According to their latest Fall Oyster Survey, the Maryland Department of Natural Resources (DNR) has reported a remarkable year for juvenile oysters in the Chesapeake Bay. The survey recorded an unprecedented number of juvenile oysters, also known as spat, with a spatfall intensity index of 86.8 spat per bushel. This figure is nearly four times the 39-year median of 23.6 spat per bushel and ranks as the fifth highest in the survey’s history.
Josh Kurtz, Secretary of the Maryland Department of Natural Resources, was enthusiastic about the findings. “We have not recorded this extent of oyster spat recruitment in the fall survey in a generation,” he said, noting the significant quantity and widespread distribution of spat across the Bay. The DNR plans to leverage these natural spat sets to enhance oyster restoration efforts and support aquaculture.
This year’s survey, which evaluates the oyster population in the Bay, marks the fourth consecutive year of above-median results for juvenile oysters. This trend is a promising indicator for restoring the bivalve species, which has suffered drastic population declines.
Apart from the spatfall intensity index, the survey also assesses the distribution of young oysters across Maryland’s oyster habitat. Notably, the 2023 survey found spat in areas where they are rarely observed, including upper Bay tributaries typically considered too brackish for effective oyster reproduction. This distribution surpasses previous records.
Significant spatfall was observed in several regions, such as the Potomac River and its tributaries, the Wicomico River, Breton Bay, the Patuxent River, and the Tred Avon River. The Eastern Bay, which has seen declining oyster numbers for over a decade, also experienced a notable increase in spat. Spat was recorded at 50 out of 53 key bars, a level not seen since 1985.
Environmental conditions like water salinity, which have been above long-term averages due to below-average rainfall, are crucial for successful oyster recruitment. However, the DNR notes that other factors also affect recruitment success.
Maryland Department of Natural Resources scientists believe the considerable numbers and distribution of spat in 2023, along with the three previous years of above-average recruitment, are encouraging signs for ongoing management efforts.
Eastern oysters are vital to the Chesapeake ecosystem. They serve as a food source, create habitats for fish and crustaceans, and help clarify water by filtering it and consuming algae. Oyster harvesting is a significant economic activity in Maryland, second only to crabbing.
In collaboration with the Oyster Advisory Commission, the department manages oysters in the Chesapeake Bay through a three-pronged approach. This strategy includes protecting oyster bars in sanctuaries, promoting oyster aquaculture, and employing data-driven management for public fishery areas.
The annual field survey, initiated in 1939, is one of the longest-running programs of its kind. It monitors various locations, including natural oyster bars and sanctuaries.
The survey also noted that oyster reproduction depends on external fertilization and the proximity of adult oysters. Despite the challenging environment for larvae and spat, some survive significantly. The 2020, 2021, and 2022 surveys reported above-average spatfall intensity indices.
Christopher Judy, Director of the DNR’s Shellfish Division, highlighted the ecological role of oysters. “Oysters are environmental engineers, meaning they create their own essential shell habitat as they grow,” he said. “This large influx of young oysters will help build a foundation for more oysters in the future.”
The Chesapeake Bay Foundation’s Maryland Executive Director, Allison Colden commented on the findings. She expressed optimism about the above-average spat set but urged continued vigilance against disease-related mortality and overfishing, particularly in areas prone to overharvesting.
