The river holds a large population of wild Brown Trout, much of which was killed in 2006 when a large quantity of aluminium sulphate was flushed into the river from the Pontsticill Water Treatment Works, which United Utilities operate on behalf of Dwr Cymru/Welsh Water. The pollution turned the water white for at least 5km downstream of the works and killed approximately 23,000 fish, including wild brown trout, bullheads, stickleback and pike, as well as wiping out uncountable numbers of invertebrates. According to the Environment Agency Wales, it is estimated that the river will take between 6 and 12 years to recover, although it is making rapid progress. As of the summer of 2009 the trout population is once again breeding. The river is much revered by fly fisherman and the fishing rights are owned by Merthyr Tydfil Angling Association.