While acknowledging that meat or shucked weight may be appropriate units for expressing production, the standard practice of FAO and other international fishery organisations is to report aquatic production as "nominal catch" which is the live weight equivalent. When the production of species reported to FAO is known to be given as dry or shelled weight, appropriate conversion factors are applied to convert these to live weight equivalent to ensure international comparability. In the case of China, the FAO statistics for three shellfish species: the blood cockle, Japanese carpet shell, Pacific cupped oyster and unclassified marine molluscs, were adjusted from shucked to live weight equivalents using conversion factors of 1.35, 2.13, 6.11 and 2.13, respectively, provided by the Chinese Ministry of Agriculture.

The implication of converting reported production from meat to live weight for Chinese production between 1984 and 1996 is shown in Figure 1. During this period the total Chinese production (live weight) statistics of these shellfish increased from 347 000 tonnes to 4.70 million tonnes. Therefore previous reporting of these shellfish by FAO underestimated their production by 255 000 tonnes or 276% in 1984 and 3.16 million tonnes or by 205% in 1996. In view of the rapid increase in their production after 1990 (see Figure 1) the impact of these changes are only highlighted here for 1990 to 1996. The exponential increase between 1990 and 1996 is due to a combination of the rapid expansion rate in the culture of Japanese carpet shell and particularly the Pacific oyster (Figure 1). Between 1984 and 1996 these two species accounted for 71-85% of total shellfish production.

or by 90.5% in 1996 (Figure 2). The contribution of Chinese shellfish production to global cultured shellfish production increased by 18% in 1990 and by 49% in 1996 (Figure 2). The increase in the quantity of adjusted shellfish production also greatly changed the statistics on estimated total Chinese aquacultural output. The total reported aquaculture production, including plants, for China increased from 7.5 to 8.2 million tonnes or by 9% in 1990 and from 20.0 to 23.1 million tonnes or by 15.8% in 1996. The new higher reported production statistics also altered the contribution of cultured fin- and shell-fish to Chinese fin- and shell-fish landings (Figure 3). Between 1990 and 1996 their contribution to national fin-and shell-fish landings increased by 1.5 and 3.8%, respectively. At the global level, the statistics on China’s aquacultural contribution to world aquaculture production increased. For 1990 its contribution rose from 46.5 to 48.7%, and in 1996 from 64.5 to 67.8%. Similarly, the contribution of global cultured finfish and shell-fish to total world fin- and shell-fish fisheries increased by 0.6% in 1990 and 2.1% in 1996 to 13.3 and 21.8%, respectively. Finally, the contribution of global aquaculture production, including plants, to world aquatic production increased by 0.6% in 1990 and by 1.8%, 1996, to 16 and 26%, respectively.