Backyard Aquaponics
A place to discuss aquaponics

I'm wondering if anyone else has encountered this , or anyone has any ides ...

I've lost about 10 - 15 trout over the last couple months in this manner - only one or two dead t a time, more often than not the dead ones seem bloated / fat stomach, and when I cut them open ( bloated or not ) they're filled with water

they're all still hungry, the dead ones even have a full load of food in them ( food is fine, not off or old ).
I'm totally stumped as to what it could be ...

the blood is not brown so I'm assuming not Nitrite poisoning ?, though I did get a spike to 2, about 2 months ago ( did 50% water change, salt to 2ppt ),

aeration is fine
16 - 20 degrees
pH 6
ammonia 0 - 0.5 depending on time of day, nitrite the same
gills all look nice and red, the dead ones gills faded alot but I'm putting that down to me not discovering them for atleast a couple hours

I'm not too bothered as we're eating them quicker than they're dying from whatever this is ( they taste fine ), I'm just curious to know what causes them to bloat up like this

I HAVE had this problem a few years back from mouldy / off food, the first one that died like this I chucked all the existing food into the compost bin just incase it was that ( dont do that - ALL the bugs / worms / slaters / cockroaches in the compost bin died within a day .. ) and got new food, so I'm pretty much ruling bad food out

oh well, the chickens are enjoying the occasional whole trout to pick at ...

oh - 4 - 5 year old system,
80 or so trout ( probably less )
4 byap growbeds
3400L

I'm not a trout expert coming from qld but don't they usually have problems when the tempreture rises? My assumption was that they are usually harvested before summer?

If the test kit reading shows a pH of 6 it is possible that it is lower than that.
Have you thought about adding some shell grit. I bury some in the grow beds and put some under the water in the fish tank. It breaks down in time easily.
Not sure what else could tbe happening, unless you have a predator that is stressing and damaging your fish eg bird, cat etc?

yeah I thought it could have something to do with the pH Faye, I've got a chunk of limestone in each tank, a little shellgrit in a couple GBs and added some ecorose a few weeks ago to try bring it up, but the pH wont budge ( no dead or decmposing fish anywhere, I checked for that first )

no predators getting through those lids ( unless you count me )

As I said Wildfire - water temp is between 16 - 20 degrees at the moment depending on time,
trout I have kept up to 32 degrees ( they werent happy so I ate them ) so I'm pretty sure its not the temperature

possibly too low pH, hangover from possible nitrite poisoning ( 2 ppt maybe ) about 2 months ago, and theyre just slowly keeling over ?

Either way whatever it is, once we've eaten all of these I'm doing a complete cleanout and water change of the system before next season, so I'm not too concerned

possibly waterlogged ( not rotting - growing well ) cape goosebery ? I thought it was poisonous to pets, so maybe fish aswell ?

but the bloaty, water filled stomach seems to indicate something else

Hi Boris, what are your nitrates at?
I have a similar problem with my trout. well i dont think of it as a problem 'cos it makes them easier to catch.
Do you notice any trout that are sluggish and swimming near the surface, while the others are behaving normally just before you find a dead one?
When you open them up and you notice all the fluid in the body cavity, is any of it bloody and are there any haemotoma?

If so, my theory is that they are getting hit at feeding time by one of the other fish. i dont think i would like to be hit by a 1.3+kg trout at full pelt at feeding and i'm a whole lot bigger than them.

since i started to spread my feed out over the water at feeding i have only had one loss like this and i think that was because i had not fed them for a day and nothing was going to get between them and dinner. spreading the food over the water is difficult due to the net covering the top and the food bouncing off!
cheers
marc

Thanks Marc I'll give that a shot

no blood or anything in the fluid that comes out when I cut them open, its almost as if theyre full of water,
and hah - mine Definitely arent 1.3+ kg !

there's always a sluggish one swimming around the surface before I find a dead one ( the same one, I guess ) usually a few hours later, but yeah the rest are still swimming around fine and going nuts for food

Nitrates - no idead, hvent checked for nitrates in 4 years, I guess I'll do that tomorrow & see where its at

Water test is probably a good idea. I'm seem to recall some threads here talking about a ph crash leading to the bacteria colony stressing and dying. If that is what's happened, then that would probably explain the trout deaths.

Also, how old is your test kit? The reagents could be stale. And how much aeration do you have in the fish tank?

I hadn't check for nitrates for about 4 months and when i did i found them up around 800ppm . This level is not going to kill the trout outright but anything above about 500ppm is not good for them.
I have some pictures of the blood and haemotoma in the trout on my thread. I have a few more pictures i can pm you if you are interested.
as soon as i see a sluggish fish on the surface i catch it (which is easy) and its dinner . Every time there is blood and fluid in the stomach cavity and haemotoma. The normal fish i catch dont have the same condition.

how are your temps after this last lot of heat?

cheers
mark

I get a few trout fry with similar symptoms and just assumed they were constipated, never seen a fully grown trout like that though. Not so sure about your theory of the cause Marc as the trout in one of my ponds are up to 2.7kg and they all come charging at the feed from 15m away and always crash into each other sometimes even in mid air. Its quite a sight but I have never found a dead or injured one after these feeding frenzies.

hmm I just had a thought, and probably this is not it, but does anyone else keep their fish food in the fridge / freezer ?
I keep mine in a bar fridge with the freezer section having no door and all frosted up, as a result he whole fridge is pretty cold
when I get the food out its not frozen, but close enough

I put it into a bucket inside a little wheelie bin so I dont have to go into the fridge every day, but once every week or so when I'm topping it up I feed the fish straight away - with food straight from the super cold freezer

I wouldn't have thought really cold food would affect trout but its another possibility I guess,
unless someone else can put their hand up and say they feed trout straight from the fridge / freezer

my main store of food is kept in the fridge except for the 1kg bucket I use for daily feeding. So for my fish the food is at room temp.

Frozen food could give the trout "brain freez" though

yeah mines the same then - about a kilo in a bucket for daily feeding & the rest in the fridge. I doubt its frozen though it is very cold when it comes out

now that I've started this thread, theres been no more deaths - see, whingeing does help !

next dead one I'll try to remember to take photos

LOL.
The last one was euthanased a week ago today. If I dont have another looking dodgy in a day or so I'll have to make the choice of who is next.

Next time you see one swimming sluggishly on the surface take him out for dinner and see if there is any blood.

Troutman makes a good point about the cause so I'm at a loss why they are showing internal bleeding. My vet friends dont think it is a pathogen and also suggested injury. I have no idea what would cause it.

This is a long shot Marc but I have read a few articles on 'electrofishing' studies done on trout. Its something that has been going on since the early 1940's from memory and it had something to do with catching trout in large quantities with minimal harm... I cant remember all the details sorry.

Anyways, they found that a large percentage of the trout returned with spinal injuries, changes in growth, internal bleeding and internal haemorrhage.

Now Im not suggesting that your dropping the toaster in your FT but I wonder if your water pump or something is giving out a slight electrical charge or something? Ive been 'tingled' by one of my submersible pumps before...

Its an out there idea but may be worth looking into.. might explain the strange growth (fat tummies) and internal issues.