Wild trout populations require cold, well-oxygenated water, a clean stream bottom, and good fish cover. In Virginia, most trout habitat losses occur through increased stream temperature, siltation, and stream channel alteration.
Water temperature requirements may be the most critical factor facing Virginia’s trout populations, and the state’s generally warm climate and normally low summer stream flows do not help the situation. Most shaded mountain streams do not exceed 70°F during the summer, which is suitable for trout. Aquatic habitat and suitable water temperature can be maintained even during logging and farming operations when streamside vegetation is left intact. In most cases, maximum stream temperatures in the low 70s are within the tolerable range for trout, but such temperatures improve the habitat for other stream fishes which trout cannot compete against.
Siltation and other more direct forms of habitat alteration, such as channelization, have also cost Virginia many miles of trout water. Silted stream bottoms decrease the stream’s insect population, an important source of trout food. Siltation also makes trout reproduction difficult. Trout lay eggs in stream gravel, and clean gravel is necessary to insure movement of oxygenated water over the eggs. As little as a quarter-inch of silt over trout eggs can result in 100 percent mortality.
Alteration of stream channels is also of critical concern, not only due to the increased siltation it causes, but also due to the removal of fish cover and the potential to raise water temperatures. Trout require overhead cover, such as undercut banks, large rocks or submerged logs. When such cover is removed, the trout leave. Lack of suitable cover limits the number of large trout a stream can support.
Virginia lost many good wild trout populations prior to the mid-1970s due to habitat degradation. However, many of the land-use practices that resulted in those losses — widespread stream channelization, poor logging techniques, removal of streamside vegetation, intensive agriculture in riparian areas, etc. — have been improved to the point where, over the past few decades, the physical habitat has been improving. In addition, the Department maintains a current inventory of wild trout streams that provides the data necessary to protect this critical habitat.
The Department’s trout stream inventory identifies over 2,350 miles of wild trout streams in Virginia. Biologists are encouraged to find that brook trout, the only trout species native to Virginia, still accounts for 80 percent of the wild trout resource in the state. Rainbow trout, a western introduction, have taken over many of the native brook trout streams in the other southeastern states. As a result, Virginia currently has more native brook trout streams than all other southeastern states combined.
Growth rates of wild trout, particularly brook trout, in Virginia are exceptional when compared with growth rates for similar streams in neighboring states. In most Virginia streams, adult brook trout average 8-10 inches by their third year of age. In respect to the number of streams available and the size of trout present, Virginia probably offers the best native brook trout fishing south of New England.
Unlike warmwater fish, such as bass and bluegill, trout have a very low ability to reproduce. Therefore, in heavily fished areas, it is imperative to protect trout until they are able to spawn at least once. In order to accomplish this objective, a 7-inch minimum size limit has been imposed on all trout creeled in Virginia. Such a limit will allow most wild trout to reach spawning age before they are subject to harvest.