Antolínez, A. (Ana)

Dueñas-Liaño, C. (Clara)

Hernández, C. (Carmen)

Villamor, B. (Begoña)

English

Repositorio Institucional Digital del IEO

WKARA2 – Workshop on Age reading of European anchovy (Engraulis encrasicolus)28 Nov -2 Dec 2016 . AZTI Pasaia (Spain)Criteria for age determination of anchovy otoliths in Sub-division IXa North: analysis  of the rings biometric measures.Hernandez, C., Dueñas-Liaño, C., Antolinez, A. and Villamor, B.  Instituto Español de Oceanografía. Probably the increased availability ofanchovy in the IXa-N region is due to anexceptional increase in local residualpopulations. But it could also be that theincrease in the availability of anchovy inthe IXa-N region is a consequence of theincrease of banks coming from one of theestablished populations (Division IXa orSubArea VIII).Still without confirming which of thesehypotheses is the true oneBackgraund01000200030004000500060001991199219931994199519961997199819992000200120022003200420052006200720082009201020112012201320142015Catches (t)YearSub-Division IXa North-Annual catches 1991-2015Biological sampling and otoliths readingonly in the years of higher catches.Typical Length range: 11-17 cm; Age range:1-3 yearsOtoliths of this area have never beenincluded in the exchanges or workshopsOccasional fishery with phenomena ofsporadic and high increases in theavailability of anchovy in the IXa-Nregion (area covering the coasts ofwestern Galicia and northern Portugal).The largest catches always in the summermonths.The catch of anchovy from the IEOannual acoustic survey (PELACUS,March-April) is very scarce.To study the growth pattern of the anchovy otoliths in the Sub-division IXaNorth:1.Age was determined by identifying and measuring growth rings formed onthe sagitta otoliths in Sub-division IXa North, in order to support theidentification of the true annual rings: The otolith radius of the hyaline ringswas measured and used as a gauge for exclude the presumed checks inageing older individuals.2.Also, the nature of the edge (hyaline or opaque) was also recorded.Objectives of this workMaterial and MethodsTo attain the first objective, 141 whole otoliths from commercial sampling in2016 were analysed under a reflected light, using a microscope applied to animage analyzer (NIS-Element). Macroscopically visible rings distances weremeasured (C08, C15, R1, R2) along the same axis used to estimate the age ofthe fish.For the second objective, 1122 whole otoliths from commercial sampling in 2015and 2016 were analysed. The nature of the edge (hyaline or opaque) was recorded.An expert reader determined the age of fish by counting the number of seasonalincrements on an annual basis following the criteria of Uriarte et al. 2002, Uriarteet al., 2016 and WKARA, 2009.Frequency distribution of rings distances C08, R1, C15, R2 Frequency distribution of  two annual age ring distancesResultsRings biometric measures051015202530350.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2FrequencyOtolith radius (mm)C08R1C15R2051015202530350.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2FrequencyOtolith radius (mm)Age1Age 205101520253035051015202530350.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2FrequencyOtolith radius (mm)Age1Age 2C08R1C15R222/06/2016. Nº 44, 132mm. Check C08. Hyaline. Age1 C08 = 844 µmR 1 = 1641 µmExamples of measures: Age 1 with a check C0822/06/2016. Nº 12, 130mm. Check C15. Hyaline. Age 2R 1 = 1137 µmC15 = 1450 µm R2 = 1601 µmExamples of measures: Age 2 with a check C1510/05/2016. Nº 4, 138mm. Checks C08, C12, C15. Hyaline. Age 2C08 = 789 µmC12 = 1381 µmC15 = 1507 µmR 1 = 1507 µmR2 = 1661 µmExamples of measures: Age 2 with checks C08, C12 & C15ResultsNature of the edge The monthly proportion of edge type of E.encrasicolus in the IXaN, indicates an annualperiodicity in the formation of the hyaline andopaque annuli, appearing the hyaline edge mainlyfrom June to October.020406080100Mar Apr May Jun Jul Aug Sept OctOtolith edge (%)2015-2016HyalineOpaque020406080100Mar Apr May Jun Jul Aug Sept OctOtolith edge (%)2015-2016 -Age 1HyalineOpaque020406080100Mar Apr May Jun Jul Aug Sept OctOtolith edge (%)2015-2016-Age 2HyalineOpaqueAt age 1, the highest frequency of occurrence ofopaque edge is in winter, descending in summer.This could be assumed as a stop growth at ageone, in summer.At age 2, the highest frequency of occurrence ofthe opaque ring is in summer.These results, contrary to expectations, could bedue:• An misinterpretation of nature of edges at age1.• A greater influence in that area of theupwelling, mainly in summer, causing adecrease of the temperature.March 16, 2016. 11.7 cmApril 21, 2016. 12. 8 cmExamples of age 1 with opaque growth in March, April and MayMay 10, 2016. 12.5 mmOr are they 2 years old, with sizes so small?ConclusionsThe biometric measurements of the growth rings (true and false) of the anchovy otoliths in the North IXa (C08 = 779µm, R1= 1213µm, R2=1649), appear to be in agreement with the anchovy otoliths of the Bay of Biscay (C08 = 852µm, R1= 1295µm, R2=1589, Hernandez et al., 2013). It is necessary to investigate more in depth the analysis of the nature of the edge, since it seems to indicate that the growth is greater in the months of winter than in summer.This could be explained by the drop in temperature by the upwelling phenomena in this area in summer and therefore influenced by a lower anchovy growth? Or is it simply a misinterpretation of the edge?

Criteria for age determination of anchovy otoliths in Sub-division IXa North: analysis  of the rings biometric measures

Hernández, Carmen

Dueñas-Liaño, Clara

Antolínez, Ana

Villamor, Begoña

Digital.CSIC

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/11095/1/Hernandez_et_al.2016_WKARA2_IXaNorthAgeDetermination.pdf

Criteria for age determination of anchovy otoliths in Sub-division IXa North: analysis of the rings biometric measures

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