The death of close to 1,100 wild Atlantic salmon in the Co Sligo river recently hasn’t been definitively linked to any particular causes, according to the national agency responsible for fisheries conservation. However, they did highlight potentially damaging phytoplankton, known for harming salmon gills, as a probable contributor.
Over the summer, the Inland Fisheries Ireland (IFI) undertook exhaustive inquiries into the fish loss in the lower Ballisodare river, situated south of Sligo town, but only potential causal factors could be pinpointed, a spokesperson for IFI stated.
The investigative study proposed that several of the salmon might have suffered from stress at sea, possibly correlating to high concentrations of phytoplankton in Drumcliff Bay, which can impair salmon gills and disrupt their respiration, according to the study.
Such stress could have been compounded by the river’s low water conditions where a large population of salmon assembled. This could have made disease outbreaks more likely, the study added.
Despite all this, there was no sign of a significant pollution event in the affected river area, the study pointed out. Nonetheless, water samples taken in mid-July may not have shown any lone pollutant that contributed to the death seen from the end of June, the study elaborated.
It was noted with concern that the Ballysadare wastewater treatment plant had exceeded its ammonia discharge limit in recent times. The results were apparent right before the first deaths were noticed close to the plant.
The actual number of fish deaths could be “somewhat higher” than the 1,079 salmon deaths reported between 28th June and 21st July in the Ballisodare river, the report mentioned. Moreover, it appears that no other fish species were affected, stated the IFI.
Feeling deeply distressed over such a staggering and tragic loss of wild Atlantic salmon, Barry Fox, deputy chief executive of IFI, expressed his grief. The report’s recommendations include weekly sampling of phytoplankton in the Ballisodare estuary before and during the return of the salmon, amongst other guidelines.
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