Abstract
The rapid growth of marine aquaculture around the world accentuates issues of sustainability and environmental impacts of large-scale farming systems. One potential mitigation strategy is to relocate to more energetic offshore locations. However, research regarding the forces which waves and currents impose on aquaculture structures in such conditions is still scarce. The present study aimed at extending the knowledge related to live blue mussels (Mytilus edulis), cultivated on dropper lines, by unique, large-scale laboratory experiments in the Large Wave Flume of the Coastal Research Center in Hannover, Germany. Nine-months-old live dropper lines and a surrogate of 2.0 m length each are exposed to regular waves with wave heights between 0.2 and 1.0 m and periods between 1.5 and 8.0 s. Force time histories are recorded to investigate the inertia and drag characteristics of live mussel and surrogate dropper lines. The surrogate dropper line was developed from 3D scans of blue mussel dropper lines, using the surface descriptor Abbott–Firestone Curve as quality parameter. Pull-off tests of individual mussels are conducted that reveal maximum attachment strength ranges of 0.48 to 10.55 N for mussels that had medium 3.04 cm length, 1.60 cm height and 1.25 cm width. Mean drag coefficients of CD = 3.9 were found for live blue mussel lines and CD = 3.4 for the surrogate model, for conditions of Keulegan–Carpenter number (KC) 10 to 380, using regular wave tests.
Highlights
The world’s population is projected to increase to ten billion people by the middle of the twenty-first century [1]
Based on the above presented state-of-the-art review on mussel marine aquaculture and force determination of bivalve-encrusted aquaculture gear, the overall objective of this work is to enhance the knowledge on the force regime acting on ultra-rough, bivalve covered surfaces and ropes, which is still strongly debated and more accurate design basis could be obtained
As the relative relativeand motion, thusvelocity relativeofvelocity the fluid field the forceisresponse is motion, and relative the fluidoffield driving thedriving force response decreased decreased the elastic of the dropper lines, differences in force coefficients, through thethrough elastic behavior ofbehavior the dropper lines, differences in force coefficients, as well as as well as force measured peaks, arehowever, expected;the the determination of the deflection maximum measured peaks,force are expected; determination of the maximum deflection amplitude was not determined as optical access in the Large Wave Flume and is greatly reduced through suspended sediments
Summary
The world’s population is projected to increase to ten billion people by the middle of the twenty-first century [1]. One aspect to a multi-faceted solution could be an efficient and sustainable marine aquaculture bivalve production [3,4], with all its health benefits as prevention of cardiovascular diseases or age-related macular degeneration [5,6]. The total aquaculture production is predicted to reach 109 million tons in 2030, as reported by the [7]. In contrast to freshwater aquaculture or agriculture, marine aquaculture has little to no dependence on the scarce resource freshwater [8,9]. Capture production is stagnating at 95 million tons per year [7,12] due to overexploitation and resulting legal restrictions [13,14]. In 2018, only 10% of total aquaculture production was molluscs [7]; fish and crustaceans marine aquaculture depends on feeds from wild fisheries [15], approximately
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