Tashkent, Uzbekistan (UzDaily.uz) — During extreme heat in Uzbekistan's Tashkent region, an automated system adjusted carp feeding according to water temperature and oxygen levels. Across four trial ponds, researchers recorded higher fish weight and survival and lower ammonium concentrations under adaptive feeding. The authors caution, however, that the findings need to be replicated across more farms and climatic zones.
How should fish be fed when the air temperature reaches 44°C, water temperatures rise above 30°C, and dissolved oxygen begins to fall?
An experiment by Uzbek researchers suggests that during extreme heat, the answer may be counterintuitive: sometimes fish need to be fed less — or not fed at all for a period of time.
The results of a field study on climate-adaptive feeding of common carp were presented at the Second Regional One Health Conference in Bishkek by Abdulla Kurbanov of Uzbekistan's Fisheries Scientific Research Institute.
The experiment was conducted from June to August 2025 in Yangiyul district of the Tashkent region.
Researchers used four one-hectare earthen ponds. Each was stocked at a density of 5,000 fish per hectare, with an initial average weight of approximately 150 grams. Two ponds served as controls and two as experimental ponds.
Sensors Decided When the Fish Should Eat
In the control ponds, carp were fed conventionally — manually three times a day regardless of temperature or water conditions.
In the experimental ponds, feeding decisions were based on sensors that measured water temperature and dissolved oxygen every 30 minutes.
Under favorable conditions — water temperatures of 22–28°C and dissolved oxygen above 5 mg/L — the fish received the full ration.
When temperatures rose to 28–30°C and dissolved oxygen declined to 3.5–4.5 mg/L, the ration was reduced by 30 percent.
When dissolved oxygen fell below 3 mg/L or water temperature exceeded 31°C, feeding was suspended entirely.
The logic is straightforward. Warmer water holds less dissolved oxygen. Continuing to provide the same amount of feed can leave more uneaten material in the pond, increasing the organic load and potentially worsening water quality.
The Trial Coincided With Extreme Heat
The summer provided a demanding real-world test for the system.
During the experiment, peak air temperatures reached 42–44°C, while peak water temperatures reached 30.5–32°C.
As conditions approached critical thresholds, the automated system reduced or suspended feeding. In the control ponds, fish continued to be fed three times per day on a fixed schedule.
By the end of the experiment, the difference was substantial.
The average final body weight of carp in the control ponds was 630 grams, compared with 975 grams under climate-adaptive feeding — 54.8 percent higher.
The difference in survival was also considerable.
Survival reached 76.5 percent in the control ponds and 93.2 percent in the experimental ponds.
At the same time, the feed conversion ratio — a measure of how much feed is required to produce a given increase in fish weight — improved from 2.25 to 1.48, or by 34.2 percent. The between-group differences reported by the researchers were statistically significant at p<0.05.
Less Feed, Cleaner Water
The differences were not limited to the fish themselves.
Average ammonium concentrations in the experimental ponds were 0.6 ± 0.2 mg/L, compared with 1.8 ± 0.4 mg/L in the control ponds — a reduction of 66.7 percent.
The authors suggest this may have resulted from reduced accumulation of uneaten feed and organic sediment. Importantly, however, that mechanism was not directly measured in the study, meaning it remains a proposed explanation rather than a demonstrated causal pathway.
This is where the experiment extends beyond a conventional aquaculture question.
From a One Health perspective, a single feeding algorithm simultaneously affects three domains: fish health, the quality of the aquatic ecosystem, and the reliability of food production.
Why Four Ponds Are Not Yet a Ready-Made Solution for the Entire Country
The results are striking, but the experiment remains small.
Only four ponds were included — two control ponds and two experimental ponds. The individual pond, rather than each fish, served as the statistical experimental unit.
The findings therefore cannot automatically be generalized to all fish farms in Uzbekistan or across Central Asia.
The researchers themselves acknowledge this limitation.
The next step they propose is multi-site testing across different climatic zones of Central Asia, using more ponds, repeating trials across seasons, and introducing standardized water-quality monitoring. Such work would be necessary to determine whether the results are reproducible before the approach could be adopted more widely.
Still, the experiment points to a potentially important direction for climate adaptation in aquaculture.
As heatwaves become more frequent, the question facing fish farms may no longer simply be how much feed to give fish, but whether a management system can recognize when feeding them at all would do more harm than good.
In a hotter climate, that distinction could mean more fish surviving, less pressure on water quality, and more resilient food production.
