The Manly Dam Monster

[juicy233]

Hi all, I've been fishing Manly dam recently and have spoken with some local old blokes and done some research online and have heard rumours about the dam being stocked with small numbers of murray cod 30 years ago. Supposedly this is why the bass wont really grow to more than 30-40cm and other species that aren't carp really struggle to sustain healthy numbers. I'm yet to really catch anything of note in the dam other than a few perch and bass but am intrigued about these stories and would like to know if anyone knows anything about this. I've also found this article (https://community.deckee.com/topic/25952-yellowbellyi-think/) from 2007 speaking about how these fish are very rare in the dam and were stocked many years ago along with Murray Cod and supposedly some trout. 

This article (https://community.deckee.com/topic/25988-manly-dam-landbase/) as well from 2007 also speaks of how there may be trout and other species that were not really known to have been stocked in there inside the dam.

More evidence (although this is a bit of a random questionable piece of evidence) is from a comment on this youtube video (https://www.youtube.com/watch?v=HCNFsdZMYD0) saying that the reason the bass won't grow big and have deformities because the few massive cod that are in there are eating alot of the medium sized bass and apparently this commenter knows that around 30 cod were released at least 20 years ago and that they would be huge now.

I guess my question is, does anyone know if there is any truth to these stories or if they are just a fishermens tale? Is there a 30+ year old monstrous 1m+ murray cod lurking around Manly Dam gobbling up all the bass and what other species would this elusive fishery hold?

[bessell1955]

Umm... a very interesting story.  I for one would be intrigued in the answer.

[wazatherfisherman]

They used to release some Trout into the dam, can't remember if it was during the Festival of Sydney, Australia Day celebrations or the old Waratah Festival.

[XD351]

 I wonder if it is the availability of food that is limiting the size of the bass ? Are they stocking the dam with bass?  I wouldn’t think that one or even two cod could cause that and as we have seen in other waterways cod can’t control the numbers of carp as they breed like rabbits . It used to be infested with carp and goldfish when I was a kid .

I doubt trout would last very long in there - too hot for them in summer. 

[james Cutler]

i have fished Manly dam. Never caught a Murray  cod. Never seen one.

[XD351]

I have never heard of one being caught or of any stocking . 

[Steve0]

I'm not about to say yes or no to fisherman's tales, but it seems a stretch of logic that the presence of large Cod would cause deformities in Bass. The other thing to consider is nature's balance. A shortage of fish for you would also be a shortage of food for large Cod. Below a critical stock level, Cod would die, and other species would increase.

Variable water quality may contribute to problems https://www.northernbeaches.nsw.gov.au/council/news/monitoring-water-quality-manly-dam

The most recent stocking seems to be 7000 Bass in 22/23. Maybe the shortage is due to fishing activity? Also, if about, Cormorants would take some.

I can find the most recent stocking on a web page DPI call fish stocking plan and a web page that discusses releasing fish in public water. What I did not find is a plan/proposal for future stocking or a detailed history of Manly Dam stocking.

A phone call to DPI may help solve your question. If you mention concerns about apparent depletion in stock, they may even make an assessment.

 

 

[Lizardboy]

Hi, I’d love to believe the story, but I’m skeptical, I’ve heard second or 3rd hand stories of aquarium fish released into the dam but never of a recapture, I think if there had been the grapevine would spread the news quickly. I know of a 3 solid golden perch caught 10 years + ago and have seen a photo of another. I’ve heard of trout stocked many years before but have not heard of recaptures. I suspect that bait/food supply, redfin and carp would have more to do with the low average size for bass.

I have seen a lot of nepean herring flicking on the surface in the creek below the dam, but wondering if anyone has seen them in the dam?

During a family bbq and brief fish with the kids recently I sounded up what appears to a wreck in there which I wasn’t expecting. 

cheers,

Gus

 

[zmk1962]

… oooh this topic is so “lochness” … Gus has brought out the hi tech gear … I’m so hooked - eagerly waiting for next update … have popcorn ready !

cheers Zoran 
 

[nal]

My mate caught a very unhealthy trout in manly lagoon about a year ago now, so definitely not impossible.

[Ganguddy Goodoo]

It is possible that a small number of predatory fish are illegally stocked in there every now and again. In Canberra we have numerous man made wetlands (for stormwater containment and recreation). Every now and then somebody will chuck a few redfin in and if there is a breeding event the ponds will be surrounded by kids on summer evenings pulling out 15cm fish. Seems to fish well for 2 summers then bugger all. This is how my son started fishing. In the autumn of his second season he finally pulled out a decent fish. It is likely that a few big redfin end up eating all the others. At one stage someone chucked in a cod at our local. It made it to about 50cm until the stress of being repeatedly caught and high temperatures/low oxygen killed it.

So not apples and apples compared to the Manly dam situation but I reckon there a few big bass eating  the stocked fingerlings (the ones the pest species don't get). If there are any goodoo in there there wouldn't be many. So it is possible that the seemingly low numbers of big bass is at least partly due to the low overall numbers rather than a few super predators. It would be cool if the dam did start producing 50cm bass.

[juicy233]

On 6/23/2024 at 9:59 AM, Ganguddy Goodoo said:

It is possible that a small number of predatory fish are illegally stocked in there every now and again. In Canberra we have numerous man made wetlands (for stormwater containment and recreation). Every now and then somebody will chuck a few redfin in and if there is a breeding event the ponds will be surrounded by kids on summer evenings pulling out 15cm fish. Seems to fish well for 2 summers then bugger all. This is how my son started fishing. In the autumn of his second season he finally pulled out a decent fish. It is likely that a few big redfin end up eating all the others. At one stage someone chucked in a cod at our local. It made it to about 50cm until the stress of being repeatedly caught and high temperatures/low oxygen killed it.

So not apples and apples compared to the Manly dam situation but I reckon there a few big bass eating  the stocked fingerlings (the ones the pest species don't get). If there are any goodoo in there there wouldn't be many. So it is possible that the seemingly low numbers of big bass is at least partly due to the low overall numbers rather than a few super predators. It would be cool if the dam did start producing 50cm bass.

Yeah what you've said about the redfin goings nuts then just dying off seems consistent with the fishing in Manly Dam as I can remember a time 5 or so years ago we could catch 10-20cm redfin like there's no tomorrow. 

 

On 6/13/2024 at 8:14 PM, Lizardboy said:

Hi, I’d love to believe the story, but I’m skeptical, I’ve heard second or 3rd hand stories of aquarium fish released into the dam but never of a recapture, I think if there had been the grapevine would spread the news quickly. I know of a 3 solid golden perch caught 10 years + ago and have seen a photo of another. I’ve heard of trout stocked many years before but have not heard of recaptures. I suspect that bait/food supply, redfin and carp would have more to do with the low average size for bass.

I have seen a lot of nepean herring flicking on the surface in the creek below the dam, but wondering if anyone has seen them in the dam?

During a family bbq and brief fish with the kids recently I sounded up what appears to a wreck in there which I wasn’t expecting. 

cheers,

Gus

 

That wreck looks spooky it looks like a proper boat (maybe a monster Murray cod pulled it under , just out of curiosity, do you think it would make a good spot to fish or nah