Carp Pituitary Gland Dosage: How Much per kg of Broodstock

The short answer

For common carp and the other Chinese carps, the total dose for a female is 2–5 mg of dried gland per kg of body weight, split into two injections. Catfish need more — typically 4–8 mg per kg in a single injection. Males get 1–2 mg per kg once, at the time of the second female injection.

Those figures are the working range used across most hatcheries. Your own batch may be stronger or weaker than the last one, which is why the label and your local extension officer come first, and this chart comes second.

How far one 1 g vial goes

Every vial I ship holds 1 g of dried granules, which is 1000 mg. Buyers usually ask this before anything else, because it decides how many vials to order for a season.

A hatchery running 200 female common carp at 2.5 kg average therefore needs 500 kg × 3 mg = 1500 mg, or two vials — one and a half, rounded up because you never want to run short mid-run.

Why the dose is split in two

A carp will not ovulate on a single shot of pituitary material. The gland works in two stages: the first, small injection starts the final maturation of the eggs, and the second, large injection triggers ovulation. Skipping the priming injection is the single most common reason a batch fails.

1. Priming injection — 10–15% of the total doseGiven in the morning. This is a signal, not a trigger; a small dose is enough to bring the eggs to the point where they can respond.
2. Rest period — 6 to 12 hoursDepends almost entirely on water temperature. See the table below. Handle the fish as little as possible during this window.
3. Resolving injection — the remaining 85–90%Given in the evening. This is the shot that actually causes ovulation, usually 8–14 hours later.
4. Check from hour 8 onwardsTest by pressing the abdomen gently. When eggs flow freely, strip immediately — waiting costs you the batch.

Timing by water temperature

Temperature drives everything. The same dose given at 20 °C and at 27 °C produces ovulation more than four hours apart, and a team that strips on the wrong clock finds either eggs that will not come out or eggs already overripe.

Write the actual injection time on the tank, not in your head. Every hatchery that spawns more than a few tanks a night uses a whiteboard for exactly this reason.

Four mistakes that waste a batch

1. Mixing the whole vial at once

Dried gland stays stable for two years in the sealed vial, but once it is in saline it is good for hours, not days. Weigh out what you need, grind it, suspend it, inject it, and discard the rest. Never store a mixed suspension overnight for the next spawn.

2. Judging ripeness by eye alone

A swollen abdomen is not proof of ripeness. Check the genital papilla — pink and slightly protruding means ready; soft eggs that come away in a smear mean overripe and you have already lost that female.

3. Dosing by fish count instead of weight

Two fish of the same length can differ by a kilogram. A batch dosed on an estimated weight usually ends up underdosed, because people guess low to be safe, and underdosing wastes a spawn just as surely as overdosing.

4. Letting the water warm up overnight

If the pond cools by five degrees between the two injections, your 10-hour interval becomes a 16-hour interval in fish time. Cover the tanks or accept that the schedule has moved.

The record sheet that pays for itself

Keep four columns per spawn: date, water temperature, dose per kg, and hours to ovulation. After one season you will know how your own water and your own fish respond, which is worth more than any chart — including this one.