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Rhombosolea retiaria aka black flounder questions


ilwis

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ive just had a look at some nz native fishes and have found out about our lovely black flounder

im wanting to find out about if it can live in fresh water in a tank for its life or if it will die because it doesnt go to salt water

also does anyone know if there is a place in the auckland region where i could find one of these guys?

also black flounder is a difrent species than the brown ones found in most beaches right? or the ones ive seen with the orange spots are just the comon one but camoed to the enviroment it was found in

(just so you know the one im refering too... )

http://www.rodmorris.co.nz/New-Zealand- ... &k=4Kp8f7X

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Hi ilwis,

I did a fair bit of work on flounder (hence the name flatfish) at uni several years ago and I have kept black flounder in a tank for a short while.

We have 4 similar species of common inshore flounder in New Zealand (all Rhombosolea species). The greenback flounder in mainly found in the lower South Island. The remaining three: the dab or sand flounder, the yellowbelly flounder, and the black flounder are found throughout much of New Zealand. The ones you've seen off beaches are likely sand flouder or yellowbellies. The yellowbelly does move into the lower reaches of many rivers but is thought to only stay there for short periods while the black flounder is a truly freshwater species and appears to only go to sea to spawn. So yes you could keep it in a freshwater tank. However the minimum legal size is 25 cm (about 1.5 to 2 years old) so thats a fairly long and wide fish to keep in a tank, and they eat quite a lot of food. The also grow fast and can get to 45 cm in just over 4 years.

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i dont know it could be a juvinile in your hand tho it looks like the common ones ive seen hundreds in the shallows of the sea, did you catch him in fresh water? the black flounder is knowen to be able to rivial the charmeleion for colour changing so thats kinda cool

there has been descusion on the fish forum years ago (with some photos)

viewtopic.php?f=41&t=39095&hilit=black+flounder

but it didnt have much about where they are so hense opening this descusion

i would like to find some and hopefully keep some if i can it would be nice to breed them too :) if at all possable

all ive been able to find out about location is upper hut and christchurch is 2 places they have been seen

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Hi ilwis,

I did a fair bit of work on flounder (hence the name flatfish) at uni several years ago and I have kept black flounder in a tank for a short while.

We have 4 similar species of common inshore flounder in New Zealand (all Rhombosolea species). The greenback flounder in mainly found in the lower South Island. The remaining three: the dab or sand flounder, the yellowbelly flounder, and the black flounder are found throughout much of New Zealand. The ones you've seen off beaches are likely sand flouder or yellowbellies. The yellowbelly does move into the lower reaches of many rivers but is thought to only stay there for short periods while the black flounder is a truly freshwater species and appears to only go to sea to spawn. So yes you could keep it in a freshwater tank. However the minimum legal size is 25 cm (about 1.5 to 2 years old) so thats a fairly long and wide fish to keep in a tank, and they eat quite a lot of food. The also grow fast and can get to 45 cm in just over 4 years.

oh wow thats awesome! i really want to find one around auckland can you seggest any ideas on where i may find some? eg what water depths, conditions, or anything that might help me find some?

how big was your tank you had them in?

also what fish lover will complain about having to get themselves a new big tank ? :happy2: oh the shame :gigl:

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:sml1: Rod and I caught that fish last week! He is doing the photos and I am doing the writing for a new fieldguide to freshwater fish in NZ! He is about to set up to take photos of a 2cm one tonight ;)

Ok, so black flounder are a catadromous species, meaning they spend most of their growing time in freshwater but migrate to the sea to breed. Larvae come in after a couple of months.They are commonly found around estuaries, but this is probably partly because they are easily caught there. There are many records of them between 60 and 250km inland, in low gradient rivers.

Sadly there is very little known about this species, despite it being the only freshwater member of its genus, and being a 'managed' ( :sml1: ) species.

The quota management thing is a problem. *Technically* you are only allowed to catch them using certain techniques

and there is a minimum size of 25cm for flatfish. I have just emailed MinFish (or whatever they are now) and will let you know. The answer probably depends on the mood of the person answering, as the laws regarding native wildlife are a complete mess.

In the meantime, the size and shape of flounder greatly affect how you keep them. Obviously they need a LARGE ground area. Given the shape of the fish, there would be little going on in the tank elsewhere. Other fish could be used, but, to quote a friend, they are 'wee predacious flying carpets'. It would be very easy to overestimate stocking due to the size and shape of the flounder.

While many little flounder could be ok together, they grow very fast, and aquatic life cannot be released into the wild without a permit. I would advise having one baby flounder and keeping other short-lived native fish with it (inanga/smelt). As the flounder grows the others will die off (and/or be eaten), creating room. Actually, what would be cool is also getting a young giant bully and growing that up along with the flounder!

They are also astonishingly good at getting out of tanks by shooting along the bottom and up the side.

All that said, the babies are seriously cute, and, given the right sized/shaped aquarium, they would be a fascinating pet!

ilwis, it is the sand flounder (I think, or perhaps yellowbelly?) that is our chameleon flounder. Someone might have a copy of 'A Treasury of New Zealand Fishes', the author clearly had a lot of fun playing with them. I think they mimiced fishing net perfectly, but an abstract triangular patterned lino was about their limit.

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Thanks Stella. I look forward to seeing the field guide. I tagged a few black and yellowbelly flounder for my thesis in the Ruamahanga River to validate annual and daily growth zones in their ear nobes (otoliths). The study was successful but the study was never published. One of the tagged flounder did travel to the Awakino River (?454 km from memory) so some do go wandering once they have spawned.

I kept my two fairly large flounder in a large five foot tank for a few weeks. It was to see how well the fish took up the antibiotic and bone marker (oxytetracycline). They were voracious feeders. I fed them mainly earthworms, a few bloodworms and white worms. I didn't have to keep them long and I guess it was a fairly boring diet but they ate it all.

I caught plenty of small black flounder in shallowwater at night in the Ruamahanga River. But they grow so fast you would have to catch them at the right time of the year if you wanted really small ones. I'd need to check what time of the year I caught them.

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Thanks Stella. I look forward to seeing the field guide.

hehe me too! Manuscript is due for submission at the end of the year *workworkwork* and the book is due to be published by the end of next year.

I tagged a few black and yellowbelly flounder for my thesis in the Ruamahanga River to validate annual and daily growth zones in thier ear nobes (otoliths). The study was successful but the work was only never published. One of the tagged flounder did travel to the Awakino River (?454 km from memory) so some do go wandering once they have spawned.

oooh would you be so wonderful as to send me a .pdf of this? There is practically no (published) work on black flounder.

I caught plenty of small black flounder in shallow water at night in the Ruamahanga River. But they grow so fast you would have to catch them at the right time of the year if you wanted really small ones. I'd need to check what time of the year I caught them.

I think they are out at the moment, following a winter spawning. The little one that I caught the other day looks very oval like the adults, will post a photo of it when I have one.

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oh wow thats really informative!

when i was a kid i use to have some yellow flounder in a tank i think i had about 20 in a tank for about 3 months and they were quite happy i realeased them then none died while i had them and they were quite fanaciting so its ok in that respect

i think i might need a very large tank for one as big as 45cm i might have to make one like a skate tank size

it will be interesting to see what minfish have to say about them

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I kept a half dozen baby flounder for a couple of years then it got too hot and they croaked. I don't know which type they were but hooked them out of the South branch of the Waimakariri (behind the belfast pub when getting blackworms from the outlet of the belfast freezing works). That discharge and the blackworms with it have now gone of course. They were fascinating critters---stick to the sides of the tank like suckers. They were in fresh water so assume blacks.

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Reply from MPI:

Black Flounder are part of the quota management system and are subject to size limits (25cm) whether caught in fresh water or salt water.

It is illegal to be in possession of fish that do not conform to the size limit regulations.

http://www.fish.govt.nz/en-nz/Recreatio ... 526WBCMODE

A special permit can be applied for and will be considered based on the information supplied to us. The person to contact for this is:

[email protected]

From the last time I tried getting undersized black flounder for an aquarium, a permit application cost $500 and was ridiculously involved.

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oh wow thanks stella!

i think i would have to keep them as above size limit and that would be a huge tank

i just sold a coffee table that i had made that was a tank it would have been perfect for half a dozen of little ones but way too small for the big fullas maybe one day if i decide to upgrade my setup to a shop i could look at making a underfloor pond in the store and have some in there it would really make a good display for people, its the only way i can think of having a big enough tank other than doing some serious landscapeing

its a shame there is no way that i know of to breed fish that go to sea to spawn it sounds like a fantastic species to find out things noone knows about them

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  • 2 months later...

Hey mate ive had a black flounder in a tank for the last 7 years,Im pretty sure he was a boy as he LOVED fighting and had bite marks on his fins,rips,tears and half his tail was bitten off,His favourite food was Inanga sadly,lol,He was definitly the king off the tank-We called him "THE GENERAL" ...Unfortunatly-he passed away 2 weeks ago i feel maybe because his time was up,Trust me i was gutted...Anyway i stay in Otaki and go to the river alot and i have seen at xmas time lots and lots and lots off Black Flounder-The best viewing was 2 dark blue and a pure white Black Flounder who i call Zoom Zoom as he comes close to you but is smart enough to not get too close/but hes there alot...thanks guys.

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Cool, thanks for sharing!

Interesting about The general lasting seven years. So little is known about these fish, and they are thought to be quite short lived. Possibly he lived longer due to being in an aquarium (I had a 3 year old inanga, and a have seen a five year old one - they can't spawn in the aquarium so they live longer).

What was he fighting with? The image of an inanga beating up a big flounder is great! :lol:

Any chance you could try and catch the white flounder and get a photo? Sounds extremely rare, especially for a fish that both hunts and avoids predators by blending in with its surroundings! It has done very well to survive :f77:

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