12 JUNE 2020 • WORLD AQUACULTURE • WWW.WA S.ORG PERFORMANCE AND WELFARE OF ATLANTIC SALMON, SALMO SALAR L. POST-SMOLTS IN RECIRCULATING AQUACULTURE SYSTEMS: IMPORTANCE OF SALINITY AND WATER VELOCITY JWAS 2020 1-20 Body weight FCR High Velocity vs. Low velocity High Velocity vs. Low velocity No early maturation Reduced skin quality High stress levels Lower body weight Cataracts No early maturation Normal skin quality Low stress levels Higher body weight No cataracts 12% 3% 9% 7% Design by Scite® Science Crunchers 12‰ salinity and moderate water velocity increase salmon growth and welfare 12‰ S a l i n i t y 32‰ S a l i n i t y I n ach issue of World Aquaculture , we highlight a new and exciting research paper from the Journal of the World Aquaculture Society. This issue’s selected research publication recently appeared in volume 51(2):373-392 and is titled “Performance and welfare of Atlantic salmon, Salmo salar L. post-smolts in recir- culating aquaculture systems: Importance of salinity and water ve- locity.” The authors are Trine Ytrestøyl, Harald Takle, Jelena Ko- larevic, Sara Calabrese, Gerrit Timmerhaus, Bjørn O. Rosseland, Hans C. Teien, Tom O. Nilsen, Sigurd O. Handeland, Sigurd O. Stefansson, Lars O. E. Ebbesson and Bendik F. Terjesen. Production of Atlantic salmon in recirculating aquaculture systems (RAS) is expanding worldwide. Significant expansion of RAS salmonid production in the USA and throughout Europe has been driven by the need to produce larger post-smolts prior to stocking at sea, as well as for the production of fresh product close to major markets. There is an urgent need to further optimize holding conditions in RAS in all stages of the production cycle to ensure the best growth performance and highest levels of animal welfare. In the February 2020 issue of JWAS, Trine Ytrestøyl and co- authors followed the growth of Atlantic salmon post-smolts from an initial weight of 68 g to approximately 450 g in RAS. They Recent Research Highlight from the Journal of the World Aquaculture Society held the fish at three increasing salinities of process water (12, 22, and 32‰) and at two distinct inflow rates leading to different water velocities experienced by the fish (1.0 body lengths per second = high velocity; 0.3 body lengths second = low velocity). Growth performance was greatest in high- velocity, low-salinity water. Between 250 and 450 g fish weight, salmon in the low salinity treatment also exhibited reduced feed conversion. In addition to the clear growth performance advantages, overall welfare improved at lower salinities. The fish held at higher salinity exhibited increased base stress levels, as indicated by higher plasma cortisol and by higher levels of expression of genes indicating stress in skin tissue. Health and survival were also impacted by higher salinity, with increased overall mortality, poorer skin surface morphology and higher incidence of cataracts. Overall, the study provides basic protocols for producing larger and healthier post-smolts in RAS with results clearly indicating salinity around 12‰and a minimumwater velocity of 1.0 body lengths per second outperforms the other treatment combinations tested. —Matthew Slater, Executive Editor, JWAS Check Out the USAS YouTube Channel I n 2019, the US Aquaculture Society (USAS), Catfish Farmers of America and National Aquaculture Association organized a forum entitled, US Aquaculture: Our Sustainable Food Solution , inWashington DC. House and Senate members, their staff, and federal agency representatives were invited for an in-depth series of presentations to showcase US aquaculture. Recordings for each of the presentations have been posted on the USAS YouTube Channel. Recent postings on the channel include presentations on biosecurity, aquatic weed control and aquatic animal nutrition.