The Scottish Government

« Previous | Contents | Next »

Listen

REVIEW AND SYNTHESIS OF THE ENVIRONMENTAL IMPACTS OF AQUACULTURE

CHAPTER SIX SUSTAINABILITY OF FEED SUPPLIES - INCLUDING RESEARCH ON PLANT MEAL SUBSTITUTION

6.1 Fishmeal and fish oil are key constituents of pelleted diets for the intensive production of carnivorous species. World capture fishery production has flattened out (against a background of increasing fishing effort) at around 86-94 million tonnes of which around 23-33 million tonnes have been used annually for the production of fish meal and oil over recent years (Table 6.1). The main species used in the manufacture of these products include anchovies, sardines, pilchards, capelin and sandeels. In 2000, 35% of the fishmeal and 57% of the fish oil produced was used in aquaculture diets, with the remainder used for livestock, including pigs, poultry and ruminants. Aquaculture production has been expanding globally at over 10% per year since 1984 and the industry is expected to double within the next decade. At the current growth rate, it has been estimated that by 2010, 56% of the fishmeal and 85-98% of the fish oil produced will be utilised by the aquaculture sector. A proportion of this projected increase in the availability of these products for aquaculture is accounted for through the relative decline in the use of fishmeal in poultry diets and fish oils in hardened edible fats.

Table 6.1 World fisheries production and utilisation (in million tonnes)

6.2 World fishmeal and oil production rates have remained relatively static over the last 10 years, except in 1998 when the El Niño phenomenon significantly reduced production in Peru and Chile. On average, global production of fishmeal was 6.6 million tonnes (product weight) and fish oil was 1.2 million tonnes in 1999. Fishmeal usage in the aquaculture sector is dominated by the Far East, particularly China (55%) and fish oil usage is largest in the Americas, particularly Chile and Canada (44%). Fish oil usage is relatively low in the Far East (14%), despite their dominance of the fishmeal markets because fish species farmed in this region typically consume low-oil diets. These diets contain approximately 1-3% fish oil (dependent on species) compared with oil-rich salmon diets that can contain up to 30% fish oil. The main source of the fishmeal and oils for diets produced for the UK aquaculture industry is from the South American fisheries, although a proportion of the meal and oil is still supplied by the 'traditional' Norwegian and Icelandic fisheries. The transfer to fisheries in the Southern Hemisphere in recent years reflects the greater fishery production and product quality compared with stocks typically found in the Northern Hemisphere. The majority of the fish feed (95%) used in Scotland is manufactured in the UK and the remainder is imported from Denmark, Norway and the Faeroe Islands. The dominant UK producers are BioMar Ltd., EWOS Ltd. and Trouw Aquaculture and the annual production of fishmeal in 1999 was 51,000 tonnes compared with the total European production of 348,000 tonnes.

6.3 Concern has been raised that as the aquaculture industry grows, extra pressure will be placed on wild stocks for the production of fishmeal and oil. The predominant geographical region of growth in the aquaculture sector is the Far East. Aquaculture production is greatest in China where the industry is dominated by carp species, although the production of tilapia and milkfish has increased significantly in the last decade. Culture species in the Far East are typically herbivores/omnivores and it is possible that the predicted increases observed in the aquaculture sector would not have any significant impacts on wild fish stocks. However, the expansion and intensification of aquaculture in China, particularly in the coastal provinces which comprise 60% of production, has led to an increase in culture systems based on formulated feeds. Even though the culture species are herbivorous, the formulated diets include fish oil to improve (a) the efficiency of the immune system; and (b) the tolerance to intensive culture systems. Because of this, even though the proportions of fish oil use by weight are low in the diet, the total tonnages used in the Far East are such that this region has considerable influence on fish oil use, with usage forecast to increase markedly over the next decade (Table 6.2).

6.4 In Norway, the aquaculture industry is also expanding rapidly with Atlantic cod production being the main new growth area, the industry is actively supported by the Norwegian government. Atlantic cod require less fish oil in their diet (12-15% fish oil) compared with salmon (~ 30% fish oil). However, a relatively low FCR will potentially require a diet that is initially high in fishmeal because of the incomplete understanding of the nutritional requirements of cod during the initial years of cultivation.

6.5 Interest in marine oils has also been increasing in the pharmaceutical, health and technical industries. These sectors currently purchase 4-6% of the annual production at prices that are significantly higher than the prices paid by the fish feed manufacturers for the premium oils.

Table 6.2 Projections of worldwide aquaculture production by species groups and estimated requirements for formulated feeds

Bass, bream, yellowtail, grouper, jacks and mullets. ² Flat fish including, flounder, turbot, halibut, sole, cod and hake

6.6 As fisheries for large, high-value carnivorous species have become increasingly fully- or over-exploited, the proportion of smaller, less valuable pelagic species, such as sardines, pilchard and capelin, are increasing in the catch. This is likely to be exacerbated by an increase in human demand for some of these fish species, particularly in Asian countries in the next few years as the economy recovers from the financial crisis in the late 1990s. The 'fishing down the food chain' principle is initially thought to improve catches before leading to a phase of stagnating or declining catches. It is proposed that this change in exploitation patterns is unsustainable.

6.7 Fisheries control over the major resources for fishmeal and oil production has been introduced. International Organisation of Standardisation (ISO) 14001 certification and FAO Code of Conduct for Responsible Fisheries have been endorsed by members of Scottish Quality Salmon. The main species, including anchovy, sardine, capelin and sandeels, are subject to management through total allowable catch (TAC), area catch limits, minimum mesh sizes, fleet capacity controls, fleet capacity controls, closed areas and seasonal bans. In the UK, a TAC of 1 million tonnes was set in 1998 for the North Sea sandeel stock and a 20 km ² area of the Moray Firth was closed to industrial fisheries in 2000 because of concern over the breeding success of locally nesting seabirds that rely upon the sandeels for food. The management of fisheries in general, however, is widely considered to be ineffective because of the poor condition of many important fish stocks. The level of enforcement of fisheries controls in the certain areas of fishmeal and oil production is also debatable, although satellite tracking has been introduced in Peru and Chile to enforce closed areas for anchovy and sardine. The long term effect of the removal of large quantities of feed organisms from the marine ecosystem is an issue that has yet to be quantified. In the North Sea, declines in certain species with economic value, such as cod, and changes in the distribution, population sizes and reproductive success of various seal and sea-bird colonies have been attributed to the over-fishing of sandeel and other small pelagic fish stocks. In addition, the industrial fishery for anchoveta in Peru was implicated in the loss of significant numbers of seabirds through a reduction of food availability and an inhibition of population recovery after crashes induced by El Niño events.

6.8 The fishmeal industry has suggested that discards, which account for approximately a quarter of the annual global landings (27 million tonnes), should be utilised by the industry. Norway, Canada and Iceland have all introduced a ban on the at-sea discarding of certain commercial species and a proportion of the by-catch is utilised by the fish feed manufacture industry. This ban has been coupled with an extensive monitoring and surveillance system whereby areas can be closed when bycatch rates exceed a certain level. The use of selective fishing gears has also become compulsory in a number of Norwegian fisheries. In Europe, EU legislation prohibits the landing of any fish that is caught outside the regulatory size range or quota allowance. The Commission favours measures such as greater selectivity of fishing gear and alterations in fishing practices rather than a ban on discards. It is clear, therefore, that although there is a trend towards greater utilisation in certain fisheries, in others there is more pressure to reduce the capture of potential discards. On balance, the probability of an increase in the availability of fishmeal and fish oils through the future utilisation of discards is low.

6.9 There can be no argument that the availability of fishmeal and oil has the potential to limit the sustainable growth of those forms of aquaculture ( e.g. salmon production) that depend on this resource. Furthermore, as pressure on fish stocks for production of these products grows, the vulnerability of an aquaculture industry dependent on these stocks is high. It is recognised that climate oscillations such as El Niño can have a major effect on fishery production: a drastic reduction in fishmeal supply would increase prices of feed such that industries where profits are low, e.g. salmon culture in Europe, could collapse. However, recovery of stocks following the most recent El Ninõ collapse (1998) was rapid in the South American fishmeal fishery indicating that these sources may be robust and sustainable at the present capture levels.

6.10 FCRs are continuously improving as feeds become increasingly tailored to the dietary requirements of the cultured species. Feed wastage continues to be reduced through the use of advanced pellet monitoring systems ( e.g. underwater cameras, Doppler, Storvic ^TM systems) and feedback loops because of economic and, partially, environmental pressures. This is particularly the case in the highly regulated northern salmon industries where studies have found that under commercial conditions Atlantic salmon can reach 5.5kg with a feed conversion ratio of 0.85 using a fishmeal and oil based diet in 1999. It is envisaged that further advances in husbandry practices and the optimisation of protein: energy rations will enable FCRs to approach 1:1 i.e. one kg fish product (whole fish, wet weight) per kg feed (compound feed, typically around 10% water). Despite these potential improvements, it still requires between 2 and 5 kg of wild fish to produce 1 kg of fishmeal-fed cultured fish.

6.11 This apparently wasteful use of the fish resource is to some extent mitigated by the fact that not all of the fish used for fishmeal production are fit or appropriate for human consumption. In addition, the conversion of low commercial value small pelagic fish into high value carnivorous species is probably more efficient in culture than in the wild where there is likely to be a much lower transmission of energy between trophic levels. It is also possible that competition with cheap, farmed fish may reduce fishing effort thus protecting endangered stocks, although this is offset by the fact that it may be possible to sell the wild product at an increased price to a sophisticated market.

6.12 Substitutes for fishmeal protein and marine fish oils are continuously being sought and progress is being made. An EU research project is currently studying 'Perspectives of Plant Protein usage in Aquaculture' (PEPPA) and research in Norway has been investigating the use of soya meal in feed for salmonids. Protein substitutes are already used in fish feed in the UK and Norway with up to 25% of the protein in the feed derived from plant origin.

6.13 The uptake of fish oil substitutes has been slower. For the first time, with the exception of 1998, the price of fish oils in 2002 is approximately the same as for plant oils. Concerns over the dioxin and polychlorinated biphenyl (PCB) levels in the northern hemisphere fish oils has increased the pressure on fish feed manufacturers to produce oils with reduced levels of dioxins. This has created a growing interest in the use of low-dioxin vegetable oils. In Scotland, Scottish Quality Salmon (SQS) has recently revised it's Quality Manual (Product Certification Scheme for Scottish Quality Farmed Salmon) to allow up to 25% of the oils added to the fish feed to be derived from a plant-based origin. This revision comes with the proviso that the diets should maintain a certain level (still to be decided) of essential fatty acids (eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA - both n-3 (or omega 3) highly unsaturated fatty acids, HUFA) in the final product. The basic problem in using vegetable substitutes was thought to be their lack of essential amino acids (such as lysine and methionine) and essential fatty acids, EPA and DHA. Concerns were also expressed over the inefficient conversion of carbohydrates in these substitutes to energy by carnivorous fish. The species used in the production of fish oils, such as herring, sardines and anchovies store large amounts of oil in their flesh that is rich in n-3 HUFA that are only found in fish. These HUFA, along with the essential n-6 HUFA arachadonic acid, are vital for the development of organs with dense neural activity and are crucial to inflammatory and cardiovascular processes.

6.14 Research has already proved that partial replacement of fish oils with rapeseed and linseed oils can successfully be used in the culture of Atlantic salmon without significantly influencing growth performance. Current research, including an EU funded project, 'Researching Alternatives to Fish Oil in Aquaculture' (RAFOA), is studying the effect of substitution of fish oils with plant oils on growth performance, fish health and product quality during the entire life cycle of salmon, rainbow trout, sea bream and sea bass. The Directorate of Fisheries Institute of Food and Nutrition in Norway has also conducted similar research. In addition, a second project, 'Fish Oil Substitution In Salmonids' (FOSIS), is currently investigating whether fish oil can be replaced by vegetable oils in the diet without reducing the nutritional value or the growth performance of the fish, whilst minimising fat deposition in the flesh. A further two EU research projects are studying the effects of plant oils on fish digestion and metabolism, 'GLUTINTEGRITY' and 'FPPARS'. Feed companies have also progressed significantly in this type of research, although, because of commercial confidentiality, access to their results is limited. In addition to vegetable oils, a EU research project 'PUFAFEED' is investigating the use of cultivated marine microorganisms as an alternative to fish oil in feed for aquatic animals.

6.15 Intensive research is studying processing methods and the genetic modification (GM) of soya oil to produce DHA and EPA, which may enable the addition of this oil to fish feeds in the future. Problems associated with modifying plants to produce sufficient quantities of essential fatty acids for use on a commercial scale has, to date, slowed progress in this area. Concern over public response to the use of GM oils has prompted SQS to specify in their Quality Manual that the fish feed used by their members, must contain 'non-GM' plant derived material if the fish oils have been substituted by vegetable oils. The difficulty in identifying whether oils have been genetically modified has also been highlighted as an area of concern.

6.16 Fish feed substituted with plant meal and oils, particularly rapeseed oil has already been used commercially in Norway. The main issue at present facing the plant meal and oil substitution option in Scotland, however, is consumer opinion and the affect that this may have on the continued acceptance of Scottish salmon as a 'high quality' product. To produce a product as 'near to the wild product as possible', research is also focusing on the 'dilution' of vegetable oils in the flesh when the fish are fed diets containing 100% marine fish oils for 6 months prior to harvest. This will potentially counteract any potential loss in flesh quality caused by the use of diets containing vegetable oils and preliminary results are promising, with EPA and DHA increasing in the flesh within a few weeks of the diet switching from plant to fish oils. In addition, research is examining the potential for salmonids to produce their own DHA and EPA. These essential fatty acids are naturally produced by fresh water fish, including salmonids, and production is inducible and repressed in the presence of dietary fish oil containing EPA and DHA. Studies on rainbow trout concluded that the synthesis of DHA by the trout was only a fraction of that obtained from the diet and thus fishmeal would still be required in the diet to maintain a constant level of DHA in the fish. It has been suggested, though, that biosynthesis of DHA and EPA by salmonids fed vegetable-based diets could be enhanced by selective breeding.

6.17 In 2000, a review published in the journal Nature raised the issue that the production of carnivorous fish species would not compensate for the decline in capture fisheries and could indeed contribute to their collapse. However, the review under-reported the influences of other global industries that relied on fishmeal production ( e.g. livestock) and largely ignored the advances being made by the aquaculture industry in utilising diets containing plant proteins and oils in order to reduce their dependence on wild fisheries.

Summary

6.18 The issues concerning the use of industrial fishmeal and fish oils in artificial pelleted diets in the Scottish salmon farming industry are wide-ranging and complex. Although aquaculture production is predicted to rise significantly over the next decades, catches from industrial fisheries are set to remain static in volume. Forecasts differ, but there are concerns over how the Scottish salmon growing industry may perform if fishmeal and/or fish oil supplies become limited. Firstly, the aquaculture industry in Scotland is relatively a very small component in the global aquaculture field and could be badly affected by global aquaculture product trends. Approximate estimates suggest that the proportion of the global fishmeal use attributable to the Scottish salmon industry is less than 0.8%. Secondly, the Scottish salmon industry is probably running at very low profit margins and is unlikely to sustain fish feed price rises as easily as sectors with higher margins of profit. Fish feed companies have been well aware of these two points for many years, and research on fishmeal and oil alternatives is well advanced. However, because of the near-market nature of that research and development, there is little published literature on which to base a thorough assessment of the current status of alternative feed types. Therefore, current and forecasted future market forces have already created a situation where fish feed suppliers are actively developing alternatives to wild fishery sources of fishmeal and fish oil.

Research Gaps

6.19 The following concerns and areas for future research relating to the sustainability of feed supplies have been identified:

• Accurate fisheries data collection and mathematical modelling of the pelagic fisheries are required in the main industrial fishing areas to ensure the sustainability of these fisheries. The influence of climate oscillations ( e.g. El Niño) and climate change on recruitment and spawning stock compared with the impact of industrial fisheries are also very difficult to quantify and little research has been published in this area. The sustainability of the Blue Whiting fishery in the North Atlantic fishery also requires urgent research as fisheries controls are still under debate.
• Peer-reviewed literature is required relating to the effects of near market use of plant meal and oil substitutes on fat and protein composition, flesh quality and taste in salmonids.
• Peer-reviewed studies are required on refining the vegetable oil and protein requirements of the cultured fish species relating to life stage and seasonal variations in digestibility experienced with certain vegetable oils.
• Knowledge regarding the blending of oils, reducing the dependency of manufacturers on a few plant oils and tailoring the taste of the final product to the customer needs.
• Information regarding nutritional studies and the implications of substitution of fishmeal and oils with vegetable alternatives on 'new' species for cultivation, particularly cold-water species such as cod, haddock, turbot, halibut, Dover sole and lemon sole.

« Previous | Contents | Next »