breeding freshwater fishes

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



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.



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.

breeding freshwater fishes

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