Development funds are requested to create a user-friendly website for calculating mooring loads and cage volume decrease for finfish, gravity-type net-pens in steady current. The website will provide critical information for potential and practicing aquaculture fish farmers, outreach/extension educators and researchers regarding the selection and response of marine fish cages to environmental loadings.
Over the last 11 years, the University of New Hampshire (UNH) Open Ocean Aquaculture (OOA) team has developed and field tested computer models for sizing fish cage components and mooring hardware. The centerpiece is the UNH net pen/mooring system finite element computer program Aqua-FE that can predict cage deformation and mooring system forces in response to tidal current as well as other environmental loads (such as waves). To implement a new Aqua-FE model for a specified design problem, however, typically requires several days to a month of a specially trained engineer’s time. This is prohibitively expensive for a small business operator or a wild harvest fisher exploring aquaculture as an alternative. Local interest, for example, includes 6 fishers that have already submitted permit applications to place cages in the Piscataqua River/Great Bay system. These initiatives have been hampered by lack of information on mooring loads as well as volume loss due to net deformation by current (which affects stocking density). In addition, the OOA team has received numerous inquiries for cage modeling assistance from around the world. In the proposed work, this problem is addressed by employing a simpler mathematical model based on equilibrium and catenary equations. The proposed model will respond almost immediately to the online user. This model will be validated by comparison with full Aqua-FE applications as well as previously obtained field data.
As noted above, obtaining the critical engineering analysis to assemble a robust cage/mooring with adequate strength is presently beyond the means of most entrepreneurs entering the industry. In addition, the majority of farmers lack the proper tools to assist in the iterative decision-making and optimization process aquaculture farming requires for successful operation. Fish farmers, regulators and the public cannot sustain the “trial and error” approach to fish grow-out and harvesting typically employed by large fish farms which can result in loss of income, broken cages and escaped fish. It is important that the farm be safe, secure, have minimal impact on the environment and be successful from its infancy. Therefore, having accessible information to assist in cage structure, net and mooring selection is critical to expand the industry. The proposed work addresses this need by providing an interactive, marine fish cage mooring load, volume deformation, and drag force calculator for a variety of net mesh sizes, cage geometries, ballast weight configurations and incident water velocities.
The development project proposed here is the first step in creating a more comprehensive website that will include information and calculators to analyze the economic feasibility of fish farming, species and quantity selection, standard operating costs, as well as tools to assist in permit applications (fish waste dispersion into the environment). After demonstrating the general usefulness and impact of the initial website, proposals to expand the site will be generated and submitted to Sea Grant. This research work addresses the Safe and Sustainable Seafood Supply priority identified in the New Hampshire Sea Grant Strategic Plan.
Model Predicts Mooring Loads and Volume Loss for Finfish Cages
Researchers developed a computer-based mathematical model for predicting mooring loads and volume loss for a gravity-type aquaculture finfish cage in ocean currents. This model significantly decreases the amount of time needed to run calculations on cage dimensions and environmental parameters, thus potentially saving time and/or money for aquaculture businesses and researchers.