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7/27/2019 Breeding Freshwater Fishes
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BREEDING
FRESHWATER FISHES
One of the great attractions of keeping tropical
freshwater fishes is that many of them will breed very
easily in the aquarium provided that they are given the
right conditions.
Most fishes are egg-layers, but there are a number
of species which give birth to living young. In these
fishes the male has an intromittent organ (gonopodium)by which internal fertilization of the female occurs, and
the development of the embryo takes place in the ovary.
The egg-layers can be classified into the following
five groups:
Egg-scatterers Fishes in this group, for example
barbs and characins, scatter their eggs on the ground or
among plants. The parental care offish spawning in thismanner is nil — they swim one way laying eggs andmay swim back the other way eating them unless
precautions are taken. In some of these groups the eggs
are semi-adhesive and stick to plants or rocks.
Egg-placers These lay their eggs in neat clusters on
rocks, plant pots or large-leafed plants. The cichlids
usually spawn in this way. In many species of cichlid,such as the Jewel Fish (Hemichromis bimaculatus), the
eggs are left to hatch where they are laid and then are
taken to a depression in the gravel for the next few days.
In other cichlids, as the Mozambique Cichlid (Tilapiamossambica), for example, the eggs are laid and
fertilized and then taken into the mouth of one or other
parent and incubated there. The fishes in this group arecalled mouth-brooders.
Nest-builders The most spectacular are the
Anabantidae, many members of which build bubblenests, as the Siamese Fighting Fish (Betta splendens).
Egg-hangers These fishes lay their eggs, one or two
at a time, on the roots of floating plants. Many species
of killifishes, such as Aphyosemion gardneri, spawn inthis way.
Egg-buryers These fishes bury their eggs in the mud
or silt at the bottom of the pond, for example the egg-burying killifishes such as Nothobranchius guentheri.
GENERAL PRINCIPLES OF BREEDINGA good fish is good for two main reasons: it inherits
good qualities from its parents, and secondly it has good
environmental conditions, that is, it gets enough of the
right foods, it has plenty of tank space, the wa
conditions are as congenial as possible, and so on.
Unfortunately, many species of tropical fishes
now said not to be as colourful as the same species wyears ago. One reason for this is the relative ease
breeding freshwater fishes which encourages aquar
to breed unselectively from any poor fish to try araise as many offspring as possible, many of them
bad as their parents. If we wish to improve our fishes
must breed with the best stock we can get and cull
any offspring which are less than perfect.
Once a good stock for breeding has been obtainthe fulfilment of the following principles leads
Successful spawning:
Siamese Fighting Fishes
(Betta splendens) spawning below a bubble
7/27/2019 Breeding Freshwater Fishes
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Once a good stock for breeding has been obtainedthe fulfilment of the following principles leads to
Successful spawning:
1. Obtain a male and female, both of which should bemature. This seems obvious to everyone but in somespecies the sexes are so similar that most experienced
aquarists will admit to having tried to breed two
fishes of the same sex or with fishes too young to
breed.
2. Condition the breeders, in separate tanks, for at least
two weeks and feed them well with live foods,
3. Give the fishes correct water conditions, checking
such points as the pH, hardness and any special
requirements of individual species. Eggs of the Neon
Tetra (Hyphessobrycon innesi), for example, will hatch in hard water and the eggs of the Madagas
Rainbow Fish (Bedotia geayi) will not hatch in s
water.
4. See that the temperature is correct; an increasetemperature of a few degrees is often a good stimu
to spawning.
5. Provide the proper spawning medium — peat fib
floating plants, nylon wool mops, a plant pdepending upon the spawning method of the fish.
6. Take care in raising the fry. This is very often
most difficult part of the whole breeding procedu
and feeding is particularly important.
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As the fry get larger they should be moved into
larger tanks for ‘growing on’ and they should beregularly inspected. All runts and fishes with
abnormalities or with poor coloration should be
removed and destroyed. Those which are growingparticularly well and are the best in colour, shape and
deportment should be ear-marked for future breeding
stock or for entering in breeders’ classes in
competitions.
GENETICS
The inheritance of various characteristics, such asshape, colour and finnage, obeys the same principles intropical fishes as in all other creatures. Many of the
characteristics are inherited in a dominant or recessive
manner, obeying the laws of inheritance laid down
Mendel. It is not possible here to go into detail about more complex principles of genetics but there is o
important practical rule which will be of value to m
fish keepers. If the hobbyist has a fish with a desircharacteristic and as a result of crossing the fish t
characteristic is not found among the offspring (that
the characteristic is recessive) then the hobbyist can
two things to improve his chances of getting t
characteristic back. He can cross the original parewhich has the desired characteristic, with one of its o
offspring, when there is a fifty per cent chance of young of this cross having the characteristic, or cr
two of the offspring of the original mating togeth
when he will have a twenty-five per cent chancegetting youngsters with the desired feature.