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BIA-Brukerstyrt innovasjonsarena

Recycling Aquaculture Waste (RAW)

Alternative title: Recycling Aquaculture Waste (RAW)

Awarded: NOK 0.49 mill.

Based on existing knowledge, we have considered the so-called "whale pump" as a model for reuse of waste from salmon farming. Recent research shows that feces from whales and other marine mammals in the sea surface provide an important supplement of nutrients consumed during the photosynthetic bloom of phytoplankton. This counteracts the downward flow of nutrients when dead marine fauna sinks towards the bottom. Whales in the baleen family are filter eaters, which means that they collect nourishment by silting the water through a brush-like filter system called baleen in the toothless jaws. Important prey for the baleen whales are different species of copepods, which make up a large part of the animal plankton in the ocean. The copepods are also filter eaters, with phytoplankton and smaller animal plankton as food. During the season blooms of phytoplankton, adult copepods go up into the upper water layers to graze and lay eggs. Common for whales in the baleen family is large body mass, and thus high energy consumption during movement. These whale species are therefore dependent on dense concentrations of food to survive. The sei whale, which is the third largest species in the baleen family, is known to hunt for dense aggregates of the copepod Calanus finmarchicus (CF). In its distribution areas in the North Atlantic, CF constitutes the main part of the animal plankton biomass. Its reproduction rate is affected by access to plant plankton with optimal composition of free essential amino acids. Differentiated replenishment of critical nutrients in the upper water layer during the growing season gives concentrations of phytoplankton that forms the nutritional basis for colonies of copepods. It has also been shown that CF responds to amino acids in faeces, and during collection of fecal samples from humpback whales in the surface water in the Bay of Maine, extremely high densities of copepods were observed on some of the samples. Around the spring bloom of plant plankton along the Norwegian coast, CF rises to the upper water layers where it is led northwards by the Norwegian coastal current. CF has diatoms as main food at the beginning of the season, but switches to ciliates as soon as these become available. One possible explanation for this change of diet is that the diatoms have an outer shell made up of silicates. Since CF does not ingest the silicates, these shells represent only an extra expenditure of energy during the digestion of diatoms. After the first peak of the spring bloom, the measured levels of nitrogen and silicates in the upper water layers sink sharply. We have assessed the effect and potential hazards of differentiated fertilizing with collected aquaculture waste during this period. In order to achieve good effect, fertilization should be directed against aggregates of CF, which can be located by means of a sonar in combination with a plankton meter. The risk of unwanted blooms of flagellates can be reduced by favoring the diatoms, which respond faster to changes, by adding silicates and fertilizing under windy conditions. Silicates are often found in high concentrations in the sediments below the salmon cages because of the high level of plant material in the salmon feed. Under special conditions, diatoms belonging to the subgroup Pseudonitzschia will develop the neuron toxin dominoic acid around the end of the exponential growth phase. There is still so much research to be done on this problem that chemical monitoring will be necessary during fertilization experiments. However, the risk for eruption of domoic acid is generally small, especially when the salinity is low. There is always some infection risk associated with the introduction of biological material into new areas. Given the low density of potential hosts and the unsuitable conditions for pathogens in fish farm waste during storage, we consider the risk of spread of infections as low, especially in relation to the situation around the fish cages in the fjords. Eggs from CF is vital food for larvae of several fish species that have adapted the spawning to the annual drift of CF with the Norwegian coastal current. Reports of experimental harvest of CF show significant by-catch of eggs and larvae from these fish species. Unless improved harvesting techniques are being developed, this contributes to lowering the amount of CF that can be harvested within sustainable limits. An alternative can be to calculate the increase of a commercial fish stock as a result of increased access to CF by strategic fertilization with aquaculture waste. This surplus can then be harvested for production of fishmeal and fish oil to be used in salmon feed. This, like our original idea of direct harvest of the surplus CF stock, will reduce the use of land area for cultivation of salmon feed and increase the content of omega-3 fatty acids in farmed salmon.

Ideen er å benytte avfall fra oppdrettsanlegg til å gjødsle havoverflaten i avgrensede områder for å oppnå midlertidige høye konsentrasjoner av planteplankton. Disse konsentrasjonene vil gi næring til dyreplankton, som i sin tur kan høstes og føres tilbake til oppdrettsanlegget som høyverdig laksefôr. Ideen er inspirert av ny viten omkring marine pattedyr og deres vertikale transport av næringsstoffer i Nordatlanteren, samt den naturlige heterogeniteten i utbredelsen av plankton i havet. Sentrale spørsmål i forprosjektet er hvor høye næringskonsentrasjoner som kan høstes ved denne metoden, hvilke områder og forhold som er best egnet og om risikoen for smittespredning og oppblomstring av giftige alger kan håndteres på en tilfredsstillende måte. Hvis svarene på disse spørsmålene er positive vil det bli opprettet kontakt med oppdrettsnæringen for å finne industripartnere til et hovedprosjekt for å implementere ideen. Metoden som er tenkt utviklet i hovedprosjektet angriper to flaskehalser i en bærekraftig ekspansjon av den lønnsomme oppdrettsnæringen. Uheldige konsentrasjoner av næringssalter rundt anleggene blir redusert ved at avfallet blir spredt som gjødsel i havoverflaten, hvor den i kombinasjon med fotosyntesen bidrar til økt produksjon av planteplankton. De resulterende konsentrasjonene av beitende dyreplankton kan høstes og erstatte en del av laksefôret. I dag har laksefôret alt for store innslag av soyabønner og raps, og legger dermed beslag på landområder. Tilskudd av marine proteiner og omega-3 fra dyreplankton i foret vil også bedre fiskehelsen og øke oppdrettslaksens nærings- og salgsverdi.

Funding scheme:

BIA-Brukerstyrt innovasjonsarena