Aquaculture antibiotics study needs more context

A new study about antibiotics in aquaculture was recently published in the Journal of Hazardous Materials, and although it provides some good, useful data, it doesn’t mean much without more information.

Study highlights

  • 5 out of 47 antibiotics were detected in shrimp, salmon, tilapia and trout.
  • Oxytetracycline is the most commonly detected antibiotic compound.
  • Antibiotic resistant bacteria in seafood increase >8-fold in the last 3 decades.
  • We report a low risk of drug exposure from consumption of U.S. seafoods.
  • We recommend vigilance toward stemming microbial risks.

Sounds pretty innocuous, but as usual, the data is already being used by third parties to suggest that antibiotic usage in seafood farming is high and a potential problem.

Not true.

Let’s clarify one thing. Seafood farming and aquaculture have different meanings. Aquaculture is a far more general term, which includes farming as well as enhancement projects.

Wild salmon DO do drugs

Let’s use the definition supplied by the American Fisheries Society.

Aquaculture is an established and growing industry in the U.S., and an increasingly important supplier of foods for U.S. consumers.

The industry also produces baitfish for sport-fishing and ornamental fish for the pet trade.

In addition, federal and state fish hatcheries raise millions of fish for stocking in U.S. waters to support commercial and recreational fisheries and species restoration efforts.

Aquaculture is an important contributor to U.S. agriculture and a cornerstone of aquatic natural resources management.

All aquaculture operations will have a demand for drugs, biologics, and other chemicals, collectively referred to as “regulated products”.

There you have it: wild salmon DO do drugs!

Unfortunately, while this new study looked at five common species, including farmed American catfish, it did not look at any aquaculture-raised American salmonids. This is a glaring oversight, considering that billions of them are raised in aquaculture facilities and released every year on the Pacific coast.

It would be very interesting to see what sort of amounts of antibiotics are used in Pacific salmonid enhancement facilities in Canada and the USA.

Antibiotic resistance predates antibiotics!

Research published in 2011 adds even more interesting context to this study.

It suggests that making judgements about antibiotic resistance in aquaculture may be difficult: DNA from 30,000 year old microbes recovered from permafrost show antibiotic resistant traits similar to their modern counterparts.

Related stories

Antibiotics in aquaculture: getting the facts straight

Alexandra Morton’s furunculosis fable


7 thoughts on “Aquaculture antibiotics study needs more context”

  1. While I tend to agree with most of what you say above, the “30,000 year old microbes recovered from permafrost show antibiotic resistant traits similar to their modern counterparts” needs a bit more perspective – there MUST be antibiotic resistance in microorganism as far back as you can go in “history” – because “resistance” is not caused by antibiotics. Simply those organisms that are not resistant die at the hands of these powerful antibiotics and those that already (!) are resistant procreate. So for resistance to flourish, it has to be already there! And, since for 30,000, nay, millions of years resistance genes saved no purpose in optimizing survival, we might even expect to find more of them “further back” than immediately prior to the onset of modern antibiotic treatment because these unused features would eventually have been lost.

  2. and better look at these two quotations. One is from the TIMES website and the other is from the abstract @ sciencedirect.
    Which one is it? Was it a literary review or a meta-analysis? Was it 8 times the incidence of bacterial resistance or 8 times the articles on the linkage to aquaculture?

    In a related meta-analysis of studies on antibiotics and seafood, Done found that antibiotic resistant bacteria in seafood has grown more than 8-fold in the past three decades.

    A literature review showed that sub-regulatory antibiotic levels can promote resistance development and publications linking aquaculture to this have increased more than 8-fold from 1991-2013

  3. It even gets better here is a quote from TIME

    “For there to still be something in there”—after untold stages of processing and months in Done’s freezer—“means that at one point, it was injected or fed a lot more,” she says. “We just don’t know how much.”

    wow this methodology must be straight from the Activist’s science handbook.

  4. I think you folks are being too kind to the authors of the paper that spawned this. Considering it conveniently sits behind a pay wall that is guarded by the slick press release from the kind folks at ASU Biodesign Institute. Not sure if you sprung the 42 bucks for the paper but the abstract alone speaks volumes as to the intent of this paper. Both the abstract and the polished intro found at ASU are clearly apologising in advance for the poor study design and shoddy science. Since when has any credible study relied on samples purchased from supermarkets?
    Sound like a familiar MO ?

    This is from the ASU ad

    “Oxytetracycline, the most commonly used antibiotic in aquaculture, was the most prevalent in the study samples. Surprisingly, the study also detected this antibiotic in wild-caught shrimp imported from Mexico, which the authors suggest may be due to mislabeling, coastal pollution from sewage contamination, or cross-contamination during handling and processing. ”

    Doesn’t this kind of sound like apologizing for the fact that in reality these researchers have no idea where the ( bleep) these samples came from. let alone the source of anti-biotic measured.

    Surprisingly? Not to me. The entire study comprised 27 samples of unknown origin and questionable species. No consideration of known presence of anti-biotics in the natural environment ( ecosystem level) and no control samples whatsoever. ( except maybe the wild shrimp that had the highest measurement)

    What are the chances of this study conforming to OIE QC/QA guidelines?


    Considering there was detectable yet extremely low amounts of anti biotic residue found in every sample tested and the one wild species was the highest recorded measurement.

    What does this study really suggest?

    My guess is that because aquaculture is generally practiced in classified or at least regulated waters: where clearance times for anti-biotics are normally observed and enforced: it could be inferred that chances are the levels of anti-biotic in farmed fish are as low or lower than that found in wild counterparts especially when the source of wild fish is proximate to large urban centres. Somehow i don’t think it will be spun that way.


    1. Excellent points Bob. Especially your point about how the wild sample, taken near larger urban centres, had the highest amount. The study should have pointed out that oxytetracycline is commonly prescribed to humans for a variety of infections, and it’s entirely conceivable that it could end up in coastal waters near large human settlements.

      1. If these researchers really wanted to know the Antibiotic residue level in farmed fish as they claim. A start might be to arrange a chain of custody with a supplier in order to know what they are sampling and subsequently access their medication history for the lot. This is standard practice and easily done. As we know, suppliers like to know what’s in their product also. Next step would be to assess the ecosystem level presence of anti-biotic in question or at least get an idea of the baseline for similar fish that have not been treated. There is a good chance that what has been measured in this study reflects only ambient levels of antibiotic in the animals. Especially considering the measurements are in a zone close to the detection limits for the anti-biotics measured.

        It should also be noted that part of the thought behind setting Maximum Residue Levels (MRL) as set out by the EU, FDA, CFIA and the like include consideration of Antibacterial Resistance. There is considerable international agreeance in this area reflected by the adoption of European MRL’s by many nations outside the EU.

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