A holistic approach to development of diets for Ballan wrasse (Labrus berggylta) – a new species in aquaculture

Wild wrasses are used for delousing of farmed salmon but increasing demands have prompted the salmon industry to develop cultures of Ballan wrasse. One of the bottlenecks has been nutrition and feed intake in the juvenile phase, while broodstock nutrition is considered critical for production of viable offspring. The present study was aimed at developing functioning ongrowing and broodstock diets for Ballan wrasse. In juveniles the best lengthwise growth was identified at 65% dietary protein, 12% lipid and 16% carbohydrate. To investigate if the requirements for the other nutrients were covered by the diets developed for the species, the nutrient composition in juveniles (whole body) and broodstock (female gonad) were analyzed and compared to the composition in wild fish. We found that the levels of the lipid soluble Vitamins A, K and D were lower in cultured than in wild fish, however, the requirements for these nutrients in Ballan wrasse are not known. Other candidate nutrients for more in-depth investigation are the bone minerals, zinc, taurine and fatty acids

Technical feed quality influences health, digestion patterns, body mineralization and bone development in farming of the stomachless cleaner fish ballan wrasse (Labrus bergylta)

Farmed ballan wrasse (Labrus bergylta) is an efficient cleaner fish used for non-medicinal delicing of Atlantic salmon in sea cages replacing to an increasing degree wild wrasse due to considerations for biodiversity and risk of overfishing local wrasse populations. Farming of ballan wrasse has been hampered by low growth rates, high prevalence of skeletal deformities and other welfare related pathologies. In this study we investigated how diets identical in composition but differing in their technical characteristics, by being prepared using different feed production technologies, affect fish performance, mineralization, bone development and gut health of the ballan wrasse larvae and juveniles. The different production technologies include the commonly used ‘high temperature’ extrusion, cold extrusion, and agglomeration, resulting in feed pellets with distinctive physicochemical properties. The results revealed that prolonged feeding periods with extruded pellets during ballan wrasse larvae weaning result in low body mineralization and the development of severe skeletal deformities. In juvenile ballan wrasse, the extruded pellet treatment resulted in higher mortality rates, fish with larger livers, indication for increased serum TAG and cholesterol in a similar manner, and increased activity of the digestive enzymes LAP and maltase, most probably as a compensatory mechanism to the assumed reduced availability of protein and carbohydrates of extruded pellets for this fish species. Smaller dietary effects were identified in terms of intestinal morphology and gene transcription rates.publishedVersio

Carbon Capture with Metal Oxides in Molten Salts: MgO, SrO and CaO AS Sorbents

Carbon Capture in Molten Salts (CCMS) is an absorption-based method of separating CO2 from a flue gas or industrial gas through a thermal swing technique, where the sorbent is dissolved or partially dissolved in molten salts. The method takes advantage of the reversible carbonation reaction of alkaline earth metal oxides and has previously been studied with CaO as sorbent, showing excellent absorption capacity, regeneration and cyclability compared to similar methods. If the molten salt contains certain alkaline metal halides, these may react with the formed metal carbonates in an exchange reaction, shifting the equilibrium towards further carbonation. The CCMS process is however energy intensive and the regeneration of the sorbent has been identified as a main cost driver due to high operating temperatures and high reaction enthalpy. In this study, a screening of alternative chemical systems with MgO, SrO and CaO as sorbents has been performed. The aim is to find chemical systems with lower operating temperatures and reaction enthalpies that work as efficiently as in previous studies, as this could reduce energy demand and thus operational costs. Promisingly high reaction stability and conversion ratio was found with MgO-FLiNaK, but more experiments are needed to see if the absorption efficiency may be sufficiently improved. SrO-NaCl-CaCl2 showed an even higher conversion ratio, but lower reaction stability which may be improved in a different salt mixture. Furthermore, it was found that the chemical system CaO-LiF-CaF2, which has been very efficient in previous studies, seemed to have no active exchange reaction when the CaF2 was replaced by CaCl2. Another new finding is that even though studies have shown that CCMS may operate well above the solubility limit of the sorbent, the sorbent does need to have a certain solubility in the melt in order to absorb any CO2.publishedVersio

Technical feed quality influences health, digestion patterns, body mineralization and bone development in farming of the stomachless cleaner fish ballan wrasse (Labrus bergylta)

Farmed ballan wrasse (Labrus bergylta) is an efficient cleaner fish used for non-medicinal delicing of Atlantic salmon in sea cages replacing to an increasing degree wild wrasse due to considerations for biodiversity and risk of overfishing local wrasse populations. Farming of ballan wrasse has been hampered by low growth rates, high prevalence of skeletal deformities and other welfare related pathologies. In this study we investigated how diets identical in composition but differing in their technical characteristics, by being prepared using different feed production technologies, affect fish performance, mineralization, bone development and gut health of the ballan wrasse larvae and juveniles. The different production technologies include the commonly used ‘high temperature’ extrusion, cold extrusion, and agglomeration, resulting in feed pellets with distinctive physicochemical properties. The results revealed that prolonged feeding periods with extruded pellets during ballan wrasse larvae weaning result in low body mineralization and the development of severe skeletal deformities. In juvenile ballan wrasse, the extruded pellet treatment resulted in higher mortality rates, fish with larger livers, indication for increased serum TAG and cholesterol in a similar manner, and increased activity of the digestive enzymes LAP and maltase, most probably as a compensatory mechanism to the assumed reduced availability of protein and carbohydrates of extruded pellets for this fish species. Smaller dietary effects were identified in terms of intestinal morphology and gene transcription rates