Cultivation of Polychaeta as raw material for feed (POLYCHAETE)

Salmon aquaculture is constantly growing and along with it the amount of waste products produced increases. Although salmon aquaculture is an efficient food production method compared to agricultural animal production, today more than half of the feed input is lost to the environment. Uneaten feed and fish faeces are by no means waste but contain minerals and organic materials such as proteins and lipids that are in high demand. In the POLYCHAETE project we utilized these otherwise discarded resources by cultivating bristle worms (Polychaeta, species Hediste diversicolor), which themselves are rich in fatty acids, proteins and minerals. The project used a multidisciplinary approach to target 1) establishment of brood stocks and controlled reproduction, 2) polychaete production biology and technology, 3) characterization and stabilization of polychaete biomass, 4) polychaete meal production, feed formulation, extrusion technology and feeding trials with salmon, and 5) economic sustainability analysis. We also built a test-unit for upscaling of industrial polychaete production. The POLYCHAETE project initiated key steps to develop circular economy through biological recycling of aquaculture waste and production of a new raw material for formulated feeds. The consortium consists of SINTEF Ocean, NOFIMA, NTNU, Norwegian Business School BI (Norway), University of Rostock (Germany), Dalian Ocean University (China) and ProChaete Innovations (UK). The project was able to establish a broodstock in house of SINTEF Ocean and artificially reproduce the worms and raise the larvae. The maturation of the worms was manipulated using different temperature and light regimes. Egg and larval development were best at around 15°C, higher temperatures produced higher degrees of deformations. Worms were successfully reared on aquaculture sludge, making it a potential feed source for future intensive worm farming. We investigated differences in the quality of parr and smolt waste, i.e., sludge derived from either the freshwater or the saltwater phase of salmon cultivation, as feed for polychaetes. Further we investigated the influence of diet ration on growth of these worms, feeding them along a low, medium high gradient (i.e., sludge equalling a nitrogen content of 5, 10, 20 and 40 percent of the nitrogen bound in worms supplied per day). Growth increased with increasing feed levels and levelled off at approximately 30percent. We found no differences in growth between worms fed on smolt of post-smolt sludge, meaning that probably all sludge types are useful for polychaete production Worms were challenged with sludge containing fish pathogens. After several weeks of exclusively feeding on this sludge, the worms contained no traceable contamination of the pathogens, pointing towards a purifying capacity, potentially by digesting the pathogenic bacteria. As the pandemic drastically reduced the possibility to conduct laboratory work in late winter/spring 2020, we decided to purchase a larger volume of worms at a commercial supplier in the Netherlands to start the work of WP4 & 5. Hediste diversiocolor, the species we used for the growth and reproduction studies of the project, is only occasionally commercially available, so we decided to purchase Alitta virens, a very near relative species. WP4 investigated different methods to process and stabilize the worm biomass for later use. Here, the effects of freezing, blanching the worms before freezing, and silaging the worms have been investigated. The results showed that both, high enzymatic activity, and lipid oxidation was a challenge during frozen storage, and that prolonged frozen storage of un-treated biomass should be prevented. Blanching was one method for hindering formation of free fatty acids during frozen storage and was also beneficial for salt reduction, however, some loss of lipids and free amino acids are anticipated. Vacuum packing before freezing the material was effectively preventing oxidation. Fish feed trials were performed with different inclusion levels of polychaete meal replacing fish meal to evaluate the suitability of polychaete meal for as a feed ingredient for salmon culture. In WP5 (Feed production and feeding trials) NOFIMA produced 15kg each of three experimental diets containing 0, 7,5 & 15percent spray dried polychaete meal. These diets were then used in a feeding experiment. The salmon smolt grew from about 70g to about 200g within 63 days. An increasing amount of worm meal resulted in a significant decrease in feed uptake, but interestingly there was no difference in growth rate of the fish. This translates into an increased feed efficiency, which in turn means that the fish fed higher degrees of worm meal were able to digest the diet better. In the framework of the POLYCHAETE project, we published so far 6 scientific papers, and educated 6 MsC and one PhD student.

The POLYCHAETE project has not only resulted in a massive knowledge increase, but played a major role in creating the current interest in polychaete worms as a mitigation strategy in the aquculutre sludge challenges the industry currently recognizes. Further sparked the projects several new project proposals, one funded EU project (SIDESTREAM-BlueBio), and one funded FHF project invesitgating bio-security aspects of using aquaculture sludge as feed input, both led by SINTEF Ocean.

Realization of the prospected six fold increase in salmon aquaculture by 2050 will require better use of valuable biological resources and environmentally sustainable solutions for feed production. Cultivation of bristle worms (Polychaeta) as raw material for feed using waste nutrients from fish farming seems promising for both objectives. In nature, marine Polychaeta effectively transform natural and aquaculture organic wastes into high quality protein and n-3 lipid rich body biomass, which are in high demand. In order to become attractive for the feed industry new raw materials must be made available in large amounts. The POLYCHAETE project will therefore domesticate and develop intensive cultivation of the polychaete Hediste diversicolor as a new raw material for formulated feeds. We will use a multidisciplinary approach to target 1) establishment of brood stocks and reproduction, 2) polychaete production biology and technology, 3) characterization and stabilization of polychaete biomass, 4) polychaete meal production, feed formulation, extrusion technology and feeding trials with salmon, and 5) economic and sustainability analysis. A test-unit for upscaling of industrial polychaete production will be build. Fish feed trials will be performed with different levels of substituting fish meal and other protein sources by polychaete meals to find the optimal level of polychaete meal and to evaluate feed efficiency and the nutritional quality of polychaete meal for salmon culture. The consortium consists of SINTEF Ocean, NOFIMA, NTNU, Norwegian Business School BI, University of Rostock, Dalian Ocean University and ProChaete Innovations. With POLYCHAETE, Norway can take key steps to develop biological recycling of aquaculture waste and production of a new raw material for formulated feeds.