More than half of Northern Ireland's rivers and three quarters of its lakes are showing signs of pollution, a new report has revealed.
Environmental campaigners say the figures show it still pays to pollute waterways.
Northern Ireland must report to the EU every four years on its Nitrates Action Plan, which aims to protect waterways from agricultural pollution.
The latest report, launched by Environment Minister Alex Attwood and Agriculture Minister Michelle O'Neill, reveals that nitrate levels in groundwater and surfaces water are generally low, either stable or decreasing, while phosphorus levels in rivers are stable or decreasing.
But more than half of rivers and three quarters of lakes show signs of nutrient enrichment, which can cause algal blooms that deplete oxygen, causing fish kills. The main cause of this enrichment is phosphorus from agricultural run-off and human waste.
Ms O'Neill said phosphorus efficiency on farms is now the highest since records began in 1926, saying farmers have invested heavily in slurry storage and advanced slurry spreading equipment. She called on farmers to remain vigilant to ensure water quality is protected so that Northern Ireland can secure agreement in Brussels during 2014 for a Nitrates Action Programme that is "workable".
Mr Attwood said good work by farmers is starting to pay off but more needs to be done to tackle pollution.
But Friends of the Earth NI director James Orr said. "The agri food industry must do more to protect our rivers and lakes, and penalties must increase for persistent offenders. So low are the fines that research from Queens University tells us that it still pays to pollute our waterways in Northern Ireland."