Engineering Support for the Development of a Submersible Fish Cage for Open Ocean Aquaculture

Abstract : The objective of this project was to utilize the University of New Hampshire, Open Ocean Aquaculture (OOA) facility to examine the performance of a new fish cage system. The fish cage was constructed with High Density Polyethylene pipe as lower and upper structural rim components. The two rim assemblies are connected using knotless net and triangular stays. Below the cage is an airlift assembly and ballast chain. The system was deployed at the exposed OOA site in the Gulf of Maine with a 4-bay, submerged grid mooring system. Two other fish cages, along with a feed buoy were also deployed within the mooring system. The goal of the field portion of the study was to examine how the new cage would survive open ocean conditions. To help quantify survival, inline load cells were installed with the attachment lines to measure loads on the surface rim. Wave and currents were also measured at the site to quantify the forcing. The field data sets were needed to investigate finite element modeling approaches so that extreme conditions could be simulated. The finite element model used in this study calculates mooring system can cage attachment loads. Environmental parameters input to the model included waves and currents that were measured at the site. Calculation results were compared with loads measured in-situ. Simulations were then performed using a more extreme case in an effort to understand what type of loads the cage structure could withstand.