BOHR EFFECT VS. FISH TRANSPORT IN BAGS
From: Dominique Bureau
To: AQUA-L@killick.ifmt.nf.ca
QUESTION:
The Ontario Ministry of Natural Resources fish culture stations asked me
to conduct a small trial or gather information on the possible
significance of Bohr effect (i.e. reduction in oxygen binding affinity
of haemoglobin with decreasing blood pH) on survival of salmonid fish
transported in bags (with oxygen) to be stocked in fresh water lakes
(water temperature = 2 to 14 ° C). There is a fear that fish
transported in sealed bags do fine during transport because of the high
dissolved oxygen level in the water but may have trouble surviving after
being stocked in a lake where dissolved oxygen of water may be much lower
than that in the bag.
I found the summary of a document from AUSEAS by Rimmer M.A. and B.
Franklin (1997) on live fish transport in which it is reported that a
detailed study showed that pH of blood of Asian sea bass (barramundi)
transported in bags did decrease to levels that may significantly diminish
the fish oxygen transport capacity but that the red blood cell swelled
considerably and regulated their pH and overall oxygen transport capacity
was not really affected. Their conclusion was that CO2 and ammonia
accumulation in water and drop in blood pH were the main factors affecting
survival of the fish, not Bohr effect.
(http://www.spc.org.nc/coastfish/News/lrf/3/15notew.htm)
Would anybody have an opinion or some results on this?
There seems to be a lot of lab bench research work but little whole
animal or practical work on this. Any good references?
Would anybody have some rough guidelines/limits for carbon dioxide
water concentration and blood pH for freshwater salmonid fish transport in
sealed bags?
Dominque Bureau
dbureau@aps.uoguelph.ca
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COMMENTS 1:
For a good explanation of the physiology see Dr. Pat Wright at your
institution...she can give you the low down on respiration physiology
and stress responses etc. As far as transport and CO2 goes, there is
almost definitely a bohr/root effect occurring.
Dr. Mark Powell
Lecturer, School of Aquaculture
University of Tasmania,
Locked Bag 1-370
Launceston, Tasmania
Australia 7250
Tel: 03 63243813 (domestic)
Tel: +61 3 63243813 (international)
Fax: 03 63243804
e-mail: Mark.Powell@utas.edu.au
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COMMENTS 2:
Fish transported in plastic bags with O2 come in at very low pH's. A
24 hr pack at about 50 to 100 gm/l should be down into the mid 6
range. The animals' blood has high CO2, low pH, and high
ammonia. If you dump him into clean water at pH up in the high 7's or low
8's, he
will have some real dynamic problems. As he dumps CO2 out the blood,
the pH will increase and the unionised ammonia will increase
in his blood. The mathematics of the water chemistry problem has
been well covered in some papers by J. Colt (don't have the specific
references handy). The real problem is seldom O2.
Solution: match the bag pH and temperature with some of the receiving
water and use that to flush out the high CO2/ammonia bag water, then
slowly add the receiving water.
PS: I have been involved in designing equipment specifically designed
to produce acclimation water for product received in bags. It made a
significant difference in survival after receiving the product.
Dallas E. Weaver, Ph.D.
Scientific Hatcheries
5542 Engineer Dr.
Huntington Beach
CA 92649, USA
Tel. 714-890-0138
Fax 714-890-3778
deweaver@gte.net
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COMMENTS 3:
You will need to buffer the water in the bags during transportation.
Some practical information regarding this is included below, although the data is not salmonids.
I recently sent some sea bream to a customer in plastic bags. The total duration of the journey (from packing to unpacking) was more than 27 hours and the mortality upon arrival was 0.03%. Prior to the shipment I carried out a number of trials in order to establish the most appropriate conditions. In one of these trials I experimented with the use of various buffers and compared the results with non-buffered bags. There were no fish mortalities in any of the bags when the trial ended (after 19 hours) despite the fact that in one of the bags the dissolved oxygen level was down to 3.8 mg/l (the bag had a leak). However, in the bags where buffer had not been added to the seawater, the pH had dropped to 5.93 and the ammonia level was approximately 4 mg/litre. In contrast, in the other test bags, which contained various buffers, the pH only dropped to 7.7 and the ammonia reading was zero. The fry used in the trials all originated from the same tank and the same fish stocking densities were used in all the bags.
Another trial confirmed the point that Dallas made that " the real problem is seldom O2". In this case dissolved oxygen levels in the bags at the end of the trial were 6.5 mg/l (89% sat.) yet nearly two thirds of the fry were dead after 10.5 hours.
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COMMENTS 4:
I found in experiments with sea bream where we packed the fish for 48 hours, that ammonia began to build up in all the bags. Because of the lower pH in unbuffered bags, the relative amount of unionised ammonia was low and survival was high. In comparison, in the buffered bags, the pH remained high and therefore the ammonia was more toxic. After unpacking the unbuffered bags, if the water was replaced very slowly, the ammonia levels disappeared quickly as the pH gradually rose. Survival remained high. I agree that oxygen was not a problem in causing mortalities. The real thing to manage is ammonia and pH.
Glen Pagelson
GlenPagelson@ardom.ardom.co.il
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COMMENTS 5:
There were a number of responses to my posting regarding the transport of sea bream in plastic bags and I will try to cover the various points raised.
Fish stocking density was kept relatively low (260g of fish in 10 litres seawater). But bearing in mind the long duration of the transport it was deemed in this particular case to be more important to have a successful result than to minimise transport costs.
The fry were sent in 38 ppt seawater. A reduction in salinity would have been preferred but was not practical in this case.
Regarding the comment that the use of a buffering agent in the water interfered with the measurement of ammonia - this would appear to be case. A simple aquarium test kit was used to measure ammonia. (Tetra test).
The buffering agent used in the final transport was called Antitox (from Dryden Aquaculture).
Peter Tarrant
mwl@otenet.gr
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COMMENTS 6:
How did you measure the ammonia in the buffered water? I thought the general lab test kits were not suitable for this as the buffer interfered in the reaction.
Brendan
Bgmannin@aol.com