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Stocking a dam with trout: how many, when, and whether you should
Start with the calculator for a rough number, then read why depth, temperature and inflow matter more than surface area.
- Fish health checked before every dispatch
- Stocking advice with every order
- You speak to the people who raise the fish
- Delivering to Dullstroom
Trout stocking calculator
Enter your dam's surface area and how you plan to manage it. The result is a starting range, not a prescription. Stillriver Trout checks it against your depth, water source and summer temperatures before quoting.
Suggested starting range
Figures are converted from published US extension pond guidance (North Carolina, Virginia and New York), not South African rules. They assume your water stays cool enough for trout.
Get a stocking plan for your dam
Send your result and dam details. We reply with a species, a number and a delivery date.
First question: can your dam hold trout at all?
Surface area gives you a number. Temperature and oxygen decide whether the fish live to be counted. Trout are cold-water fish, and stocked trout in farm dams are most at risk in late summer, when shallow water warms up and holds less oxygen.
US pond guidance puts the line at about 21.1 °C: water above that for more than a few hours can kill rainbow trout, and ponds that stay below it may support trout if dissolved oxygen stays above about 5 parts per million. Brown trout are more sensitive. They grow best near 13 °C, and above about 19.5 °C they are under stress.
In South Africa, late summer is the hard stretch. Researchers at Stellenbosch University reported that water temperatures of 25 °C combined with poor water quality cause disease outbreaks and high losses on trout farms, worst in February and March.
Signs your dam is a good fit
- Spring-fed or stream-fed, with water flowing in through summer.
- A deep section where the bottom water stays cool in the afternoon.
- Shade, wind exposure or altitude that keeps the surface temperature down.
- No history of algae blooms or summer fish kills.
Signs it may not be
- Shallow throughout, fed only by run-off, and still in summer.
- Thick green water or heavy weed in summer.
- Livestock or fertiliser run-off into the dam.
If you are not sure, take the water temperature in the afternoon on the hottest days of the year, at the surface and as deep as you can reach. That single reading tells us more than anything else. Or ask us to look at it with you.
How many trout per dam: where the numbers come from
We could not find a South African body that publishes a per-hectare stocking rate for trout in farm dams, so the calculator uses published guidance from US extension services, converted to metric. Treat it as international guidance and a sensible starting point.
| How the dam is managed | Published guidance | Per hectare (converted) |
|---|---|---|
| Fed pond, rainbow trout | 500 per acre | about 1,236 |
| Fingerlings, autumn stocking | 400 to 500 per acre | about 988 to 1,236 |
| Unfed pond, rainbow trout | 300 per acre | about 741 |
| Sub-adult trout, under about 20 cm | 200 per acre | about 494 |
| Adult trout, longer than about 20 cm | 100 per acre | about 247 |
The same guidance says a pond of average fertility grows natural food for roughly 112 kg of trout per hectare. That is the useful ceiling for an unfed dam: divide it by the weight you want your fish to reach and you have a rough upper limit. Fewer fish grow bigger.
How stocking works with Stillriver Trout
Tell us about the dam
Surface area, deepest point, water source, and a summer afternoon temperature if you have one. Photos help.
We recommend species and numbers
Rainbow, brown or neither, how many, and whether you will need to feed. If trout are the wrong fish for your water, we say so.
You check the permit position
We explain what is likely to apply and who to ask. See the permits section below.
We deliver in cool weather
Fish travel in oxygenated water. On arrival they are tempered to your dam's temperature before release, because temperature shock is one of the most overlooked causes of stocking losses.
We follow up
A check-in after release, and advice on feeding and restocking. Pond guidance suggests restocking every two to three years, depending on how many fish are taken out.
Permits for stocking trout in Mpumalanga
National level. Rainbow and brown trout appear on the national Alien and Invasive Species Lists, 2020, but Notice 115 of 2021 excluded both trout listings from coming into effect until further notice. We found no later notice bringing them into force.
Provincial level. Provincial rules still apply. As reported by the Federation of Southern African Flyfishers, the Mpumalanga Tourism and Parks Agency has required permits for the sale and stocking of live trout, except in dams that are not connected to rivers, and both suppliers and recipients of live trout have needed permits.
Rules change. Confirm the current position with the Mpumalanga Tourism and Parks Agency before you stock. This page is general information, not legal advice.
Rainbow trout or brown trout for a farm dam
Rainbow trout feed best between about 7 and 18 °C and are the usual choice for stocked dams and fishing venues. Brown trout prefer colder water and grow best around 13 °C, which makes them a better fit for deep, cold dams. Compare both on trout fingerlings for sale.
Related
Dam stocking questions
How many trout per hectare should I stock?
Published pond guidance ranges from about 247 adult fish per hectare up to about 1,236 per hectare for fed ponds stocked with fingerlings. Those figures come from US extension services, not South African rules. Your dam's depth, summer temperature and inflow decide where in that range you should be, which is why we ask before we quote.
When is the best time to stock trout?
When the water is cool and will stay cool for months. Pond guidance is to stock only when the water is consistently below about 21.1 °C. In the Highlands that usually points to autumn and winter, giving the fish the cool season to settle and grow.
Do I need to feed trout in a dam?
Not always. A dam of average fertility produces natural food for roughly 112 kg of trout per hectare, according to US pond guidance. Stock more than that and you need to feed. Never feed when the water is warm, because uneaten food rots and uses up oxygen.
Why did my trout die after stocking?
The common causes are temperature shock at release, warm water, and low oxygen. Fish should be tempered to the dam's temperature before release. If fish die weeks later, read why are my trout dying.
Do I need a permit to stock trout in Mpumalanga?
Possibly. The national invasive species listing for trout has not come into force, but the Mpumalanga Tourism and Parks Agency has required permits to sell and stock live trout except in dams not connected to rivers. Confirm the current rules with the MTPA before you stock.
Rainbow or brown trout for my dam?
Rainbow trout tolerate a little more warmth and grow quickly, so they suit most stocked dams. Brown trout prefer cooler water, grow best around 13 °C and are better suited to cold, deep dams. See trout fingerlings for sale for both.