Difference Between Capture Fisheries and Aquaculture

FISH TECHNOLOGY: SOURCES OF FISH

Diagram

Figure 1: Capture fisheries take fish from the wild; aquaculture grows them on farms. Drawn in our own style from Davenport et al., Aquaculture: The Ecological Issues, Wiley, 2009, chapter 2, Wild resource harvesting, p. 7.

Introduction

Capture fisheries and aquaculture are the two ways the fish we eat is produced, but one catches fish and the other grows them. Capture fisheries catch wild fish from seas, rivers and lakes, while aquaculture farms fish and shellfish in ponds, tanks, cages or pens. Davenport et al. describe both: their book opens with wild resource harvesting (p. 7) and goes on to the culture of carp and oysters, catfish and crayfish, salmon and tiger prawns.

The core difference is production: a capture fishery takes what nature grew, and an aquaculture farm grows what it will sell.

Quick comparison

Table 1: Capture fisheries compared with Aquaculture

Scientific explanation

Definition

Capture fisheries are the catching of wild fish and shellfish from natural waters, by boats using nets, lines or traps. Davenport et al. give wild resource harvesting its own chapter (p. 7), covering the taking of wild stocks and the collection of brood stock.

Aquaculture is the farming of fish and shellfish: breeding, feeding and growing them in ponds, tanks, cages or pens under the farmer’s control. Swift’s Aquaculture Training Manual is a practical introduction to fish farming, covering the biology of farmed fish and shellfish and the methods of farming them.

Working principle

A capture fishery depends on nature: the fish grow, breed and feed on their own, and the fishery takes a share of them. The catch is limited by how many fish nature provides, so a fishery that takes too many shrinks the stock and the catch falls.

Aquaculture depends on farming: the farmer breeds the fish, feeds them, keeps them healthy and harvests them at the size wanted. The harvest is limited by feed, space, water quality and disease, not by the wild stock, which is why farming can supply fish all year.

Apparatus

Capture fisheries use boats, nets, lines, traps and sonar to find fish. Aquaculture uses ponds, tanks, cages or pens, with feeders, aerators and nets, and hatcheries to breed young fish. 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

For capture fisheries, boats go to the fishing grounds, set their gear, haul the catch, and land it for sale, often with limits on how much may be caught. For aquaculture, young fish are stocked, fed on a schedule, watched for disease, and harvested when they reach the size wanted.

There is no single standard measurement procedure for this comparison in the books used here: whether fish came from a capture fishery or a farm is judged by its label and its source.

Factors affecting readings

The weather and the season set the catch for capture fisheries, and the size of the wild stock sets how much can be taken without harm. For aquaculture, the feed, the water quality, the stocking density and disease matter most: crowded, badly fed fish grow slowly and fall sick.

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

• Capture fisheries are used for tuna, wild cod and other species that are not farmed, and for traditional fishing communities.
• Capture fisheries supply fish markets with the day’s catch.
• Aquaculture is used for salmon, tilapia, carp, catfish and shellfish, where a steady supply is needed.
• Aquaculture is used to breed young fish for restocking and for farming.
• Both supply the world fish trade, with the label telling the buyer which one it is.

Advantages and limitations

• Capture fisheries, advantage: no feed or farming is needed, and the fish live a natural life.
• Capture fisheries, limitation: the catch is uneven and seasonal, and overfishing can shrink wild stocks.
• Aquaculture, advantage: steady supply all year at a steady size, and it can ease pressure on wild stocks.
• Aquaculture, limitation: needs feed, space and care, and farms can affect local water, habitats and wild fish through escapes and disease.

FAQ

Is aquaculture the same as fish farming?

Yes: aquaculture is the farming of fish and shellfish, and fish farming is its common name. It covers fish, shellfish and other water animals grown under the farmer’s control.

Can aquaculture replace capture fisheries?

Not fully: many species, such as tuna, are mostly wild caught, and farming suits only some species. Greenberg notes that wild and farmed fish now occupy equal parts of a complex marketplace, so both are needed.

Why do farmed fish need feed?

Because the farm holds more fish than the water can feed on its own: the farmer must give them feed, often pellets, so they grow to the size wanted. That feed is a main cost of farming.

Do farmed fish escape and mix with wild fish?

Yes, escapes happen, and Davenport et al. cover genetic pollution by escapees from fish farms and the spread of disease from farmed to wild populations. Good farm design and nets reduce escapes.

Which is better for the sea, fishing or farming?

Both have effects: fishing can shrink wild stocks and disturb habitats, while farming needs feed and space and can affect local water. The books used here describe both sides rather than ranking one above the other.

References and further reading

• John Davenport et al., Aquaculture: The Ecological Issues, Wiley, 2009 (Google Books page read)
• Donald R. Swift, Aquaculture Training Manual, Wiley, 1993 (Google Books page read)
• Paul Greenberg, Four Fish: The Future of the Last Wild Food, Penguin, 2010 (Google Books page read)