Natural Resources Wales said its officers had been informed of a large quantity of sprat on Benar beach in Gwynedd on Sunday. "Although it may appear worrying it is only nature at work," Natural Resources Wales tweeted. "The calm seas this week means that larger predators, such as seals or mackerel can often end up chasing smaller fish all the way on to the sand. "The fish in these bait balls then ground themselves on beaches in an effort to escape." Natural Resources Wales thanked the public for reporting the incident to their hotline 0300 065 3000.