Wijkström and New (1989) applied relatively general assumptions in their calculations. On the other hand, New and Csavas (1995) developed a rather elaborate system for estimating current and future usage of fishmeal and fish oil. Firstly, this entailed estimates of FCR on a species group basis. Secondly, estimates of the proportion of the farmed production for each group achieved through the use of commercial feeds were made on a regional, sub-regional, or sometimes even a country basis. Finally, inclusion rates for both fishmeal and fish oil were estimated on a species group basis.
In retrospect, the use of differential inclusion rates on a geographical basis by New and Csavas (1995) was a little too ambitious, and some of the species group categories used were not fully defined in the paper, or did not completely correspond with normal FAO statistical categories. For example, the term other carnivorous aggregated freshwater, diadromous and marine species and included groupers, which might have been better linked with seabreams and seabasses.
Some more recent reports and forecasts, while being less ambitious, have lacked clarity. For example, some IFOMA (IFFO) forecasts (e.g. I.H. Pike, pers. comm., 2000) list carp as a category without making it clear whether this applies only to common carp or to all carps, or catfish without specifying whether this includes channel catfish alone, or other cultured catfishes. Tilapias were also included, without clarifying whether this referred only to Nile tilapia or to other tilapias, or indeed to other cichlids. These documents also introduced more than one category of marine fish. The first linked seabass, seabream, yellowtail, grouper, jacks, and mullets, without defining whether this included the whole of the ISSCAAP categories 33 and 34. The second marine fish category linked flounder, turbot, halibut, sole, cod and hake, presumably corresponding to the ISSCAAP categories 31 and 32. Some carnivorous species (such as barramundi) and freshwater species (such as mandarin fish and pike) seem to have been omitted. The recent presentation by Chamberlain (2000) appears to have followed these IFOMA (IFFO) categories, except that the second marine fish category was re-named flatfish. Differences in the species included in each general category also existed. For example, the category named carp in the study by Tacon (1998) included all carps and other cyprinids, whereas New and Csavas (1995) only included (and clearly specified) common carp from this group of fish. Such differences and lack of clarity help to explain some of the apparent differences in the estimated FCRs, proportions of fish fed by commercial feed, and marine resource inclusion rates (see Annex 1).
These issues have been addressed in the current study by providing more detailed definitions of the categories and terms used.
The species using aquafeeds containing fishmeal and fish oil have been aggregated into groups with similar characteristics, including the level of inclusion of marine resources in their diets, their rearing technology and their biological similarity. Allotment into these groups is based on previous studies but some adjustments have been made. A summary of the species groups used in this study is given in Table 1. For clarity, details of the actual species included in each group, [and their production history from 1990-1999] are listed in Annex 2.
Within ISSCAAP group 11, common carp have been selected for inclusion in this study (Table 1) as being the major cyprinid species for which commercial feeds containing marine resources exist or are expected to be developed. The inclusion of the large production figures for other cyprinids would distort the estimates of marine resource use derived. The whole of group 12 (tilapias and other cichlids) has been included.
In group 13, the various types of catfishes have been separated from the category called selected freshwater fish in this study (Table 1) because differing production expansion rates (Table 2) and other parameters (Table 3) have been applied to them. The study category selected freshwater fish includes snakeheads, pikes, perches, gobies and mandarin fish. Other freshwater fish contained in ISSCAAP group 13 have been omitted from this study altogether because they are not regarded as carnivorous [e.g. cachama (Colossoma macropomum)]. It is recognized that the omission of the category freshwater fishes nei in group 13 from the species listed in Table 1 may have resulted in an underestimation of the marine resources used in aquafeeds. This category probably contains unspecified carnivorous species; however it certainly also contains many species which are not fed commercial feeds containing marine resources. The category freshwater fishes nei, whose volume (e.g. nearly 1.9 million tonnes in 1999) would have distorted the estimates made in this study, has therefore been omitted.
Some diadromous species, (e.g. eels, milkfish, salmon) have been separated (Table 1) because of the differing characteristics shown in Table 2 and 3, while others (trouts and sturgeons) have been linked because of their similarities in these respects. The category salmon includes all salmon species, as well as sea trout and chars.
Amongst the marine finfish, selected species from a number of ISSCAAP groups have been aggregated as selected marine fish but separated from redfish, for which different parameters appear in Table 2 and 3. The category redfish includes the whole of ISSCAAP group 33, and primarily consists of seabasses, seabreams and groupers (Table 1).
The crustaceans included in this study have been separated, for similar reasons to those mentioned above, into marine shrimp, freshwater prawns, and crabs and lobsters. The category crabs and lobsters used in this study includes both freshwater and marine crabs, drawing upon statistics contained in different ISSCAAP groups. It is recognized that the production statistics contained in the category freshwater prawns are incomplete, because an undefined quantity of Macrobrachium rosenbergii is contained in the FAO category freshwater crustaceans nei (see footnotes to Table 1). In addition, substantial quantities of other Macrobrachium spp. are farmed (New and Valenti, 2000) but do not yet appear in FAO statistics.
Other species groups, for example turtles (reared principally in China, Malaysia, and Taiwan Province of China) and frogs (farmed mainly in Taiwan Province of China, Brazil, and Thailand) may be fed feeds containing marine resources. However, production is relatively small and the expansion pattern of these groups cannot yet be determined; they have therefore been omitted from consideration in this study.
In the course of this study, average percentage growth rates (APR) were calculated for each of the species groups defined in Table 1, covering the historical periods 1984-1999, 1990-1999, 1995-1999, and 1997-1999.
The further expansion of the aquaculture for each species group was considered on a global basis, with and without China. The latter calculations were made because of the dominant influence that current Chinese levels of production and historical growth rates have on the global total for some of the species groups. Estimates of future expansion for each species group were constructed on the basis of past growth rates. In general, the lowest growth rates achieved in the four historical periods listed above were selected for use in this study. Expansion in the culture of certain species groups, especially in China, has been extremely rapid. In some cases, all the historical growth rates are well over 10 percent (some exceeding 40 percent per year). Applying such growth rates to the future results in grossly excessive projections. In some cases, partly for this reason, a cap has been applied to the growth rate used for projections. Other artificial expansion rates were also set, for reasons explained in Table 2.
More accurate forecasts than those developed in this study, can be obtained by consideration of developments in capture fisheries and livestock production. However, such forecasts are complex and demanding in terms of information and specialist knowledge. As FAO has already initiated such studies it was decided not to duplicate those efforts, but instead to present detailed information about the growth rates used in this study, so that when more accurate information is available, it can be inserted in the analysis presented in this report.
The feed conversion ratio (FCR) is a measure of feed efficiency that is used for all livestock production. In this case FCR represents the number of units of dry aquafeed required to produce a unit of wet fish or crustacean. A more comparable measure of efficiency would be to reduce both the aquafeed and the product to a dry matter basis. However, it is traditional to compare the units of so-called dry aquafeed [despite the fact that it typically contains approximately 10-12 percent moisture (depending on the processing technique, storage conditions, etc.)] on an as-received basis and to use wet animal weight for the other segment of the ratio.
FCR is the traditional measure of efficiency in commercial animal feeding, although its deficiencies have been pointed out by New and Wijkström (1989). These authors devised an annual profit index, which took into account not only the concept of feed efficiency but also the cost of other inputs and the value of the harvested products. There are several other ways of measuring comparative efficiency besides FCR. One is the relationship between total energy input and live weight gain. In this concept, all energy inputs to the farming process are included, not only the energy used in the production and processing of feed ingredients. Many efficiency ratios, including FCR, take no account of the inedible parts of the animal carcasses. They also discount the relative nutritional value of the animals being farmed. Such considerations are especially important in the assessment of the relative efficiencies of alternative uses of resources. These matters have been discussed by Forster and Hardy (2001), who pointed out that if efforts are made to find and utilize proper (i.e. they can be substantiated and defended) measures of efficiency, they are likely to demonstrate that species produced through aquaculture are more efficient converters of feed into animal tissue than poultry, pigs and cows. A step towards such comparisons was taken by Åsgård and Austreng (1995) who noted that while approximately 30 percent of feed protein, fat and energy is retained in the edible part of salmon, only 18, 13, and 2 percent is retained in the edible part of chicken, pigs, and sheep, respectively.
Despite these important long-term considerations, FCR is adequate for the purposes of this study, which seeks to determine the quantity of marine resources utilized in aquafeeds.
FCR varies according to several factors, including the nutritional and physical quality of the aquafeed; environmental variants, such as temperature; the intensity of production (and therefore the availability or not of natural feed); and other factors, including genetics. Martín (1998), commenting that there are no statistics for global feed production (although an American trade journal regularly publishes reviews containing estimates, e.g. Gill (1998, 1999, 2000), noted differences between what he described as biological FCR and economical FCR. While the former, the true FCR, indicates feed potential, it is the latter (which takes fish mortalities and losses into account) which controls actual feed demand. The concept of economical FCR is similar to the apparent feed conversion ratio (AFCR) used by New (FAO, 1987), which also took into account the contribution from natural food in less intensive forms of aquaculture. In assessing the actual volume of current or future levels of aquafeed production for carnivorous species, a series of apparent feed conversion ratios (AFCR) have been derived for the current study. This approach is more realistic than applying the more accurate feed conversion ratios obtained in controlled experimental work.
Apparent feed conversion ratios (AFCR) have been estimated for each target species or species group (Table 3), so that these can be used to calculate estimates of the quantity of commercial feed required. In deriving the AFCRs for 2015 and 2030, the following factors have been borne in mind, in addition to the FCRs used in earlier studies (Annex 1):
General progress (based on improvements in nutritional quality and feeding techniques, and on other factors) is being made towards FCRs of 1.0:1. Even greater efficiency has been achieved for some species, both experimentally and, it is claimed, commercially. For example, FCRs were quoted by one European aquafeed manufacturer to have ranged between 0.85 and 1.16:1 for Atlantic salmon in 1998, an improvement from 1.25:1 in 1990. The same company gave a range of 0.75-1.35:1 for rainbow trout in its marketing literature. FCRs of 0.9:1 were used for salmon and trout in one forecast for 2010 (Chamberlain, 2000). FCRs of 1.1:1 have been claimed by an Asian manufacturer of marine shrimp feeds (Ridmontri, 2001).
Progress towards what might be regarded as an ideal FCR of 1.0:1 is faster for high-value species that require high unit cost feeds and that have become global commodities, such as farmed salmon and marine shrimp. Progress towards this goal has been and will be slower for other high-value species (e.g. freshwater prawns) until the volume of their production increases to a level at which product value typically falls and the pressure to reduce the cost of feeding increases. Such pressures are also unlikely to occur so rapidly for species with lower product values.
Although the literature is replete with FCRs achieved under experimental conditions, almost no FCRs achieved in commercial practice are published, either in the scientific press or in manufacturers literature (with some exceptions, as noted above). Fish and crustacean producers may regard such information as proprietary, while aquafeed manufacturers often avoid quoting specific FCRs since so many other factors besides feed quality affect actuality; they do not relish the possibility that farmers may complain that target FCRs have not been achieved because of feed quality.
This is mainly a consideration of the level of intensity of production. Most species for which feeds containing high levels of marine ingredients are used are high-value species. These are grown in highly intensive rearing systems (cages, tanks) and the tendency is towards 100 percent being fed on commercial feeds. Trout and salmon are already in this category. Estimates of the proportion of production of each species group used in earlier studies (Annex 1) have been taken into account in deriving the estimates shown in Table 3.
It is well recognized that marine resources are generally over-exploited. Supplies of fishmeal and fish oil have remained relatively steady for many years (Figures 1 and 2). The responsible use of this finite supply, principally by the animal feeds industry but also, in the case of fish oil, as human food and for pharmaceutical use, is therefore important. The use of fishmeal and fish oil for aquafeeds has increased as the culture of carnivorous species has expanded. The aquafeed industry is taking an increasing proportion of the supply.
In common with other livestock feed producers, aquafeed manufacturers are normally legally obliged to list the ingredients that they use on feed bags and in their promotional literature. In addition, there is usually a requirement for the ingredients to be listed in order of the magnitude of their inclusion rate. However, there is no requirement for them to state the actual inclusion rates of major ingredients in terms of percentages; formulations are proprietary information, and carefully guarded as such. The inclusion rates used for fishmeal and fish oil used in earlier reviews (see Annex 1), and in the current study (Table 3) are partially based on published (and therefore) experimental information. However, the total protein and lipid levels of commercial feeds (which manufacturers always state), together with the list and order of ingredients, provide further clues to actual inclusion rates for fishmeal and fish oil.
Considerable reductions have been made in the inclusion rates of fishmeal in carnivorous fish and crustacean diets over the past decade. In some species, such as channel catfish, fishmeal has almost completely been replaced, not only in experimental diets but also in commercial feeds.
 International Standard
Statistical Classification of Aquatic Animals and Plants (ISSCAAP)|
 Biomar Ltd., UK.
 Charoen Pokphand Foods.