Risk assessment of water and shellfish quality in Clew Bay

Fergal Guilfoyle

Terence O’Carroll

Why carry out a risk assessment?

• Problems with current legislation/directives• Proactive rather than reactive• More than just monitoring required• Identifies problem areas• Allows potential to improve situation

Why Clew Bay?

• Has a good record in respect of shellfish safety• The Clew Bay Marine Forum Ltd.• Active CLAMS group• Good working relationship with Authorities• Good existing sampling programme

Shellfish Water Quality

• Shellfish water quality traditionally assessed by E. coli and Faecal coliforms

• Main health concern are viruses (Hepatitis A and Norwalk-like viruses)

• Viruses survive longer in environment and are slower for shellfish to depurate

• Other potential contaminants, heavy metals, hydrocarbons etc.

• New methods needed

Sources of Information.

• Shellfish Industry• DoCMNR • Marine Institute• An Post Geodirectory and CSO figures• Local Authority (Mayo Co. Co.)

• Wastewater Treatment Plants

• Licensed industries.

• Blue Flag Beaches

• EPA

Area RiskMurrisk Low-mediumWestport Bay Very HighRosmoney Shellfish LowKilmeena LowRoslaher LowInishlaughill LowNorth Bay Low-medium

Native BedsWestport Bay Very HighOuter islands LowInner Islands LowNewport Bay HighNorth Bay Low-medium

Level of risk assessed for each main area:

Practical Assessment

• 10 sites selected• Mussels and Gigas Oysters at each site• Sub Samples tested for E. coli and Bacteriophage• Water chemistry also collected at each site and

from main rivers

Bacteriophage as indicators

• Bacteriophage may be useful indicator• Easy to detect

• Cheap to test for (?)

• Present in human sewage

• Able to show same or better survival characteristics than the pathogens

• Not pathogenic themselves

Preliminary Results

• 4 months sample results collected• Results confirm the level of risk assessed

Site Level of risk. Shellfish Species E. coli BacteriophageWestport Inner Very High C . gigas 11400 401600

Westport Inner Very High M . edulis 10167 332000

Westport Outer High C . gigas 343 5600

Westport Outer High M . edulis 620 5600

Newport Inner Very High-High C . gigas 8283 34010

Newport Inner Very High-High M . edulis 8933 20000

Newport Middle High C . gigas 2133 13500

Newport Middle High M . edulis 1067 <30

Newport Outer Medium-High C . gigas 457 520

Newport Outer Medium-High M . edulis 1220 <30

Inishquirk Low- Medium C . gigas 310 <30

Inishquirk Low- Medium M . edulis 647 <30

Murrisk Low- Medium C . gigas 107 <30

Murrisk Low- Medium M . edulis 103 <30

Inishlaughill Low C . gigas 147 <30

Inishlaughill Low M . edulis 233 <30

Roslaher Low C . gigas 147 <30

Roslaher Low M . edulis 233 520

Rosmore Low C . gigas 1233 <30

Rosmore Low M . edulis 2167 <30

Preliminary Results•4 months sample results collected

•Results confirm the level of risk assessed

•What level is safe?

•-5000 pfu/100g?

•-2000 pfu/100g?

•-<30 pfu/100g?

Conclusion:

• Currently farmed shellfish are mainly in ‘low’ risk areas

• Microbiological & biotoxin contamination main concern for shellfish

• Human population and treatment most important influence

• Clew Bay water quality is very good for most part• Risk assessment seems to tally with bacteriophage

results• Thank you