Skip to Main Content

St. Marys River

Cascading through one of Virginia’s most scenic canyons runs St. Marys River. This breathtaking native brook trout stream has long caught the interest of businessmen, scientists, government, and the public in general. A hike through St. Marys gorge yields both a natural feast for the eyes and a reminder of the days when the area was heavily mined for manganese. In fact, old cables and slabs of concrete are testimony to the heavy mining activity that occurred in the watershed around 1910. A railroad spur was built by the Pulaski Iron Company along St. Marys River up to its confluence with Chimney Branch. St. Marys River was adversely affected by heavy mining through World War I. The stream slowly recovered and scientific investigations began in 1936 with groundbreaking chemical and aquatic macroinvertebrate (bug) work done by Eugene Surber. His findings provided invaluable baseline biological information that is still used by scientists today. St. Marys River was also used as “proving grounds” for a DDT experiment conducted by the federal government in the 1940’s. This was a one-time test and no permanent damage was done to the river. The U. S. Congress declared the 10,000 acres in the watershed a wilderness area in 1984.

The Virginia Department of Wildlife Resources‘ (VDWR) management activities date back to 1948, when St. Marys River was stocked with catchable brook and rainbow trout. Stocking continued until 1974, after high water washed out the access road along the stream. From that point on, St. Marys has supported populations of native brook trout and naturalized (wild) rainbow trout. DWR began monitoring fish and macroinvertebrate populations in 1976, and the process continues to this day. The database constructed with the information collected in these biological surveys tells an interesting story about the river, its inhabitants, and man’s influence on it.

Part of the puzzle that was missing from the DWR surveys was good chemical analysis of the water itself. This gap has been filled by DWR by funding a long-term study with the University of Virginia and citizen volunteers. Since 1987, chemical data has been collected at different points in the watershed and analyzed in the lab. The results show that St. Marys River is an “acidified” stream, as a result of both acid precipitation and the impervious rock that the water flows over. The chemical data helps explain why certain “acid sensitive” fish and bugs have been declining over the decades. In an effort to stem the slide of the stream into biological oblivion, the Forest Service, James Madison University, VDWR, and other organizations organized a campaign to lime St. Marys watershed to help ameliorate the negative impact of acidification. In March, 1999, St. Marys River and five of its major tributaries were “dosed” with 140 tons of limestone sand. This was done with a helicopter and the sand was applied directly to the stream. This type of liming exercise was tested in other watersheds to great success, so it was reasoned that it would be of some short-term relief to St. Mary River. Chemical and biological monitoring continue to this day and the results are encouraging.


Brook Trout

Brook trout are very hardy fish, having the ability to survive floods, drought, and even acidic environmental conditions. Brook trout are also fall spawners and their eggs undergo long winters in the nest. A strong brook trout year class is usually determined by the severity of local climatic conditions during any given winter. Hence, warm, dry winters are beneficial to hatching success and survival of the fry. Strong year classes were documented in the late 1980’s and early 1990’s, and have again shown up in recent years.

Fisheries biologists have been sampling St. Marys with electrofishing gear on an annual basis since 1998 (prior to that, sampling took place every other year). Six permanent stations were established in 1976, and the very same areas are revisited every time St. Marys is sampled. A backpack electrofisher is used to stun fish, where they are immediately netted, placed in water, identified, measured, weighed, and released. Long-term electrofishing data sets create a good picture of fish abundance, health, and distribution in the watershed. Although trout are the target species, non-game fish such as blacknose dace, mottled sculpin, and fantail darter also help scientists evaluate the stream’s overall environmental health.

Brook trout are currently thriving in St. Marys River. Successive strong year classes of brook trout since 1997 made a positive impact on the fishery prior to liming. The lime was introduced at a time when several solid brook trout spawns were being “recruited” into the fishery, hence making environmental conditions more favorable for the growing population. Brook trout in St. Marys River exceeded 1,000 fish per mile in 1999 for the first time in our investigations. Brook trout density soared to over 1,600 fish per mile in 2000 and has dropped to 1,200 per mile in 2001. What kind of size will you find? In 2001, over a quarter of the brookies collected were young-of-the-year (under 4 inches), close to 56% were between 4 and 6 inches, and the remaining 18% were 7 inches and up. Brook trout growth was good, with fish reaching 7 inches in 2.5 years. Most of the brook trout in St. Marys live only 3.5 to 4 years of age. A few brookies will reach 10 inches in this stream, but the majority of quality size fish will be 8 – 9 inches long.

Rainbow Trout

Rainbow trout were last seen in St. Marys River in 1992, when only a few specimens were collected. Wild rainbow trout once provided some great “fast water” angling in the middle reaches of the stream, but have been victimized by poor water quality.

Other Fish Species

Blacknose dace, a common mountain stream minnow, is an important food source for trout, as well as an environmental barometer in St. Marys River. Blacknose dace once thrived in St. Marys River, but their numbers have declined since the 1970’s. They are much less tolerant of low pH water than brook trout, so they make an excellent biological indicator of how well the stream is doing. Blacknose dace densities improved dramatically between 2000 and 2001, and they have expanded their range in the watershed. These are good signs for both the dace and other fish species such as sculpins and darters.


Macroinvertebrates are simply those creatures that have no backbone and can be seen with the naked eye. In aquatic ecosystems they include insects, mussels, snails, clams, worms, leeches and crayfish. These animals are important players at the lower levels of the food web in aquatic environments. Active sampling or monitoring a stream reach for macroinvertebrates can tell you how healthy your waterway is.

Because of St. Marys River’s low pH, it would make sense that only acid-tolerant macroinvertebrates would thrive in its waters. Data from as far back as the 1930’s show that as many as 32 types of macroinvertebrates inhabited St. Marys River, and many of them were sensitive mayfly species. When macroinvertebrate sampling resumed in earnest in the 1980’s, the number of taxa was reduced by half. Water chemistry, subtly altered over time by changes in air quality, was largely responsible for the decline in macroinvertebrate life.

Taxa richness is one way to look at the big picture. The more families and genera found usually means a healthier environment with diverse habitats. In 2001, St. Marys River averaged 29 taxa throughout the watershed. This has steadily improved through the 1990’s, partially due to a change in sampling techniques and partially as a response to liming. Mayflies, stoneflies, and most caddisflies are sensitive to poor water quality. A measure called the EPT Index examines the diversity of these three groups of insects. Beginning in 1998, the EPT Index began to improve, and, in the post-liming years, it has improved to a record high of 18 (from a low of 7 in 1990).

At the individual level, an acid sensitive mayfly, Epeorus sp., was not found in samples for 2 decades. After liming, Epeorus reappeared in significant numbers. Other mayfly species have also fared well in recent years. The acid tolerate stonefly, Leuctra sp., has also benefited from better pH levels in St. Marys River.

Biologist Reports

  • None available at this time.
  • Regulations


    Six trout per day with a minimum size limit of 9 inches. Only single hook artificial lures may be used; no bait allowed or in possession. All trout under the minimum size must be returned immediately to the water unharmed. This regulation applies to that portion of St. Marys River beyond the entrance gate within the National Forest.

    Facilities, Amenities, and Nearby Attractions

    St. Marys River lies within the St. Marys Wilderness Area, so no developed facilities are available. The stream has three trailheads: one at the lower parking lot, one at the head of Mine Bank Branch, and one at Green Pond. Camping is allowed within the Wilderness Area, except in the riparian area between the lower parking lot and the lower waterfall. Refer to the following link for more Forest Service information

    More Information

    Fisheries related inquiries

    Virginia Department of Wildlife Resources
    Verona Office
    Phone: (540) 248-9360

    Maps, camping, facilities:

    United States Forest Service
    Pedlar-Glenwood Ranger District
    P.O. Box 10
    Natural Bridge Station, VA 24579
    Phone: (540) 291-2189
    James Madison University
    Dr. Dan Downey
    Phone: (540) 568-6246

    Virginia Trout Stream Sensitivity Study

    Rick Webb
    University of Virginia
    Clark Hall
    P. O. Box 400123
    Charlottesville, VA 22904
    Phone: (434) 924-0569