Fish Farming | 3 Commonly Farmed Fish
Just how much of the seafood that we see on our shelves is farmed or cultured? And how exactly is it produced?
Average annual increases in fish consumption have now surpassed that of all terrestrial animals combined. With capture fishery production remaining all but static since the 1980’s, aquaculture has filled the void created by growing consumer demand.1
Here are 3 commonly farmed fish you are likely to have seen in your shops and the stories of how they got there.
As one of the most well-known fish on the market, salmon is one of the staple fish on menus around the globe. Recent technological advancements, selective breeding and high market value have made the familiar pink fleshed fish available to meet customers’ demands. Farmed salmon comprises over 70% of the salmon market, so chances are if you have eaten salmon, then you have eaten farmed fish.2
Wild caught salmon are generally caught using hook and line, gill netting or purse seines depending on the species. Up until this point, the fish live an entirely natural existence until they are caught. Although these capture processes can be damaging to both fish and the environment, there are strict regulations for both commercial and recreational fisheries on gear, fish size, seasonality and how much is allowed to be caught. A quick online search for your respective regions or countries regulations will provide all the answers you need if you wish to know more.
Farmed salmon, on the other hand, are the product of carefully selected brood stock (larger breeding fish). In order to breed the most ideal traits into fish cohorts, breeding fish are chosen based on the most desirable genetic characteristics to be passed on to future stockings--characteristics include fish size, fat content, physical appearance and fish health. Eggs and milt are collected, with hatchlings held in land-based rearing tanks.
Recirculating aquaculture systems (RACs) in these tanks minimizes wasteful water use, and allow factors like temperature, oxygen and salinity to be carefully controlled.3 The juvenile salmon will generally spend between 8-16 months in these holding tanks until they are large enough for transport to sea cages or ‘net pens’.
In the net pens, the fish remain for another <18 months until they grow large enough (~5kg) to be gathered with float-lines or seine nets. The farmed salmon are then fished out to be prepared for commercial handling.4
Wild vs. Farmed Salmon
Created by Kirstyn Byrne
Lighter Pink Colour
In a wild fish diet, salmon eat shrimp and krill, which naturally contain pigments from the algae they consume (astaxanthin and canthaxanthin) that will cause flesh to retain a deeper reddish-orange colour. In a farm, salmon are fed pellets usually containing a mixture of fish meal (made up of either less desirable small fish, by-catch or offal and off-cuts), fish oil and vegetable-based fillers, which don’t include the same algae pigments. Some farming operations aiming to reduce impacts on marine species have even started experimenting with insect-based feed pellets. But because these pellets lack shrimp and krill, the colour of the flesh in farmed fish is actually closer to grey.
To make up for this, astaxanthin is often added into feed to give farmed salmon their familiar colour. However, pigment retention is also linked to higher Omega-3 levels in feed. Farmed fish tend to have lower omega-3 diets than wild-caught salmon, meaning their flesh doesn’t tend to hold the same rich colour.5 So, if the flesh appears lighter in colour, closer to a marbled pink, then chances are it has come from a farm.
Wild salmon are seasonal fish much like fruit and veg, so if fresh salmon is presented as ‘wild caught’ outside the species known season, chances are you’re buying farmed. Although rare, illegal mislabeling does still occur.
Wild caught salmon will generally fetch a much higher price, especially in the case of fresh fish. If it’s cheap, it's more than likely farmed.
MSC vs ASC Label
One way to ensure your salmon is responsibly sourced is by looking for either the Marine Stewardship Council (MSC) certification for wild catch, or Aquaculture Stewardship Council (ASC) certification for farmed fish. These certifications are only given to operations that have been assessed and meet a number of criteria surrounding their efforts towards sustainability throughout the operation procedure. It is important to note that this does not necessarily mean all fisheries without a MSC or ASC are unsustainable in practice. The high cost of gaining certification can put off many small-scale operations unable to afford such costs. So, looking for things like good traceability in your fish’s story can also be a good indicator as to what kind of an operation it has come from. If you can’t see where it has come from or how it got there, then you may want to think twice about putting it in the shopping basket.
Despite what many think, farmed tuna only account for less than 1% of the total tuna market.6 All the tuna that you would typically eat for sushi or even canned is wild caught. The only tuna species that are commercially farmed is Bluefin tuna. While yellowfin tuna is currently being grown in small-scale, experimental farms. But, farmed tuna will rarely be seen in the tins on shelves at your supermarket. Instead, they are sold at fresh markets or exported frozen to high-end restaurants.
Wild caught tuna will generally be caught using either trawled purse seine nets, or via hook and line. But, to help monitor tuna populations, quantities of allowed tuna catch, and equipment used are heavily regulated. Unfortunately, impacts of increased demand for the tinned variety of this protein-packed snack have placed huge pressure on a number of tuna species.
In farming operations, unlike salmon or land-based species, we still cannot rely on tank-rearing populations of tuna. Limited success with spawning and juvenile success rates in controlled environments has left tuna producers opting for open water ‘ranching’ as their farming option.
With the open water ‘ranching’ method, seine nets capture schools of juvenile tuna. The fish are then transferred through underwater gates into floating sea-cages to be grown over a course of months or even years before they are sold commercially.7
Wild vs Farmed Tuna
Created by Kirstyn Byrne
Knowing exactly which species you are eating is key to knowing where it has come from. If it is not Bluefin tuna, then it has not come from a farm.
A good rule of thumb for most threatened species; if you can’t live without your wild-caught fish, then you better get ready to spend. Wild catch will fetch up to three times the market price of farmed tuna.
3. Pangasius (‘basa’)
Ever heard of this fish? Sold in over 130 countries, the humble ‘basa’ or ‘pangas’ as it is commonly labelled, is one species many of us have come across (even if you might not know its name).8 Basa fish are sold primarily as frozen fillets, so this Indo-China based catfish has seen itself as the fish of choice for many on a budget.
Wild-caught pangasius lack any regulation, so almost all basa sold globally is now derived from farmed sources.9 Due to the demand for more regulated pangasius, increased farming scale has led to a number of questions surrounding its environmental and health impacts for consumers.
Farmed Pangasius Basa
Pangasius fish doesn’t require much oxygen to breathe, is pollutant tolerant and quick breeding by nature, all making it an ideal species for productive aquaculture.10 Pangasius basa fish also have a low food conversion ratio (FCR). Put simply, it takes less to grow more when it comes to pangasius.
How are they farmed?
Brood stock are often given hormonal treatments to induce spawning, while its eggs and milt (sperm) are fertilized in separate facilities. Newly hatched larvae are then transferred from hatchery to a nursery, usually into ‘earthen ponds’, running adjacent to rivers or waterways where water exchange can be easily controlled by flushing ponds with river water. In some cases, small fish are then transferred into grow out net-pens that are located on the tributaries or rivers themselves. Here the pangasius spend another 6-8 months until they reach harvest size of ~1kg.11
Important note: Brood stock are maintained in controlled and enclosed systems, and so hormonal treatments do not leak into the outside environment.
Are they really safe to eat?
By all accounts, the short answer is yes. With mass media claiming the pangasius is unsafe to eat due to its ability to live in polluted environments, many have turned away from the fish. But if toxicological evidence is anything to go by, all reports point to it getting the thumbs up.12
The bottom line
If you, like me, do your best to choose fish based on what you think to be the most sustainable option, then you also know it can be tough to know what’s what. So, whether it is farmed or wild-caught, one safe bet is to keep an eye out for either an MSC or ASC certification on what you are buying.13,14 For the most part, these certifications are a pretty good way to know whether your fish is coming from a sustainable operation. If you are still in doubt, double checking the species on the Monterey Bay Seafood Watch program can also help in making the most informed decision on your seafood.15
Would you eat farmed fish? Let us know in the comments below!