Fish Farming – A Major Food Source

Global fishery statistics are not very reliable, but it can be asserted with reasonable confidence that aquaculture and the catching of wild fish are about equally important as human food sources.

In a previous post, I noted the FAO’s prediction that “by 2012 more than 50% of global fish consumption will originate from aquaculture” (1).  The FAO has now published its 2012 figures, so how did this prediction turn out?

Before trying to answer this question, let’s note some pitfalls in the interpretation of the FAO’s statistics.  Firstly, the FAO publishes figures both for fish only (sometimes termed finfish), and for a wider group of aquatic animals.  The latter includes not only fish but also crustaceans (shrimp, prawns, crabs, etc) and molluscs (oysters, clams, squid, etc.), but not aquatic mammals (whales, seals, etc.).  These other groups account for a higher proportion of production from aquaculture (34%) than of capture production (14%) (2), so the relative importance of aquaculture will tend to be under-stated if comparison is made in terms of fish only.

Secondly, the FAO’s figures are derived from those submitted to it by individual countries which may, for various reasons, be either over- or under-stated.  So far as capture production is concerned, much small-scale fishing in poor countries is probably omitted from the figures simply because for logistical reasons the data is never collected.  More significant, however, is deliberate under- or over-reporting which may occur at local, regional or national level.  Local under-reporting may occur where fishing is carried out in breach of national policies such as gear restrictions, closed seasons or catch quotas.  Higher-level under-reporting may have as its aim to disguise the extent of fishing (legal or otherwise) in foreign waters.  On the other hand, over-reporting can occur at regional level where politicians are judged on their success in promoting economic growth.  These factors probably apply to many countries, but China’s figures have attracted particular attention, partly because they are so large as to have a major impact on global totals.  Watson and Pauly (2001) (3) concluded that China was greatly over-reporting its capture production in its own waters, while a report for the European Parliament (2012) (4) estimated that China was under-reporting capture fishery production in distant waters.  Aquaculture production may be less likely to be under-reported, partly because aquaculture installations have a certain permanence that is hard to conceal. Politically-motivated over-reporting, however, could apply just as much to aquaculture as to capture production. The overall effect of misreporting is hard to assess.

Thirdly, the distinction between aquaculture and capture production gives rise to borderline cases.  The FAO Yearbook 2012 presents a three-way classification into aquaculture and two categories of capture production – traditional and enhanced -, with the enhanced category including production from lakes and rivers that have been stocked with fish or enhanced via predator control (5). However, this is offered as a proposal, to foster international harmonization of data, strongly suggesting that such borderline cases may not have been treated consistently in the 2012 figures.

Fourthly, only about 86% of overall production is for human consumption, the remainder being used mainly for the manufacture of fish meal and fish oil (6).  Nearly all of the fish not used for human consumption is from capture production (7).  Thus the proportion of aquaculture in production for human consumption is higher than that in total production.

Fifthly, consumption may be measured by weight or by value.   Value per unit weight may vary for several reasons: on the demand side, different proportions of inedible bones, shells, etc. and consumer preferences for particular species which may vary between countries; and on the supply side, the location of production and consequent differences in transport costs to consumers.  The average value per tonne of aquaculture production is 64% higher than that of capture production (8).  One reason is that aquaculture production includes a higher proportion of higher-value species such as salmon, trout, shrimp and prawns.  Another is that, even within species groups, the value per tonne of aquaculture production is in most cases higher (9).  This is not surprising since aquaculture facilitates improved production quality via species selection, control of feeding and timing of harvesting, and transport costs may be lower than for marine fishing.  However, the 64% difference relates to all production including that not for human consumption.  The average value of capture production is probably pulled down by its lower proportion of production for human consumption, but even if the value of production not for human consumption were valued at nil, the difference would still be 29% (10).  A reasonable assumption, given that production not for human consumption certainly has value, might be a difference of 40%, implying an average value per tonne of production for human consumption of $1,500 for capture production and $2,100 for aquaculture.

The following table summarises the conclusions supported by the above analysis:

Fish & Aquaculture 2012 Table

So the prediction that more than 50% of global fish consumption will originate from aquaculture has probably been fulfilled if fish is taken to include crustaceans and molluscs, and if consumption is measured in terms of value.  On any other basis it may not yet have been fulfilled, although with continuing growth in aquaculture it probably will be within a few years.

Notes and References

(1) FAO

(2) FAO Yearbook 2012: Fishery and Aquaculture Statistics   These percentages may be derived from figures on p xvi (for aquaculture) and p 7 (for capture production)

(3) Watson, R & Pauly, D (2001) Systematic distortions in world fisheries catch trends  Nature 414: 534-536

(4) Blomeyer R et al (2012) The Role of China in World Fisheries

(5) FAO, as 2 above, pp 21-22.

(6) FAO, as 2 above, p xvii

(7) FAO, as 2 above, pp xvi & xxiv. This may be inferred by comparing Figure 1 on p xxiv, which shows food fish supply from capture fisheries and aquaculture respectively as about 70 Mt and 65 Mt, with the total supply figures on p xvi of respectively 91 Mt and 67 Mt.

(8) FAO, as 2 above, p 50.  The average value per tonne for capture production is $114.8 Bn divided by 91.3 Mt = $1,260, while that for aquaculture is $137.7 Bn divided by 66.7 Mt = $2,060.

(9) FAO, as 2 above, pp 48-50.

(10) Capture production $114.8 Bn divided by 70 Mt = $1,640; aquaculture $137.7 Bn divided by 65 Mt = $2,120.

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