Validation of Jack Mackerel Age Determination Methods in Chile

Age determination and validation on jack mackerel in IFOP-Chile: a brief review Rodolfo Serra 2ndMeeting 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 Mediterr neo de Estudios Avanzados, Spain. Instituto de Fomento Pesquero - Chile

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

Progression of Strong year-classes 24 1500000 600000 3000000 25 1000000 400000 2000000 500000 1987 1987 200000 1000000 1999 0 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 28 27 2000000 2000000 1000000 150000 1500000 1500000 100000 Number of Fish (x103) 1000000 500000 1000000 1988 1988 1976 50000 2000 500000 500000 Number of Fish (x103) 0 0 0 0 Numero de ejemplares (10^3) Numero de ejemplares (10^3) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 30-31 3000000 200000 800000 2000000 31 150000 1500000 2000000 600000 100000 1000000 400000 1000000 1977 1989 1989 2001 50000 500000 200000 Numero de ejemplares (10^3) 0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 800000 35 2000000 200000 1500000 34 1500000 600000 150000 1000000 1000000 400000 100000 1990 1990 500000 2002 500000 200000 1978 50000 0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 37 2000000 37 1500000 800000 200000 1500000 600000 150000 1000000 1000000 400000 100000 1991 500000 500000 2003 1991 1979 200000 50000 0 0 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 12 17 22 27 32 37 42 47 52 57 62 Age Group Fork Length 1500000 1000000 500000 1992 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 From Cerna and Bocic, 2011 Instituto de Fomento Pesquero - Chile

Bomb Radiocarbon Analysis 16 CV = 0,072 n = 21 15 14 13 Whole Otolith Ageing 12 11 10 9 8 7 6 5 4 4 5 6 7 8 9 10 11 12 13 14 15 16 Age 14C From: Cerna and Bocic. 2011. 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 1stand 2ndring, 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. 1981. Determinaci n de la edad y crecimiento del jurel (Trachurus symmetricus murphyi) en la zona Arica-Coquimbo y Talcahuano. Informe T cnico. IFOP/SUBPESCA. 88 p gs. Araya, M., M. Medina and H. Arancibia. 1993. Edad y crecimiento del jurel Trachurus murphyi de la zona centro sr de Chile mediante el m todo de lectura de micro-incrementos diarios de los otolitos y confecci n de claves talla/edad. Informe Final. Departamento Ciencias del Mar. Universidad Arturo Prat, Iquique, Chile. 72 p. Cerna, F. and V. Bocic. 2011. 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, 2011. Gili, R., V. Bocic and R. Serra. 1995. An lisis de la periodicidad de formaci n del anillo hialino en otolitos de jurel de la costa e Chile. Informe T cnico Interno. IFOP. Kochkin. P.N. 1994. Age determination and estimates of growth rate for the Peruvian jack mackerel, Trachurus symmetricus murphyi. J. Ichth. 34(3): 39-50- Instituto de Fomento Pesquero - Chile