An increase over recent weeks in the presence of Pacific pink salmon, a non-native species, in prime Irish rivers is a cause of growing concern for Inland Fisheries Ireland (IFI).
The invasive species may affect indigenous salmon populations in the future by, for example, introducing parasites and pathogens in native salmonid fish.
The state agency responsible for the inland fisheries appealed to anglers and the public on Monday to “remain vigilant and report the presence of any Pacific pink salmon” in Irish river systems. They advised anglers not to return the fish to water. To date, 30 pink salmon have been recorded in nine Irish rivers since the first catch was reported on June 27th from Galway Weir fishery.
Pink or humpback salmon are a migratory species of salmon, native to river systems in the northern Pacific Ocean and nearby regions of the Bering Sea and Arctic Ocean. The species also has established populations in rivers in northern Norway and in the far northwest of Russia – it is believed to have originated from commercial stocking programmes undertaken in this part of Russia in the 1960s and 1970s.
Their presence here is a mystery, the IFI said, and they are not believed to have originated from fish farms, as there is evidence they are occurring this year in big numbers in Norway, Iceland and Scotland. In Ireland, there is no licence to farm Pacific pink salmon. Ireland’s own native salmon species is the Atlantic salmon.
"Interbreeding with Atlantic salmon is unlikely as pink salmon spawn in late summer whereas Atlantic salmon spawn in winter. However, competition for food and space in nursery areas between juvenile pink and Atlantic salmon is possible," said IFI senior research officer Dr Paddy Gargan.
One of the most recent captures of pink salmon was a mature male ready to spawn on the River Erriff in Co Mayo, Ireland’s “National Salmonid Index Catchment” where a wide range of scientific research and monitoring activities on resident salmonid populations is undertaken.
Catches of pink salmon have also been reported on rivers usually renowned for their healthy Atlantic salmon stocks including the Foxford Fishery and Coolcronan Fishery on the River Moy in Co Mayo; the River Corrib and the Cong River in Co Galway, and the Drowes and Crana Rivers in Donegal. The most recent catch was on the Owengarve River in Mayo on August 10th.
IFI is appealing to anglers to report catches of pink salmon to their 24-hour confidential number – 1890 34 74 24 or 1890 FISH 24. As these fish die after spawning, some dead specimens could also be encountered along Irish rivers.
Anyone who catches a pink salmon is asked to keep the fish and not to release it back into the water, even in rivers only open for “catch and release” angling. The date and location of capture, length and weight of fish should be recorded and a photograph taken. They are also advised to tag the fish and present it to Inland Fisheries Ireland, and a new tag will be issued to replace the tag used.
IFI said it would arrange collection of the fish for further examination. “This will help establish the abundance and extent of distribution of the species in Irish waters,” Dr Gargan said.
During their spawning migration into freshwater, males develop a pronounced humped back, hence their nickname “humpies”. Pink salmon can also be distinguished by other unique characteristics which are different to Atlantic salmon. They include large black oval spots on the tail; 11 to 19 rays on the anal fin, very small scales (much smaller than a similarly-sized Atlantic Salmon), no dark spots on the gill cover and an upper jaw typically extending beyond the eye.