Quantifying Safe Working Sea States for Longline Shellfish Farms

Commodities

• Animals: shellfish

Practices

• Animal Production: aquaculture
• Education and Training: decision support system, on-farm/ranch research

The US presently imports 79% of its seafood and incurs a $20B trade deficit due to a lack of domestic supply (Rexroad & Davis, 2024). To become a leader in the $165B global aquaculture market, the US must overcome high costs of production (FAO, 2020; Vilsack & Parsons, 2024) for high-value species like Atlantic sea scallops and other shellfish farmed on backbone structures while protecting the health and safety of persons involved in the farm system.

Establishing workable weather windows for on-farm operations is a key driver of worker safety and farm profitability. Installation, maintenance, thinning, cleaning, and harvesting all require workers to interact with gear while the vessel is connected to the backbone. Even moderate winds, waves, and currents induce unfavorable vessel motions and high tensions in the working lines. However, the number of workable days on the water is a significant predictor of farm profitability (Moscicki et al., 2025). Thus, worker safety is directly at odds with a farm's economic viability.

At present, farmers decide safe working limits from experience and judgment alone. This project will combine on-the-water experience with rigorous aquaculture engineering methods and seakeeping analysis to establish quantitative limits on safe working wind speed, current speed, and wind-driven waves.

Kelson will use wind, current, and wave data and advanced numerical seakeeping and mooring-response models representing Vertical Bay's workboat, backbone-raising operation, and associated farm loads to quantify vessel accelerations and working line tensions in a range of operating conditions. Vertical Bay will work directly with Kelson to define the operational scenarios that matter most on the farm and to collect low-cost field measurements during routine work. Using a smartphone and the Physics Toolbox app, Coleman will measure accelerations on deck during field operations and record qualitative observations in a structured log.

Kelson will then apply the validated modeling approach to simulate a matrix of operating conditions spanning relevant wind speeds, current speeds, and wind-driven wave conditions. From these results, the project will identify safe working limits based on crew accelerations on deck, lifting-line tensions during backbone raising, and anchor-load conditions associated with increased risk of anchor displacement. Kelson and Vertical Bay will translate these results into an online farmer-facing operating guidance document and estimates of workable days under site conditions relevant to scallop farming and present findings at a regional conference.

1. Establish criteria and relevant load cases for worker safety.
   Vertical Bay and Kelson Marine will collaborate to define operational requirements and define the priority farm tasks to be analyzed conditions relevant to workability.
2. Validate seakeeping and load-response model.
   Vertical Bay will collect smartphone-based acceleration measurements on deck using Physics Toolbox during field work. Kelson Marine will pair this field data with hindcast wind, current, and wind-driven wave conditions to validate and calibrate the numerical modelling approach.
3. Quantify operational thresholds for safe working conditions.
   Determine the combinations of wind speed, current speed, and wind-driven wave conditions that produce unacceptable crew accelerations, elevated lifting-line tensions, or increased anchor-load risk.
4. Estimate workable days for representative sites and produce farmer-facing guidance.
   Convert model results into practical operating thresholds and estimates of workable days for a representative site.
5. Share results and practical guidance with regional aquaculture producers.
   Publish findings in a report and share results with shellfish growers and agricultural service providers in the Northeast.