Collecting Sea Trout scale samples

One of the most important parts of the CSTP programme is the collection of sea trout scale samples from 100 rivers, estuaries, coastal waters and further offshore, over the three years of the project. 20 rivers have been targeted for detailed sampling and this protocol is designed to assist anglers in accurate collection of scales for use in subsequent scientific analysis, e.g. stock structuring and distribution (from genetics and scale micro-chemistry) and features such as age and sex composition, life history, growth and survival.

For scale samples the target is 300+ sets of scales per river, to be collected over a two year period, starting in 2009. The samples must be collected in a scientifically unbiased way to ensure that the sample is representative of the stock. This means that fish of all sizes (smallest to largest) and spread throughout the entire angling season should be sampled.

Collect Scale Samples

Anglers are being asked to collect scales and take a length measurements and other relevant information from each sea trout that they catch according to the protocol below. However, for the remainder of the project (summer 2012 onwards), for the rivers in Wales, Northern Ireland, England and Scotland we are not able to accept scales taken from fish returned alive. In those waters scales can only be supplied by anglers from fish that are killed and taken for consumption. Scales from killed or returned fish continue to be acceptable in the Republic of Ireland. The sample required for analysis is about 10-15 scales per fish which should be placed in an individual scale envelope/scale packet.

STEP 1: Request Scale Sampling Pack

If you would like to contribute to the project by collecting scale samples, you will need to request a scale sampling pack. This pack will provide you with scale sample envelopes, tape, plastic knife and instructions on how to correctly take a scale sample.These packs are free of charge and can be ordered in two different ways:

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STEP 2: Taking a sea trout scale sample

Equipment Needed (provided in scale sample pack):

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Note: You should only handle live fish with wet hands and ensure measuring device is wet to minimise any potential damage to the fish. Placing a wet hand or damp cloth over the head of the fish while being measured, will calm the fish and allow for the sample to be taken.

Instructions On collecting scale samples

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Envelopes containing scale samples should not be stored in plastic bags as the scales will rot. Envelopes should be stored in dry conditions as soon as possible to ensure that the scales will remain viable for analysis. If stored under good conditions, the scales will provide genetic material for many decades.

Note: If sampling sea trout in a bag with other sea trout/fish, cross-contamination must be avoided. To prevent this from happening, run the back of the knife over the sampling area in the direction of the tail. This removes any loose scales that may have transferred from the other fish to the skin/mucus of the fish that is to be sampled. Clean the knife thoroughly and follow step 9-12, as detailed above.

STEP 3: Recorded information on each scale sample

For each scale sample taken, information relating to the scale sample must be recorded. These details must be filled out on Scale sample envelopes. These details include:

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STEP 4: Return scale sample

Store scale sample envelopes in dry conditions to prevent scale deteriorating and rotting. Do not store in a refrigerator or a damp environment. On a monthly basis, please post any scale samples to the following address

For Ireland and Northern Ireland:

John Coyne,
Inland Fisheries Ireland, Swords Business Campus, Swords, Co. Dublin, Ireland.
Tel: +353 (0)1 8842600

For England, Wales, Scotland and Isle of Man:

Dr Carys Ann Davies,
School of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, LL59 5AB, UK
Tel: +44 (0)1248 388603


We want to give feedback to fishermen and other interested groups. The CSTP can provide information on scale readings, but responses may take some time because of the volume of analyses to be done. We have already done many talks to angler groups and we are keen to continue this to give updates and here anglers’ views on the project. If you want to have talks given to your association or club please contact the relevant CSTP contact in your area and arrangements will be made for a CSTP person to address your group.

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