Giant octopuses living in Puget Sound are being counted by divers, in an annual drive to record the number of these animals living off the coast of Washington state.

Seattle Aquarium conducts the survey every year, in order to determine how populations are changing over time. Because the species is not on the federal endangered or threatened species lists, there is little study on population levels of the marine lifeforms.

Giant Pacific octopuses can grow to lengths up to 20 feet, and the animals can weigh as much as 150 pounds, making them the largest octopus in the world.  The creatures live throughout many regions of the Pacific Ocean, including waters off northwestern United States. They are difficult to count, in part due to their short life spans. Members of the species live between three and five years, and they die soon after mating.

A team of 27 volunteers divers explored 11 sites around Puget Sound during the octopus survey. They found 28 animals during their search, up from 17 during the previous year.

"We've been watching the numbers go up, then kind of go down, then kind of go back up. That could be having to do with population and mating. As they all peak and mate, they slowly die off, then they start to grow back up again," Kathryn Kegel, a biologist with the Seattle Aquarium, said.

Divers taking part in the study note the number of octopuses they see, the depths at which the animals are residing, and the types of hiding spot they are using. The process is not scientifically precise, but this still represents the best such study of the animals currently being conducted.

Puget Sound is a popular destination for local divers, many of whom enjoy viewing the giant octopus. The water body is dark, making it difficult to observe the animals.

Giant Pacific octopuses live on a diet of scallops, crabs, and shrimp, which they hunt during nightime hours, During the day, they stay hidden away in dens. Divers, prowling areas known to be octopus habitats, use flashlights to see the animals in the darkness.

Seattle Aquarium will be celebrating Octopus Week from February 14 to 22, which will kick off with an "octopus blind date." Wildlife professionals will introduce a male and female giant octopus to each other for the first time.

"Aquarium biologists will set the mood with decorative hearts, roses and romantic music at the Octopus exhibit. Will the octopuses decide that love is in the water? Join us to find out!" Seattle Aquarium officials wrote.