FISH TECHNOLOGY: SOURCES OF FISH
Diagram
Two ways fish reach the table
Wild-caught fish
Caught in seas, rivers or lakes with nets, lines or traps. The fish eats what it finds, swims freely and grows at nature’s pace.
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Farmed fish
Raised in ponds, tanks, cages or pens. The fish is fed by the farmer, kept in a set space and harvested when it reaches size.
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The same species
The same species can be wild or farmed: salmon, sea bass, cod and tuna are the four fish Greenberg follows through both worlds.
Figure 1: Wild fish are caught where they live; farmed fish are raised by farmers. Drawn in our own style from Paul Greenberg, Four Fish, and the wild resource harvesting chapter (p. 7) of Davenport et al., Aquaculture: The Ecological Issues.
Introduction
Wild-caught fish and farmed fish can be the same species on the fish counter, but they lived different lives, and that shows in their diet, fat, colour and price. Wild-caught fish are caught in seas, rivers or lakes, while farmed fish are raised in ponds, tanks, cages or pens. Greenberg’s Four Fish follows salmon, sea bass, cod and tuna through both worlds, and notes that three decades ago nearly everything eaten from the sea was wild, while today wild and farmed fish occupy equal parts of a complex marketplace.
The core difference is control: a wild fish eats what it finds and swims where it likes, while a farmed fish eats feed chosen by the farmer and lives in a space the farmer controls.
Quick comparison
Table 1: Wild-caught fish compared with Farmed fish
| Aspect | Wild-caught fish | Farmed fish |
|---|---|---|
| Where it lives | Free in seas, rivers or lakes | In ponds, tanks, cages or pens run by a farmer |
| Diet | Eats what it finds: small fish, crustaceans, plankton | Eats feed chosen by the farmer, often pellets |
| Exercise | Swims freely, often over long distances | Swims in a set space, so it moves less |
| Fat | Usually leaner, because it swims more and eats less regularly | Often fattier, because feed is regular and movement is limited |
| Colour | Colour varies with the wild diet; wild salmon flesh is coloured by the crustaceans it eats | Colour can be steadier, because the feed is steady; farmed salmon feed often includes the pigment that colours the flesh |
| Size | Varies: the catch brings what the sea gives | Steadier: fish are harvested when they reach the size wanted |
| Supply | Seasonal, and depends on the catch and the weather | Steady all year, because the farmer plans the harvest |
| Price | Often dearer, and the price moves with the catch | Often cheaper and steadier in price |
| Effect on wild stocks | Fishing takes fish out of wild stocks, so overfishing can shrink them | Farming can ease pressure on wild stocks, but it needs feed and space of its own |
| Typical examples | Wild salmon, wild cod, wild tuna | Farmed salmon, farmed sea bass, farmed tilapia |
Scientific explanation
Definition
Wild-caught fish are fish taken from their natural waters by fishing: nets, lines or traps in seas, rivers or lakes. Davenport et al. open their book with a chapter on wild resource harvesting (p. 7), which is the taking of wild fish and shellfish from nature.
Farmed fish are fish raised in aquaculture: ponds, tanks, cages or pens where the farmer controls feeding, stocking and harvest. Swift’s Aquaculture Training Manual describes the farming of salmonids, catfish, tilapia, carp, milkfish, mullet, turbot and other species, and Greenberg notes that salmon was the first large scale domestication project for the fish we eat.
Working principle
A wild fish lives by its own effort: it hunts, it migrates, and it eats what the season offers, so its fat and colour change with the season and the place. A farmed fish lives by the farmer’s plan: it is fed on a schedule, kept at a set density, and harvested at a set size, so its fat and colour are steadier.
That is why the same species can taste different wild and farmed: the wild fish is usually leaner and its flavour changes with its diet, while the farmed fish is usually fattier and more even from one fish to the next.
Apparatus
Wild fishing uses boats, nets, lines and traps. Fish farming uses ponds, tanks, cages or pens, with feeders, aerators and nets. The books used here name no single standard apparatus for the comparison itself, because the equipment belongs to fishing on one side and to farming on the other.
Measurement procedure
There is no standard measurement procedure for this comparison in the books used here. In practice the fish is identified by its label and its source, and its fat and colour are judged by eye and by eating. Where the origin is in doubt, a laboratory can check the fat profile and the pigments, which differ with diet.
Factors affecting readings
The season matters for wild fish: fat and flavour change with spawning and with what food is in the water. For farmed fish, the feed matters most: the feed sets the fat, the colour and the flavour. The species matters for both, because some species farm easily and some do not.
Formulas and calculations
The books used for this article give no formula for this comparison, so none is given here. The comparison is qualitative: it rests on definitions, materials and method, not on a calculation.
Industrial applications
- Wild-caught fish is used where a lean, seasonal fish is wanted, and for species that are not farmed.
- Wild-caught fish is used in traditional fisheries that supply local markets with the day’s catch.
- Farmed fish is used where a steady supply all year is needed, for shops and restaurants.
- Farmed fish is used for salmon, sea bass and tilapia, which are now mostly farmed.
- Both are used in the fish trade, with the label telling the buyer which one it is.
Advantages and limitations
- Wild-caught fish, advantage: natural diet and life, so the fish is usually leaner and its flavour follows the season.
- Wild-caught fish, limitation: supply is seasonal and uneven, and heavy fishing can shrink wild stocks.
- Farmed fish, advantage: steady supply all year at a steady size and price.
- Farmed fish, limitation: needs feed, space and care, and the fish is usually fattier and more even in flavour.
FAQ
Is farmed fish the same species as wild fish?
Yes, often: farmed salmon is the same species as wild salmon, and the same holds for sea bass and tilapia. The species is the same; the life it lived is different.
Why is farmed salmon fattier than wild salmon?
Because it is fed regularly and swims in a set space, so it moves less and stores more fat. A wild salmon hunts and migrates, so it burns more of what it eats.
Is wild fish always better than farmed fish?
Not always: wild fish can be leaner and more seasonal in flavour, but farmed fish is steadier in supply, size and price. Which is better depends on the dish and the buyer.
How can I tell wild from farmed fish in a shop?
By the label: the law in most markets requires the fish to be labelled wild or farmed. Colour and fat can hint at it, but the label is the reliable guide.
Does fish farming help wild fish stocks?
It can ease the pressure on wild stocks by supplying fish without catching them, which Davenport et al. note as a reduction of pressure on wild stocks (p. 73). But farming still needs feed and space, so it brings its own effects on habitats.
