Fish ponds in winter: how to prevent ulcer disease and slow growth

12 November 2026 · 2 min read · Krishoker Thikana desk

From December to February, many pond farmers find fish with red sores and wounds on the body. This ulcer disease, known to scientists as EUS (epizootic ulcerative syndrome), is the disease Bangladeshi pond farmers report most, and it appears mainly in the cold season. In cold water fish also eat less and grow slowly, so winter care matters for the whole year's profit.

Which fish are most at risk

Snakehead (shol, taki), catfish, barbs (puti) and Indian major carps such as mrigal and rui are most often affected. Chinese carps such as silver carp and grass carp are usually less affected, but they can also get sores.

Get the pond ready before the cold

• Apply lime in early winter, before the cold sets in. The Department of Fisheries recommends lime (or salt) before the cold season; ask your Upazila Fisheries Officer for the right amount for your pond size.
• Do not overstock. Studies of Bangladeshi ponds found stocking two to three times the recommended number of fish was common; crowded fish get sick more easily.
• Keep the water deep enough so it does not get too cold, and clear floating weeds so sunlight reaches the water.
• Sell or harvest some fish before deep winter if the pond is crowded.

Feeding in winter

• Fish eat less in cold water. Reduce feed and give it at the warmest time of day, around midday.
• Uneaten feed rots and spoils the water, so watch how much is left.
• Do not add a lot of fresh cow dung or fertiliser in cold weather.

If you see sores

1. Catch a few fish with a cast net and look closely. Note which species are affected and how many.
2. Remove dead and badly affected fish and bury them; do not throw them into a canal or another pond.
3. Call your Upazila Fisheries Officer. In a farmer trial in Kishoreganj and Rajshahi, salt and lime treatments helped most ponds recover, but the right dose depends on your pond, so ask before treating.
4. Do not use antibiotics or chemicals on guesswork, and do not move fish or nets from a sick pond to a healthy one.

The Fish page of this site lists the Department of Fisheries, research institutes and other help for fish farmers.