A field study to understand the currents and loads of a near shore finfish farm

An extensive field study was conducted to investigate the current velocities and mooring system tensions in a 20-unit net pen fish farm located in Eastport Maine, USA, near the Bay of Fundy where extreme tides create strong currents loading fish farm components. To understand the flow characteristics at the site, currents meters were deployed at external and internal farm locations during three distinct operational conditions: (1) clean nets for smolts, (2) clean nets for standard grow out and (3) nets for standard grow out at the end of the stocking schedule, when the gear is fouled with biological material. Also, several load cells were deployed at the same time on important anchor leg and net pen attachment components to measure system loads. The current meter data sets provided evidence of velocity flow reduction through the farm by examining the current meter statistics and tidal harmonic constituents. Tidal analysis also showed substantial tidal harmonics or shallow water tides. The load cells measured maximum loads of 104 kN for anchor leg and 11 kN for net pen lines. The results are significant because few extensive fish farm engineering data sets exist, especially for different combinations of nets and levels of biological fouling. These results are being used in complementary studies to quantify flow reduction, to validate Morison equation type numerical models and as a baseline for specifying offshore fish farm gear.