~ 300,000 km – focus multi-frequency vessels at 18 and 38 kHz
www.imos.org.au
©MESOPP consortium
Acoustic-Ecological Model reference data set most at 38 kHz
http://www.mesopp.eu/data/catalogue/Following ICES standardised metadata format for acoustic data
©MESOPP consortium
Acoustic selectivity at 38 kHz
Gas-bladdered fish and siphonophores are the dominant sources of backscatter in the mesopelagic zone.
Factor of 30 Factor of 1000
©MESOPP consortium
Acoustic observation model
Predict acoustic signal from output of ecosystem models and then compare to acoustic observations.
Group 1
Group 1
Group 2
Ecosystem
©MESOPP consortium
Predicting acoustic signal
To predict acoustic backscatter (sa, area-backscattering coefficient) from ecosystem model output we need to know the size and depthdistributions of the group and also the proportion of the group that have gas bladders:
sa ≅Abundance × proportion × 10 TS(size, depth) 10
Area
Where TS is the mean target strength of gas bladders and the area is specified by the ecosystem model. This can then be compared to acoustic observations:
sa = 200
1000
svdz ,
Where sv is volume backscattering coefficient and z is depth.
©MESOPP consortium
Predicting acoustic signal
Where that information is not output from the ecosystem model, we use values taken from the literature:
Size
range
(mm)
Depth
range
(m)
Orientation Gas-
bladder
volume (%
of body
volume)
Length-
width
ratio
Proportion
with gas-
bladders
Fish 20-
300R1
200-
1000
N(0,30) 0.01-2.63R3 4-12R4 0-1
Siphonophore
pneumatophore
0.01-
40R2
200-
1000
N(0,30) NA NA 0-1
R1: www.fishbase.orgR2: (Barham 1963, Robison et al. 1998, Lavery et al. 2007)R3: (Yasuma & Yamamura 2010)R4: (Flynn et al. 2012)
©MESOPP consortium
Predicting acoustic signal
We also need to consider spatial and temporal resolutions of ecosystem models:
Scale Atlantis Ecopath
(high
latitude)
Ecopath
(Kerguelen)
SEAPODYM MIZER WOMBAT
Space Multiple
irregular
polygons
Single
region
Single region Various
(0.08°- 2°)
2 boxes Various
(0.1-1°)
Depth 10 depth
layers
NA NA 6 depth
layers based
on euphotic
depth
NA 2 depth
layers
Time User defined
(e.g. 12
hours,
monthly,
annually)
Monthly Monthly 7 days Various
(weekly,
monthly,
annual)
Various
(weekly,
monthly,
annual)
Large spatial and temporal extent require more acoustic data
©MESOPP consortium
Acoustic observation model
Acoustic observations can be partitioned into groups (e.g. anatomical). Multi-frequency methods
Group 1
Group 2
Frequency 1
Frequency 2
Faculty of Edit this on the Slide Master The University of Adelaide
Vessel acoustics pelagic habitat, what biologically
does this represent?
38 kHz
18 kHz
18 kHz >>
38 kHz
Highly
influenced by
resonance
scattering by
depth
18kHz <<
38 kHz
©MESOPP consortium
Summary
• We can validate the mesopelagic components of ecosystem models by converting predicted abundance/biomass to acoustic signal and comparing to echosounder observations i.e. Acoustic Observation Model.
• To convert model output to acoustic signal, we need information concerning the size and depth distribution of the group and also the proportion that have gas bladders.
• Information that is not provided by the ecosystem model can be obtained elsewhere (e.g. literature and catch data).
• We can use archived echosounder observations e.g. IMOS (www.imos.org.au) and MESOPP (www.mesopp.eu) to make the comparison – particularly at multi-frequencies.
• Partitioning echosounder observations into different anatomical groupings may help reduce uncertainty in the Acoustic Observation Model.