Optimizing Wild Mussel Spat Collection in the Gulf of Maine: Plankton Indicators for Better Timing and Reduced Tunicate Fouling at Bangs Island Mussel

Commodities

• Animals: shellfish

Practices

• Animal Production: aquaculture
• Pest Management: field monitoring/scouting, integrated pest management

In the Gulf of Maine, blue mussel aquaculture offers sustainable seafood, coastal jobs, and ecosystem benefits, yet farmers struggle with unreliable wild spat collection and heavy biofouling by invasive tunicates. Inconsistent plankton dynamics and shifting ocean conditions make traditional "rule-of-thumb" collector deployment timing unreliable, resulting in low settlement rates, increased labor costs, and limited farm expansion. Small- and medium-scale operations like Bangs Island Mussels in Casco Bay are particularly affected, as poor seed supply and fouling reduce profitability and discourage new entrants into this low-impact sector.

This project addresses the challenge by translating ongoing plankton monitoring into practical, science-based decision tools. The three main objectives are:

1. Identify specific plankton indicators (such as diatom abundance peaks and tunicate larvae thresholds) that reliably signal optimal collector deployment windows.
2. Quantify relationships between high-resolution phytoplankton data and on-farm outcomes including mussel spat settlement success and biofouling pressure.
3. Develop and test replicable protocols that improve seed supply reliability and reduce tunicate management labor for Northeast shellfish growers.

Working in close partnership with Bangs Island Mussels, the Gulf of Maine Research Institute (GMRI) will implement standardized, replicated plankton sampling and collector trials across two growing seasons (2026-2028). Sampling will occur 2-3 times per week during key settlement periods using vertical tows and water bottles at raft sites. A University of Southern Maine intern (10 hours/week) will support field collection and rapid analysis with project-specific equipment including a PlanktoScope for detailed phytoplankton imaging and enumeration and a drop camera and field microscope to monitor mussel settlement. Data on plankton community composition, settlement density, and tunicate fouling will be collected and analyzed with statistical methods to establish actionable thresholds. Bangs Island Mussels will actively participate in protocol design, collector deployments, and feedback to ensure practicality for real-world farm operations.

Results will be shared widely with the Northeast shellfish community through a concise, farmer-friendly fact sheet co-created with Bangs Island Mussels, hands-on workshop demonstrations at Maine Aquaculture Innovation Center events, and presentations to Cooperative Extension and service provider networks. The intern's involvement will also build future capacity by linking academic training with industry needs.

By optimizing wild spat collection and minimizing biofouling through plankton-informed management, this project will enhance economic viability, resource stewardship, and resilience for mussel farms across Maine, Massachusetts, Connecticut, and beyond. It directly supports Northeast SARE's goals of conserving marine resources, improving water quality through efficient shellfish filtration, and increasing sustainable employment opportunities in coastal aquaculture.

Objective 1: Determine whether specific plankton community indicators-particularly peaks in nutritious diatom abundance and thresholds in tunicate larvae density-can serve as reliable, farm-level triggers for optimal collector deployment timing in Gulf of Maine mussel aquaculture, measured by comparing settlement success rates and tunicate fouling levels across replicated deployment windows.

Objective 2: Quantify the relationship between high-resolution phytoplankton monitoring data (abundance, composition, and size spectra) and on-farm outcomes, including wild mussel spat collection efficiency and biofouling pressure, using standardized sampling protocols and statistical analysis to develop practical decision-support guidelines.

Objective 3: Evaluate the effectiveness of the refined monitoring protocols through on-farm implementation at Bangs Island Mussels and assess their potential for broader adoption by other Northeast shellfish farmers, documented via intern-supported data collection, farmer feedback, and outreach products that improve seed supply reliability and reduce labor costs associated with tunicate management.

These three objectives address the core research question: Can plankton-based environmental indicators be translated into simple, actionable tools that help Northeast blue mussel growers optimize wild spat collection timing, maximize set success, and minimize invasive tunicate impacts under changing ocean conditions?

By achieving these objectives, the project will move from current observational monitoring at Bangs Island Mussels to systematic, replicable protocols that strengthen economic viability, resource stewardship, and resilience for small- and medium-scale shellfish farms across the Northeast.