Backyard Aquaponics :: View topic - what the hall am I doing to my fish?

Jim,

I spent quite a few years in Qld consulting for recirc barra farms and in my experience it appears to come down to a number of things.

1. developmental abnormalities - it just seems that at some stage during their growth the fish that have an inherent swim bladder problem eventually seccumb.

2. CO2 and dropping pH levels in the tank - challenge with this one is that the levels may not be abnormal eveytime you measure them. If they do vary its within an hour of feeding. An increase in CO2 and any possible variation in pH associated with it(depending on the water alkalinity) will cause a amongst other things, a shift in blood pH and a corresponding shift in partial gas pressures in the swim bladder and the end result is excess gas in the swim bladder. It's usually the end stage fish that appear floating around as they are just about gone before the bladder increases in size. The cure is to increase your degassing ability or reduce your stocking loads eg reduce the CO2.

3. numerous infectious causes - Streps, residual nodavirus infections etc
etc.

4. variablility in the diet - used to see the incidence increase when new batches of feed arrived or when producers changed manufacturers. Now I know this smacks of 'if in doubt blame the feed company', however like most intensely reared animals the gut flora does change dramatically with diet.

Research has shown that gut flora directly reflects what is in a fishes environment however there does appear to be a transition period where the flora is upset, when the diets change. It may be that these fish are just hanging in there and the diet change is the last straw, not sure but feeds with higher carbohydrate loads will increase the incidence of floating fish. And yes it appears to be intestinal bloat rather than swim bladder. Same result different cause.

Anyway just a few thougths having dealt with this conundrum a number of times.

Regards

----------------------------------------------------

Dr Stephen B. Pyecroft BVSc (Hons) MACVSc
Veterinary Pathologist
Diagnostic Services
Department of Primary Industries, Water and Environment, Tasmania
Fish Health Unit
Mount Pleasant Laboratories
PO Box 46
Kings Meadows TAS 7249

e-mail : Stephen.Pyecroft@dpiwe.tas.gov.au
Ph : 03 63365275
Fax : 03 63365374

Author:	monya [ May 14th, '07, 11:59 ]
Post subject:	what the hall am I doing to my fish?
Does anyone have a technical explanation for what is happening to my barra. Every time I have purged a batch, on has ended up upside down swimming around for 4 days almost as if they feel it is the right way to do it. I just took 7 perfectly healthy fish and put them into the bath. 2 feaked out when I scooped them out they went upside down in the bucket. They were fine in the tanks. One is massive (by my standards LOL) he swam flat out into the net and hasn't gone upright since. The other one just flipped out... It is almost as if their centrof gravity swaps or something. When you help him onto the right way up, it is fine, then as soon as you let go, he rolls back upside down. Anyone with an answer would be appreciated. The fish are otherwise healthy apart from appearing to be quite close to death. I have no doubt they both will survive the week

Author:	Jaymie [ May 14th, '07, 12:10 ]
Post subject:
odd..........

Author:	RupertofOZ [ May 14th, '07, 12:11 ]
Post subject:
I would have said it was due to the fish's swim bladder..... common sight for fish raised too quickly from depths when fishing..... BUT..... Barra don't have a swim bladder .... Quote: Barramundi have developed a method of using fats secreted directly into its tissues as a means of flotation. Beats me Mon

Author:	monya [ May 14th, '07, 12:16 ]
Post subject:
Is the white lining that form like a balloon in their guts their actual stomach? On a couple of them, it has been really inflated like a balloon when I have cleaned them. It's the sack that adjoins the underside of their backbone at the top of their guty cavity

Author:	RupertofOZ [ May 14th, '07, 12:30 ]
Post subject:
From what you're describing though it does sound like expansion of a swim bladder, which I'd always been told didn't exist in Barra and my next guess would have been CO2 level in water.... I've certainly never encountered an expanded "swim bladder" problem in all the barra fishing I've done .... but having said that.... I came across this article (included in full)..... maybe give the bloke a ring .... Quote: Jim, I spent quite a few years in Qld consulting for recirc barra farms and in my experience it appears to come down to a number of things. 1. developmental abnormalities - it just seems that at some stage during their growth the fish that have an inherent swim bladder problem eventually seccumb. 2. CO2 and dropping pH levels in the tank - challenge with this one is that the levels may not be abnormal eveytime you measure them. If they do vary its within an hour of feeding. An increase in CO2 and any possible variation in pH associated with it(depending on the water alkalinity) will cause a amongst other things, a shift in blood pH and a corresponding shift in partial gas pressures in the swim bladder and the end result is excess gas in the swim bladder. It's usually the end stage fish that appear floating around as they are just about gone before the bladder increases in size. The cure is to increase your degassing ability or reduce your stocking loads eg reduce the CO2. 3. numerous infectious causes - Streps, residual nodavirus infections etc etc. 4. variablility in the diet - used to see the incidence increase when new batches of feed arrived or when producers changed manufacturers. Now I know this smacks of 'if in doubt blame the feed company', however like most intensely reared animals the gut flora does change dramatically with diet. Research has shown that gut flora directly reflects what is in a fishes environment however there does appear to be a transition period where the flora is upset, when the diets change. It may be that these fish are just hanging in there and the diet change is the last straw, not sure but feeds with higher carbohydrate loads will increase the incidence of floating fish. And yes it appears to be intestinal bloat rather than swim bladder. Same result different cause. Anyway just a few thougths having dealt with this conundrum a number of times. Regards ---------------------------------------------------- Dr Stephen B. Pyecroft BVSc (Hons) MACVSc Veterinary Pathologist Diagnostic Services Department of Primary Industries, Water and Environment, Tasmania Fish Health Unit Mount Pleasant Laboratories PO Box 46 Kings Meadows TAS 7249 e-mail : Stephen.Pyecroft@dpiwe.tas.gov.au Ph : 03 63365275 Fax : 03 63365374

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Author:	RupertofOZ [ May 14th, '07, 12:39 ]
Post subject:
Hey Mon, maybe next time try "stunning" them with a few drops of clove oil and then gently transfer them to the bath.... Soon as they hit the "fresh" water they'll revive almost immediately

Author:	steve [ May 14th, '07, 12:45 ]
Post subject:
so monya, to clarify, they went "na-na's" in the bucket just after you scooped them out of the main tank? Was the bucket filled with system water, or fresh water? have heard of this happening with..........i THINK it was a saratoga...........will do some more reading later on for ya

Author:	monya [ May 14th, '07, 12:45 ]
Post subject:
thanks Rupert..... Interesting thought that taking them from the tanks may be "the last straw". I doubt they are inherently unhealthy, certainly hope not. Have certainly eaten them to no ill avail lol The big one certainly was absolutely fine, swam bang into the net and hasn't looked up the right way since lol

Author:	monya [ May 14th, '07, 12:46 ]
Post subject:
steve, bucket had system water in it. And yes, na na's in the bucket.

Author:	steve [ May 14th, '07, 12:48 ]
Post subject:
my highly specialized opinion is.................."they were nearly frack anyways "

Author:	RupertofOZ [ May 14th, '07, 14:00 ]
Post subject:
Mon, I'm still leaning toward low oxygen..... Remember when you went fishing when you were a kid.... some of the fish in the bucket always turned belly up.... others seemed quite happy... When doing catch and release fishing you sometimes see fish lying belly up if you don't "swim" them first.... ultimately they die... Swimming them (holding by mouth (open) and moving them from side to side in the current) forces extra oxygen over the fishes gills and revives them very quickly and restores their "vitality".... Maybe have a small bubbler in the bucket when you're transferring them.... or one in the bath and swim any affected fish for a while and see what happens

Author:	monya [ May 14th, '07, 14:09 ]
Post subject:
but if it was low oxygen, wouldn't the rest of the fish be gulping at the surface?

Author:	Jaymie [ May 14th, '07, 14:12 ]
Post subject:
maybe it's just that those fish are the slightly dodgy ones, "asthmatic" fish

Author:	EllKayBee [ May 14th, '07, 16:11 ]
Post subject:
Did you try putting them back into the main tank to see if they revived

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