Fish, Tanks and Ponds


Fish, Tanks and Ponds
A comprehensive guide to fish

Culling

update
They all fit at the moment, but what happens when they reach three times this size just before being sold on. Be realistic when deciding how many fry to raise, and what the market requires. Otherwise...

Introduction

Culling is the practice of killing (usually young fry) in order to weed out the sickly and undersized fry in order to give the most resources to the best and healthiest fry.

Culling in this way is essential if the bloodlines of captive fish are to remain healthy. More and more fish are being bred in captivity because there are already to many pressures on wild fish and due to the popularity of some species wild stocks would not be able to cope. With this in mind it is important that captive stocks are kept pure and healthy.

There are those who will say each small fish has a right to live but in reality if this leads to a brood of sickly runts is it really the best way to proceed?

In a wild population, for that population to remain stable each pair of fish only has to produce two fry which live to breed in their lifetime. So out of the hundreds or even thousands of fry they will have in a life time only two are needed to keep the population as it is.

Why cull?

When breeding fish particularly using domesticated parent fish as opposed to wild caught parents it is likely that the odd baby fish may be malformed in some way or after a few days some fry will be bigger and stronger than others in the brood. These differences will become more apparent as time passes by and some of the smaller weaker fish will struggle to keep up and may even eventually die naturally.

Some fish produce thousands of fry if it was possible to raise all of them to a saleable size, then what? If 1,500 one inch oscars were suddenly on the market quite simply most would remain unsold, no dealer would take more than a couple of dozen if they even took so many. If you sold them in small amounts to every dealer for miles around then they would remember you and most probably wouldn't deal with you again.

It is better for everyone if you raised 30 -50 good healthy uniform fry than it would be to raise a few hundred stunted fry which varied in size.

Method of culling

Young fry don't need to be culled using oil of cloves there are more simple and faster methods available which involve less fussing about. If you aren't squeamish simply 'pinching' the fry is a very fast method which involves no suffering for the fry. If the fry are born in a community tank it is a simple matter of saving the fry which you can raise and letting nature take it's course with the rest.

Finally

Culling isn't cruel, it is essential.

Animal Welfare Act

Under UK law it is illegal to use live vertebrates as food, this obviously includes fish.  Although this isn't written specifically in the act it will apply under the clause of:

an act of his, or a failure of his to act, causes an animal to suffer,

Allowing a large predator to chase and eat the fish where they have no chance of escape will cause suffering.

Do not use live fry as food.