Bayesian age and growth analysis of the shortfin m

Authors: Florencia Doño Santiago MontealegreQuijano Andrés Domingo Paul G Kinas

Publish Date: 2014/05/24

Volume: 98, Issue: 2, Pages: 517-533

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Abstract

Age and growth estimates of shortfin mako sharks Isurus oxyrinchus from the western South Atlantic Ocean were obtained through the analysis of vertebral sections of 245 specimens 126 females 116 males and 3 with undetermined sex ranging in size from 78 to 330 cm fork length FL using a flexible growth model Schnute model and a Bayesian approach A significant linear relationship was found between FL and vertebral radius for sexes combined Marginal increment analyses were inconclusive about periodicity of growth band deposition and an annual periodicity was assumed to make age estimations Specimens were estimated to be between 0 and 28 years of age The Schnute model provided a good description of the individual growth for both sexes up to 15 years of age Shortfin mako growth during the first year of life was 339 cm ICr95 = 199–408 for females and 305 cm ICr95 = 256–354 for males Until approximately 15 years of age both sexes showed similar growth and reached ~217 cm FL Sigmoid shaped growth curves obtained for both sexes indicated a change in the growth pattern close to 7 years of age Inconclusive results about periodicity of growth band deposition in the study area make necessary the application of more robust validation techniques in the future Meanwhile a precautionary approach that assumes an annual deposition pattern in the western South Atlantic can be used for the assessment and management of stocks of this species characterized by low fecundity and late maturityWe are grateful to the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq for the scholarship provided to the first author We thank the Oceanographic Museum Univali and its Program of Life Resources Survey at the Rio Grande Rise in the person of Jules M R Soto for logistic support of the field work We are grateful to fishery firm Kowalsky Ind e Com Ltda for permission to embark in the fishing vessels Yamaya III and Macedo IV and especially to Captain Miranda and his crew members for their generous cooperation at sea We also thank scientific observers who collected additional vertebrae and F Mas for its contribution in vertebral processing Thanks to the Laboratório de Mamíferos Marinhos Instituto de Oceanografía FURG and Laboratorio de Edad y Crecimiento DINARA especially Inés Lorenzo for logistical support provided for vertebrae processing Special thanks to Gregor Cailliet Jorge Pablo Castello and Manuel Haimovici for their valuable suggestions and comments to the manuscript This research is part of the MSc Dissertation written by the first author under the guidance of the second and last authors

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