Balancing Fisheries Management and Water Uses for Impounded River Systems

<em>Abstract</em>.—<em>Prymnesium parvum</em>, the golden alga, is a toxin-producing, microscopic alga first identified in U.S. inland waters during a 1985 fish kill on the Pecos River, Texas. Golden alga has been reported in 16 states, and toxic blooms have caused substantial fish kills and loss to recreation. Golden alga releases toxins (prymnesins) that affect gill-breathing organisms but do not affect most aquatic insects and higher vertebrates. The toxins complete formation externally with the addition of cations, and water quality variables such as salinity, temperature, pH, and nutrients influence the toxicity of a bloom. Algae control treatments have been developed for ponds and small reservoirs but are usually too costly and labor intensive for practical use on large water bodies. Potential treatments include ammonia compounds, copper compounds, acid applications, potassium permanganate, ozone, ultraviolet light, and nutrient manipulations. The decision to use treatments must balance expected benefits with costs and possible impacts to the aquatic ecosystem. Treatments must meet federal, state, and local rules and regulations and be coordinated with stakeholders. Research is ongoing to determine bloom dynamics and potential management options for large water bodies.