Characteristic current flow through a stocked conical sea-cage with permeable lice shielding skirt. (1st March 2021)

• Record Type: Journal Article
• Authors: Jónsdóttir, Kristbjörg Edda; Klebert, Pascal; Volent, Zsolt; Alfredsen, Jo Arve
• Is Part Of: Ocean engineering. Volume 223(2021)
• Publication Date: 2021-03-01
• Subjects: Conical sea cage -- Current flow -- Atlantic salmon -- Permeable lice shielding skirt; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2021.108639
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: The characteristic current flow field around a 55 m deep full-scale stocked conical Atlantic salmon sea-cage equipped with a 10 m permeable skirt was studied experimentally using acoustic Doppler velocimeters and profilers. The weakest current speed was inside the cage at 6 m depth and the highest reduction downstream was recorded behind the shielded volume. Downstream of the cage the reduction in speed became little to non-existing at 22 m depth, probably due to the decreasing diameter of the cage with depth. To reduction in current speed through the cage was compared with estimated reduction from theoretical expressions. The results compared reasonably well downstream of the shielded cage, while the reduction inside the cage was higher than the estimates. The difference in current flow field behind a conical cage compared with a cylindrical cage may have implications for the dispersal of waste, feed pellets and microorganisms from the cage influencing the benthic impact of the farm. Highlights: No reduction in current speed was observed from 22 m depth and down behind the 55 m deep cage. Highest reduction in current speed was behind the skirt volume, and the highest reduction inside the cage was at 6 m depth. Analytical expressions adequately estimated the speed reduction downstream of the cage, but underestimated it inside.