New system design for the cultivation of extractive species at exposed sites-Part 2: Experimental modelling in waves and currents

Aquaculture is projected to be a major supplier of marine proteins to large parts of the global population. This includes bivalves, which have a high potential to offset protein deficits, as they are highly adaptable to varying water temperature, salinity, desiccation, and oxygen conditions. This work is part of a two-piece contribution on novel marine aquaculture technology and details physical laboratory tests of a new cultivation system for bivalve farming called Shellfish Tower. The tested 1:20 model consists of a rectangular cage (2 x 2 m prototype scale) with a central buoyancy element and a height of 2 - 4 m. Testing was done in a current flume as well as a wave basin for current velocities between 0.4 - 2.2 m/s and wave heights of 1.6 to 5.0 m with periods between 5 to 14 s. The tests were conducted to prove the feasibility and functionality of this aquaculture system, which is usable for the collection and cultivation of mussel spat as well as for the grow-out of oysters, scallops, and seaweed in marine environments. Tests carried out in a current flume revealed that drag coefficients decrease with increasing current velocities, and range from Cd=0.5 to 2.5, while the mooring inclination increases from 12 degrees to 84 degrees with increasing flow velocity, which is highly dependant on the buoyancy related pretension. The examination of the mooring line tensions recorded in a wave basin showed that the largest values of snap-induced tension were up to 10 times that of the semi-static tension. The maximum-recorded tension on the system was 48 kN for a single and 89 kN for a double configuration, compared to non-snap tension values, which were in the range of 6 - 10 kN. The insights gathered in this study will inform the future design of aquaculture systems in high-energy environments and allow for an integration into numerical models.

Automated summary

Aquaculture is projected to be a major provider of marine proteins for a large part of the global population, with bivalves showing a high potential for cultivation in varied water conditions. This study tested a new bivalve cultivation system called Shellfish Tower, demonstrating its feasibility and functionality for growing mussels, oysters, scallops, and seaweed in marine environments. The research provided valuable insights for designing aquaculture systems in high-energy environments and integrating them into numerical models.