FISH AGEING – EA NATIONAL SCALE READING SERVICES (2013 – ongoing)
Client: Environment Agency
Based on extensive previous experience of ageing fish from scales and applying these data to population level stock management, BUG was awarded a three year contract to determine the ages of fish collected as part of the Environment Agency’s national monitoring programme.
The analysis involves the examination of magnified images of fish scales to determine the relative position of annuli (rings) on each scale. Not unlike ageing a tree, the number of rings provides information of the total age of individual fish, while the spacing between rings (which is proportional to the growth of the fish) provides more detailed insight to the growth rate in each year and the size of the individual at the end of each year’s growth.
To date ~50,000 scales have been aged from a range of coarse and salmonid species across all EA regions.