The Shenandoah River is legendary for its bass fishery. In the late 90’s catches of up to a hundred fish per person a day were not uncommon, but this is not always the case. In fact, bass are not even native to the Shenandoah River. You wouldn’t be wrong in calling them an invasive species.
Legend has it bass were introduced to the river by a railway worker who was an avid fisherman and hailed from up state New York where bass are native. He loved fishing for the feisty bronze backs that put up such a fight. They say in the 1880’s he loaded a passel of bass into the water tender of his steam locomotive, transported them to Virginia, and dumped them into Overall Creek as the engine passed over the trestle (I know, sounds like a fish story to me too). Be that as it may, the bass somehow found their way to the Shenandoah River in the late 19th century and there they thrived, ….to a fault. Today, the small mouth bass is unquestionably the king of the river, to the point of total dominance. As a result the Virginia Department of Wildlife Resources maintains a long standing slot limit for bass. All bass between 11 and 14 inches (ideal breeding size) must be returned to the river, but you may keep up to five fish smaller than 11 inches or greater than 14 inches. The population is not particularly stable either with alternating population surges and crashes, even after a century of adaptation.
Even though the Shenandoah river appears healthy and clean, significant fish kills have occurred over the years. In the 1940’s a kill was caused by industrial pollution from the new Rayon plant in Front Royal (now defunct). In 1977 up to 80% of the fish in the river succumbed, cause never determined. In 2003 there was a major fish kill starting on the North Fork of the Shenandoah River spreading to the South Fork and Main Stem the next year and then on to the James River in 2007. The die off lasted about two years and primarily affected mature bass and red breasted sun fish with losses of about 70%. In 2014 there was a similar event with losses in the 30% range, and smaller annual die offs occur fairly regularly. Is this something new or something we have just not noticed before? No one knows.
The state of Virginia has spent a lot of time and effort (and money) trying to solve the riddle of these fish kills, but no obvious chemical or environmental smoking gun has been found. Scientists have determined a combination of factors have combined to stress the immune systems of the fish making them vulnerable to attack by Aeromonas Salmonicida, a cold water bacteria which is toxic to fish (and helps explain why die offs occur in early Spring when the water is still cold). The bacteria causes lesions and general tissue deterioration. Some fish will recover as the water warms in summer suppressing the S A bacteria.
Fish immune systems can be degraded by a number of factors. Some chemical compounds and heavy metals have been shown to suppress the immune system and influence development of certain aquatic organisms. These contaminants are referred to as “endocrine disruptors”. Natural and synthetic forms of the hormone estrogen fit into this category, and elevated levels have been detected in the Shenandoah River. At this point the effect on fish health is speculative, but alarmingly, a significant number of male bass in the river have actually developed female eggs in their testes.
Currently, the fishery remains fairly stable with usually good, and sometimes spectacular fishing, but pressure on river water quality remains with increasing human population in the Valley and enhanced agricultural production. In fact, Rockingham County (located just up river) is the most productive agricultural county east of the Mississippi River. Some progress has been made by upgrading sewage treatment plants and adopting best management practices in agriculture. Can science save us? Do we have the will to do what needs to be done? I guess time will tell, but for now the river remains an incredible resource. Small mouth bass still rule.