Researchers in Western Australia who waded through 11 years of underwater footage have found habitats favoured by young sharks are not protected.

University of WA PhD researcher Beverly Oh found many of the nursery habitats were outside protected marine areas.

"Sharks are really important to our oceans and they contribute to a healthy fish population, but at the same time they produce very few offspring that take quite a long time to mature, which makes individual offspring very important," Ms Oh said.

"The young sharks tend to spend time in nursery areas which allows them a safe space to grow faster and where they're less vulnerable to predators."

Researchers dropped about 2,000 underwater cameras in the ocean covering about 3,000km of WA's northern coastline in 2003, giving researchers 11 years of data.

Ms Oh used the data to predict where the key habitats were for the next generation of sharks.

Sorry, this video has expired Researchers trawled through 11 years of footage

"Then we can evaluate whether these key habitats are being offered adequate protection," she said.

The study showed there was very little overlap between the proposed and existing marine reserves in the area with those suitable shark habitats.

"If we want to have sustainable protection for them for the long term, we need to be able to identify where [young sharks are] and protect the habitat of the next generation so they can grow to adulthood," Ms Oh said.

Globally shark numbers are in decline, Ms Oh said.

"That's partly because of over-exploitation from fishing as well as cumulative impacts from habitat loss and climate change are affecting areas where sharks can actually grow," she said.

"Ideally, we hope our predictions can be a useful tool that can be integrated into the decision-making process to improve conservation and management of sharks."