Ding dong! Utrecht's famous fish doorbell returns for a new season

It's o-fish-ial - the world's first fish doorbell is back for another season.

Located in Utrecht in the Netherlands, the underwater camera was first set up five years ago, to help the different fish species that swim in the canals in the Dutch city.

It streams video to a special website, and internet users who spot any fish waiting at the lock gate can ring a 'digital doorbell' to help the marine life carry on their journey.

But how does it work and why do fish need the doorbell? Keep reading to find out..

Every spring, fish swim upstream around the Dutch city of Utrecht looking for a place to lay eggs.

However, the Netherlands is a country with lots of canals and waterways and, in spring, the lock gates along these canals aren't opened much, which can make it difficult for fish to travel to their breeding grounds.

That's why five years ago experts came up with a plan to help the aquatic animals - a digital fish doorbell.

An underwater camera was installed at the lock which is live-streamed to a website which people can watch anytime of day.

As soon as they spot a fish, viewers can press a digital doorbell on the website to let the lockkeepers know when to open the gates and let the fish through - helping the fish to continue on their route to breeding grounds.

The keeper checks if there are enough fish there to open the gates and the fish can swim on their merry way.

Researchers say that the best time to see the fish is either in the morning or at dusk - when they are at their most active.

Last year, the doorbell was pressed more than 200,000 times and 13 different species of fish were spotted.