Gathering evidence

Gathering evidence for a fish kill prosecution.


Acting on a report of water pollution from a member of the public to the local River Basin District office, one of our officers inspected the site and confirmed that an incident was occurring. Senior Fisheries Environmental (SFEO) staff initiated an immediate investigation.


The investigation was undertaken in a manner that evidence gathered would support a prosecution under the Fisheries/Water Pollution Acts. Once the source of pollution was identified the key objective was to ensure that the pollution immediately ceased and that corrective measures were taken to prevent such an event in the future.  

The priority objectives were to 1) find the source of the water pollution as quickly as possible; 2) stop the discharge to prevent further damage occurring; 3) identify the persons responsible; 4) collect information including samples which would determine the nature and extent of the impact on the river environment. 

Environmental officer gathering a water sample


On arrival at the location it was apparent from the presence of dead trout and eels on the riverbed, and the colour and smell of the water, that a serious water pollution event was underway. The challenge was to locate the source of pollution and get it stopped.

The section of the river identified as the general source was then checked by starting downstream of the unknown source and walking upstream following the flow of pollution and dead trout and eels. Field instrumentation to measure water oxygen and pH levels were utilised to gather information on water quality conditions as the source of the pollution was reached.

The area affected was established by a systematic bridge check to find where water was polluted, and the upstream extent of the polluted water. Eventually, a concrete pipe was found discharging a large outflow of liquid. No evidence of dead fish or polluted conditions were observed upstream of this point. Samples and photos were taken of the river water and pipe outflow, ensuring sampling techniques were appropriate for potential legal action.

The pipe was traced to its source, the property owner was identified and advised of the seriousness of the situation and the potential for legal proceedings. The owner was formally questioned under caution and instructed to stop the discharge immediately.

Replicate samples were offered to the owner who was given the opportunity to inspect the outfall location and damage caused. The samples were delivered directly to a certified laboratory for scientific analysis and the impact on the river was assessed for habitat and aquatic ecological damage.

Other water users and authorities downstream of the location were notified at the time of the event. A fish population impact study was conducted which established that fish had been affected over 3 kilometres of river and that near the point of discharge, aquatic insects including mayfly, stonefly and freshwater shrimp had also been killed.   


While the pollution was stopped as soon as possible, extensive damage was caused to the river habitat and fish life with more than 2,000 trout and eels affected; analyses of samples confirmed a discharge of polluting effluent from the property.

Legal proceedings were taken against the owner of the property and a conviction under the Fisheries Acts and a fine of €500 was secured. Costs and expenses of €2,500 were awarded to us. The owner contributed €5,000 towards instream habitat improvements and undertook civil works on the property costing €15,000 to prevent a recurrence.

Sampling Kit for Fish Kill investigation