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Age determination and validation on jack mackerel in IFOP-Chile: a brief review Rodolfo Serra

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. Age readings in Chile.

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Age determination and validation on jack mackerel in IFOP-Chile: a brief review Rodolfo Serra

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  1. Age determination and validation on jack mackerel in IFOP-Chile: a brief reviewRodolfo Serra 2nd Meeting of the Scientific Committee South Pacific Regional Fisheries Management Organization Honolulu, Hawaii, USA1-7 October 2014 Instituto de Fomento Pesquero - Chile

  2. 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

  3. 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 InstitutoMediterráneo de EstudiosAvanzados, Spain. Instituto de Fomento Pesquero - Chile

  4. Margin analysis following strong year-classes From Gili, Bocic and Serra, 1995. Instituto de Fomento Pesquero - Chile

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

  6. Bomb Radiocarbon Analysis From: Cerna and Bocic. 2011. Instituto de Fomento Pesquero - Chile

  7. 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 1st and 2nd 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

  8. References • Aguayo, M., E. Estay and V. Ojeda. 1981. Determinación de la edad y crecimiento del jurel (Trachurussymmetricusmurphyi) en la zona Arica-Coquimbo y Talcahuano. Informe Técnico. IFOP/SUBPESCA. 88 págs. • Araya, M., M. Medina and H. Arancibia. 1993. Edad y crecimiento del jurel Trachurusmurphyi 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. 2011. Agevalidation and growthfunction of Chileanjackmackerel (Trachurusmurphyi) off Chile. Documentpresented at theChileanjackmackerel Otolith Interpretation and AgeingWorkshop. Lima, Peru. July, 2011. • Gili, R., V. Bocic and R. Serra. 1995. 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. 1994. Agedetermination and estimates of growthrateforthePeruvianjackmackerel, Trachurussymmetricusmurphyi. J. Ichth. 34(3): 39-50- Instituto de Fomento Pesquero - Chile

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