Expert issues warning over impact of Rainbow Trout

Loughs Agency staff carry out a Rainbow Trout survey on some of the rivers affected by the escaped fish.

ANGLERS on the River Mourne can expect to catch a Rainbow Trout every two minutes – this is according to an expert who recently completed a study on last August’s unprecedented fish escape.

Writing in his ‘Rainbow Trout Assessment’ Prof Ken Whelan – one of Ireland’s foremost fisheries scientists – also noted that none of the methods employed by Loughs Agency have proved successful in significantly reducing the numbers of escaped Rainbows.


It is also now known that when the incident occurred during flooding last August some 387,000 Rainbow Trout escaped from Rocks Lodge Trout Farm on the Bunderg Road, near Newtownstewart.

Prof Whelan also warned that environmentally and economically, these invasive fish have already made a “major” impact on the local rivers eco-system.

“Since escaping into the River Mourne in late August 2017, the AFT (all female triploid) Rainbow Trout have caused very serious impacts to the wild salmonid game fisheries downstream and immediately upstream of the trout farm,” Prof Whelan reported.

“There is low level leakage of Rainbow Trout from the two Rainbow Trout farms in the catchment and two larger scale escapes, one from each farm, have occurred previously.

“As a result anglers frequently encounter Rainbow Trout as a by-catch while fishing for salmon or trout downstream of both farms.

“However, the mass escape of this past summer was unprecedented in its scale and magnitude and largely brought to a premature close salmon fishing on several key salmon fisheries immediately downstream of the farm.”

He continued, “As a result, some eight key weeks of the prime salmon angling season were lost, as anglers could not fish effectively for salmon given the high concentrations of Rainbow Trout packed into the pools. Brown trout fishing in the river was practically impossible, as Rainbow Trout escapees were densely packed into the fishing pools and grabbing at any trout fly, lure or bait used by anglers.

Economic losses
“This loss of angling resulted in significant economic losses to proprietors, angling clubs and business associated with angling on the river (accommodation, tackle shops, angling guides, grocery stores etc).

“It was also socially disruptive to an area where a very significant number of residents are dependent on traditional angling as a source of relaxation and enjoyment.”

After the floods and the subsequent fish leak the Loughs Agency carried out an initial assessment of the damage caused to the fishery habitat and raised concerns with the Department of Agriculture, Environment and Rural Affairs (DAERA) Marine and Fisheries Division, who are the licensing authority for fish farms in the North.

As part of the body’s fisheries management response, scientific staff undertook a number of initiatives including electrofishing and fyke netting to inform what actions could be undertaken to remove the farmed fish from the rivers and to conserve and protect the native fishery.

However, according to Prof Whelan these methods have proven ineffective vis-a-vis reducing the population.

“Given the scale of the escape from the trout farm none of these methods proved successful in significantly reducing the numbers of escaped Rainbows,” the professor reported.

“Over the course of the angling season, which ended on October 20, 2017, anglers have, on a voluntary basis, put in a very determined effort to remove as many escaped trout as possible from the main stem of the river.

“Using sweetcorn and worms anglers have reported on social media catches of up to 360 in four angling sessions, with a catch rate of one Rainbow Trout every two minutes.”

He added, “As outlined previously AFT brown trout survive well over winter and are very free-rising early in the season, having fed all winter long (Noble et al 2004).

“If the escaped Rainbow Trout behave in the same manner and if significant numbers of trout over-winter in the prime salmon and trout pools, the Rainbow Trout escape of August 2017 could continue to have serious consequences for fishing for both salmon and trout during 2018 and result in additional losses to the local economy and to the enjoyment of a highly prized sporting resource, of local and national importance (Dillon et al, 2000).”

Report their catches
Sharon McMahon, designated officer at Loughs Agency added, “We will continue to work with the relevant statutory agencies to ensure robust biosecurity mechanisms are put in place at fish farms within our catchments to prevent or minimise the risk of further escapements.

“We have been, and will continue to, engage with local angling clubs and umbrella bodies such as the Foyle Association of Salmon and Trout Anglers (FASTA) to inform and update anglers as the situation progresses.”

The agency said it appreciates the concerns of anglers and greatly values the efforts anglers have made in removing Rainbow Trout from the rivers. It further encourages anglers to continue with this and would ask that they report their catches to Loughs Agency.

A reporting sheet is available from the Loughs Agency website.

This sheet is only to be used for reporting on catches of Rainbow Trout in rivers within the Foyle system and excludes still water lakes. This information will be used to monitor how many fish have been removed, their size and location. Any Rainbow Trout which are over 30cm in length should be given to the agency so that they can conduct further analysis.

Please contact the agency directly on 02871 342100 if you catch a fish of this size to arrange for collection.


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