Monsoon rain, El Niño and pond water quality: a practicalguide for shrimp farmers

Shrimp live in the water, so every change in the weather reaches them through the pond. A night of heavy rain, a week of heat without wind, or a season shaped by El Niño can each move pH, salinity and oxygen far enough to stress a crop that looked healthy the day before.

Recent reporting from Shrimp. News on pond pH and El Niño explains much of what goes on in the water when the weather turns, and what farmers can do about it.

How rain changes pond pH

After heavy rain, many farmers expect the pH to drop. Sometimes it does, sometimes it barely moves. Shrimp.News explains that rain acts on a pond in several ways at once:

• Dilution. Rainwater lowers the concentration of dissolved minerals that help hold the pond’s pH steady.
• Less sunlight. Cloud cover slows photosynthesis by the algae. Algae use carbon dioxide during the day, so when they slow down, the balance of carbon dioxide in the water shifts and pH can change with it.
• Runoff. Water that flows into the pond over surrounding soil can carry acidic material, and runoff from acidic soils has caused serious pH problems on shrimp farms.
• Layering. Heavy rain can leave a layer of fresher water on top, so the pond no longer has the same conditions from surface to bottom.

Because these effects pull in different directions, the only reliable answer comes from measuring. Shrimp.News’s advice is to test pH after significant rain instead of assuming what happened, compare the reading with the pond’s normal values, and look at the surroundings, including soil type, runoff sources and how the algae are doing.

That comparison only works if you know what normal looks like for your pond. In a second piece on pond pH, Shrimp.News describes the daily cycle most ponds follow. Algae use carbon dioxide during the day, which pushes pH up, while respiration by everything in the pond keeps releasing carbon dioxide through the night, which pulls it down. A pond might read around 7.8 in the morning and 8.2 in the evening. Alkalinity is what buffers those swings, and it is a separate measurement from pH.

So instead of asking only what today’s pH is, ask why it is changing and whether today’s pattern differs from your pond’s normal one. Keep regular records in good weather as well as bad, so you have a baseline to compare against.

What El Niño means for shrimp farms

Shrimp.News has reported on the pressure a strong El Niño is putting on shrimp farmers in Andhra Pradesh this year. For any shrimp farm, the effects show up in three places: oxygen, salinity and feed.

Warmer water holds less dissolved oxygen, while warm shrimp need more of it. The risk is highest in the early morning, after a night in which algae have been using oxygen instead of producing it. During long hot spells, early morning dissolved oxygen deserves particular attention.

Salinity becomes less stable. Long dry periods raise salinity as water evaporates, and when rain finally arrives it can drop sharply. Sudden swings in salinity put osmotic stress on shrimp.

El Niño does not cause shrimp disease directly, and Shrimp.News is careful to say so. But the stress of unstable water conditions makes shrimp more vulnerable, and it makes health management harder.

Feed costs are under pressure too

El Niño also reaches the farm through the feed bill, because it reduces the catch of the small fish used to make fishmeal off Peru and Chile. Shrimp.News reports that fishmeal production in the first seven months of 2026 was 49 percent lower than in the same period of 2025, with the shortfall coming from Peru and Chile. Peruvian super prime fishmeal reached around US$2,500 a tonne in May 2026.

Feed makers can adjust their formulas, but overall feed costs face upward pressure. The same report notes that the fishmeal industry body IFFO expects higher fishing activity in the final quarter of the year from regions including China, India and Oman, which may ease supply. Feeding to the shrimp’s actual appetite matters more than usual when every kilo of feed costs more.

A weather checklist for the pond

Shrimp.News’s recommendations, combined with what our field team sees on farms in South Gujarat, come down to a few habits:

1. Test water quality more often when the weather is changing, especially pH, dissolved oxygen and salinity.
2. Take dissolved oxygen readings in the early morning during hot spells.
3. Measure pH after heavy rain and compare it with your pond’s records.
4. Service aerators before the hot season starts, so they are ready when oxygen runs low.
5. Stock at a density the pond can support if the weather turns against you.
6. Check feed trays and adjust feeding to what the shrimp are eating.
7. Watch the weather forecast and plan water exchange and aeration around it.
8. Investigate any change in shrimp behaviour straight away.

How Olpad Aqua supports farmers through the weather

Our aquaculture team visits the ponds of farmers in our network through the crop, checking growth, water quality and shrimp health, and advising on feeding and on what to do when conditions change. Our four coastal outlets at Olpad, Maroli, Navsari and Valsad stock more than 20 categories of chemicals and minerals for pond preparation and water quality, aerators from six manufacturers and more than 64 types of farm equipment.

We also supply medicine with guidance on when and how to use it. Weather stress tempts farmers to treat early, and a wrong treatment can show up later as a failed residue test. Advice from someone who knows the pond helps avoid that.

If you farm shrimp in South Gujarat and want support through the season, visit the nearest Olpad Aqua outlet or contact our team.