Management of Prymnesium parvum at Texas State Fish Hatcheries
Edited by Aaron Barkoh and Loraine T. Fries
Management Data Series No. 236, 2005
Table of ContentsPREFACE and ACKNOWLEDGMENTS
CHAPTER 7: Use of Hydrogen Peroxide as an Algaecide for Prymnesium parvum
( This chapter is currently being updated and will return at a later date)
Although golden alga Prymnesium parvum appears to have been in Texas for more that 20 years, it only became a public issue in 2001 when it caused massive fish kills at Dundee State Fish Hatchery and in major economically important reservoirs in north and central Texas. Following the devastating effects of P. parvum on fish at the Dundee State Fish Hatchery, a group of Inland Hatcheries biologists formed the P. parvum Task Force to develop strategies to control the alga and maintain the viability of the fish hatcheries – Dundee and Possum Kingdom State Fish Hatcheries – located in the affected region.
After months of synthesizing available information, group discussions and conducting various research studies, the task force developed strategies for controlling the alga to allow successful culture of fish at the affected hatcheries. This document contains some of the written reports prepared by members of the task force on research findings, review summaries and management plans; a few reports published in mainstream journals are not included here. The purpose of this document is to consolidate the reports for easy access and to share what strategies work at Texas hatcheries and how to implement them. Because of design shortfall (e.g., small sample sizes or inadequate replications) associated with some of the research studies, we caution readers to consider some of the results as preliminary. Efforts continue to revisit some of these studies, as resources become available, to confirm findings as well as to conduct new research to find more effective and efficient ways of dealing with the alga. As new strategies are developed, the management plans in this document will be updated. We invite interested persons to call the Dundee or Possum Kingdom State Fish Hatchery from time to time for any future updates.
Loraine T. Fries
This document is the culmination of cooperation, assistance and efforts provided by several individuals willing to serve in whatever capacity possible to contribute to finding a solution to the Prymnesium parvum problem in Texas. We thank Gary Saul and Dick Luebke for approving the formation of the Inland Hatcheries P. parvum Task Force, members of the task force for their dedication to duty, Roger McCabe and Joan Glass for participating in some of the task force meetings, and Annette Sudyka for help with literature search.
We appreciate the zeal and commitment of the contributing authors for making publication of this document possible as well as all those who helped them with their research efforts particularly the Inland Fisheries staffs at Dundee State Fish Hatchery, Possum Kingdom Fish Hatchery, Fish Health and Genetic Lab, and Management District 1C. These individuals spent long hours collecting data or water for research, or provided analytical assistance.
Jerry Brand and Alexandra Holland of the University of Texas – UTEX Culture Collection of Algae in Austin, Texas donated a pure P. parvum culture for research, and Isaac Bejerano and Elizabeth Maor of the Central Fish Health Laboratory in Israel offered expertise and protocols for monitoring P. parvum ichthyotoxin and treating toxic blooms in fish culture ponds. We are indebted to them for their generosity and professionalism.
Funding for the studies published in this document was provided in part by Federal Aid in Sport Fish Restoration, Grants FFD95-PARVM and FFD96-PARVM to the Texas Parks and Wildlife Department.
GREGORY M. SOUTHARD AND LORAINE T. FRIES
This report contains general information on the toxin-producing haptophyte, Prymnesium parvum, which began to threaten the Texas Parks and Wildlife Department (TPWD) Inland Fisheries Division hatchery program in 2001. Included are methods to identify and enumerate the organism, a bioassay to determine the ichthyotoxin level, and treatment or control methods. Additionally, this report documents efforts to modify the bioassay protocol for easier or efficient implementation at TPWD fish hatcheries.
CHAPTER 2: Control of Prymnesium parvum using Ammonium Sulfate or Copper Sulfate in Plastic-Lined Ponds for Koi Carp Production
DENNIS G. SMITH
Prymnesium parvum is a toxic alga that has been responsible for numerous fish kills in reservoirs, rivers, and hatcheries in Texas and many other locations around the world. We compared the effectiveness of ammonium sulfate and copper sulfate treatments in controlling P. parvum and its associated toxicity in plastic-lined ponds for rearing koi carp, a strain of common carp Cyprinus carpio, fingerlings. Treatments were 9.5-mg/L ammonium sulfate, 2-mg/L copper sulfate, and control (no chemical treatment). After the initial treatments, treatments were reapplied to all ponds if weekly bioassay results revealed ichthyotoxin in any pond. All ponds were harvested after 75 or 76 days of koi carp rearing. Bioassay and cell density results revealed that ammonium sulfate and copper sulfate were effective in reducing P. parvum density and toxicity. Fish production was highest in ammonium sulfate ponds, followed by the copper sulfate ponds and was zero in the control ponds. The copper sulfate treatment ponds had a mean net loss of 0.9 kg in fish biomass while the ammonium sulfate treatment ponds had a net gain in mean fish biomass of 266.8 kg. Both chemical treatments were effective in controlling P. parvum; however, ammonium sulfate is recommended because fish production was significantly (P = 0.05) better in ponds treated with that chemical.
Highly toxic water containing Prymnesium parvum and associated ichthyotoxin was subjected to potassium permanganate treatments to determine the minimum effective concentration required to detoxify the toxin and allow fish survival. Potassium permanganate concentrations of 0-6 mg/L were tested at 2-mg/L intervals. Bioassays using fathead minnows were performed shortly after the toxic water was treated and test fish were observed for mortality at 15-minute intervals for 2 hours. All fish died in the control (0 mg/L KMnO4) and 2-mg/L KMnO4 treatments within 30 min and 90 min, respectively, while no fish died in the 4- or 6-mg/L potassium permanganate treatments. Because the potassium permanganate demand of the toxic water was 2 mg/L, it was concluded that potassium permanganate mitigated the ichthyotoxin at a minimum residual concentration of 2 mg/L (i.e., concentration above the potassium permanganate demand). Further research involving better resolution of potassium permanganate treatment concentrations would be needed to define the true minimum effective concentration of potassium permanganate that would detoxify the ichthyotoxin.
CHAPTER 4: Toxicity of Copper Sulfate and Potassium Permanganate to Rainbow Trout and Golden Alga Prymnesium parvum
TOM DORZAB AND AARON BARKOH
The effects of copper sulfate and potassium permanganate on Prymnesium parvum cell density and ichthyotoxicity and on rainbow trout Oncorhynchus mykiss survival were investigated in 0.1-ha plastic-lined hatchery ponds. Treatments were 4 mg/L KMnO4, 1 mg Cu/L and 0.5 mg Cu/L as CuSO4, and untreated ponds which received no chemical addition. Treatments were applied once and rainbow trout were stocked at 5 fish/pond 4 days thereafter. The KMnO4 and 1 mg Cu/L treatments appeared to eradicate P. parvum and eliminate ichthyotoxin within 3 days after treatment application. The 0.5mg Cu/L did not appear effective to control cells or toxicity. P. parvum persisted in the control ponds throughout the study and sublethal levels of the toxin also existed in these ponds. The potassium permanganate demand of the toxic water was 2 mg/L. Rainbow trout survival did not significantly differ among treatment and control groups. The mortalities that occurred were caused by factors not measured in this study.
TOM DORZAB AND AARON BARKOH
The effect of copper sulfate on survival of 230- to 250-mm rainbow trout Oncorhynchus mykiss was investigated in indoor tanks for seven days. Rainbow trout were exposed to three copper concentrations (0.5, 1.0 and 2.0 mg Cu/L) and a control (0 mg Cu/L). In a 3 X 4 study design (replicates X treatments), 12 2,271-L circular tanks were stocked at five fish per tank. Mean survival of rainbow trout in copper sulfate treated tanks was 74% for 2 mg/L, 86% for 1 mg/L, 94% for 0.5mg /L treatments, and 100% for the untreated controls. The differences in survival were not significant among treatment and control groups. Survival declined progressively with increasing copper concentration, and the onset of fish mortality was sooner for the highest copper concentration treatment and later for the lowest (0.5 mg Cu/L) treatment. No mortality occurred in the control tanks. Although the differences in survival were not statistically significant, the observed differences could be biologically or economically important. Because of the small sample size, the effect of the copper concentrations on survival of rainbow trout was unclear.
GREGORY M. SOUTHARD AND DAVID KLEIN
Toxic water obtained from E. V. Spence Reservoir during an ongoing Prymnesium parvum-related fish kill was used to evaluate the effect of lower pH levels on P. parvum cell integrity and toxicity. Hydrochloric and sulfuric acids were used separately to lower pH in toxic water to see if the P. parvum cells and ichthyotoxin would be destroyed or deactivated. The treatments ranged from pH 5.5 to pH 7.0 in 0.5-SU increments. Untreated water (control) had a pH of 8.3. The acidic pH levels were effective in reducing the density of viable P. parvum cells, and the percent reduction in density increased as the pH decreased. Reductions in density were 23.6% and 87.6 % for pH 6 and 5.5, respectively, 3 hours after treatment and 41.6% and 94%, respectively, 28 hours after treatment with hydrochloric acid. Sulfuric acid treatments reduced cell density by 38.3% and 61.7% for pH 6.5 and 6, respectively 1 hour after treatment and 35.8% and 82.3% 18 hours after treatment. A bioassay demonstrated that at pH 6 and 6.5, toxicity was reduced but not completely eliminated.
(This chapter is currently being updated and will return at a later date.)
CHAPTER 8: Efficacy of Nitrogen:Phosphorus Ratios for Controlling Prymnesium parvum in Fish Culture Ponds: Summary of 2002 Experiments
GERALD KURTEN AND DENNIS G. SMITH
The goal of this project was to determine if two specific concentrations and ratios of nitrogen and phosphorus would deter dominance and toxin production by Prymnesium parvum in warmwater fish culture ponds at the Dundee State Fish Hatchery. The initial objective was to establish phosphorus fertilization rates that would sustain 60 µg P/L in hatchery ponds and simultaneously determine if phosphorus fertilization alone would reduce P. parvum density and toxicity. An average phosphorus addition of 99 µg/L (82 – 137 µg/L) was required to achieve a target concentration of 60 µg/L. Pond temperatures averaged 13ºC and neither pond productivity nor P. parvum cell densities appeared to be affected by phosphorus fertilization alone. The second objective was to determine if nitrogen concentration of 300 µg/L and phosphorus concentration of 30 µg/L (N:P = 10:1; low-P) or nitrogen concentration of 300 µg/L and phosphorus concentration of 60 µg/L (N:P = 5:1; high-P) would reduce the incidence and toxicity of P. parvum and produce water quality conditions and food sources suitable for zooplanktivorous fish. The number of fish produced was significantly different between low-P and control ponds as well as between high-P and control ponds. Numbers of fish produced in high-P and low-P ponds were statistically similar but relatively more fish were produced in the low-P ponds. At temperatures typical of striped bass Morone saxatilis culture (22ºC), P. parvum cells appeared to be eliminated in ponds fertilized with high concentrations of phosphorus (92 µg/L).
DENNIS G. SMITH
The effects of ultraviolet (UV) radiation on Prymnesium parvum cells and ichthyotoxicity were investigated using water from Lake Diversion, Texas. Reservoir water was toxic to fish on three of four testing days and sublethal on the remaining day. P. parvum cells were present in the water throughout the study. The water flowed through the UV unit at 11.5-11.6 CFM (i.e., cubic feet per min). The radiation was emitted at a mean dose of 210 (range = 193- 220) mJ/cm2 and mean intensity of 91.5 (range = 84-96) mW/cm2. The radiation completely destroyed all P. parvum cells and reduced toxicity from lethal to sublethal levels or from a sublethal to undetectable level.
CHAPTER 10: Evaluation of an Ultrasonic Device to Control Golden Alga Prymnesium parvum in Fish Hatchery PondsTOM DORZAB
An ultrasonic device (i.e., Aquasonic Algae Controller) was evaluated to determine its efficacy at controlling Prymnesium parvum in hatchery ponds. This pilot study consisted of one pond with one Aquasonic Algae Controller (treatment) and two untreated ponds (control). Each 0.1-ha pond was stocked with five adult rainbow trout Oncorhynchus mykiss. Cell density P. parvum cell density was monitored in each pond for 21 days. The ultrasonic device appeared to be ineffective in reducing P. parvum cell density and had no discernable effect on survival of rainbow trout.
GREGORY M. SOUTHARD
Prymnesium parvum is an algal species responsible for toxic fish kills in Texas reservoirs and two freshwater fish hatcheries. The current Texas Parks and Wildlife Department (TPWD) method for identifying and estimating densities of P. parvum in water samples uses a compound light microscope, hemacytometer, and trained personnel adept at identifying this particular species among mixed algal communities. Repeated observations of P. parvum-infested water samples using epifluorescence microscopy suggest that P. parvum may yield distinct fluorescence emission pattern(s) compared to the other types of algae in mixed samples. This observation lead to an investigative effort regarding the feasibility of specialized microscopic techniques, flow cytometry, and other fluorescence-based applications that might facilitate P. parvum cell enumeration. The following report is an overview of that investigation.
DENNIS G. SMITH
This management plan was prepared as a guide to control the toxic alga Prymnesium parvum and its ichthyotoxin and eliminate, or at least minimized, its adverse impact on fish production. The plan includes monitoring presence and abundance of P. parvum and concentration of un-ionized ammonia nitrogen, and application of effective chemical treatments. Ammonium sulfate is applied at concentrations to raise the un-ionized ammonia nitrogen concentrations to 0.2-0.4 mg/L when water temperatures are 15ºC or higher, and copper sulfate (or Cutrine-Plus) is applied at 0.2-0.4 mg Cu2+/L when water temperatures are up to 15ºC. The selected target concentrations of un-ionized ammonia nitrogen and copper depend on the tolerance of the fish that would be exposed to the treatments.
DALE D. LYON, JAKE ISAAC, AND JOHN PARET
This Prymnesium parvum management plan was prepared to provide a systematic approach to controlling this toxin-producing alga to make fish production possible at the Possum Kingdom State Fish Hatchery. The essential facets of the plan are monitoring presence and density of P. parvum and un-ionized ammonia levels, and application of chemical treatments. Ammonium sulfate is applied at 10 mg/L or concentrations to raise the un-ionized ammonia concentration to 0.2-0.4 mg/L when water temperatures are 15ºC or higher and copper sulfate or Cutrine-Plus is applied at 0.75-1.0 mg Cu/L when water temperatures are up to 15ºC. The target concentration of un-ionized ammonia or copper depends on the fish species being cultured.