05/06/2026
【Dr.Fish Weekly Literature Insight】
Aquaculture Cannot Depend on Antibiotics Long-Term: The Real Risk Is Not Only Residue, but Antimicrobial Resistance
In aquaculture, when fish or shrimp begin to die, many farmers’ first reaction is often not to identify the real cause, but to immediately search for medicine.
What antibiotic should be used?
What medicine can stop the mortality?
Should we switch to another drug?
Should we combine several antibiotics together?
This situation is not uncommon in real farming operations. In many cases, antibiotics enter farms through both formal and informal channels, and some farmers even treat them like a “miracle solution.” Once fish or shrimp stop feeding, mortality increases, body color changes, gill problems appear, red body symptoms occur, or white f***s is observed, the first reaction is often medication.
But the real question is:
Is every mortality case truly caused by pathogens?
From practical aquaculture experience, the answer is no.
In many cases, fish and shrimp mortality is not caused by a single pathogen suddenly becoming stronger. More often, the system has already been moving toward imbalance, involving water quality, pond bottom condition, stocking density, feeding, stress, and microbial ecology. The pathogen is often only the visible expression at the final stage, not the only root cause.
In Recirculating Aquaculture Systems (RAS), if the nitrification system is not mature or water quality management is insufficient, ammonia, nitrite, and organic loading may accumulate, placing fish and shrimp under long-term stress. In traditional pond aquaculture, the situation can be even more complex. Weather changes, algal imbalance, pond sludge, overfeeding, high stocking density, and polluted water sources can gradually push the system toward disease outbreak.
Under such conditions, antibiotics may sometimes produce short-term improvement.
This is because when a system becomes imbalanced, certain bacterial problems may already have been triggered. Antibiotics may temporarily suppress part of the pathogen load. However, this does not mean that the real problem has been solved.
Antibiotics can kill part of the pathogen, but they cannot kill the problems within system management.
They cannot reduce ammonia.
They cannot remove pond sludge.
They cannot stabilize algal balance.
They cannot establish a nitrification system.
They cannot repair organic loading caused by long-term overfeeding.
And they cannot replace a stable aquaculture system.
Therefore, antibiotics are treatment tools, not stabilizers for aquaculture systems.
The real danger begins when farmers turn antibiotics from a treatment tool into a daily management method. Once this happens, the farm may enter a vicious cycle.
At first, one antibiotic appears to be effective.
After repeated use, its effect gradually weakens.
Mortality starts to increase again.
Then another antibiotic is used.
After some time, that also becomes less effective.
Eventually, one or two, or even several antibiotics, may be mixed together.
On the surface, this may look like stronger treatment.
But in reality, it may be increasing the selection pressure for antibiotic-resistant pathogens.
Long-term or repeated use of the same antibiotic can eliminate susceptible bacteria while allowing more resistant bacteria to survive. When this pressure continues, resistant pathogens are more likely to dominate. Eventually, farmers may find that medicines which used to work are becoming less effective, and mortality becomes harder to control.
Misusing antibiotics today may be cultivating pathogens that are harder to control tomorrow.
This is the most serious danger of antibiotic abuse.
When people talk about antibiotics, the first concern is often drug residue. Residue is certainly a serious issue because it affects food safety, consumer trust, market access, and export inspection.
But in the long term, the risk that is even harder to reverse is antimicrobial resistance.
Residue affects whether this batch of products can safely enter the market.
Antimicrobial resistance affects whether future diseases can still be treated effectively.
If one farm abuses antibiotics over a long period, the problem is no longer limited to that particular pond or tank. If dozens or even hundreds of farms in the same farming region use similar antibiotic sources and similar antibiotic types, the issue becomes much larger than one farm.
It becomes a regional ecological issue.
The water environment may be affected.
Pond bottom microbial communities may be affected.
Pathogen pressure in the environment may change.
Antibiotic-resistant bacteria and resistance genes may spread.
Eventually, the impact may extend beyond farmed animals to the food chain, the environment, and public health.
In other words, antibiotic abuse is not only a risk for one farmer. It is a shared risk for the entire farming region, the food safety system, and future disease management capacity.
More seriously, humans may also be slowly blocking their own path to effective disease treatment.
If antimicrobial resistance continues to expand, it may not only make fish and shrimp diseases harder to treat. It may also threaten the effectiveness of important antibiotics used in human medicine. This is no longer only an internal issue within aquaculture. It is a global public health concern.
Of course, I am not saying antibiotics can never be used.
When a bacterial disease is clearly diagnosed, professionally assessed, legally regulated, properly administered, and withdrawal periods are strictly followed, antibiotics may be necessary treatment tools.
But antibiotics must not be used casually.
They must not be relied on long-term.
They must not be used without diagnosis.
They must not become routine preventive additives.
And they must not be used in a cycle of switching, adding, and mixing whenever one drug becomes ineffective.
True professional aquaculture management should shift from treatment-based management to prevention-based system management.
Treatment-based management looks for medicine after mortality occurs.
Prevention-based system management reduces risk before disease occurs.
This includes stable water quality, pond bottom management, appropriate stocking density, precise feeding, healthy seed selection, biosecurity, microbial system management, daily monitoring, SOP implementation, and early risk adjustment before weather changes.
Traditional aquaculture often reacts after problems appear.
Modern aquaculture should place greater emphasis on system stability, early warning, and risk control.
This is also why, in RAS and modern aquaculture system management, the direction should not be to depend on antibiotics to maintain production. Instead, disease occurrence should be minimized through stable water quality, biological filtration, biosecurity, controlled environments, standardized SOPs, and continuous monitoring.
RAS emphasizes environmental control and food safety. Antibiotics should not be used as a tool to maintain system operation. A truly mature modern aquaculture system should reduce dependence on medication, not use medication to hide management failure.
The future competitiveness of aquaculture will not depend on who uses stronger medicine.
It will depend on whose system is more stable, whose risk is lower, and whose products are safer.
Antibiotics can treat certain bacterial diseases.
But they cannot replace water quality management.
They cannot replace pond bottom management.
They cannot replace biosecurity.
They cannot replace healthy seed.
They cannot replace system design.
And they cannot replace professional management.
If aquaculture is to become truly sustainable, it cannot depend on antibiotics long-term.
Because the real risk is not only residue.
It is antimicrobial resistance.
When antibiotics are abused, what appears to solve today’s mortality problem may create tomorrow’s disease problem that is far harder to control.
Therefore, aquaculture must redefine the role of antibiotics:
Antibiotics are treatment tools, not stabilizers for aquaculture systems.
Truly sustainable disease management is not about using more medicine.
It is about building a more stable system with fewer disease outbreaks.
📖 References
Okocha, R. C., Olatoye, I. O., & Adedeji, O. B. (2018). Food safety impacts of antimicrobial use and their residues in aquaculture. Public Health Reviews.
Yuan, X., Lv, Z., Zhang, Z., Han, Y., Liu, Z., & Zhang, H. (2023). A Review of Antibiotics, Antibiotic Resistant Bacteria, and Resistance Genes in Aquaculture: Occurrence, Contamination, and Transmission. Toxics.
World Health Organization. (2017). WHO guidelines on use of medically important antimicrobials in food-producing animals.
Food and Agriculture Organization of the United Nations. Responsible use of antibiotics in aquaculture.
Yusoff, F. M., Umi, W. A. D., Ramli, N. M., & Harun, R. (2024). Water quality management in aquaculture. Cambridge Prisms: Water.
✍️ Author: Ryan Tan Hong Joo
RAS Eco-Tech Aquaculture Expert | Dr.Fish Founder
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