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Fishes Spawning In The Wild

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In the wild the climate usually varies a lot more than in the aquarium. Rainy seasons and dry seasons are examples of large changes in the natural environment of many fishes. To these fishes it's usually most important to adjust the spawning to the time when the supply of food is the greatest, both for the fry and the parents, and all the odds for succesfully getting surviving fry are at their peak. This usually means the rainy season when the lifegiving water is filled with tiny organisms.

Factors that trigger spawning in species that spawn during the rainy season are, for example, the temperature of the water, pH value, hardness value, oxygen level, water level, water flow, food supply (some species even need to eat special types of food, for example black mosquito larvae, to spawn), availability of appropriate spawning sites (that are above water level during the dry season), the diurnal rhythm, atmospheric pressure, other fishes that spawn, etc. Over and above these factors some fishes even have a "biological clock" that triggers spawning only at a certain time of year. Different species are different in their sensitivity to these factors, but if you want a "stubborn" species to spawn in your aquarium you may have to consider all triggering factors that make that fish spawn in the wild.

Nature is hard and most of the fishes die young. It is always a struggle to survive according to the principal of "survival of the fittest" and to spread their genes. The most sensitive time is as egg and fry. It's usually only a small number of the original amount of eggs that make it.

The fishes have developed methods to ensure reproductive success. It's that development that has led to some species laying thousands of eggs where the chance for any particular fry to survive is very low, but the large amount of eggs ensures that there are still a few survivors. Other fishes have put their money on another method, to lay only a few eggs. These species then often protect this smaller amount of eggs and fry. These eggs are often a lot larger and one or both of the parents guard the offspring until the fry are large enough to take care of themselves. Yet other fishes have adapted by giving birth to live young instead of laying eggs. Through natural selection the genes of individuals that don't manage to get their offspring to survive will not be passed on to the next generation in the cycle of life.

The fishes have different enemies and dangers in the wild. There are predators, drought, diseases, mould, rivals, lack of food and so on. Over and above this they must also find an appropriate fish of the same species, but the opposite sex, to reproduce with so that the species may live on and keep adapting through the generations. That's life in the natural world of fishes!



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