Police will carry out increased patrols of seal pup hotspots after reports of stones being thrown.
The patrols along a part of the Pembrokeshire coast in West Wales aim to protect seals and their pups during pupping season.
Regular visits will be paid by Natural Resources Wales (NRW) and Dyfed-Powys Police to Pwll y Wrach, also known as the Witches’ Cauldron, to ensure seals are left in peace.
Stones have reportedly been thrown at an area where seal pups are congregating.
There were further reports of people getting too close to them while taking part in water sports.
Last week, NRW said a dead pup was spotted floating inside the Witches’ Cauldron – a collapsed cave along the coast – after numerous sightings of female seals in the area.
The Pembrokeshire Coast Park Authority has put temporary signs in place to raise awareness.
Seals a protected species
PC Roger Jones from Dyfed-Powys Police has been seconded to NRW.
“We have growing concerns for the welfare of the seals who are using the area to breed and have pups at the area known locally as the Witches’ Cauldron,” he said.
“We urge people to take heed of our request to stay away from the area to give seals the space and time they need.
“Getting too close to the seals could frighten and disrupt them and remember, seals are protected, and it is a criminal offence to intentionally injure, kill or remove them from their natural habitat.”
Pupping season for seals in the UK takes place between late August and January, but the exact time depends on the region.
On Skomer Island just off the Pembrokeshire coast, seal pups are born from late August into November, according to The Wildlife Trusts.
In Norfolk they are born later, sometime between late October and January.
Last winter, a record number of seal pups were spotted along a five-mile stretch of the Norfolk coast.
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Visitors during pupping season are advised to keep off beaches where seal pups are present and are urged to keep quiet with dogs kept on leads.
If a pup is alone on a beach, its mother is usually nearby so people are asked to keep their distance so she can return when she needs to.
Anyone who witnesses seal pups being disturbed or mistreated are asked to contact police on the non-emergency number 101.