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I have my developmental biology students raise fish in ~2 gallon white plastic food service buckets lined up on "bookshelves'. The air supply line is a 1/4" gum rubber tube that works as a manifold. Each branch is 18" of tube with an inserted Pasteur pipette as an outlet and a disposable hypodermic needle in the other end to "Plug into" the manifold tube. Since the needles serve to limit the openings, any number can be inserted without any balancing or equalizing problems. This is a very simple solution to maintaining 20 "tanks" on one air supply. Punching 2 small holes near the rim of the bucket permits threading a twist-tie loop to retain the air line inside the bucket and attach an express tag outside for student/bucket-specific info.
St. Anselm College
One of the major advantages of the zebrafish, Danio rerio, for the study of vertebrate development is its high reproductive potential. However, it can sometimes be difficult to get consistently high levels of egg production from these organisms, particularly in a small facility maintaining a relatively small population of fish. One very important factor to consider in maintaining a healthy breeding colony is the level of stress that the fish endure prior to the attempted breeding. We have found that if the fish are placed together in a breeding trap first thing in the morning then the success rate is low, presumably due to the stress of netting the fish from one tank to another. However, we have also run into problems when the fish are placed into the breeding trap the night before. To begin with there is a lot more feces and other particulate matter in with the embryos and we have a more significant problem with fungus. More importantly though, we find the fish will frequently not breed or will breed prior to the lights coming on (possibly due to small amounts of light leaking in from the corridors) with the result that we frequently miss the early stage embryos or get more mixed populations of different stages. This too may be a stress-induced problem as the fish have spent up to 18 hours in a relatively small amount of water.
We have devised a breeding method that minimizes the stress involved in setting up the breeding fish. The fish are maintained in a large population with a consistent environment and the time spent in transfer between tanks is minimal. Using this method we have achieved fairly consistent high level breeding with a high survival rate for the embryos. It also has the added benefit that it negates the need to be constantly chasing the fish around aquaria with nets to move them from one aquarium to another which decreases time taken and stress levels of the researcher as well.
|What we have done is build a mesh bottom, plexiglass aquarium that is as tall as our normal aquaria and just fits inside those aquaria (fig A). Plastic plants are anchored to the mesh and when the plexiglass box is inside a regular aquarium it sits on the bottom and is, for all intents and purposes, a 'normal' aquarium (fig B). However, there are slots on the outside ends of this aquarium insert through which glass rods longer than the aquarium is wide are passed with the result that the aquarium insert can be suspended with the mesh bottom only half way down the aquarium (fig C).|
In the morning, just prior to or immediately after the lights come on, the insert is lifted out of the first aquarium and put into a second containing only water. However, in the second aquarium the glass rods are used to suspend the trap above the bottom. The eggs can then fall through the mesh to the bottom. After the breeding period is over the glass rods are removed and the entire insert is moved back into the first aquarium where it again rests on the bottom and becomes a normal aquarium until the next morning when the process is repeated. The eggs can then be easily collected by siphon.
We keep a relatively large population of fish in this system which, again, helps to reduce stress since these are schooling fish. But it also means that, although not every female will spawn every morning, there should always be at least a few females ready to breed. The environment remains fairly constant in that all of the plastic plants and such are present in the same places in both the normal and breeding aquaria (since they are anchored to the mesh) and the amount of time spent out of the water is measured in seconds. The eggs can be collected very soon after being shed so they tend to be fairly free of debris. We have not checked to see if any early breeding still occurs but even if they do it is not important (except perhaps for a slight reduction in total yield) because any eggs shed before transfer of the insert to a second aquarium will remain in the first tank not being used. All of the eggs found in the second tank will, of course, be newly shed.
Clearly, this method can be adapted to any sized aquarium and any number of fish just by altering the size of the mesh-bottomed aquarium insert. Also, any number of aquaria can be set up in this way. Once this system is in place the fish remain in a large group and never have to be netted for breeding purposes again. Even cleaning the aquaria becomes much simpler since all of the fish are merely removed to another aquarium by moving the insert while the first aquarium is cleaned.
Ross A. McGowan
Department of Zoology
University of Manitoba
R3T 2N2 Canada
Last updated 05/15/02 / contact webmaster