MURRAY AND MARY COD

[Member]

Fitz,
Still have those same lingering doubts about BRC, Gordons 84 cm fish brought them on again.
Are there any BRC left ? this unfortunately is not known.
DNA sampling of large fish in the system may prove this.
BRC would be similar to MRC but as they have most likely been seperated since the same geological event which initially seperated MRC from MC (MRC being a subspecies of MC) there would be quantifiable differences.
If in fact if BRC do remain the now adult population of MRC and the most likely presence of MC would result in hybridization and introgression of any subsequent recruitment. This would be very difficult and costly to address and a massive undertaking, unlikely to be considered by the powers that be. Sadly it may be to late.
Have been looking forward to the results of the genetic study being undertaken by DERM.

cheers,
Steve.

[Member]

I think you have the clear picture of the history Steve.  The landowners have had this property for over 100 years now and their verbal records on the history of fish that have been caught are great to hear.

All been noted by Sweetwater but it probably is just that history. 

I have armed myself with several photos of MC and MRC.  And 2 of these have been taken from the fisheries fish identification site.  If anybody can suggest other examples showing the variation between the 2 please let me know.

Regards Gordon

[Member]

"Are there any BRC left ? this unfortunately is not known."

Steve, when the Brisbane Valley Anglers were doing the SMP for the river below Wivenhoe, we asked Alex Hamlyn from the DPI the same thing. he replied that to the BEST of the departments knowledge there were NO BRC in the waters below Wivenhoe, since construction of that dam.
One assumes that they did some electro sampling during numerous river studies done back then, but that doesn't preclude BRC from existing in the Stanley, Upper Upper Brisbane or even the 2 dams for that matter.
As a few have said, maybe the introduction of MRC will dilute the gene pool, of if I remember rightly, they found that if MC & MRC are crossbred, the eggs remain infertile,,,(can't be sure on that, it was a long time ago) perhaps the same is true between BRC & MRC

Brad

[Member]

"Are there any BRC left ? this unfortunately is not known."

One assumes that they did some electro sampling during numerous river studies done back then, but that doesn't preclude BRC from existing in the Stanley, Upper Upper Brisbane or even the 2 dams for that matter.

Brad

Full marks to Alex, Brooksy & their teams, however I would think the survey work was limited by accessability. I've done over a dozen full trips down that 60km section of river, there's alot of river they just cant get an electrofishing boat to.

There's a huge cod on one log we've seen a few times in the mid - Brisbane River (Wivenhoe to Mt Crosby section) that's got to be pushing 80 - 100 pound. I've not seen him there for a while tho (hope he didn't adorn the local butcher shop scales)
That fish has got to be pre-stocking, its just too big to get to that size since MRCs were stocked. That or its a translocated Murray Cod as MRCs aren't supposed to grow that big.

Same for one spot in the upper river (above the lake), we spotted a huge cod up there but havent been able catch it to get a sample.

I think the only way to get an answer is to get DNA samples. In the mean time IMHO stocking of MRCs should stop throughout the whole system.

fitz..

[Member]

Gary can you get a bunch of the tubes to me soon plus directions on how to use.

I intent to put a few days a week into my patch until we get some results.  It would be a shame to catch measure and photograph without taking a DNA sample.

I guess I should be sampling large and very small ?  On a brag mat, camera on flash anything else to consider ?

Gordon

[Member]

Sorry very busy at the moment.
Cant find Rowland (1985 1993) which has the crossbreeding/hybridisation results. But all Maccullochella species do or have the potential to hybridise
Quote from Simpson and Jackson 1997 "the introduction of closely related cod species into the existing range of Mary River Cod, namely Murray Cod and Eastern cod, is considered a key threat to this species due to the potential for hybridisation". BRC undoubtably would have faced the same threat with a much smaller population if it existed. Maybe Jim or Kurt or somebody better qualified than me would add to this ? 
Not likely to be any stocking for awhile Fitz apart from the few fish Russell produces, hopefully the Genetic study is completed by then.

cheers,
Steve.
 

[Member]

Also tagging, to avoid too much double handling.

Gordon

[Member]

Personally I would argue strongly against the use of dart or anchor tags in them, far too precious too risk for many reasons. PIT tags inserted by experienced persons into large fish could be justified.

cheers,
Steve.

[Member]

are any hatcheries producing MRC at present?
do any genetic samples for BRC exist?

[Member]

are any hatcheries producing MRC at present?
do any genetic samples for BRC exist?

Yes, one at Cooroy who is a part timer / hobbyist,

 and

No, Qld Museum has no specimens. So officially BRC is a myth. Strong anecdotal evidence suggests otherwise for the Brisbane & its tributaries (Stanley, Bremer, Warrill etc)

fitz..

[Member]

Thanks Fitz. As you know, I love my rustwater, but the ozzy freshwater cods fascinate me.

Australian freshwater fish have shown an amazing propensity to speciate, or too at least throw regionally different colour forms, look at the rainbows for example. Its not uncommon for different and distinct colour varieties to come from neighbouring drainages for some species, as you know.

I heard rumours once of a different looking, very dark coloured cod coming from a creek very high in a murray darling drainage. Big river blackfish? or something else? who knows... could have just been BS. Wish I had more details to check it out. Have you ever heard anything similar?

What does the cooroy breeder do with his fish?

[Member]

EDIT

Below is a picture taken on the upper Brisbane River, up past Linville. Cleared banks are endemic, cattle permitted to graze into the water, swim across, cr@p in the water & cave in the banks even more. What chance do our native fishes have? We can restock as many as we like, but without suitable habitat, there's little chance of the cod being able to re-establish. NOTE - that farmer brown is content to run a fence across the river at this crossing making kayak / canoe access dangerous, but obviously cares little for the river. The river is just a resource to be exploited for self gain. The scenario is repeated throughout this & many other river system.   

Fortunately Fitz, we are not all like that.  Here is a photo of the creek (Tinana) at the bottom of my property.  Fenced off, weeded, not desnagged, off course water points.  Should be mandatory practice.  I must say that I get around alot of farms each year and there is more and more of this practice being undertaken.

All the best

Steve.

[Member]

G'day fella's.  Before this subject passes into the mists of time can you help with some good photographs of  M R Cod, large and small so I can look for variations in the ones I lift.

Just click on my name and my email address is there.

There are differences between Murray and Mary and also patten variations between Mary and Mary.  If you could also let me know the size of the fish we are looking at where it was caught.  The restocking boys will probably point out reasons for these variations.

Thanks in advance for this.

Regards Gordon

[Member]

This pic was sent to me in November last year Gordon. Found dead in the Stanley........