The water vole is becoming increasingly rare in Welsh rivers
The Welsh Assembly Government has extended the law to help save five under-threat animals from harm.
Environment Minister Jane Davidson has announced improved protection for angel sharks, water voles, Roman snails and spiny and short-snouted seahorses.
It means it will be an offence to kill, injure or take any of the species from their natural habitats in the future.
In addition, possessing or selling a water vole, roman snail or any of the seahorses will also become an offence.
The new provisions come under the Wildlife and Countryside Act 1981 with each of the animals now sharing the same protection as the already protected otter and grass snake.
All of the species are very elusive and difficult to spot, according to experts.
The water vole is found throughout the rivers of Wales, although is becoming increasingly rare. Roman snails are more common in central England and larger than most snails.
Short snouted seahorses are not usually found in Wales but in the Channel Islands and the coast of southern England.
The Spiny seahorse is mainly found off the coast of southern England, although there have been sightings along the west Wales coast.
The Angel Shark is very rare but there have been sightings along the north and west coast of Wales - off Anglesey, Llyn peninsula and Pembrokeshire.
Anyone found not obeying the new legislation could face a maximum £5,000 fine and six months imprisonment.
The same legislation was introduced in England in February and further species will be considered for addition to the list of protected species later this year.
Ms Davidson said the move will ensure a more secure future for each of the species now covered by the law.
"It is in all our interests that Wales's valuable wildlife is protected, and a lot of work has been done to ensure that the list of species being protected is comprehensive," she said.
Iwan Hughes, a species protection officer for the Countryside Council for Wales (CCW) said: "CCW welcomes the addition of these species to the protected species list. These additions indicate the vulnerability of these species in Wales and the need to protect them for future generations."