improving empirical ground truthingfor interpreting

Improving empirical ground

truthing for interpreting

plankton echoes

M. Iglesias, J. Miquel & A. Castellón

Instituto Español de Oceanografía.- Centro Oceanográfico de Baleares

Instituto de Ciencias del Mar, CSIC.

IDEADOS PROJECT Final Meeting

Palma de Mallorca, Spain 14-17 November 20121

The IDEADOS project has applied a multidisciplinary

approach on the dynamics of deep water exploited

ecosystems in the Balearic Islands.

For that reason, this project has expanded the study to

the pelagic domain, on which deep ecosystems of the

Balearic Islands seem to depend, implementing

acoustic technology.

Here we present two softwares, developed during this

project, that improves 1)the accuracy of the acoustic

samplers (e.g. pelagic trawl) and 2)the post-process of

the acoustic data. 2

Fisheries acoustics•Fisheries acoustics focus principally in post-

larval teleost fish (i. e. sardine, anchovy, etc).• Continental shelf (20-200 m depth).•During the day, when pelagic species formschools.•Echosounder detect echotraces (i.e. schools)

•Schools are identified by means of a pelagictrawl.• A netsonder is used to determine the geometryof the gear.

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120 kHz

200 kHz

38 kHz

12 kHz

70 kHz

18 kHz

ME70

The use of several frequencies,

together with the correct location

of the transducers (coincident

beams), permits the processing of

acoustic data and to develop

algorithms to obtain masks or

virtual echograms to identify

species.

Multifrequencies

4

The application of acoustic techniques to biological

oceanography involves three primary tasks:

1. Collection and standardization of the acoustic

measurements (obtaining an accurate measurement of

acoustic backscatter from a volume of water or an

individual target)

2. Target identification (knowing what type of target(s)produced the backscatter), and

3. Based on the above knowledge, scaling of the acoustic

measurements to abundance or biomass of the target

population(s) present in each acoustically-sampled volume.

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Ground truthing echotraces

•Anchovy schools near de bottom (80 m depth), day time.

•Plankton layer (40 m depth)

•Continental shelf.

•Threshold -70 dB.

•Netsonder.

6

Netsonder: Simrad FS20/25

Helps to define the geometry of the gear (pelagic trawl).

7

Netsonder: Simrad FS20/25

Vertical presentation Horizontal presentation

8

Helps to define the geometry of the gear (pelagic trawl).

IDEADOS project: Plankton acoustics

• The plankton: less important in economic terms, but theyare central to ecological research, being at or near thebottom of the food chain.

• Micronekton: small actively swimming organisms rangingin size between plankton (< 2 cm) and larger nekton (> 10cm).

• Micronekton: operationally defined as taxa too agile to becaught with conventional plankton nets and too small to beretained by most large-meshed trawls.

• Principal groups: fishes (mainly mesopelagic species),crustaceans (euphausiids, pelagic decapods and mysids),and cephalopods (small species and juvenile stages of largeoceanic species).

9

IDEADOS surveys• 2 multidisciplinary surveys: December 2009; July 2010.

• R/V Sarmiento de Gamboa.

• Silent ship (according to the ICES CRR 2009).

• Scientific echosounder EK60 (Simrad) equipped with 5 frequencies: 18, 38, 70, 120 and 200 kHz.

• Pelagic trawl gear:15m opening.

• Netsonder: FS20/25 (Simrad); trawl eye (Scanmar).

Goal: to identify the pelagic

layers: Deep Scattering

Layer (DSL) and Benthic

Boundary Layer (BBL).

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Echogram: Plankton layers

-Deeper waters

(1000 m)

-Different plankton

layers (surface,

DSL, BBL).

- Layers: 300- 400

m width

-Small organisms

-Low density.

-35 pelagic hauls18

kHz

38

kHz

70

kHz

11

Diversity of life forms considered as

micronekton.

Vertical distribution, diversity and assemblages of mesopelagic fishes in the western

Mediterranean.M.P. Olivar, A. Bernal, B. Molí, M. Peña, R. Balbín, A. Castellón, J. Miquel, E. Massutí. Deep-Sea Research I 62 (2012) 53–69.

Influence of external variables in the distribution of the Deep Scattering Layers off

Mallorca.M. Peña, M.P. Olivar, R. Balbin, J.L. Lopez-Jurado, M. Iglesias, J.Miquel. Submitted

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Target identification: where do we have to fish? In the denser areas.

Two software's have been developed duringthe IDEADOS project.

1. TKM software permits to see on the EK60screen the depth of the pelagic trawl.

2. GORI software allows to create a evl datafile with the depth of the pelagic trawl, thatcan be imported into the Echoview file.

Goal: to improve the accuracy of theground truthing.

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The EK60 scientific echosounder is able to receive and

transmit messages on serial lines or ethernet, all based

on the NMEA 0183 code.

NMEA 0183 is a combined electrical and data

specification for communication between marine

electronic devices.

Trawl eye (Scanmar) EK60 echosounder 14

Trawl eye (Scanmar) is able to send string datagrams

(pressure data) to the EK60 echosounder. It is

necessary to translate them into ITI string datagrams

by means of a software (TKM).

The EK60 receives the datagrams and include them

into the raw file. The string is written into the RAW

file.

Trawl eye (Scanmar) EK60 echosounder15

Result: we are able to observe on the EK60 screen the

track of the pelagic trawl (during the survey).

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Post processing of the acoustic data• Acoustic data are stored in raw format and they are processed

with the software Echoview (Myriax Ltd).

• The ITI string doesn't get automatically read by Echoview whenyou read a RAW file.

• A software has been developed (Gori) to localize the NMEAsentences in the raw file, obtain the pressure data (=depth), andconvert them into an evl file. EVL files are structured text datafiles.

• The evl file can be imported into the Echoview file (ev) to createa virtual line = the haul track.

• That makes possible to work on the echogram and integrateexactly the volume of water fished by the pelagic trawl.

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Example of a raw

data file generated

by the EK60

echosounder.

NMEA sentences

define the depth of

trawl below surface:

$IIDBS (pressure

sensor).

The software finds

the sentence and

creates an evl file.

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EVBD 3 3.50.57.3955

3939

20091207 1537114545 179.63 1

20091207 1537186576 180.75 1

20091207 1537258607 182.06 1

20091207 1537330638 183.5 1

20091207 1537402670 185.88 1

20091207 1537474701 186.19 1

20091207 1537546732 188.44 1

20091207 1538090795 191 1

20091207 1538162826 191.94 1

20091207 1538234857 193.25 1

20091207 1538306888 195.19 1

20091207 1538378920 195.69 1

20091207 1538522982 198.69 1

20091207 1538595013 200.06 1

20091207 1539067045 200.81 1

20091207 1539139076 202.88 1

20091207 1539211107 204.44 1

20091207 1539283138 205.56 1

20091207 1539355169 206.81 1

20091207 1539427201 208.13 1

20091207 1539499232 210 1

20091207 1540043295 211.69 1

20091207 1540115326 212.19 1

20091207 1540187357 214.31 1

20091207 1540259388 216.06 1

20091207 1540331420 216.88 1

20091207 1540403451 218.06 1

20091207 1540475482 218.88 1

20091207 1540547513 221.75 1

20091207 1541019545 222.38 1

evl file (datetimefile)

Every line includes

date and time

records with an

associated depth.

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The evl file can be imported into the Echoview file (ev) and create a

virtual line = the haul track. Moreover, another virtual line is created

to define the opening of the gear (e.g. 15 m, 30 m).

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TKM software

21

Raw file

EK60 ECHOSOUNDER

GORI software

EVBD 3 3.50.57.3955

3939

20091207 1537114545 179.63 1

20091207 1537186576 180.75 1

20091207 1537258607 182.06 1

20091207 1537330638 183.5 1

20091207 1537402670 185.88 1

20091207 1537474701 186.19 1

20091207 1537546732 188.44 1

20091207 1538090795 191 1

20091207 1538162826 191.94 1

20091207 1538234857 193.25 1

20091207 1538306888 195.19 1

20091207 1538378920 195.69 1

20091207 1538522982 198.69 1

20091207 1538595013 200.06 1

20091207 1539067045 200.81 1

20091207 1539139076 202.88 1

20091207 1539211107 204.44 1

20091207 1539283138 205.56 1

20091207 1539355169 206.81 1

20091207 1539427201 208.13 1

20091207 1539499232 210 1

20091207 1540043295 211.69 1

20091207 1540115326 212.19 1

20091207 1540187357 214.31 1

20091207 1540259388 216.06 1

20091207 1540331420 216.88 1

20091207 1540403451 218.06 1

20091207 1540475482 218.88 1

20091207 1540547513 221.75 1

20091207 1541019545 222.38 1

Evl file22

Summary• The acoustic monitoring, along with the use of depth sensors (e.g.

trawl eye) used with fishing or plankton nets (e.g. pelagic trawl,MTN, Bongo…), allows better monitoring and determination of thedepths of the catches, optimizing the work of the nets used.

• The implementation of the track of the sampler (e.g. pelagic nets) inthe Echoview file allows to integrate the water volume fished by thetrawl and permits:

– Calculate the volume of water filtered by the net

– Compare the sv (mean scattering value) with the density (catches),to see the goodness of the sampler (in process, myctophids andkrill).

– Estimate “in situ” target strength measurements of mesopelagicfish and krill. Such measurements are few and new results couldimprove the precision in acoustic estimates of the biomass of thesespecies.

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This technology has yet been

successfully applied in other surveys

• CRAMER project: Looking for hake larvae.

Systematic grid,

MultiNet

Positive stations (1

hake larvae).

Adaptive sampling

Bongo 60, 9030

This technology has yet been

successfully applied in other surveys

• MEDIAS project: acoustic Mediterranean

project: identifying the plankton layer

(ecosystem indicator).

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improving empirical ground truthingfor interpreting

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