1 JUNE 1999
Date: 23 May 1999
From: PAUL MACISAAC <PMACISAAC@cadmin.nsac.ns.ca>
To: <AQUA-L@killick.ifmt.nf.ca>
QUESTION:
We're rearing striped bass larvae with water pumped from more than 20 metres depth and heating 10 C water to 17 C. We are degassing with high surface area balls and aerating header tanks with oxygen. As a result, the total gas saturation is down to approximately 103%, but the oxygen is up towards 150% saturation. Are there negative effects of exposing eggs and post-hatch larvae to such high oxygen
concentrations? Our larvae are only 1-2 days old now so we haven't
began feeding nor observed many changes as a result of the oxygen
supersaturation.
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COMMENTS 1:
Water supersaturated with O2 has been found to cause gill
necrosis, "burning", in salmonid fry. As to the physiological reason
behind this, and how fish size/O2 supersaturation level is related, I am not sure.
owner-AQUA-L/OU=fisheries@mi.mun.ca
***************
COMMENTS 2:
From memory of many years back, Nick Parker did some work with striped bass and oxygen concentration...but I'm not sure if it was at the larval stage...anyway as I remember it everything was OK until above 20ppm. You're roughly at 15 ppm so you should have no problems. But why not just cut down the flow of oxygen to the header box to reduce the ppm (and cost) down to saturation. Or, if that's not possible for some reason and you like wasting oxygen, since you're coming from a header box and you have a fall for the water, pass the water again through a packed column..this time using bio-barrels..to reduce the oxygen to saturation.
But make sure that your total gas saturation isn't really nitrogen as often when heating water pressures build up (boiler principal) and nitrogen can get out of control, causing pop-eye.
As an aside.. everyone ships fry in sealed poly bags. Just before sealing them it's common practice to inject oxygen into the water for several minutes and top off the aerated space above the water with oxygen. I don't ever remember seeing anyone measuring the oxygen level of the water during this process, so I suspect the DO is in excess of that which you're using.
Rick Eager
Swimming RockFish and Shrimp Farm
Meggett, South Carolina 29449, USA
<dreager@awod.com>