Local fishermen were concerned after 'thousands and thousands' of small fish were washed up dead on Benar Beach near Barmouth, Gwynedd.
The fish are believed to be sprats, which belong to the clupeidae family of ray-finned fishes.
The incident was reported to Natural Resources Wales on Saturday after the fish were spotted washed up along the shore.
Natural Resources Wales said that whilst the number of fish washed up on the beach 'may appear worrying', it was simply a result of 'nature at work'.
It says the fish ended up on the shore because they were trying to escape larger species in the water.
Natural Resources Wales said: “Our officers received a report on Saturday of a number of fish that have washed up on Benar beach, near Barmouth in North Wales.
“The calm seas this week mean that larger predators, such as seals or mackerel, can often end up chasing smaller fish all the way onto the sand."
The spokesperson added: “The fish in these bait balls then ground themselves on beaches in an effort to escape.
“Although it may appear worrying it is only nature at work. Thank you to everyone who got in touch to report this."
Natural Resources Wales said that it would not be launching a clean-up operation on this occasion as the incident was not caused by pollution or any similar factor.
It says it's thought to be more beneficial for the nutrients in the sprats to be recycled back into the sea, and that high tide would result in most of the fish being washed back into the water.