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ABSTRACT
Age information is an essential component in growth rate, mortality rate and productivity calculations, hence it is classified among the most influential of biological variables. In the case of bony fishes, age determination methods based on annual growth marks are reasonably well established and are constantly applied. However, age determination methods in elasmobranchs have lagged behind those applied to teleosts. In this manual, the most recognized age determination methods for elasmobranchs have been brought together so as to provide a detailed and hands-on guide to successful and validated methods for ageing sharks, skates and rays. Particular emphasis is given to vertebral sections and image analysis techniques as applied to elasmobranch species from the Mediterranean Sea, suited to both novice and experienced age readers.
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PREPARATION OF THIS DOCUMENT
This document stems from the Workshop on Age Reading of Eiasmobranchs in the GFCM area, funded by the European Union, which was organized by the General Fisheries Commission for the Mediterranean (GFCM) of the Food and Agriculture Organization (FAO) of the United Nations and held at the Mediterranean Fisheries Research Production and Training Institute in Antalya (Turkey), from 8 to 12 October 2012. This hands-on workshop with an important training component was attended by participants from the GFCM Member countries and from non-Member countries. The purpose of this document is to provide a detailed and hands-on guide to successful and validated methods for ageing sharks, skates and rays of the Mediterranean.
ACKNOWLEDGEMENTS
The author truly thanks Anna Dorey and Warren Joyce for their expertise in preparing countless numbers of elasmobranch vertebrae and spines. Many of the examples used in this manual came from the enthusiastic and skilled participants in the Workshop on Age Reading of Eiasmobranchs in the GFCM area, held in Antalya, Turkey in October 2012; special thanks go to them for their active involvement, as well as to Pilar Hernández and the GFCM Secretariat for organizing the workshop which made this possible.
1. INTRODUCTION
Age information is an essential component in growth rate, mortality rate and productivity calculations, hence it is classified among the most influential of biological variables. Calculations as simple as growth rate, or as complex as virtual population analysis, all require age data, since any...