Science · River TorrensHackney koi carp: Nets deployed after more than a dozen suspected fish spottedAired October 26, 2026 at 11:01 PM UTCWritten October 26, 2026 at 11:06 PM UTCRead the write-upThis storyTranscript · LOADING0:07Bright orange, black, and multicolored fish have appeared in the River Torrens.0:10They're suspected koi and nets are being used to catch some upstream.0:13The concern is another lasting population competing with native wildlife in0:17Adelaide's River.0:18Can the fish be intercepted before their numbers grow?0:20The brightly colored group appeared last week between St.0:23Peter's Weir and Hackney Bridge, near Hackney.0:25A smaller number were seen farther upstream at Dernancore.0:28That's where nets are being used to try to catch them.0:31Green Adelaide manages the Torrens environment and suspects members of the public0:34released the fish.0:35Nobody responsible has been identified, and how the fish entered the river hasn't0:39been confirmed.0:40More than a dozen suspected koi were seen near Hackney.0:43That gives a sense of the group people spotted, rather than the river's total.0:47Identifying them as koi still needs confirmation through capture or examination.0:51Green Adelaide's Stuart Collar described that concentration as unusual.0:55He said there had been few records of koi in the river at all.0:57The concern is what these fish could become if they survive and spread.1:01Goldfish already provide a warning.1:03Green Adelaide regularly catches them during river surveys.1:06And Collard says tea here is understood to be a self-sustaining population.1:09Unwanted aquarium fish can survive beyond the moment someone releases them.1:13That existing goldfish population explains the urgency around the new sightings.1:17Whether these suspected koi have reproduced is still unknown.1:20The capture effort aims to stop another invasive population gaining a foothold.1:24Koi compete with native fish for food, much like European carp.1:27As they feed along the bottom, they stir sediment and disturb riverbed plants.1:31That can affect plant growth and put more pressure on the river's habitat.1:34Those feeding habits explain the ecological concern.1:37The response is aimed at preventing harm before an additional population expands1:41through a waterway where people are already working to help native wildlife recover.1:45James Johnston from the Invasive Species Council expressed disappointment at the1:48sightings, given the money and effort supporting native fish, Rakali, and other1:52wildlife.1:52Collard's priority is catching invasive fish early before they occupy more of the1:56river.1:57The state government announced another four million Australian dollars in August to2:01help return platypus to the Torrens.2:03They were last recorded there in the eighteen eighties.2:05Collard said the river was getting close to supporting them again, with reintroduced2:09animals likely to come from Victoria.2:11South Australia requires a permit from the Minister for Primary Industries to keep2:14Koi, which are treated as a noxious species.2:18Releasing koi, goldfish, or other non-native fish into the state's rivers is2:22illegal.2:22The original2007 law set maximum penalties of one hundred and twenty thousand2:27Australian dollars for individuals.2:28For corporations, it was two hundred and fifty thousand.2:31Those provisions covered unauthorized dealings in or possession of noxious aquatic2:35species.2:36Dumping fish could reportedly bring a fine of up to one hundred and twenty thousand2:40Australian dollars.2:41That maximum hasn't been confirmed for the current release offense.2:45The practical rule is clear: unwanted aquarium fish must stay out of waterways.2:49Collard says early interception gives the river its best protection against these2:52fish expanding.2:53Nets are being used at Dernancourt, but no catch total has been announced.2:57Whether the effort has removed the fish or more remain in either stretch is still3:01unknown.Explore with HeyDexFollow via RSSThe shortThe short ↗
