Age determination and validation on jack mackerel in IFOP-Chile: a brief review Rodolfo Serra 2 nd Meeting of the Scientific Committee South Pacific Regional Fisheries Management Organization Honolulu, Hawaii, USA 1-7 October 2014 Instituto de Fomento Pesquero - Chile

Age readings in Chile For the age determination the left whole otolith is used, which is submerged in a Petri’s plate with black bottom, where the otolith is covered with transparent oil, and read under a stereoscopic microscope with magnification of 10X and using reflected light. In fish, larger than 45 cm fork length a transversal section of the right otolith is used, which is polished and toasted. The section reading is complementary to the reading on the whole otolith to avoid bias in ageing the fish Instituto de Fomento Pesquero - Chile

Jack Mackerel Age Validation Age determination has been validated by the analysis of the border of the otolith first by Aguayo et al., (1981) and also by other researchers. Also through daily rings; the age-size relationship shows a strong agreement for the two first ages in a work done by Araya et al. (1993). Progression of Strong year-classes Bomb Radiocarbon Analysis The work done in Chile agrees with Nekrasov (1987) and Kochkin (1994) which identify one growth ring per year. Independent review of the Chilean jack mackerel age determination done by IFOP by Dr. Beatriz Morales-Nin from the Instituto Mediterráneo de Estudios Avanzados, Spain. Instituto de Fomento Pesquero - Chile

Margin analysis following strong year-classes From Gili, Bocic and Serra, Instituto de Fomento Pesquero - Chile

Progression of Strong year-classes From Cerna and Bocic, 2011 Instituto de Fomento Pesquero - Chile

Bomb Radiocarbon Analysis From: Cerna and Bocic Instituto de Fomento Pesquero - Chile

Main conclusions of the Otolith Interpretation and Aging Workshop held in 2011 The results of the age reading exercises show particularly good agreement when ageing otoliths of juveniles. In juveniles it is far easier to identify the 1 st and 2 nd ring, although it is not always possible to do so. For fish up to about age 11 there are reasonably high levels of agreement between readers. However, there are still high CVs on age readings, and statistically significant differences between readers. In older fish, and particularly using whole otoliths, it is frequently difficult to identify the first one or two rings, and this then affects age readings for subsequent rings. Use of otolith sections results in better ageing of larger fish (> 40 cm FL) than using whole otoliths. Instituto de Fomento Pesquero - Chile

References Aguayo, M., E. Estay and V. Ojeda Determinación de la edad y crecimiento del jurel (Trachurus symmetricus murphyi) en la zona Arica-Coquimbo y Talcahuano. Informe Técnico. IFOP/SUBPESCA. 88 págs. Araya, M., M. Medina and H. Arancibia Edad y crecimiento del jurel Trachurus murphyi de la zona centro sr de Chile mediante el método de lectura de micro-incrementos diarios de los otolitos y confección de claves talla/edad. Informe Final. Departamento Ciencias del Mar. Universidad Arturo Prat, Iquique, Chile. 72 p. Cerna, F. and V. Bocic Age validation and growth function of Chilean jack mackerel (Trachurus murphyi) off Chile. Document presented at the Chilean jack mackerel Otolith Interpretation and Ageing Workshop. Lima, Peru. July, Gili, R., V. Bocic and R. Serra Análisis de la periodicidad de formación del anillo hialino en otolitos de jurel de la costa e Chile. Informe Técnico Interno. IFOP. Kochkin. P.N Age determination and estimates of growth rate for the Peruvian jack mackerel, Trachurus symmetricus murphyi. J. Ichth. 34(3): Instituto de Fomento Pesquero - Chile