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Literature Review of the Microalga Prymnesium parvum and its Associated Toxicity

Sean Watson, Texas Parks and Wildlife Department, August 2001


Global Occurrence of Fish Kills

Prymnesium parvum was first identified as the culprit of mass fish mortalities in the brackish waters of Denmark and Holland (McLaughlin 1958, Shilo and Aschner 1953). According to records of these mortalities, thousands of pike, perch, roach, eels, bream, and tench were killed in 1938 in the Ketting Nor off the coast of Jutland, and again in 1939 in the Selso So located on a peninsula of Sjalland Island (Reichenbach-Klinke 1973). In 1947, Israel reported mass mortalities in carp ponds, and it has been a reoccurring problem (Shilo and Shilo 1953). P. parvum has been implicated in fish kills in Palestine, in rock pools of Scotland, Germany, Spain, Bulgaria and in South Africa as well (Comin and Ferrer 1978, Dietrich and Hesse 1990, Johnsen and Lein 1989, Linam et al. 1991, Rahat and Jahn 1965, Reichenbach-Klinke 1973).

Bales, Moss, Phillips, Irvine and Stansfield (1993) noted that well-documented accounts of multiple fish mortalities associated with P. parvum were recorded in the River Thurne system (Norfolk Broads, England) starting in 1969 and becoming less severe until 1975. They stated that large kills occurred in mid-August 1969 at Horsey Mere and Hickling Broad, in early September at Heigham Sound, Candle Dyke and the River Thurne, and another large kill occurred in April 1970 with smaller kills in 1973 and 1975. The authors believed that P. parvum was stimulated by gull-guano from the large number of black-headed gulls (Larus ridibundus L.) nesting in the area. They remarked that guanotrophication may have lead to an abundance of P. parvum due to supply of associated organic nutrients and noted that a decline in gull numbers was followed by a decline in P. parvum numbers. Anecdotal records described brown-colored water (possibly P. parvum) associated with fish kills in 1894, 1911, 1914, 1925 (kill comparable to the 1969 kill), 1934, 1954, 1966, and 1967 in this same area (Holdway et al. 1978).

In July-August 1989, Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) died in aquaculture enclosures in the Sandsfjord system (southwest Norway) with fewer of the free-living fish in the brackish water fjord system affected (Kaartvedt et al. 1991). From 1989-1996, mixed blooms of P. parvum have occurred every summer in the Sandsfjord system (Larsen and Bryant 1998).

Hallegraeff (1992) noted that since the 1970’s, P. parvum blooms have been related to recurrent fish kills in Vasse-Wonnerup estuary (W. A.) of Australia with kills most common in January-March. The author remarked that these fish kills, like those of the Sandsfjord system in Norway, show that wild fish stocks are less vulnerable to the P. parvum toxins than caged fish since they can swim away from toxic areas. Fish kills in Oued Mellah Reservoir in Morocco occurred in November-December 1998 and again in September-October 1999 (Sabour et al. 2000). Recurrent kills in carp ponds due to P. parvum in the People’s Republic of China have also been reported since 1963 (Guo et al. 1996).

Occurrence of Fish Kills in Texas

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

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