Common skate Photo-Identification Database for Scotland

Anglers’ photos can tell us much about the skate population of Loch Sunart to the Sound of Jura Nature Conservation Marine Protected Area.

Skates have very varied patterns of spots, and it may be possible to identify individuals from the spot patterns on their dorsal or upper surface.

Scottish Association for Marine Science (SAMS) scientist Steven Benjamins has been testing this theory, using an archive of about 400 photos of flapper skates. Skipper Ronnie Campbell took the photos in the Loch Sunart to the Sound of Jura NCMPA from 2011 onwards.

We are working with SAMS on this exciting project, along with:

  • the Scottish Sea Angling Conservation Network
  • volunteer charter skippers and anglers

Skate identification

Some skates have:

  • very few spots
  • a symmetrical pattern of large spots, forming arcs and whorls
  • small spots scattered all over, giving a mottled appearance
  • distinct, and often large, black spots

Benjamins was able to identify 232 individual skates from their spot patterns and recognise them in recapture photos. Of the 232 fish, 76 (32%) were recaptured at least once between 2011 and 2016.

On average, about 10 months elapsed between the capture and recapture of a fish. The longest time between a capture and recapture was 4 years 5 months.

Photos have so far been matched by eye. We are testing software to automate this process to some extent, to speed up identification in the next phase of the project.

Identification over time

The identification of recaptured skates has shown that their spot patterns don’t vary significantly over time. This proves that it’s possible to recognise individuals from photos over the long term.

A time series of photos of individual skates taken during recaptures over several years will help to reveal:

  • the number of skates resident in the area
  • how many skates migrate into and out of the area, and how regularly they do so
  • changes in size and body condition (e.g. leech load, pregnancy, healing) over time

We hope that using photos to identify skates will end the need to tag fish and allow more anglers to help monitor the skate population of the Loch Sunart to the Sound of Jura NCMPA.

Passive integrated tagging will continue initially while new photos are collected, to serve as a check on the photo identification process.

How you can help

Anglers and skippers are invited to add skate photos to the historic photo library and database. You should upload your photos directly to the Common Skate Photo-Identification Database for Scotland.

To find out how best to submit a large number of photos, email skates@sams.ac.uk.

Just starting to take skate photos? Our poster sets out how to take a good photo for identification purposes and what details to include with it.