Clochán Uisce: Stressed trout and a Shannonvale shout-out

The Clochán Uisce group has started to compile a list of the various species of bird, plant, insect, invertebrates and fish that are found in the river Feagle and its tributaries.  

The river Feagle has a small population of brown trout and on some rare occasions a couple of large sea trout can be seen up as far as Bridge street in the centre of Clonakilty. Little is known about why some brown trout make the decision to leave the river where they are born and head to the sea and become sea trout. Migration takes place in healthy rivers as well, but research has shown that competition, reduced food supply and poor ecological conditions can trigger migration behaviour; but changes in water temperature, due to global warming, are also affecting the brown trout’s decision to migrate or not.

Researchers from UCC asked how changes in water temperature and food availability can influence the migration of brown trout? By rearing the offspring of wild trout for two years under conditions of reduced food and increased temperature, and then recording the numbers of future sea-going migrants, the team found that food reduction increased the numbers of fish migrating to sea, but warm temperatures had the opposite effect, with increased numbers remaining resident in fresh water.

With conflicting pressures mounting from global warming and environmental degradation, trout will come under increased pressure to make complex decisions about whether they should migrate. The study noticed that fish choosing migration were smaller and in poorer condition than fish that remained in fresh water, indicating sea migration occurred when the fish urgently needed to consume more food. But how will they balance this with the urge to remain in the ever warmer rivers? Sea trout populations have shown dramatic declines across Europe. Warming temperatures cause fewer fish to migrate to sea, with more fish remaining in fresh water to reproduce earlier. Research suggests that climate warming, which in turn is warming our rivers, may cause us to see further declines in sea-going trout.

As a local rivers group, Clochán Uisce aims to highlight the problems that resident flora and fauna face and look for ways to improve the overall ecology of our rivers. The group will highlight these issues on World Rivers Day on September 24.

Also, later this month the groups plans on gathering in Shannonvale to highlight the massive environmental issues that the community there has been battling for years, as a result of the sewage and pollution that drains into the Argideen river. Keep an eye on Instagram or email the group for more details. You can find Clochán Uisce on Instagram or join the mailing list by emailing 

WCP Staff

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