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Based on the previous work from WKARHOM3 (ICES, 2018), the Working Group on Biological Parameters (ICES, 2020) identified the need for a new otolith exchange followed by an age read-ing Workshop. The Workshop on Age reading of Horse Mackerel, Mediterranean Horse Macke-rel and Blue Jack Mackerel (Trachurus trachurus, T. mediterraneus and T. picturatus) (WKAR-HOM4) had several main objectives; to review the current protocols of ageing Trachurus species, to update the advances in the validation of the ageing criteria (i.e. the annual deposition of one annulus, coherency of the interpretation), to evaluate the new precision of ageing data of Tra-churus species and to update guidelines, common ageing criteria and reference collections of otoliths. An online otolith exchange was performed using SmartDots during 2021 and 2022, and results including the three Trachurus species were published in advance of the meeting, showing a low Percentage of Agreement (PA) both when considering all the readers (44-55%) and the advanced readers only (52-54%) (Massaro and Jurado-Ruzafa, 2022). For T. trachurus the Coef-ficient of Variation (CV) was lower for the sliced samples (22-18%) than for whole otoliths sam-ples (44-38%). Readers participating in the exchange, following discussion during the WKAR-HOM4 meeting, agreed that the main cause of age determination error for T. trachurus was due to the different otolith preparation techniques (whole/sliced). These differences reflect the stunted growth and compactness of the annuli in older specimens (from the 4th-5th annuli on-wards). Anyway, for the three Trachurus species, there are several difficulties in age determina-tion: identification of the first growth annulus, presence of many false rings (mainly in the first and second annuli) and the interpretation and identification of the edge characteristics (opaque/translucent). The second reading exercise was performed during the workshop orga-nized in four different events (i.e. Trachuru

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. In 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. As well as, to obtain the age length keys of the survey

Este manual tiene como objetivo describir los métodos para la determinación de la edad anual del estornino (Scomber colias, Gmelin, 1978). Las técnicas para la determinación de la edad en estructuras calcificadas de especies pelágicas y bentónicas (disección, preparación y métodos) en el área del ICES (aguas atlánticas europeas) se han descrito recientemente en un manual publicado tanto en inglés como en castellano (Villamor et al., 2015; 2016). Este nuevo manual que presentamos aquí se centra sólo, pero en mayor profundidad, en los criterios utilizados y estandarizados a nivel europeo para la interpretación de los anillos de crecimiento anual en los otolitos (lectura de otolitos) del estornino del Atlántico Nordeste. Este manual tiene como finalidad servir de referencia para los lectores de edad del estornino en los laboratorios del IEO y pretende también ser una guía para el entrenamiento de los nuevos participantes (lectores) en la determinación de la edad en los otolitos del estornino, para suplementar y complementar el entrenamiento que reciben del lector experto asignado para entrenarlos. También pretende ser una guía dinámica, que pueda cambiar a medida que sean introducidos nuevos criterios de interpretación tras ser evaluados y adoptados a nivel europeo. Este manual se basa en los últimos intercambios, talleres y publicaciones sobre la determinación de la edad del estornino (ICES, 2015; Navarro et al., 2015). También se hace referencia a la biología de la especie ya que es fundamental tener conocimiento de ella para poder interpretar los otolitos con mayor precisión.

Based on the results of a full-scale otolith exchange held in 2014, the Working Group on Biological Parameters (WGBIOP 2015) identified the need for an age reading workshop on European Anchovy otoliths (WKARA2). This workshop (chaired by Andres Uriarte, Spain, Begoña Villamor, Spain and Gualtiero Basilone, Italy), was held in Pasaia, Gui-puzcoa (Spain) from the 28 November to 2 December 2016. Five countries took part in this workshop (Spain, Italy, Croatia, Greece and Tunisia), with a total of 16 participants from 9 laboratories. In total 17 areas/stocks were analysed (4 from the Atlantic area and 13 from Mediterranean Sea) The aim of this workshop was to review the information on age determination, discuss the results of the previous exchange (2014), review the validation methods existing on these species, clarify the interpretation of annual rings and update the age reading pro-tocol and a reference collection of well-defined otoliths. Age validation studies, in the Bay of Biscay and preliminary validation studies in Divi-sion 9a, Alboran Sea and Strait of Sicily areas were presented, including a compilation of age validation studies of this species as well in the literature. There are several ar-eas/stocks in which validations of the anchovy annual age determination have not been done yet. Due to the poor percentage of agreement achieved in the 2014 Exchange (mean agree-ment of 66%; mean CV of 58%), the workshop proceeded with a detailed and joint dis-cussion on the growth patterns shown by otoliths from the different areas to find out the major reasons for discrepancies in age determination among readers. At the same time, the joint discussion allowed a better understanding of the pattern of otolith growth in-crements by areas to improve the guidelines for their interpretation. The discussions on examples among otoliths which generated discrepancies in the age determination led to conclude that there were two major sources of disagreements: a) Divergent otolith

Este manual tiene como objetivo describir los métodos para la determinación de la edad anual del jurel blanco (Trachurus mediterraneus, Steindachner, 1868). Las técnicas para la determinación de la edad en estructuras calcificadas de especies pelágicas y bentónicas (disección, preparación y métodos) en el área del ICES (aguas atlánticas europeas) se han descrito recientemente en un manual publicado tanto en inglés como en castellano (Villamor et al., 2015; 2016). Este nuevo manual que presentamos aquí se centra solo, pero en mayor profundidad, en los criterios utilizados y estandarizados a nivel europeo para la interpretación de los anillos de crecimiento anual en los otolitos (lectura de otolitos) del jurel blanco del Atlántico Nordeste. Este manual tiene como finalidad servir de referencia para los lectores de edad del jurel blanco en los laboratorios del IEO y pretende también ser una guía para el entrenamiento de los nuevos participantes (lectores) en la determinación de la edad en los otolitos de jurel blanco, para suplementar y complementar el entrenamiento que reciben del lector experto asignado para entrenarlos. También pretende ser una guía dinámica, que pueda cambiar a medida que sean introducidos nuevos criterios de interpretación tras ser evaluados y adoptados a nivel europeo. Este manual se basa en los últimos intercambios, talleres y publicaciones sobre la determinación de la edad del jurel blanco (ICES, 2012; 2015). También se hace referencia a la biología de la especie ya que es fundamental tener conocimiento de ella para poder interpretar los otolitos con mayor precisión.

Validation of the age determination procedure using otoliths of European anchovy in the Bay of Biscay was achieved by monitoring very strong year-classes in successive spring catches and surveys, as well as the seasonal occurrence of edge types. Historical corroboration of the ageing method was obtained by cross-correlation between successive age groups by year-classes in catches and surveys (1987–2013). Summary annual growth in length is also presented. Yearly annuli consist of a hyaline zone (either single or composite) and a wide opaque zone, disrupted occasionally by some typical checks (mainly at age-0 and age-1 at peak spawning time). Age determination, given a date of capture, requires knowledge of the typical annual growth pattern of otoliths, their seasonal edge formation by ages and the most typical checks. Most opaque growth occurs in summer and is minimal (translucent) in winter. Opaque zone formation begins earlier in younger fish (in spring), and this helps distinguish age-1 from age-2þ.

The white anglerfish (Lophius piscatorius) is a bottom-living and commercially important species for European fisheries (∼38.000 t in Atlantic waters in 2015). Weight-length relationship, weight conversion factors and condition factor for this species are estimated from a decade (2006-2015) in northern Iberian waters (ICES Div. VIIIc-IXa, southern stock) and in Celtic Seas (ICES Div. VIIb,c,h,j,k, northern stock). A total of 7219 white anglerfish were collected from commercial landings and research surveys and the total length (Lt), total weight (Wt), gutted weight with liver (Wgl) and gutted weight (Wg) were obtained. The weight-length relationships for the combined sexes were: Lt = 0.025 Wt2.853; Lt = 0.02 Wgl2.868; Lt = 0.024 Wg2.861 in Div. VIIIc-IXa, and Lt = 0.027 Wt2.826; Lt = 0.023 Wgl2.825; Lt = 0.023 Wg2.816 in Div. VIIb,c,h,j,k. The commercial landings of this species are available in gutted weight, and therefore the conversion factor (total-gutted weights) was also estimated. All these results can be used in the annual assessment of the state of both stocks in the ICES working group. The condition factor was estimated along the year for immature and mature individuals of each sex and it could provide additional information regarding the spawning season. The results are compared to the previously estimated in other studies.

This handbook presents a summary of the age estimation procedures used in Spanish Institute of Oceanography (IEO) for some of the main commercial small and medium pelagic species and benthic species of the Spanish fleet. It provides information about the sampling program, otolith extraction and preparation, and the age estimation criteria. A summary of the information related to the age accuracy, validation and corroboration of each species is also presented, as well as that related to the age precision, quality control and verification.

Comprehension of the annual pattern of annulus formation throughout the anchovy life span was first achieved from the observations of the strong 1982 year class which showed a neat annual progression of modal lengths passing through the fishery until the exceptional age of 5. Validation of the proposed method was subsequently obtained through monitoring of the progression of the strong 1987, 1989 and 1991 year-classes, both by spring annual surveys and by continuous sampling of the commercial catches, coupled to the monitoring of the seasonal marginal edge formation of the otoliths. Since then Age validation has been confirmed by the correlation between the pulses of recruitments (at age 1), as reflected in their relative occurrence in the population in Spring, and the abundance of those recruitments according to surveys. Typically, annual growth of anchovy otoliths of the one and two years old diminish to about 2/3-1/2 and 1/3 of that occurring in their previous ages respectively. Growth of older ages (three and four) are rather similar as, or slightly lesser than, at age 2. Maximum growth (white band formation) occurs in summer and growth detentions (with translucent annulus formation) in winter time. However the opaque edge formation begins sooner at the age of 1 (around February-March) than at older ages (May or June). During the first winter several translucent rings are occasionally formed resulting in a composite annulus formation. In addition during June/July, at peak spawning, a check is formed in many of the one year old anchovies. However, not all year classes, neither all anchovies lay down the same amount of checks and many of them may not show any. As such age determination requires the knowledge of the typical annual growth pattern of otoliths, of their seasonal edge formation by ages and of the most typical checks.

This handbook presents a summary of the age estimation procedures used in Spanish Institute of Oceanography (IEO) for some of the main commercial small and medium pelagic species of the Spanish fleet: anchovy (Engraulis encrasicolus), sardine (Sardina pichardus), mackerel (Scomber scombrus), chuck mackerel (Scomber colias), horse mackerel (Trachurus trachurus), Mediterranean horse mackerel (Trachurus mediterraneus) and blue whiting (Micromesistius poutassou). It provides information about the sampling program, otolith extraction and preparation, and the age estimation criteria. A summary of the information related to the age accuracy, validation and corroboration of each species is also presented, as well as that related to the age precision, quality control and verification.