The Skinny on Shallow Water: Protected but Vulnerable
By Dave Secor
Kayaking is such a simple and therapeutic pleasure. Shallow waters abound in the Chesapeake Bay, and car roof racks attest to its popularity. In tidal creeks, rivers and protected bays, passive glides bring nature’s envelopment. Arms work against wind and tide. Immersion and exertion shed worries in the kayak’s wake.
These skinny waters are also therapeutic for the Bay itself. They are its highest-functioning habitats: nurseries for fish, beds for reefs and underwater grasses, and incubators for the forage species that sustain oysters, crabs, fish and wildlife.
Little wonder then that these shallow waters receive the government’s highest safeguards. The Chesapeake Bay Program applies its most stringent water quality standards to two classes of habitats: skinny tidal waters, including shoreline waters less than 2 meters deep, and migratory spawning reaches and nurseries, which are mostly shallow, upper estuarine waters where striped bass, perch, shad and other fish reproduce.
Twenty years ago, I worked with a team to develop these protections, and they have stood up well. Still, left in the wake of that effort are larger perils to skinny waters: climate change, invasive species and development in coastal rural counties.
Along the shores of the Potomac River, we summertime paddlers share skinny waters with countless 2-inch juvenile striped bass. Their numbers vary wildly year-to-year, depending on springtime egg and larval survival. Upriver to Nice Bridge, large females cast billions of eggs to the whims of spring weather. Early mortality is brutal, and bass have adapted by spawning repeatedly over long lifespans. A 30-year-old striped bass has more than 20 times at bat to replace herself.
Enter climate change. Spring is now a less predictable transition between seasons, narrowing the window of favorable conditions. Combined with recent overfishing and disease, most females get only one or two times at bat.
Protecting the nursery function of skinny waters against climate change thus has more to do with fisheries management ― maintaining older spawners ― than improvements to water quality.
Enter blue catfish. From 1974 to 1985, Virginia introduced hundreds of thousands of them into freshwater rivers of the Lower Bay. But the fish had an unexpected predilection for brackish water, and within 20 years they had exploded in abundance, invading all major tributaries.
In a 2013 survey of a 7-mile stretch of the James River, Dr. Mary Fabrizio and her team at the Virginia Institute of Marine Science put the number of blue catfish at 1.6 million — more than the Bay’s entire commercial harvest of striped bass. As the dominant predator, they’re taking a big bite out of the juveniles that sustain our native fish. There is no obvious fix, but promoting harvests of blue catfish would help young striped bass and other native fish to evade predation.
Kayaking near Great Mills on the St. Mary’s River requires a good deal of maneuvering between obstacles: submerged snags and overhanging trees and vegetation.
This weaving and dodging, great sport in a kayak, is the result of coastal zone protections: Homeowners and small businesses along the river have helped conserve and even enhance shoreline vegetation. These zones of trees, swamps, marshes and undergrowth provide habitat and buffer skinny waters from runoff.
Enter coastal development. Strategic planning for Lexington Park in St. Mary’s County concentrates a corridor of retail, industry and high-density dwellings along MD Route 235 ― away from coastal zones.
Yet the county is a narrow peninsula, so the corridor straddles the headwaters of the St. Mary’s River within 1–3 miles of tidal waters. Impervious surfaces exceed 10%, the threshold at which the conveyance of sediment, nutrients and other pollutants harms living resources.
In coastal rural counties and towns, these impervious spines of development continue to grow, paralleling and crossing skinny waters — for instance, along Southern Maryland’s state routes 2, 4 and 5; Virginia’s I-64 and state routes 3 and 17; and the Delmarva Peninsula’s U.S. routes 50 and 13.
The stringent EPA protections for skinny waters, though notable in their achievements, have not kept pace with the threats.
The most important battle for conserving skinny waters is not in improving agricultural practices in Pennsylvania, nor is it in restoring oxygen to the Bay’s deepest waters. It’s proximate to the skinny waters themselves: actions that give living resources a fighting chance against climate change and other assaults. Essential actions include reversing overfishing, reining in blue catfish and extending coastal zone protections to those spines of coastal rural development.
On a recent paddle in the brackish part of the St. Mary’s River, I reached down from my kayak and plucked a large live oyster from the sandy bottom. The water was crystal-clear except for dense patches of seagrass. There is much worth savoring and conserving here.
About the Author: Dave Secor is a fisheries and environmental scientist at the University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory.
The views expressed by opinion columnists are not necessarily those of the Bay Journal. This piece printed with permission. Bayjournal.com