Managing White Shrimp Through Heat — Above 34 ℃ It Is a Different Pond

In summer the same pond suddenly becomes hard to manage. A stocking density and feed rate that caused no trouble through spring start producing mortality in August. The pond has not changed — the amount of oxygen the water can hold has. ■ The shape of a summer kill — two curves separating The amount of oxygen that dissolves in water falls as temperature rises. Shrimp, being poikilothermic, run a faster metabolism as the water warms, so their oxygen demand climbs. Supply drops, demand rises. The distance between those two curves is the danger. That is why a pond that was comfortable at 5 mg/L in spring is running tight at the same reading in midsummer. ■ 34 ℃ — where survival replaces growth White shrimp feed and grow best between 29 and 31 ℃. Above 32 ℃ growth efficiency starts to slip, and past 34 ℃ the goal of management changes entirely. From there the question is not how much you will grow, but how little you will lose. Held near 33 ℃ for several days, the hepatopancreas takes real damage — hepatic tubules atrophy and, in severe cases, rupture. That organ handles both digestion and immunity, so once it is compromised almost any disease can follow. High temperature is not itself a disease; it opens the door for one. ■ Water depth — check this first Deep water heats slowly. In a shallow pond the surface layer climbs fast under midday sun and the daily swing widens. Hold at least 1.2–1.5 m through summer, and 1.8 m or more in mid-to-late grow-out. Adding depth costs less than adding aerators and the benefit lasts longer. ■ Aerators — run them at midday too Many farms run aerators only at night. In summer you need them during the day, for two reasons. First, at midday the temperature difference between surface and bottom grows and the water separates into layers. Once that stratification sets in, the bottom layer stops mixing and its oxygen is consumed with nothing replacing it — and the bottom is where the shrimp are. Second, aerators do not only add oxygen, they mix. Turning the cooler bottom water into the hot surface water narrows the temperature spread across the whole pond. ■ Feed — what they leave becomes poison Holding the feed rate steady through a heat spell is dangerous. When water gets too warm shrimp actually eat less. Feed at the usual rate and it will be left behind. Uneaten feed settles, breaks down, consumes oxygen and drives ammonia up. In a period when oxygen is already tight you are spending more of it and adding a toxin at the same time. Check the feed trays, cut the ration based on what is left, and cut it further on any day dissolved oxygen drops below 5 mg/L. ■ Measure before dawn, log every day Even in summer, oxygen bottoms out between 4 and 6 in the morning. A daytime reading tells you nothing about whether the pond will get through the night. Do the same with temperature — track the high and the low, not a single reading. A daily swing beyond 3 ℃ is a burden by itself. If yesterday peaked at 33.2 ℃ and today at 33.8 ℃, you are still under 34 but the trend is unmistakable. Trouble is announced when that trend begins, not when the threshold is crossed. Shrimp365 logs temperature and dissolved oxygen per tank and alerts you the moment a value leaves its range. It is free to use.