I am not going to go into great detail about the various reproductive habits of specific species of fish, but if you are planning on raising a sustainable population it is important that you create the proper conditions for your young fish to survive in. A short summary of important information about raising young fish follows:
- Mouthbrooders–which can be either paternal or maternal–as their name suggests, raise their young in their mouths. Such fish may require special attention in order to produce successful offspring. This is because such fish will often (ironically) eat their young within several days of releasing them from their mouths. It’s a tough world. Therefore, brooding fish will need to be removed from your primary fish pond and transferred into a special breeding tank. Once the fry have been released from their parent’s mouth and are swimming on their own, you should transfer the parent into an intermediate tank for it to eat a bit of food (it may not have eaten in over a week while brooding) before putting it back into your primary pond. Fry should be raised separately for a few weeks until they are of reasonable size before being moved into your primary pond.
- Herbivorous fish are the easiest to work with as far as reproduction is concerned. Eggs and fry will require no special attention on your part, as they will grow into healthy adults safely and naturally. However, you should do some research to make sure your fish are completely herbivorous before giving them the benefit of the doubt; fish that seem to eat only plants may still eat little organisms (like their fry) that they come across.
- Many species of fish that are vulnerable upon hatching can actually have very high survival rates if simply given some place to hide. Providing some plants and/or pondweeds for new fry to hide in for the first few days of their lives does not take any great effort and will increase survival rates dramatically.
- Some species of fish actually prefer to lay sticky eggs within some sort of weeds in order to hide their young from potential predators. Ironically, such fish usually snack on a couple of their own fry every day. Such fish, however, can be easily tricked. ”Spawning mops” can be created simply by unwinding some nylon rope and dangling a good portion of this “mop” into the water. When you notice any number of eggs stuck to a particular spawning mop, simply pull it out and transfer it into a new tank. Once your fish begin to hatch, they will eat microscopic pond matter for a few days (make sure you transfer them to pond water, NOT clean water). After a week or two, they will be large enough to return to your primary pond to go have a talk with their parents.
- Though it is rare, some fish actually reproduce using internal rather than external fertilization. These fish may release either fertilized eggs or young fry into the water, but will not usually eat them.
Though studying the reproductive and brooding habits of your particular species of fish will give you the best chance of raising a large number of successful offspring, let me end by giving you a good general strategy for ensuring relatively high success rates without too much effort on your part.
- Find out at about what age your fish reach sexual maturity. This is not hard. When they are close to this age, take a few of the largest fish (you want your fastest-growing specimens to reproduce) out of your primary pond and transfer them into a special breeding tank. If you cannot tell the difference between the males and females in your species, transfer enough fish that you are confident you have some of each gender. Do not forget that in some species males are substantially larger than females.
- Raise these fish normally. Once you see a good number of eggs have been released or a good number of fry are swimming around in the water (depending on if your fish are mouthbrooders or not), transfer their parents back into your primary pond. Raise the fry separately for a few weeks.
- Put some sort of plants and/or pondweeds in both your primary tank and your breeding tank. This will increase the rate of survival among your fry in either scenario.