Capture Mark Recapture Data for Scottish Elasmobranchs: 2009-2018

Quality Control

The dataset has been checked using NBN Record Cleaner

Method steps

1. Data was provided by volunteer sea anglers all using individual baited hooks and line. Bait used depended on the species being targeted. Each fish was either measured (to the nearest cm) at the side of the boat or on board if the necessary equipment is present. We do not encourage anglers to weigh fish directly, instead they use length to weight conversion curves which, while increasing welfare standards, will reduce the accuracy of weight measurement slightly. The fish is then tagged with a unique ID number and relseased unharmed back into the water. The data shown here are only those records that contained a GPS co-ordinate, a known sex and either weight or length. In addition, the dataset also contains records of any re-captures.

The data is focused primarily on the West coast of Scotland from Luce Bay in the south to the Sound of Mull. Effort is focused on good fishing locations through invaluable and accurate local knowledge but this will still introduce some bias. Anglers will avoid certain areas thought to be devoid of good numbers of target fish even if those areas had good historical numbers. The Clyde Estuary is a good example. All data is displayed here with summary 10km grid references.