Four years photographing killer whales in the waters off Bremer Bay in Western Australia has culminated in the state's first publicly available orca catalogue.

Eighty-one killer whales with nicknames such as Cookie, El Notcho and Lucky were catalogued by researchers from Curtin University's Centre for Marine Science and Technology (CMST).

The Project ORCA database, published online on April 28, hopes to fill knowledge gaps about the health, size, and migration of Australia's killer whale population.

CMST PhD candidate Rebecca Wellard studied the orcas during expeditions to the Bremer Sub-basin between January and April each year since 2014.

The sub-basin is a vast area covering 11,500 square-kilometres, including the Bremer Canyon orca hotspot.

Mysterious marine mammals

Killer whales' transient nature makes it tough to study the marine mammals.

"We're still very much learning about the killer whales here in Australia," Ms Wellard said.

The first catalogue of Bremer Sub-basin killer whales has been published. ( Supplied: Rebecca Wellard, Project ORCA )

"Much of our information on killer whale distribution through Australia is from incidental sightings.

"There's been no reliable estimate of the population of killer whales in Australia and population trends are still unknown."

Ms Wellard said encounters with orcas were very rare but the waters off Bremer Bay supported an abundance for a few months of the year.

"The Bremer Sub-basin is a very, very special area," she said.

"It provides an opportunity to study this little-known population we have here in Australia."

As well as the number of whales, the new catalogue will help scientists monitor their migrations around Australia.

It can also be used to document orcas birthing, calving and death rates.

How do you identify killer whales?

Cookie and El Notcho are two of the catalogued killer whales in the Bremer Sub-basin. ( Supplied: Rebecca Wellard, Project ORCA )

The 81 individual killer whales were characterised mainly by their dorsal fin.

"This is as unique as a human fingerprint," Ms Wellard said.

"We look at little nicks and notches and the shape of the dorsal fin."

Cookie gets her name from a biscuit-shaped section missing from her dorsal fin, while El Notcho has a large notch missing from his.

A killer whale called Bindi and her calf are part of the WA orca catalogue. ( Supplied: Rebecca Wellard, Project ORCA )

Unique white markings on each whale's back — called a saddle patch — and near their eye — called an eye patch — were also used to tell them apart from each other.

Some of the catalogued orcas' names come from the Australian Aboriginal language spoken by the Noongar people of south-west WA.

Kwilana is the Noongar word for dolphin.

Miro, which translates to 'spear thrower', was chosen for a female orca documented attacking a beaked whale in the Bremer Sub-basin in 2016.

A growing database

Ms Wellard said another 20 killer whales will be added to the catalogue soon.

She hopes citizen scientists submit their photographs of killer whales spotted along other sections of WA's coastline to Project ORCA for comparison.

"I've had photos donated to us from animals seen all up the west coast," she said.

"From Rottnest, from Lancelin, there's also another population of killer whales we know of on the Ningaloo Reef.

"We have tried to match them with the Bremer animals and we still haven't had any matches yet."

Curtin University's Rebecca Wellard photographs killer whales in the Bremer Sub-basin. ( Supplied: Curtin University CMST )

Although the total Australian killer whale population remains unknown, Ms Wellard said more than 100 orcas was a significant amount.

"It's quite a good catalogue to have from just one region," she said.

"The New Zealand catalogue has over 200 individuals and that's the whole way around New Zealand."

The first catalogue of Eastern Australian orcas was released by Killer Whales Australia in 2016.

To contribute to the catalogue visit the Project ORCA website.