The processing of fish for human consumption gives rise to by-product in the form of heads, viscera, frames, skins and others such as tails, fins, scales, mince, blood, etc. This material may constitute up to 70% of fish and shellfish after processing where fish fillet yield is species-dependent and is often in the range of 30 -50% of the fish. The waste generated after processing is actually valuable raw material from which fishmeal and fish oil may be produced.
As a raw material source, this material is still underutilised, and there is scope for increased fishmeal and fish oil production from seafood by-product. The main source of the by-product is from finfish such white fish trimmings (pollock, cod, hake, haddock and others) as well as salmon (wild and from aquaculture), tuna, herring, mackerel and can come from wild caught fish or aquaculture processing. Other raw material sources include cephalopods such as squid, and crustaceans such as shrimp (both wild and farmed). Some modern fishing vessels have equipment to preserve or process by-product on board into fishmeal and oil or alternatively, established coastal facilities have prompt collection methods to ensure that processors have a reliable outlet for their byproduct. Larger aquaculture operators may also have access to advanced facilities that preserve and process by-product raw material into fishmeal and oil and this is particularly the case for farmed Atlantic salmon.
The total global capture fisheries are in the region of 96.4 million tonnes (FAO figure for 2018) where these capture levels have remained relatively stable since the late 1980s mainly because of the increasing awareness of the need for sustainable fishing. Figures reported in the FAO State of the World Fisheries and Aquaculture report from 2018 state that the share of capture fisheries that is utilised for direct human consumption is roughly 74 million tonnes and around 14 million tonnes of the remaining capture fish is used as raw material to produce fishmeal and fish oil. In addition to capture fisheries, the aquaculture industry is responsible for an impressive growth in the supply of fish for human consumption and has produced around 82.1 million tonnes of fish in 2018. The stable world capture fisheries and growth in aquaculture production can be seen in Figure 1.
Figure 1: World capture fisheries and aquaculture production from FAO, The State of World Fisheries and Aquaculture (2020).
It is a positive development that the fish processing by-product is increasingly used as raw material to produce fishmeal and fish oil. Utilising the by-product reduce waste and produce high value products that contribute to the improved health of humans and animals. It must be kept in mind though that some countries have restrictions on using animal by-product in animal feed. For instance, EU regulation, EC 1069/2009, stipulates that animal by-product may not be used to feed animals or farmed fish of the same species.
It is calculated that currently around 33% of the world’s fishmeal production comes from by-product. An indication of the share of raw material from different sources for the production of fishmeal can be seen in Figure 2. The data used in the figure have been taken from Jackson and Newton (2016) on the use of fisheries by-product to produce fishmeal and fish oil.
Figure 2: Source of raw material for the production of fishmeal in percentage (Jackson and Newton, 2016)
The global production of fish oil from by-product accounts for 26% of the total fish oil production as can be seen in Figure 3 (Jackson and Newton, 2016). The lower value compared to fishmeal is mainly because Asia processes a large volume of farmed shrimp waste which does not yield any oil.
Figure 3: Source of raw material for the production of fish oil (Jackson and Newton, 2016)
The growth in the utilisation of often wasted byproduct is encouraging although there is still a large proportion of the by-product of fish for human consumption that is wasted instead of being turned into high value products that contributes to the supply of nutrient rich food. It is estimated that globally there are an additional 11.7 million tonnes of by-product produced in processing plants that are not collected for the production of marine ingredients (Jackson and Newton, 2016). According to Jackson and Newton (2016), Asia (excluding China), at 4.6 million tonnes, is the area with the largest potential for the utilisation of by-product and even in Europe it is estimated that there are an additional 0.6 million tonnes that could be used.
World fishery production is expected to be 17% higher by 2023 mainly due to the growth in aquaculture fish production. According to the OECD-FAO Agricultural Outlook (2014), the aquaculture growth rate is expected to slow down slightly compared to the previous decade but it still expected to grow by 2.5% per annum. The increased production of aquaculture will ensure a growing potential supply of raw material for the production of fishmeal and fish oil. Fishmeal production is in fact estimated to grow by 25-30% over the next 10 years as a result of increased by-product availability whereas fish oil production is estimated to increase by only around 5-10% over the same period (Jackson and Newton, 2016). Developing and optimising the collection and processing of this valuable source of raw material should be encouraged as much as possible.
All raw material used in the production of fishmeal and oil should originate from catches of fisheries that is managed based on the FAO Code of Conduct for Responsible Fisheries (CCRF) http://www.fao.org/fishery/code/en. Every effort should be taken to avoid the use of raw material that originates from illegal, unreported and unregulated fishing (IUU). IUU depletes fish stocks, destroys marine habitats, distorts competition, puts honest fishers at an unfair disadvantage, and weakens coastal communities, particularly in developing countries.
Managing the quality of by-product raw material
The freshness of raw material is important as it effects the quality of the protein in the end product. Spoilage of fish and its products occur mainly due to enzyme and bacterial action and begins as soon as the fish perishes. It is important to minimise the time spent between catching, processing the fish for human consumption and the processing of the by-product into fishmeal and fish oil. Fish by-product, especially when it contains viscera, deteriorate very rapidly and it is therefore important that it is preserved as soon as possible after being produced. The raw material should be kept at a low as possible temperature during the various processes to minimise spoilage.
In some instances, there can be a quality advantage in using by-product as raw material since processing can occur very soon after harvest into fishmeal because fish processing and fishmeal plants are often on the same site or in close proximity to each other. Aquaculture by-product are often processed very quickly into fishmeal leaving little time for spoilage of the raw material.
Managing the preservation and quality of by-product is more challenging if the fish are processed at sea, mainly due to limited space and manpower on-board most fishing vessels. The viscera, as well as the heads and frames of fish that is further processed to fillets on-board, are often discarded because of the lack of additional availability of ice, refrigeration or freezing facilities onboard. An alternative option to utilise by-product should there be a lack of facilities and the volume produced is not sufficient to justify fishmeal production, is to produce fish silage. The by-product are liquefied by the action of enzymes in the fish in the presence of added acid such as formic acid which reduces the pH to less than 4. The liquid silage product can be stored at ambient conditions for long periods.
Containers that transport raw material should be covered, leak proof, resistant to corrosion and easily cleaned and emptied. The containers and storage areas should be cleaned daily to prevent build-up of odorous deposits and promotion of bacterial contamination. Where possible, the drainage liquor should be separated from the raw material.
The quality of the raw material is often measured by the total volatile base nitrogen content which should be in the region of 50mgN/100g raw material. The composition of fishmeal made from byproduct are slightly different than fishmeal made from whole fish where the ash content in the by-product fishmeal is slightly higher because of the fish frames in the raw material with a resultant slightly lower protein content.
Fishmeal and oil produced from byproduct have an increasingly important role to play in providing nutrient rich feed ingredients for pig, poultry and aquaculture production but also in the growing pet food market where good quality, high value ingredients are used to manufacture pellets, pouches and treats.
 Olsen, R.L., Toppe, J. and Karunasagar, I.2014, Challenges and realistic opportunities in the use of byproduct from processing of fish and shellfish. Trends in Food Science & Technology 36: 144 -151
 FAO 2020, The State of World Fisheries and Aquaculture
 Regulation (EC) No 1069/2009 of the European Parliament and of the Council of 21 October 2009 laying down health rules as regards animal byproduct and derived products not intended for human consumption and repealing Regulation (EC) No 1774/2002 (Animal byproduct Regulation). http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:32009R1069
 Jackson and Newton, 2016. Project to model the use of fisheries byproduct in the production of marine ingredients, with special reference to the omega 3 fatty acids EPA and DHA. Institute of Aquaculture, University of Stirling, UK and IFFO, The Marine Ingredients Organisation
 Olsen, R.L., Toppe, J. and Karunasagar, I. 2014, Challenges and realistic opportunities in the use of byproduct from processing of fish and shellfish. Trends in Food Science & Technology 36: 144 -151
 Fish meal production, 1981., Windsor, M and Barlow, S., IN: Introduction to fishery byproduct, Fishing News Books ltd, Farnham, England. pp3 - 51
 Pike, I.A., 1999. Fishmeal – Quality price and availability outlook. IFOMA, International Fishmeal & Oil Manufacturers Association. Presented at Feed Ingredients and Grain Processing Asia 99.