Reply to Kalk and Vitz about breathing bags.
You both have expressed important concerns.
Kalk's concerns (if I understand them) are the following.
1. Fish excrete carbon dioxide and ammonia. About 2/3rds or 3/4ths of the volume in a regular bag is oxygen and the rest water. In the test situation described previously with AMRI, there was no dissolved oxygen in the bags. Hence, the bags occupied a smaller volume in the shipping box. Theoretically, one could pack more bags in the box, but this would increase the weight of the shipping box. I packed pieces of styryfoam around the bags. It is necessary to ensure that there is no empty space, where the bags can be jostled around during shipping. the simplest way is probably to added styrofoam sheeting to partition the box, in order to keep the bags firmly in place.
2. The first thing we did was prepare a 80 gallon plastic pail of shipping water. To this we added about one teaspoonful of nitrofurazon powder and one teaspoon of Amquel (from Kordon/Novalek). The Amquel neutralized the ammonia excreted by the fish during the shipping period. The nitrofurazon controlled the proliferation of bacteria. The breathing bags did not drop in pH as much because the carbon dioxide given off by the fish was expelled across the membrane of the bag. I suspect that the drop in pH by itself (under the normal bag situation) is detrimental to the fish. My main point here is that nitrofurazone and Amquel need to be added (as I mentioned in my original post).
3. The breathing bags come in four sizes. For small fish the smallest bag is suitable, for larger fish a larger bag is needed. The largest bag can act as the outside "Liner bag" to keep water from leaking from the box if the other bags leak. Unnfortunately, the smaller bags do frequently leak and this needs to be brought to Novalek's attention. So, if one packs fish in bags, one should put them on a table or shelf long enough to determine which bags leak and not pack those bags. These bags could be (re) sealed with a heat sealer, prior to being packed in the box.
4. Kalk's point is that the outer Liner bag needs to be tightly sealed shut. The outer breathing bag is thicker and has less gas exchange capability. I suspect that if the Liner bag is tightly sealed, all the fish may die in the box containing breathing bags. Dr. Labbish Chao had this happen when testing the bags in the Amazon with neon tetras. One solution to this problem is to use a regular liner bag. Dr. Rofen suggested that the regular liner bag be inflated with oxygen and sealed after the breathing bags containing fish and water are put inside. I have not yet tested this approach.
My new approach (which I have not yet tested) is not to use small breathing bags. Put seawater into the large regular liner bag (or two liner bags insider one another if necessary). A fairly large breathing bag is inserted inside the Liner bag. Then plastic containers with the fish are packed around the breathing bag inside the liner bag.
The individual plastic contrainers have holes in them to allow the water to circulate and come in contact with the large breathing bag. The seawater still needs to have nitrofurazone and Amquel. This would allow the carbon dioxide from the fish to be absorbed by the breathing bag, and oxygen from the breathing bag to be passed to the water containing the fish. The advantage is that there is not much accumulation of carbonic acid in the shipping water, and no chance of leakage from either the liner bag or the smaller breathing bags (since the latter are not utilized). Breathing bags are more expensive than regular bags, and Filipino exportes are aware of this. Even, if what I describe is more expensive (I still need to evaluate the relative costs of the new approach). I am sure that the fish would be in much better condition and could survive in the boxes for a much longer period.
I have pointed out that the approach described still needs to be studied. Many of you could try it for yourselves (and hopefully let me know the results). Hopefully this response helps to address your concerns.
Peter Rubec
