Antolínez, A. (Ana)

Carrera, P. (Pablo)

Dueñas-Liaño, C. (Clara)

Garrido-Faustino, S. (Soledad)

Soares, E.

Villamor, B. (Begoña)

English

Villamor, Begoña

Garrido-Faustino, Soledad

Carrera, Pablo

Antolínez, Ana

Dueñas-Liaño, Clara

Digital.CSIC

Age Calibration Exercise Analysis for Anchovy in Division 9a (IBERAS survey 2018)

Repositorio Institucional Digital del IEO

Age Calibration Exercise Analysis for Anchovy in Division 9a (IBERAS survey 2018) IEO-IPMA ReadersDate: January-February 2019Coordinators: Begoña Villamor, [IEO-Spain],   Susana Garrido[IPMA-Portugal], Pablo Carrera [IEO-Spain]Participants (in alphabetical order): Antolinez, A. (IEO), Dueñas-Liaño (IEO), Soares, E.(IPMA) WGBIOP 2019, Lisbon, Portugalü In November 2018, a new acoustic survey (IBERAS) coordinated by IEO and  IPMA was carried out in order to estimate the strength of sardine and anchovy recruitment in the Atlantic waters of the Iberian Peninsula (ICES Division 9a)  and to map its distribution area. As well as determine the main biological characteristics of these species in the area.2WGBIOP 2019, Lisbon, PortugalBackground and ObjetivesüIn January-February 2019, an otolith reading exercise was carried out on the anchovy from the survey to determine its age, with the objective of calibrating the age readings among the anchovy readers of the IEO and the IPMA, and estimating the accuracy and discrepancies in the determination of anchovy age among these readers in this area. As well as, to obtain the age length  keys of the survey.üIntercalibration exercises by areas (for the different countries taking part in otolith age reading on the same stocks or adjacent stocks) are required by the last Anchovy workshop and Exchange (ICES 2017; Villamor et al. 2019)Exchange Procedure3WGBIOP: 2015üSamples analysed : Ø A set the 334 otoliths (not images)  of anchovy distributed in Atlantic waters of Iberian Peninsula (ICES Division 9a) from the IBERAS 2018 survey were reading and analyzed.  Ø For the analysis of the results, AGE COMPARISON excel workbook (Eltink, 2000) has been used and the analysis has been made for the whole area, since the number of otoliths in the Subdivision 9a CS was very small.üNumber of  participants involved in the age reading: Ø A total of 3 readers were involved in the present Calibration of anchovy,  two of them from IEO (Experts readers) and the third from IPMA (intermediate reader). Ø The three readers participated in the last International Exchange of 2018, but nevertheless the reader of the IPMA did not participate in the last workshop of 2016 (ICES WKARA2), where the current criteria for determining the age of the anchovy were standardized and implemented.üNumbers of participants delivering data for “assessment”: 2 readers (1 expert from IEO and 1 intermediate from IPMA).WGBIOP 2019, Lisbon, PortugalDivision 9aNumber of OtolithsSize range MonthCentral-South (9a- CS) 30 100-162 mm NovemberCentral North (9a-CN) 304 107-183 mm NovemberWhole area 334 100-183 mm NovemberResults: PA, CV and BIAS4WGBIOP: 2015WGBIOP 2019, Lisbon, PortugalüAnother fact is that there are no signal biases of each reader with the modal age and neither between them, which means that they have a good precision in the determination of the age of the anchovy in the studied area Modal Age Otolith N CV% AgreementBias0 70 91.9% 0.081 236 5.9% 95.8% 0.032 26 25.8% 75.0% -0.253 - - -4 - - -5 - - -Total 332 8.4% 93.4% 0.02CD ES AAReader 1 Reader 2 Reader 3Reader 1 95.8 - -Reader 2 81.8 86.2 -Reader 3 94.0 84.3 97.9MODAL age - - --  = no sign of bias (p>0.05)*  = possibility of bias (0.01<p<0.05)* *  = certainty of bias (p<0.01)= percentage of reading agreement between each reader and the MODAL ageüThe weighted average percentage agreement (PA) based on modal ages for all readers and samples are 93.4 %, with the weighted average CV of 8.4 %. üMost of the anchovy otoliths were well classified by the readers during the 2019 calibration, with a good agreement and precision.  ü267 out of the 334 otoliths reached 100% of agreement üThe best agreements are reached for age 0 (91%) and age 1 (95.8%), and the lowest agreement for age 2 (75%). No individuals over 2 years of age were assigned in the sample.Conclusions5üIn general, it can be said that in view of the results (high agreements, low CV and without biases) of this Calibration the three readers apply well the current age determination criteria updated in the last workshop of the anchovy age (ICES WKARA2, 2016).üTaking as reference the Bay of Biscay anchovy where several workshops and exchanges have regularly taken place (since 1989) (and age validations are achieved), WKARA2 suggested threshold values of agreements around 80% and of CVs around 20% in the training process as a minimum for age readers to be operative to deliver inputs for assessment. And targets should be for agreements above 90% and CV of 10% or less. The results of this Calibration among of these readers are in the levels of the objectives of agreement and CV suggested by WKARA2. üThe three readers have achieved higher agreements and lower CVs in this Calibration than in the last International Exchange of anchovy in the Bay of Biscay in 2018 (Villamor et al., 2019), especially noted the improvement of the IPMA reader. In 2018 Exchange, the two readers of the IEO had a PA above 90% (91 and 92% respectively with the modal age) and a CV of 15% and the IPMA reader had a PA of 76% and CV 21%.üIf we compare this Calibration with the results of the 2014 international exchange of the anchovy from the same area (Division 9a), we see that the improvement is great for the three readers (in 2014, PA between 45 and 71% and CV between 34 and 37% with respect to modal age) (Villamor et al., 2015).WGBIOP 2019, Lisbon, PortugalConclusions6üThe biggest discrepancies found in this Calibration were in age 2. This is mainly due to the fact that in some cases the false spawn ring that deposits the anchovy in summer is confused with the annual winter ring.WGBIOP 2019, Lisbon, PortugalAge Reading for anchovy AP.17.nº 22, 14.1 cm, caught November 2018. 67% agreement: Age 1 (IEO readers ages 1; IPMA reader age 2).  Conventional birthdates: 1st January.  This otolith illustrates that a bad recognition of the typical growth pattern and of checks leads to over estimation of the actual age (resulting in that case in a less intense growth pattern than expected in particular during the second year of life –as age 1)Recommendations for future work7üIt is recommended to continue and follow the protocols and criteria for the interpretation of anchovy age in all areas proposed in WKARA-2.üWe recommend the readers to review and read the WKARA2 report (where there are many examples) and to review the collection of otoliths of reference which is in the Age Reader’s Forum website (https://community.ices.dk/ExternalSites/arf/default.aspx)  in the folder called ‘Engraulis encrasicolus Otolith Reference Collection’üIn IPMA,  there are two new anchovy readers who have not participated in this calibration, since they still need a period of training, and for this a workshop will be included in November 2019 in the IEO of Santander.üAll anchovy readers of the two institutes should participate in future exchanges and workshops of the anchovy ageWGBIOP 2019, Lisbon, PortugalThank you for your kindly attention!8WGBIOP 2019, Lisbon, Portugal

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Age Calibration Exercise Analysis for Anchovy in Division 9a (IBERAS survey 2018)

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