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Ribbed Mussel Pilot Project Summary

Students from Rocking the Boat help hang lines during the raft installation.
Mussel Raft Installation, Photo by NOAA Milford/Mark Dixon

Project: Ribbed mussel nutrient bioextraction in the Bronx River Estuary, New York City
Dates: 2011-2017
Team: National Fish and Wildlife Foundation, Maine Shellfish R&D, Rocking the Boat, NOAA, Long Island Sound Study, Gaia Institute
Funding: New York State Office of the Attorney General, NOAA Fisheries Office of Aquaculture (https://www.fisheries.noaa.gov/about/office-aquaculture)

Project summary:
Ribbed mussels are a shellfish species native to Long Island Sound and New York City, with historically large populations providing important services such as reducing nutrients and stabilizing shorelines. As these shorelines have become developed, most of the salt marshes that used to be ribbed mussel habitat have been lost to bulkheads, ports, and other waterfront infrastructure. By putting a raft stocked with mussels into the Bronx River Estuary, our goal was to restore some of the ecosystem functions that were once provided by historic ribbed mussel populations. At the same time, the project team’s researchers were interested in the ribbed mussel species because their notoriously poor taste reduces the likelihood of people eating them. Therefore they can be safely grown in places like the Bronx where high numbers of bacteria make shellfish aquaculture for human food not possible.

This project was a pilot study designed to address as many practical questions related to the use of ribbed mussels for nutrient bioextraction as possible. The researchers learned that, although ribbed mussels naturally grow in the intertidal zone where they are regularly exposed to air, ribbed mussels can grow constantly submerged underwater using methods typical of blue mussel aquaculture. The team monitored small local ribbed mussel populations in the Bronx and found that they were healthy even in an environment highly impacted by humans, and that local ribbed mussels naturally reproduce in June and July. It used a technique called stable isotope analysis to determine that the nitrogen used by the ribbed mussels to grow their tissues and shell originally came from human sources. This finding was good news for local nitrogen management programs that are focused on reducing excess nitrogen coming from human activities on land. The team also found that growing mussels in the water instead of on the seafloor reduced the amount of metals and organic contaminants such as pesticides that ended up in mussel tissue.

Ribbed mussels suspended from a “pegged rope.” These ropes are hung underwater from the mussel raft. The cage is used to protect the mussels from predators.

The project showed that ribbed mussels on a single 20×20 foot mussel raft could filter more than 3 million gallons of water every day.  Harvest of the mussels on that raft would remove 140 pounds of nitrogen contained in their shell and tissue. Given these impressive results, the researchers were very interested to also discover that our location at Hunts Point was not an ideal place to grow mussels. Particles in the water that were filtered by mussels were dominated by sediments and other inorganic material, instead of mussel food such as plankton and other organic material. The mussels were able to adapt to these challenging conditions by increasing the amount of time they spent sorting through the particles they filtered, selecting food to ingest and rejecting material that was not food. But a different location with more food available may have resulted in faster mussel growth.

Some questions remain following our study.  The project team tried a variety of methods to catch young ribbed mussels in the natural environment to stock our raft, but none of them worked. This was identified as a key bottleneck to future implementation projects. Recent research by Rutgers University and the Partnership for the Delaware Estuary have made great progress in reducing this bottleneck. The question of what to do with ribbed mussels after harvest also remains. Obviously the hope is that the mussels would be able to be recycled instead of ending up in a landfill. Some options for using the mussels include as feed for other animals and as fertilizers or compost. Researchers in Europe have studied the use of blue mussels for chicken and pig feed, and found that adding mussel meal as a supplement improved the quality of the feeds. It is possible that parts of the mussel could be used as supplements for plant-based fish feeds, such as the omega-3 fatty acids in the mussel tissue, but this is an area needing more research.

Link to scientific publication:

Links to recent media stories about the project:

Paul Greenberg features the Bronx project prominently in his book, The Omega Principle

Links to older media stories about the project:

 

 

 

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