Irish fishing survey suggests salmon surviving dace invasion

6 Jun 2017

Fishing for Dace. Image: hasky2/Shutterstock

A major investigation into fish in Ireland’s River Barrow found dace, and other invasive species, to be thriving. Salmon and brown trout, though, are still doing fine.

Invasive species are a nightmare, whether it’s fish in a river, birds at nesting sites or squirrels in a park. As the term implies, they invade. As it hints at, they often conquer.


Competition is fierce

Future Human

That’s why red squirrels are a rarity in certain countries where they were in abundance only a couple of decades ago. It’s why rhododendrons have played their part in restricting growth of native oak tress in Ireland. And it’s why the number of dace in Irish rivers is a concern.

A recent piece of research from Inland Fisheries Ireland has revealed that dace – a fish native to mainland Europe and northern Asia – is thriving throughout the River Barrow, Ireland’s second-longest river.

More than 60pc of sites investigated found stocks of fish (including invasive species) were at levels that were moderate, or less than desirable. The reasons for this include water quality, habitat standards, migration barriers and competition from dace.

More than 10,000 fish were caught and released as part of the survey, with a total of 14 fish species and one hybrid species identified.

Dace, dace, dace

Dace was pretty much everywhere, found at 90pc of all sites, with roach – another invasive species and the second-most common fish – found at 81pc of sites. The latter has further reach than dace throughout the country.

Atlantic salmon was found at more than half of sites, with brown trout found at a similar number of locations, though in low numbers.

The latter is not a huge concern to Inland Fisheries Ireland, as the spread was even throughout, though further studies are needed to establish how many, and of what species, are a constant fixture in Irish rivers.

Inland Fisheries Ireland staff electrofish the River Barrow as part of the research. Image: Inland Fisheries Ireland

Inland Fisheries Ireland staff electrofish the River Barrow as part of the research. Image: Inland Fisheries Ireland

First of its kind

“This survey is the first of its kind within this large catchment area and it tells us a great deal about what is happening on these sites,” said Dr Fiona Kelly, senior research officer at Inland Fisheries Ireland.

“It is evident that we have an abundance of different types of wild fish species present. However, we also know that there are challenges for the catchment in terms of water quality, habitat and invasive species, which will need to be addressed.

“Ultimately, this research will inform future fisheries management and protection strategies.”

Inland Fisheries Ireland has been very active in 2017, with this study one of several initiatives taking place on the country’s waterways.

Last month, a new fish counter facility opened in Co Donegal, with several key species now monitored at the designated spring salmon fishery on the River Lackagh.

The site will monitor spring salmon, grilse (a salmon that has returned to fresh water after a single winter at sea) and sea trout, compiling key data for stocks in Lough Beagh and Glenveagh National Park.

Big job

The organisers call it a major infrastructural project, with the building of a crump weir, Logie fish counter and an access road to the Lackagh River at Creeslough all included.

It is hoped that we will now be able to access verifiable, accurate data on the size, duration and timing of fish migration through the fishery.

Elsewhere, a River Erriff study, backed by EU funding, was revealed in late April.

Catching, tagging and monitoring of juvenile salmon (smolts) in the area was logged online, to allow more people to keep track of what’s flowing up and down the Erriff.

The Co Mayo study saw researchers catch juvenile salmon in traps in the Black River, a tributary of the Erriff, before attaching sensors to them and releasing them back into the wild.

Gordon Hunt was a journalist with Silicon Republic