'Extremely unusual' sunfish spotted in the River Derwent in Hobart northern suburbs - ABC News & Headlines – Australian Broadcasting Corporation

Chris Reed says he thought he and his kids had spotted a seal in the river at Monstrose Bay during their morning walk, but when they got closer he realised it was something he'd never seen before.

"I would say it was over two metres long and just as high. It was stuck on its side in the shallow," he tells Kylie Baxter on Hobart Drive.

He sent a video of the fish to a friend who identified it as a sunfish.

Neville Barratt is a marine biologist and research associate at the Institute for Marine and Antarctic Studies (IMAS) and he tells Kylie that sunfish are an oceanic species and not generally found in rivers and estuaries.

"It's extremely unusual I have to say," he says.

"They're found in tropical oceans as well as temperate ones about as cold as Tassie, as far south as Tassie. 

"But really they live out on the ocean and we hardly ever see them in coastal waters, much less up in an estuary like the Derwent. So it is quite an unusual feature."

Chris Reed spotted the sunfish in shallow water off the GASP walkway at Monstrose Bay on Thursday.(Supplied: Christopher Reed)

Chris ReedHoly doly! She's **** huge! She's not going to bite me, I don't think she will. Holy **** it is massive.

Kylie BaxterGood afternoon Chris, great to have you on the program. How are you going?

Kylie BaxterTell us about the fish you spotted.

Chris ReedI was going for a walk with my two kids, Rose and Sven, and then we thought we saw a seal, so we went over and had a closer look and there was already a lady there saying that it was an injured shark, but there was just something a bit funny about their fins and then I thought maybe it might have been a young whale or something, so I thought maybe if I get in there and push it back out it would be alright. And then as I got closer I realised it wasn't, so I had to take a video of it and send it to my good friend Elliot Stiles who knew exactly what it was.

Kylie BaxterAnd how big was it roughly?

Chris ReedI would say it was over two metres long and just as high. It was stuck on its side in the shallow.

Kylie BaxterHow amazing. And have you ever seen a sunfish before?

Chris ReedNo, hence why I had to take the video and send it to a mate to see what it was.

Kylie BaxterAnd what did you try to do? I mean it's a pretty big fish. I mean do you know what happened? I mean have you returned to see if it's still there for example?

Chris ReedYeah, yeah, well we tried to push it back out. I got it probably up to about just over waist deep and it was just getting too rocky with all the shells and I was getting cold and then someone on the shore had said that they had actually called up about it and there was going to be some assistance coming and so I just had to sort of tap out. But then when we went back earlier this afternoon around three to see if it was still there it had actually moved its way all the way back into the shallow water again. So I'd say it's definitely confused or injured or something.

Kylie BaxterNeville Barrett is a marine biologist and research associate at IMAS and joins us now to talk everything sunfish. Is it unusual to see a sunfish in the River Derwent?

Neville BarrettIt's extremely unusual I have to say. Yeah, they're an oceanic species pretty much. They're found in tropical oceans as well as temperate ones about as cold as Tassie I guess, as far south as Tassie. But really they live out on the ocean and we hardly ever see them in coastal waters, much less up in an estuary like the Derwent. So it is quite an unusual feature.

Kylie BaxterAnd what about other parts of the state? Have they been spotted elsewhere over time? Do you know of other sightings?

Neville BarrettYeah, we certainly know of other sightings. In fact I was just talking to some of your colleagues last week in northern Tasmania because they've had one wash up there near Burnie. But again it's a very unusual event. We occasionally see them, they somehow just seem to get trapped. A natural trap is the funnel I guess, the Derwent narrows down from Storm Bay as it comes in and they think they're swimming around in the ocean but they're not. And you know, get funnelled up into the Derwent and get a bit confused about where to go. And occasionally that happens around Norfolk Bay. They end up in around the Tarana area and I've actually seen one there just like the gentleman described with the fin flapping around and I thought it was an injured shark and actually swam out to take a photograph thinking, I had my heart in my mouth thinking it was going to be a great big shark and it ended up being a great big sunfish instead. So it was quite an exciting moment.

Kylie BaxterYeah, now Chris who you just heard a little while ago tried to move the sunfish into deeper water but what can a sunfish weigh? Is there an average sort of weight that they reach?

Neville BarrettWell, yeah, I mean they can get up to two and a half tonnes or more which is pretty big.

Kylie BaxterTwo and a half tonnes, wow, that's incredible.

Neville BarrettThat's incredible but you know the average one's probably somewhere between 250 kilos and one tonne. So it's still not light, he certainly couldn't pick it up or anything like that and yeah, they're very difficult to move. So it is a tricky situation trying to rescue something like that because it's a very cumbersome size as well.

Kylie BaxterAnd what do you think the fate of the sunfish, the one that was seen today by Chris in the River Derwent at Montrose, what will the fate of that fish be?

Neville BarrettI think unfortunately it probably will, you know, it will die. It's obviously not in very good condition if it is washing ashore anyway. You know, by the time you get up to that part of the river, there's fresh water for example at the surface from the usual river runoff and they're a fully marine species so they're not designed to live in that kind of environment. So they'll literally be being poisoned or it'll be being poisoned by the fresh water in the Derwent at the moment. Which is never going to be a happy ending.

Kylie BaxterYeah, but is there something that people can do like to report a sighting of a sunfish? Would you want them to do that? Is that something that you'd like if people do see them so we get a better idea?

Neville BarrettWell, yeah, I think for rarely sighted species and especially for anything that's a tropical species, not that this is, it's found in tropical and temperate waters, but there is a website that colleagues run at IMAS called Red Map and I think it's just redmap.org or something, very easy to find and people can report sightings of unusual fish on that website.