Monday 26th April, 2021
Last week a new project was launched to track the progress of juvenile salmon migrating from the river Usk to the sea. The initiative, carried out by Natural Resources Wales with support from the Wye and Usk Foundation will establish the major challenges facing these small fish on course of their journey.
In April and May juvenile Atlantic salmon in our rivers ready themselves for the sea phase of their life cycle. Their bodies begin to make the transformations that enable them to live in salt water, giving them a more silver appearance.
Known as “smolts”, these small fish group together in shoals for safety as they begin to make their way downstream.
The success of the annual smolt migration can be affected by numerous factors but it is low flows, barriers and predation that usually combine to provide the major limitation. If water levels are low the fish can suffer heavy losses to a range of avian and piscine predators. This is further compounded by barriers to their migration such as weirs, where the fish can pause and become easy targets for hungry mouths.
Up to 100 Usk smolts will be caught and tagged in the next few weeks with acoustic transmitters. A series of 30 receivers deployed along the river will then monitor their progress as they make their way downstream.
The study will provide us with survival rate and migration behaviour data, which will help target future salmon management and conservation work. It will tell us what can be done to improve their chances of successful migration.
Oliver Brown, Aquaculture Officer for Natural Resources Wales, who is leading the project said:
“Salmon numbers, both adult and juvenile, are at record lows in Welsh rivers as well as in other parts of the world. When we see species numbers dropping like this, we need to do all we can to understand what’s causing the problem and determine what can be done to safeguard the species’ survival.
By tagging these salmon smolts and using our network of receivers to track them during their journey to sea, we can find out what’s making life so difficult for these fish, be it delays at barriers, predation, low river flows or anything in-between.
We’re grateful for the support of the Wye and Usk foundation in the roll out of this project. Ultimately, the information and data we gather will inform our collaborative work in the area of salmon conservation, which will prove invaluable in our efforts to tackle the cause of the population declines in the long term.”
We look forward to publishing the results of the study as soon as they are available.