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Estimates of the age composition of hake (demersal) and sardine (pelagic) in Iberian Atlantic waters in 1999 are analysed, paying specific attention to sampling variability. Two methods are applied, one based on an analytical approach and the other on simulation using a non-parametric bootstrap technique. The methods were used to estimate the catch at age by numbers per species for 1999, and the associated variability. They provide a useful means of analysing the precision of the estimates, of assessing data quality, and of optimising different sampling schemes. The estimates are precise for the reference ages used in assessment (CV < 13% for both species). The bootstrap method is considered better owing to its non-parametric nature, despite its more complicated implementation and greater need of computational resources., Se analizan las estimaciones de la composición por edad y su variabilidad en el muestreo para la merluza (demersal) y sardina (pelágica) en aguas Ibero-Atlánticas de 1999. Se han aplicado dos métodos: uno basado en un desarrollo analítico y el otro basado en una técnica por simulación utilizando un bootstrap no-paramétrico. Estos métodos se utilizaron para estimar la captura por clase de edad en número por especie para el año 1999 y la variabilidad asociada. Ambos métodos son herramientas útiles: para analizar la precisión de las estimas, evaluar la calidad de los datos, y para optimizar los diferentes esquemas de muestreo. Las estimas obtenidas son precisas para las edades de referencia empleadas en la evaluación (CV < 13% para ambas especies). El método bootstrap se considera mejor debido a que es una aproximación no-paramétrica, aunque sea más complicada su implementación y tenga una mayor demanda de computación.

This report is one five parts of the report of SG MOS 10-06, the STECF sub group on management objectives and strategies dealing with historic Evaluations of and future Impact Assessments of multi-annual plans for fisheries. In total five separate reports are prepared by STECF-SGMOS 10-06 WGs, the first, scoping meeting report STECFSGMOS 10-06a. contained preparatory work, the other four report the individual assessments:- STECF-SGMOS 10-06b Report of the Impact Assessments for North Sea plaice and sole multiannual management. STECF-SGMOS 10-06c Report of the Impact Assessments for Western Channel sole multiannual management. STECF-SGMOS 10-06d. Report of the Evaluations of Southern hake and Nephrops Multi-annual plan STECF-SG MOS 10-06e. Report of the Evaluations of Baltic cod Multi-annual plan This report describes an evaluation of the performance of the multi-annual plan for fisheries of southern hake and Nephrops in ICES sub divisions VIIIc an IXa., JRC.DG.G.4-Maritime affairs