Salmon being released by angler. Photo courtesy of Christine Breuker.

National Salmon Scale Project

Fish scales are useful to fisheries scientists because they tell us a lot about a fish, including its age, growth rate and life-history experiences. Each year, new rings of growth are added to a fish scale, in much the same way as the rings of a tree trunk, thickening during the summer and thinning during the winter (see fish scale aging).  By counting the rings and measuring the gaps between them, we can tell what age a fish is, and estimate its growth rate.

Using a microscope to read a salmon scale.

Citizen science initiative

The National Salmon Scale Project is a citizen science initiative for anglers to collect and submit salmon and sea trout scales to the National Salmon Scale Archive. This archive is hosted by Inland Fisheries Ireland and aims to help researchers understand the challenges that salmon and sea trout are facing today.

Citizen science is research that is carried out members of the public who volunteer to collect data for scientific projects. The National Salmon Scale Project was developed as part of the International Year of the Salmon 2019 as an initiative to encourage salmon anglers to contribute towards conservation research that will help to protect their favourite into the future.

Close-up image of a salmon scale.

Collecting & submitting scales

Anglers who are willing to become citizen scientists for this project can collect vital information by taking scales from salmon and sea trout that they catch in Irish rivers and lakes. If you would like to contribute, please follow the instructions below.

  1. On catching a salmon, measure it from the tip of the snout to the end of the middle of the tail (i.e. fork length).
  2. Remove about approximately 10 scales from left side of the fish just behind dorsal fin. Use a clean knife and gently scrape the sample area a couple of times in a head-to-tail direction. 
  3. Transfer scales to a scale sample envelope provided (see below for details).
  4. Spread scales across inside of envelope and leave them to dry thoroughly.

Fish that are caught and released should be handled carefully. Only remove the fish from the water for a brief moment to take the scale sample, and make every effort made to avoid injury or undue stress to the fish. If this is not possible, a sample should not be taken. For salmon being released, estimate the weight, rather than use weighing scales on the fish unnecessarily.

Removing a small number of scales from fish being released provides valuable information, and the fish will most likely survive the experience unscathed, and perhaps even to be caught another day!

Diagram of how to take a scale sample from a salmonid.

Collecting & submitting information

The following information should be recorded on the scale envelope:

  1. River/Lake where fish was caught.
  2. Capture location within the river/lake where fish was caught.
  3. Date of capture
  4. GPS location if available.
  5. Capture method: What angling method was used?
  6. Species: Are scales collected from a salmon or sea trout?
  7. Length in centimetres (cm) from tip of snout to end of fork in tail.
  8. Weight in kilograms (kg) if possible. Estimate weight for salmon being released.
  9. Sex: Is fish male or female, or unknown?
  10. Predation marks: Are there any signs of predation on the fish, e.g., injuries, bite marks?
  11. Net marks: Are net marks present?
  12. Sea lice: Are sea lice present? If so, record the number of lice.
  13. Comments: Note any other observations & record whether length/weight was estimated or measured.


Who do I contact?

Sample envelopes are distributed along with salmon licences. If you have not received envelopes with your licence and you would like to take part in the National Salmon Scale Programme, please email:

Scale samples can be submitted to Inland Fisheries Ireland staff in your local area or sent by post to:

National Salmon Scale Archive (NSSA), 

Inland Fisheries Ireland, 

3044 Lake Drive, 

Citywest Business Campus, 

Dublin 24.

International year of the Salmon logo.