Notification of Karenia mikimotoi and Noctiluca scintillans blooms; Diarrhetic Shellfish Toxin Events in Southwest and Southeast
Diarrhetic Shellfish Toxin Event – Offshore Southeast Coast
Updated 04-09-26
Please note quantifiable levels of Diarrhetic Shellfish Toxin (DST) have been detected in whole tissues of king scallops (Pecten maximus) in non-classified offshore harvesting grounds of the Southeast coast since w/c 06-08-26.
Whole scallop samples analysed to date during this week (w/c 31-08-26) from ICES rectangle 32 E2 are observed to have significantly increased on previous weeks and are above the recommended toxin limits for DSTs in whole scallops(0.342µg/g)
Fishers of offshore scallops should be aware that recent increasing trends in DST concentrations detected in scallops from statistical rectangles to the southeast of Ireland (particularly 33E2, 33E3, 32E2, 32E3, 31E2, 31E3). This upward trend in levels indicates significantly increased risk for DST levels in this species. These elevated results include the detection of a whole scallop sample test result for statistical rectangle 32E2 from the end of August which significantly exceeded the DST whole body recommended limit rendering shucked scallops from this area ineligible for market. For this reason, it is strongly recommended that the scallop super area described by 33E2, 33E3, 32E2, 32E3, 31E2 and 31E3 and adjacent areas should not be fished until further notice due to the increased risk of DST levels exceeding the recommended limit. As always, the rules as described in the Biotoxins Code of Practice, specifically summarised for scallops in the Food Safety Information Notice (both available here), should be consulted should there be any uncertainty regarding appropriate testing processes for offshore scallop fishing.
Further updates on this notification will be issued following publication of further scallop test results from September samples taken the southeast which are expected early in the week beginning Monday the 7th of September
Noctiluca scintillans bloom event – Southwest Coast
Updated 01-09-26
Please note cell densities of the bloom forming dinoflagellate Noctiluca scintillans have been observed to be present at low cell densities in multiple inshore locations in the Southwest(Bantry & Kenmare) and South coast (Kinsale) last week (w/c 24-08-26) in samples submitted for the Phytoplankton National Monitoring Program.
While this species is non-toxic, it may cause mortalities among marine organisms, particularly as the bloom decays and depletes oxygen in the water column. It may also cause an unpleasant smell as the bloom breaks down due to the release of ammonia.
It is a naturally occurring bloom which happens annually around the coast of Ireland along South and Southwest coasts, and historically has also been observed off western coasts.
Please report any mortalities and seawater discolouration’s to HABS Team Marine Institute (habs@marine.ie)
Karenia mikimotoi declining bloom event – Southwest Coast
Updated 01-09-26
Analysis of water samples submitted through Phytoplankton National Monitoring and BIM Southwest Mussel Larvae programmes, have revealed cell densities of the bloom forming dinoflagellate Karenia mikimotoi have been significantlydecreasing in multiple inshore locations along the Southwest and West Southwest over the last 3 weeks. However, low to moderate persistent cell densities are still being observed in Roaringwater Bay (>800,000 cells/l) and Kinsale (>20,000 cells/l). the Phytoplankton National Monitoring Program and BIM Southwest Mussel Larvae programme. There have been no observations of water discolouration or mortalities reported during the last two to three weeks.
Very low cell densities have been reported in along West coast (Achill, Killala and Mannin) in samples submitted this week (24-08-26).
Please beware previous Karenia mikimotoi blooms in Ireland have also been associated with mortalities of marine organisms including flatfish, benthic invertebrates, as well as farmed shellfish and finfish. It is thought that these mortalities are as a result of depleted or low oxygen levels that can occur when the bloom begins to decay.
Please report any mortalities and seawater discolouration’s to HABS Team Marine Institute (habs@marine.ie)
Diarhettic Shellfish Toxin Event – Southwest Coast - Castlemaine, Kenmare, Bantry.
Updated 01-09-26
Low quantifiable concentrations of Diarrhetic Shellfish Toxin (DST’s) concentrations have been observed in a number of mussel sites in various production areas in Kenmare, Bantry, and Castlemaine, well below the regulatory limit (0.16µg/g) during last week (w/c 24-08-26). Over the last two weeks, DST concentrations have been observed to be decreasing in all sites in Southwest.
However, please note there maybe potential variability of DST concentrations within shellfish from these areas.
During last week (w/c 24-08-26) cell densities of the causative toxin producing phytoplankton species Dinophysis acuminata has decreased in multiple sites within the Southwest and West Southwest. Additionally over the last two weeks, there has been no occurrence of Dinophysis acuta observed in samples submitted.
