Fishers are now banned from using hooks larger than 56mm shank length and 23mm gape, to better protect the dolphins that call the Adelaide Dolphin Sanctuary home.

The new rule follows a successful trial - and subsequent implementation - of a ban on using fishing line, either by hand or rod, within 50m of a visible dolphin in the inner waterways of the Port Adelaide River system.

The Adelaide Dolphin Sanctuary was established in 2005 to protect its resident population of Indo-Pacific bottlenose dolphins. It is also an important fish nursery and breeding area.

Today, it is home to around 30 resident bottlenose dolphins, with another 400 transient dolphins visiting the area at various times to feed, play, socialise and nurse their young.

The marine park is one of the gems of metropolitan Adelaide, located only 20 minutes from the city and accessible via Port Adelaide, Garden Island, Outer Harbour, North Haven and St Kilda.

Department of Primary Industries and Regions Executive Director Fisheries and Aquaculture Gavin Begg said the measures were necessary to protect dolphins while also allowing for recreational fishing within the sanctuary.

"Historically the area has been a popular recreational fishing spot, enjoyed by many families," Prof Begg said.

"If you are fishing in the area, which is home to a sensitive dolphin population, it is important to fish responsibly.

"If a dolphin pops up, pull up your line, stop fishing and allow for the dolphin to pass before resuming."

The new restrictions have been introduced for a period of 12 months, with permanent regulations set to be implemented before the year is out.

For more information about the Adelaide Dolphin Sanctuary and what you can see and do, visit the National Parks and Wildlife Service SA website.