Zombie fish thought to be extinct was released back to nature after 24 years

A freshwater fish once thought to be extinct has been released back into the wild after researchers found it produced more than 3,000 offspring in a successful trial.

The southern spotted gudgeon, also known as the zombie fish, is rare and was once considered extinct. However, a group of biologists at Middle Creek Aquaculture have bred some of the species’ few fish in captivity so they can reproduce at the right time.

The return of these creatures to the environment occurred on Tuesday (6) in a swampy area in the Australian city of Bendigo.

According to the American broadcaster ABC News, the study of the breeding of fish of this species was much higher than the team at Middle Creek Fisheries had estimated for the experiment, after the confirmed volume of fry. Experts decided to release them into the swamp at the Riley Street Recreation Reserve near Sydney.

The southern spotted gudgeon, which resembles a goldfish, was considered extinct in 1998. Reaching a length of 12 cm, the fish breeds best in summer and likes to live in the depths of rivers.

The released offspring are expected to breed and navigate natural floodplains over the next 12 months.

Peter Rose, who led the group of researchers, celebrated the result of the experiment and detailed his expectations for the evolution of the species.

“This captive breeding program has been very successful with over 3,000 fry produced. Now these fish have been released to other wetlands around Bendigo, as far as Deniliquin and Mildura,” explained the biologist. “They will grow quickly if moved to other areas where we release them. I hope they mature next fall.”

Chris Lamin, who also participated in the breeding study developed by Middle Creek Aquaculture, said that the test was done only through unbridled sex of one mature male and five mature females.

“It was necessary to gradually increase the temperature of the water in a controlled environment, relative to the hours when the sunlight was strongest. We then observed the behavior of the females and noticed that gradually their abdomen and fat were increasing, with the appearance of many eggs”.

In recent years, 3,000 pups have been produced by eight females and just three males.

The fish are now released into an area with “no natural competitors” for ground or food so they can breed peacefully in their new habitat.

Bendigo Wildlife Sanctuary Team Leader Mark Toohey pointed out that the Riley Street Recreation Reserve was chosen as the home of the zombie fish, as swamps and other wetlands facilitate their breeding.

“We’re going to leave it to nature. We’re basically going to leave them alone and let the fish do what they naturally do.”