WP3.1 TS equations for anchovy and sardine

Lead participant: IEO Magdalena Iglesias

Harmonization of the acoustic methodology in Harmonization of the acoustic methodology in terms of applied TS equations for anchovy and terms of applied TS equations for anchovy and

sardine sardine

Currently applied TS equations in Currently applied TS equations in Aegean SeaAegean Sea

Aegean Sea

Anchovy -71.2

Sardine -72.6

No TS equations available based on in situ estimations with the split beam method

Data requirements for Data requirements for in situin situ TS TS estimationestimation

Appropriate TS detection parametersAppropriate TS detection parameters Fish communities scattered enough to Fish communities scattered enough to

limit multiple targets detectionlimit multiple targets detection Roughly monospecific fish Roughly monospecific fish

assemblagesassemblages Distinct length modesDistinct length modes Relationship between modes in TS Relationship between modes in TS

distribution to catches distributiondistribution to catches distribution

HCMR data for in situ TS equationsHCMR data for in situ TS equations

Night trawling 2004-nowNight trawling 2004-now Echoes were collected during trawlingEchoes were collected during trawling 172 trawls in total172 trawls in total 66 cases >90% anchovy by weight66 cases >90% anchovy by weight 12 cases >90% sardine by weight12 cases >90% sardine by weight 92 cases where 1 dominant species occurs 92 cases where 1 dominant species occurs

either anchovy or sardine >60% by weighteither anchovy or sardine >60% by weight The majority refers to 38kHz with 23 referring to The majority refers to 38kHz with 23 referring to

120 kHz120 kHz

Issues for discussionIssues for discussion

Harmonize the analysis up to the maximum Harmonize the analysis up to the maximum degree possibledegree possible

Propose possibly the same software for all Propose possibly the same software for all studiesstudies Myriax EchoviewMyriax Echoview Movies + (Ifremer Data)Movies + (Ifremer Data)

Decide on a common protocol for analysis that Decide on a common protocol for analysis that will facilitate comparisons and increase the will facilitate comparisons and increase the credibility of our workcredibility of our work

Ideas-Suggestions on hauls Ideas-Suggestions on hauls selectionselection

Night hauls preferablyNight hauls preferably Monospecific hauls >90% or >85% by weightMonospecific hauls >90% or >85% by weight Having an idea on the mean TS per species if Having an idea on the mean TS per species if

possible from monospecific hauls thenpossible from monospecific hauls then

In the case of discrete TS and Length modes In the case of discrete TS and Length modes also hauls with 2 species and less percentage also hauls with 2 species and less percentage can potentially be usedcan potentially be used

Single target selection parametersSingle target selection parameters

Pulse lengthPulse length Min TS thresholdMin TS threshold Max gain compensationMax gain compensation Max phase deviationMax phase deviation Min echo lengthMin echo length Max echo lengthMax echo length

TS Detection Parameter Recommended valuesPulse length 0.5 msMin TS threshold 0.8Max gain compensation 1.8Max phase deviation -60 dbMin echolength 6 dBMax echolength 4 to 8

Suggested by WGACEGG 08Suggested by WGACEGG 08

Fish Track detection algorithmFish Track detection algorithmEchoview’s default alpha and beta values, which define the algorithm’s Echoview’s default alpha and beta values, which define the algorithm’s

sensitivity to unpredicted changes in the target’s position and sensitivity to unpredicted changes in the target’s position and velocity, can be used because there was no a priori information on velocity, can be used because there was no a priori information on variability in anchovy or sardine swimming behaviourvariability in anchovy or sardine swimming behaviour

- Track Detection

Major axisMajor axis Minor axisMinor axis RangeRange

AlphaAlpha 0.70.7 0.70.7 0.70.7

BetaBeta 0.50.5 0.50.5 0.50.5

- Target gates

Major axisMajor axis Minor axisMinor axis RangeRange

Exclusion Exclusion distance (m)distance (m)

44 44 0.40.4

Missed ping Missed ping expansion (%)expansion (%)

00 00 00

WeightWeight 3030 3030 4040

Moreover….Moreover….Are there any available acoustic data prior or after trawling ? Are there Are there any available acoustic data prior or after trawling ? Are there cases where two hauls are applied to the same echogram? Decide on cases where two hauls are applied to the same echogram? Decide on the approach to followthe approach to follow

Acoustic Target Selection for analysis: Entire water column or based Acoustic Target Selection for analysis: Entire water column or based on the hauling depth?on the hauling depth?

Filtering based on Filtering based on Tortuousity Tortuousity : :

is used to measure the linearity of a target’s swimming path. A perfectly is used to measure the linearity of a target’s swimming path. A perfectly linear track is indicated by a tortuosity value of one. To ensure that linear track is indicated by a tortuosity value of one. To ensure that tracks were derived from a single individual and not multiple fish in close tracks were derived from a single individual and not multiple fish in close proximity, any track with a tortuousity value greater than 1.2 was proximity, any track with a tortuousity value greater than 1.2 was excluded from analysis.excluded from analysis.

Density filtering:Density filtering:

Can we set a certain echo density above which we assume high Can we set a certain echo density above which we assume high occurrence of multiple echoes and overestimation of TS, therefore we do occurrence of multiple echoes and overestimation of TS, therefore we do not consider these areas/ hauls? not consider these areas/ hauls?

•Barange & Soule 1996: 1 target per sampled volumeBarange & Soule 1996: 1 target per sampled volume

•Ona & Barange 1999: Ona & Barange 1999: N of 0.03/m3 corresponds to only a one N of 0.03/m3 corresponds to only a one percent probability of multiple targets detected within the sample percent probability of multiple targets detected within the sample volume.volume.

Regression analysisRegression analysis

Previous studies have primarily used two methods to regress Previous studies have primarily used two methods to regress target strength and length: target strength and length:

• the average target strength (Foote, 1980b; Miyanohana the average target strength (Foote, 1980b; Miyanohana et al., 1990).et al., 1990).

Suggested Total Length bin range for analysis : 0.5 cm, L-W Suggested Total Length bin range for analysis : 0.5 cm, L-W relationship to be estimatedrelationship to be estimated

Use mean TL per haul (weighted with total abundance per Use mean TL per haul (weighted with total abundance per hour sampling hour if more than 2 hauls are assigned to 1 hour sampling hour if more than 2 hauls are assigned to 1 echogram)echogram)

Two regressions can be conducted for each data set: Two regressions can be conducted for each data set:

• 1) best-fit, and 1) best-fit, and

• 2) a slope forced to 20 (Foote, 1979). 2) a slope forced to 20 (Foote, 1979). Can we apply both and use a t-test (Can we apply both and use a t-test (αα=0.05) to test whether =0.05) to test whether

slopes of the best-fit regressions are significantly different slopes of the best-fit regressions are significantly different from 20.from 20.

Regression fit will be evaluated based on least squaresRegression fit will be evaluated based on least squares

Agree on common TS analysis export parametersAgree on common TS analysis export parameters

Decide on a minimum of parameters of TS export Decide on a minimum of parameters of TS export in order to be able to post-process output and in order to be able to post-process output and apply some filtering if necessaryapply some filtering if necessary

Agree on a common table to present resultsAgree on a common table to present results

Planning of workPlanning of work Kick off meeting (March 2010)Kick off meeting (March 2010) First results of biomass estimates with different First results of biomass estimates with different

TS equationsTS equations First results of TS estimates per areaFirst results of TS estimates per area Joint TS estimation (November 2010)Joint TS estimation (November 2010) Interim Report (beginning March 2011)Interim Report (beginning March 2011) Biomass estimates with agreed TS equationsBiomass estimates with agreed TS equations Suggestions, AdviceSuggestions, Advice Final Report (beginning March 2012)Final Report (beginning March 2012)