Recent flooding has impacted state parks across Texas. Status of ParksVideos, Photos, News


Literature Review of the Microalga Prymnesium parvum and its Associated Toxicity

Sean Watson, Texas Parks and Wildlife Department, August 2001


Occurrence of Fish Kills in Texas

Mass fish mortalities have occurred in Texas in recent history. In October 1982 in the Brazos River Basin, an estimated 2,300 fish were killed in California Creek with the suspected killer being Prymnesium parvum (Glass et al. 1991). The first confirmed fish kill due to P. parvum occurred in October and November 1985 on the Pecos River with approximately 110,000 fish dying during this time in the stretch of river between Iraan, Pecos Co., to the mouth of Independence Creek (James and De La Cruz 1989, Rhodes and Hubbs 1992). Additional kills occurred in November and December of 1986 where an estimated 500,000 fish died in the same stretch of the Pecos River, and in November and December of 1988, a number of fish kills resulted in more than a million and a half fish dying in the reach of the Pecos River from Malaga, New Mexico to below the town of Imperial in Pecos County, Texas, as well as in the segment between Iraan and Sheffield (James and De La Cruz 1989, Rhodes and Hubbs 1992). In November of 1988, another 48,000 fish were killed in the Paint Creek tributary of the Brazos River, in Throckmorton and Haskell counties near Abilene, Texas (James and De L Cruz 1989). In April 1989, another fish kill on Paint Creek claimed another 15,000 fish, and an estimated 180,000 fish were also killed in August through October 1989 in a stretch of the Colorado River below Spence Reservoir (Glass et al. 1991).

According to a TPW news release, on January 11, 2001, Prymnesium parvum blooms were responsible for the death of approximately 175,000 fish in the Brazos River basin at Possum Kingdom Lake, 261,000 fish at Lake Granbury since January 26, 2001, and this microalga has been implicated in recent kills at Lake Whitney (Cisneros 2001a and Cisneros 2001b). P. parvum has also wiped out the striped and hybrid bass production at Dundee State Fish Hatchery near Wichita Falls recently (Lightfoot 2001).

James and De La Cruz (1989) noted that, during the 1986 Pecos River fish kill, cell densities of 150 million cells per liter were recorded. They also reported that all species of fish in the fish kill areas were affected. The authors noted that some of the species of fish affected include Cyprinus carpio, Etheostoma grahami, Gambusia affinis, Lepisosteus osseus, Micropterus salmoides, and Pylodictus olivaris. They also remarked that the bivalves of the Unionidae family and the Asiatic clam, Corbicula fluminea, were also adversely affected. The authors discerned that C. fluminea was once common to the Pecos river with densities in the past as high as 100 per square foot, and that no live C. fluminea have been observed since the 1985 kill on the Pecos River. The authors remarked that this suggests a recent introduction of Prymnesium parvum to the Pecos River, and noted that results from recent data suggests that P. parvum is expanding its range in Texas.

Environmental Requirements

Aditional Information:

Would you like to know more?
The Biology of Golden Alga summarizes what we know about the alga and its toxins.

Where does golden alga fit compared to other single-celled organisms?
The Golden Alga Family Tree gives examples of and information about golden alga and other protists.

What does golden alga look like?
TPWD Golden Alga Images has photos of fish kills, golden algal cells, and short videos of live golden alga. These images may be used for noncommercial/educational purposes as long as TPWD is given credit and other site policies are followed.

Golden Alga Information Card: TPWD has collaborated with the Texas Commission on Environmental Quality and other entities to produce a golden alga information card. Download a PDF from the TCEQ website or request a free hard copy from TPWD at

Back to Top
Back to Top