Piscifactorías solucion sobrepesca

Farm fishing: the solution to overfishing?

We have heard many times that fishing grounds are being depleted due to the overexploitation of species. It is also widely said that farm fishing could solve this problem. But, are farms the solution to overfishing?


In general terms, the status of wild fish stocks has not improved. By 2013, 58.1% of fish stocks were fully exploited, 10.5% were under-exploited and 31.4% were overexploited (FAO, 2016). Thus, 30% of the populations suffered from overfishing.

This is due to the increasing consumption of fish. According to a report published by FAO, in 2014 each person ate on average about 20 kg of fish, twice as much as in 1960.

On the other hand, since the 1980s, wild catches have remained stable. However, the supply of fish for human consumption has increased considerably. So, if consumption has increased and fishing has remained stable, where does the rest of the fish come from?

The explanation for this fact is in aquaculture: in 2014, catch production was 93.4 million tonnes, while aquaculture production amounted to 73.8 million tonnes. In other words, 44% of the fish came from aquaculture.

Evolution of capture production and aquaculture production (Source: FAO, 2016).

Looking at this scenario, it does not seem far-fetched to think that farm fishing could solve the problem of overfishing.


According to the UN World Population Prospects report, by 2050, the world population will have risen to 9.7 billion people.

Given these figures, we can think that the increase in fish consumption will grow well above the production capacity of the oceans and seas. Aquaculture could therefore respond to this increase in the demand of fish for human consumption, in order to meet protein requirements.

Wild populations, therefore, will not be subject to greater pressure than they are now.

Another advantage of fish farms is that production is constant because they have more control over them, that is, there are few fluctuations during the year. This is not true for wild populations, either because of their biological cycle or because they are overexploited.

Finally, farms could reduce the environmental impact caused by fishing: there would be no incidental catches of non-interest species, seabed would not be eroded by trawling…

If you want to know more about aquaculture, I recommend you to watch this video (in this case is about river fishes):

Despite all these advantages, not only are not farms a solution, they also increase the problem of overfishing and cause many other problems.


Half of the cultivated species (including both animals and algae) in aquaculture do not require food from outside, because they feed by filtration. Anyway, it is true that this is not the case for carnivorous species.

Without going any further, according to FAO (2016), in 2014, 21 million tons of fish were destined for non-food products, three quarters of which were used to produce fishmeal or fish oil, the main component of feed for carnivorous species of the fish farms.

piscifacotrias solucion sobreexplotacion
Fish from farm fishing is feed by feed based on wild fish (Picture: Yousuf Tushr, Creative Commons).

In other words, to feed fish from fish farms, wild fish have to be caught, which exacerbates the problem of overfishing. According to FAADA, between 3 and 5 tons of wild fish are needed to feed a ton of farm fish.


We have already seen that aquaculture needs to catch wild fish in order to feed the species under cultivation. Now we are going to see other problems for the animals themselves and the environment.

Due to the fact that the cages are installed at fixed points, in the surrounding waters and on the seabed there is a significant accumulation of nutrients and chemicals from feces and uneaten food. This can cause a bloom of algae, which deplete oxygen and, depending on the species, can cause the production of toxic substances.

However, in some cases some measures have been implemented, such as changing the position of cages every year or placing them in areas with strong currents.

The use of antibiotics and vaccines is frequent to prevent or treat diseases as the stress makes them more susceptible. In fact, in the cages the mortality is around 10 to 30%.

impactos ambientales piscifactorias
Diseases and parasites, such as sea lice, are a common problem in farmed fish (Picture: 7Barrym0re, Creative Commons).

Another important problem is that genetically modified fishes are often used. If by accident or by the effect of predators, these organisms escape and mate with their wild relatives, a significant change in the genetic composition of the species can occur (genetic pollution). In fact, between 1992 and 1996, about 1.3 million salmons escaped each year from farms in Norway. Another effect of the leaks is the transmission of diseases and parasites to the wild organisms.

Another disadvantage of farms is that non-native species are often cultivated, that is, species that do not belong to the area in which they are caged. Their escape may involve competition for resources (both food and habitat) with native species. We have already seen that exotic species are a problem for biodiversity.

As we have said, predators can be a problem for companies engaged in fish farming. The solution to this threat is their control or killing, thus affecting their populations.



We have seen that farms have a number of advantages to solving the problem of overfishing. In any case, feeding farmed fish with wild animals further increases the problem of overfishing; in addition to the other existing problems.

What do you think: are the advantages of fish farms more important than their drawbacks? Leave your opinion in the comments of this article.



7 pensaments a “Farm fishing: the solution to overfishing?”

  1. I find this a biased article, particularly all the SHOUTING in the final figure. Fish farming and other types of aquaculture will be essential to meet the nutritional needs of the growing global population. Yes, fish farming does have some negative environmental impacts, but all of these are being addressed, such as alternative feeds based on cultivated algae that do not rely on wild fish. You should not be encouraging any expansion of wild fisheries, as these have brought many ocean ecosystems to the point of collapse and stripped out most of the mature fish, in addition to having much greater negative impacts on bycatch species and seabed habitats.

    1. My question is: How do you feed carnivorous fishes: with algae fish? On the other hand, I’m not encouraging any expansion of wild fisheries, what I am saying is that, seeing that aquaculture is unsustainable, it is preferable to eat wild species which are fished in the close area.

      1. So aquaculture is unsustainable… Do you have anything to day about other animal protein production sectors? Aquaculture is far more sustainable than any other animal protein production on land, so basically you are saying we should go back to wild Buffalos for us to hunt. This is so biased, grow up and read some stuff.

    2. I think the author actually points out, very clearly, that aquaculture can help meeting the increasing demand for fish. And even though if I can agree with you in many of the points you make, I still think it it important to be demanding and critic with the aquaculture industry. Precisely because it is “novel” (compared to cattle, poultry, etc.) and because it can contribute to meet nutritional needs, we have to be very careful about how it expands and works (look at nutrient pollution levels due to farming… we don’t want to repeat that same mistake now with aquaculture). It is true that some of these negative impacts are being addressed, but it is also true that they are being addressed at a research level (or at least not at fully commercial level). In short, even though I do not fully agree on the conclusion of the article, I think the caution it raises is more than relevant and necessary.

      1. Thank you very much for your comment and for sharing your knowledge on that interesting topic. I hope all those involved in farm fishing projects will find a solution to all these environmental problems so that aquaculture can reduce the pressure on wild populations. 🙂 Moltes gràcies Aleix! 😀

  2. Hi there!
    First of all, I would like to thank you guys for writing about aquaculture, I feel like it often is a highly overlooked field. As a guy who works in the aquaculture industry and who has also studied aquaculture (and marine biology) I would like to comment some of the things you mention, just to hopefully contribute to give a clearer picture about aquaculture.
    I mostly agree on what you say about how aquaculture could contribute in giving answer to the rising demand for fish. With world population increasing, especially in near-shore areas, fish consumption has increased a lot. It is generally true that aquaculture production is more stable and reliable and therefore can ensure a steady amount to the markets (as you say, steadily increasing!).
    Regarding the pros and cons, I have though a few issues I would like to mention. The first thing that I would like to say though is that this article focuses in one production method, sea cages. There is another one which is actually very environmentally friendly: Recirculating Aquaculture Systems (RAS). It consists of having fish on land, in tanks, and re-circulate the water through some filters (mechanical filter to remove particles, biofilter to transform ammonia to nitrate, UV filter to eliminate pathogens, degassing unit to aerate the water and sometimes nitrification units, which turn the nitrate into nitrogen gas, therefore eliminating it from the water). This production method has several advantages compared to sea cages or to flow-through farms in freshwater bodies, which are: FULL control of the whole production, increased productivity (water has a very high quality due to filtration and therefore more and bigger fish can be produced faster!), decreased risk of escapees and highly decreased water usage, since up to 95% of the water is recirculated (there are actually some farms that are 100% recirculated, which means that they barely discharge water into the environment). RAS are increasingly popular in northern countries like Norway and Denmark and are gaining supporters. Fun fact: in Denmark there is, in some regions, a lot of pollution in the water due to pig farming and researchers have found that if this water goes through one of this RAS farms it comes out significantly cleaner (in terms of N and P content)! Also in Denmark, they have established mussel and sea weed farms to remove pollution from the water (called bioremediation and you can also google Integrated Multitrophic Aquaculture, IMTA, for more information about this). So, aquaculture can have also positive impacts =)
    Secondly, I think there can be no doubt that the whole fish oil thing is quite unsustainable. Nevertheless, I am not entirely sure about the figures, what I can say is that fish are among the most metabolically efficient farmed organisms and while for instance the feed conversation of a cow is around 7 (7kg of feed to produce 1kg of meat), in fish this actually goes down to 0.7 in some cases (0.7kg of feed to produce 1 kg of meat). Basically, what I am trying to say is that it is to a great extent species-specific and in any way, it is still better than any other “common” farming activity. Also, it is important to say that there is A LOT of research within the aquaculture industry focusing on identifying new sources to produce fish oil such as microalgae, some vegetables and even insects – the industry is probably doing it because fish oil price is increasing fast, not because of environmental concerns, but whatever, let’s change that! –.
    You also mention the problems related to waste generated from the sea cages. That is absolutely true, it can damage the sea floor below it. Another aspect that I can add here is that sea floor right under sea cages (when those are place in shallow areas) can become anoxic, which is a further thread to the ecosystem. I would also like to mention another problem that can arise from sea cage aquaculture: farmed fish can more easily than wild ones get diseases (nutrient rich environment + crowding = heaven for any microorganism!) and since they share the same ecosystem, some wild populations may suffer also from those diseases. There are also cases where those diseases occur naturally but that are then worsen, since sea cages can act as vectors in the transmission of the disease and help spread it out.
    Regarding the mortality, I think there can be events where fish farms experience 30% (and even higher) mortality, but on average I would say is quite lower, probably below 10% (otherwise, they would be shutting down since the profit margins for the farmers themselves are not high at all).
    Then there is the genetic contamination due to escapees (although GMO fish can NOT be farmed anywhere, let’s clarify that! There is and have been selective breeding which has definitely modified the genome of some fish, but just in the same way that cows, pigs, poultry or bananas have been genetically modified. Nothing to do with Monsantos or any other GMO crop available on the market). I think this has been and still is a problem. Nonetheless, things are also improving. Sea cages experience less escapees every year due to improved technology and gear. It is also worth mentioning though that normally farmed fish die quite fast in the wild since they have a lot of problems to feed naturally. In addition, quite many are sterile and don’t produce viable gametes. Still, I think that there is room for improvement in that sense.
    Finally, I would like to add another point which has not been covered in this article, and that I think is crucial: management. Laws (and enforcing them!) are extremely important and I would like to illustrate that with an example. In Denmark, they changed a law that regulated the amount of fish that each farm could produce. It used to be limited by the amount of feed that you could give to the fish (which obviously limits the production). Now the law restricts the amount of nutrients (N and P mainly) and chemicals (antibiotics, disinfectants, etc.) that each farm can discharge. What this “new” law (about 10-15 years ago) tells farmers is: you can produce whatever amount of fish you want, as long as you do not discharge more than XX amount (established to minimize environmental impact). The consequence is that more and more fish farmers are now using RAS instead of traditional sea-cage and flow-through farming, which is far more sustainable, because it allows them to produce more and in a more controlled manner.
    Anyway, sorry for such a long comment I just got carried by the topic haha! Hope I have contributed a bit more to the topic! Keep up the good work!

  3. As usual it`s matter of control-balance. We have the means, and we can always improve them, to do good fishing and good aquaculture. In the other hand, we can always do the things in a bad way. Science, Ethic and regulations acting together should show us the right path…

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