Mary River Majic

[wamjam]

Gday Jim
Any chance you can repost your pics so we can have a look ,don't know about everyone else but I'm not getting them.Please let me know if its only me.
Thanks wamjam

[Jim_Tait]

Photos of Cod re-attached

[Jim_Tait]

Photos of Mary River Valley, bass and dead cod in observed fish kill re-attached.

Regards - Jim

[wamjam]

Thanks Jim nice looking country be a shame to flood it.
wamjam

[turley]

Just wondering jim, has anyone looked into the genetic diversity of mary cod within the river and whether inbreeding will be a problem when they effectively create 2 isolated populations with the dam (presuming they ain't building a fish ladder as they never seem too).

[Jim_Tait]

Will be a question that gets considered in the Impact Assessment Study as you say the dam wall will most likely end up being an effective disrtribution barrier for the already marginal cod population.

Regards - Jim

[DaMaGe]

Wow, an awesome insight of the behind the scenes action of this controversial dam.

[robyoung2]

G’day Jim, thanks for all that. The Mary River’s a very interesting subject and I wonder if flooding it would be such a bad thing.
I’m not saying it is or it isn’t, I’m just thinking of an old report done by someone doing the same as you just have.
I guess it was more than ten years ago now, but that report concluded the slow deep water needed for the Mary River Cod to breed was seriously stuffed, by unrestricted cattle access causing serious bank degradation, along with bad cultivation practices causing much erosion. I’m sure you’ve read it, or others similar.
The upshot in that report was that until the banks could be fenced off, and farmers educated, the river’s ability to realize a natural return of the cod was bleak.
I think the report I read resulted in just 3 fish for a whole week’s effort (cod I mean).

So to my way of thinking, if we could make every grazier fence off his marauding cattle, and somehow stop erosion, then arguing for the river to remain “pristine” would be solid. But as far as I can understand it’s far from pristine (regardless how pretty it may look), and is why the cod are in danger in the first place.

From the little I’ve read (and it was along time ago, so maybe thinking has shifted?); Mary River Cod need clear, slow deep water to do well. As it stands, by the impact of agriculture and grazing, the river is shallow, wider than it should be with it’s steep banks in no way the condition they need to be (gone?), and what may be worse than all this, it’s now fluvial, making the breeding success so low, well they’re endangered.


I was just thinking, that given all that, would their future be better secured if the dam was to go ahead, and a good stocking program was undertaken?

Hell, nothing I say, or anyone else much will make a big dif, so I’m not trying to convince anyone of anything. I’m just wonder what you think from your professional point of view? I’m not saying it isn’t beautiful, a shame to loose.. just from the Mary River Cod’s perspective is all.
Cheers
rob

[Jim_Tait]

Rob,

the concerns you refer to in the report you previously read still do stand i.e. bank slumping leading to the broadening, shallowing, and increased flow velocity in the river do impact on the quality of Mary River Cod habitat - but daming of the river is not a counter solution to these impacts. I'll try to list the key reasons why it wouldn't workin the case of the upper Mary and its cod.

Generally, all Australian freshwater cod have poor breeding success in impoundments. This is because they are predominantly river channel habitat associated and rely on the hydrological cues of river flows (& temperature) for breeding success and the plankton production associated with flow events for good laval survival to fingerlings. In a dam the channel habitat is drowned and the hydrological cues and plankton reponses associated with flow events modified by the impoundment habitat.

One of the key distinctions betweeen an impoundment environment and a river channel is the riparian (water edge) zone. In a dam there is usually a broad 'dead' or bare zone associated with fluctuating water levels - in the case of the proposed Mary River dam this zone could be quite broad due to the shallow nature of the dam and the shallow gradient of its banks. This bare riparian zone is in contrast to a river channel with its less fluctuating water levels, flowing riffles, established riparian trees and other vegetation and associated snags, undercuts and aquatic plant communities. The fluctuating levels of a dam do not allow these riparian habitats to become established - all of which are important feeding, breeding and nursery habitat for cod.

In the case of the Mary River the slumped, infilled and degraded river reaches are more associated with the alluvial (floodplain) land forms of the lower catchment. While the steeper valley and incised river channel areas are in the upper catchment (thats what makes it a better dam site) - these steeper valley areas and incised river channels retain relatively more of the deeper cod hole habitat you refer to (and asociated riparian vegetation) than downstream areas due to the greater difficultly that was historically associated with clearing them and their flow characteristics which serve to better flush out bed load sediment slugs than broader and more impacted downstream channels.

In a nut shell, there is a real concern that the quality of cod habitat left post dam construction will be inferior to what currently exists in the upper Mary River catchment. Also the viability of the remnant cod population could be ifurther impacted if the dam acts as a passage barrier effectively dividing the population into two.

Also the possibility of the Mary River channel habitat being improved over time through landholder initiatives is a real one. In my experience there has been a major shift in riparian landholder attitudes along the river (and others) reflected in riparian fencing, revegetation and improved habitat conditions.

Regards and tight lines - Jim

[Hardb8]

Hi Jim,
Awsome read!I've never caught a Mary River Cod.Not through lack of casting or effort.I've climbed gorges,Scaled cliffs,Swam pools and rock hopped,For no result.But when I do finaly get rewarded,I'd really like it to be a local fish.From the Mary.

I hope your informative research falls on the right ears,And they take notice of your findings and knowledge of this special fish,And it's required habbitat.I fear without decisive action in favour of this creature.Future generations may never experience the true jewel in our freshwater crown,In it's true enviroment.



Keep up the good work m8. Kind regards.

[robyoung2]

Mate, thanks heaps for that. I wasn't exactly wondering if daming it would counter all the damage there, I was more in truth wondering "well if it's stuffed, why bother?" mentality.
It's encouraging to hear you're positive about landholders actually re-acting positive in time, because that's the very point I was making, I think you noticed.

My expereince with farmers (and I come from a line of them, so I mean nothing offensive) is that they consider the water edge, water itself etc all theirs, and resent anyone telling them otherwise. "Them and all them univeristy buggers.."

I did like the government's attitude at that time (the report I mentioned). Actually it was a year or so after it, maybe '95, '96? They announced graziers had to make water accessible adjacent to the creek, and fence their cattle out, or else the gov was going to fence all the waterways in the state, and bill the landholder. of course it never happened, but it gave a lot of landholders a wake up call of just who's creeks they are.

Kinda makes me think, to hell with it then, dam the thing, forget their ability to ever recover and stock the dam artificially. You have a much more encouraging outlook but.
even so, what dif will any of our views make? it'll be a political outcome I think and that's that.

I've never had the opportunity to walk around up there, let alone fish and canoe etc. It looks awsome. How is it for public access? Is it difficult?

thanks again.
rob

[Jeremy87]

Thats great stuff. I'm very keen to get the canoe up there and have a go myself. Is that all near travestons crossing or thurther up around Kenilworth. I've fished yabba creek from the canoe before and it has a healthy population of bass from borumba dam in it. I also noticed that where you cross the Mary on the way into imbil it is choked with weed, is that normal for this time of year.

[Jim_Tait]

Jeremy,

the reaches we canoed were from above Kenilworth all the way to Traveston Crossing working reaches between public road crossings each day.

Weed choking during low flow periods is 'normal' but in the current case of the Mary is also affected by changed flow conditions, extended drought, elevated nutient loads, reduced riparian vegetation cover and the pressence of exotic aquatic weeds.

Regards - Jim

[robyoung2]

Thanks again, that sounds like reasonable access hey, have to give it a go maybe. Some of those bridge entrences can be forboding lol. Well, it's all good huh.

cheers
rob