WRWA, Massachusetts DMF, and The Nature Conservancy Partner on Oyster Restoration Monitoring
By: Roberta Carvalho, Science Director
This summer, WRWA has been working with the Massachusetts Division of Marine Fisheries (DMF) and The Nature Conservancy (TNC) to better understand oyster recruitment in the Westport River. This collaborative monitoring effort is an important first step in planning and evaluating future oyster reef restoration in the River.
The goal is to establish a baseline of oyster recruitment and environmental conditions before restoration takes place. By understanding what is happening naturally today, we will have a point of comparison for measuring changes after restoration projects are implemented.
Oysters begin their lives as free-swimming larvae in the water column. When they reach the point where they are ready to settle, they search for a suitable hard surface where they can permanently attach and develop into juvenile oysters, known as spat. Oyster larvae are particularly attracted to calcium carbonate, the material that makes up oyster shells and other shell material.
In natural oyster reefs, larvae commonly settle on the shells of older oysters, often referred to as cultch. Over time, generations of oysters build upon this shell base, creating the complex reef structure that supports continued recruitment. For this study, the recruitment tiles were specifically selected because they are made of calcium carbonate, providing a biologically relevant surface that mimics the shell material found on natural oyster reefs.
What We're Doing in the Field
To monitor this natural recruitment process, oyster recruitment tiles (settlement tiles) have been deployed at potential restoration locations in the Westport River. The tiles provide a standardized surface where newly settled oysters can be detected and counted.
WRWA’s Science Director and DMF staff have been going out every two weeks throughout the summer to check the tiles and document oyster recruitment. Regular visits are important because oyster settlement can occur in pulses during the spawning season. Rather than simply looking at the total number of oysters at the end of the season, repeated monitoring allows us to begin understanding when recruitment occurs and how it varies among locations.
During these field visits, we are also measuring dissolved oxygen at the monitoring locations. Dissolved oxygen is an important indicator of estuarine conditions because oysters and other aquatic organisms require oxygen for respiration. Oxygen concentrations can change with temperature, tides, weather, biological activity, and water circulation. By collecting dissolved oxygen measurements alongside our recruitment observations, we can begin to look at the relationship between oyster settlement and the environmental conditions present at these sites.
Establishing a Baseline Before Restoration
One of the most valuable aspects of this project is that the monitoring is occurring before restoration begins. Several locations in the Westport River are being considered for oyster restoration. The information collected this summer will provide baseline data against which future monitoring can be compared.
If restoration moves forward, we can continue monitoring the sites and determine whether oyster recruitment changes over time. This will allow us to evaluate whether restored areas are beginning to attract and support new generations of oysters, not simply whether oysters have been placed there. The project also includes plans to identify an existing wild oyster bed as a reference site. Monitoring a natural oyster population alongside the restoration areas will provide an important comparison for understanding how restored habitat develops relative to naturally occurring oyster habitat.
This project brings together three organizations with complementary expertise. Massachusetts DMF provides expertise in oyster biology, fisheries science, and restoration. The Nature Conservancy is helping develop the monitoring approach and project funding, ensuring that the information collected will provide a strong scientific foundation for evaluating restoration. WRWA contributes local knowledge of the Westport River and a consistent field presence to carry out the biweekly monitoring.
This partnership builds on WRWA's long history of collecting water quality data throughout the Westport River while expanding our monitoring program into habitat restoration and ecological research. The data collected this summer will help inform future restoration decisions and give us a scientifically defensible starting point for measuring ecological change.
Every tile tells a story
By checking them throughout the season, we are beginning to piece together the story of oyster recruitment in our River and help establish the baseline we will need to measure the success of restoration in the years ahead. Oyster restoration is not simply about putting oysters back into the river. Successful restoration depends on understanding the conditions that allow oysters to survive, reproduce, and create functioning habitat.
To learn more, listen to our Nature Talk: Restoring Oyster Reefs with Dan Goulart
