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Effects of simazine treatment on channel catfish and bluegill production in ponds
Aquaculture, 15 (1978) 345-352 0 Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
345
EFFECTS OF SIMAZINE TREATMENT ON CHANNEL CATFISH AND BLUEGILL PRODUCTION IN PONDS
CRAIG S. TUCKER and CLAUDE E. BOYD Department of Fisheries and Allied Aquacultures, University, Auburn, Ala. (U.S.A.) Research supported by U.S.A.I.D.
Agricultural Experiment
Station, Auburn
Contract 211-d
(Received 22 May 1973; revised 29 August 1978)
ABSTRACT Tucker, C.S. and Boyd, C.E., 1978. Effects of simazine treatment on channel catfish and bluegill production in ponds. Aquaculture, 15: 345-352. Application of 13.4 kg/ha of simazine to the bottom of channel catfish (Zctalurus punctatus) ponds before flooding resulted in an extended period of low dissolved oxygen, a 19% reduction (P < 0.01) in channel catfish yield, and poorer feed conversion by fish when compared to control ponds. A single application of 1.6 mg/l of simazine to the water of fertilized bluegill (Lepomis macrochirus) ponds also decreased dissolved oxygen. The 11% reduction in bluegill yield was not statistically significant (P > 0.05). Simazine treatment caused an initial reduction in macrophyte coverage in bluegill ponds, but macrophyte coverage increased as simazine concentrations in the pond water declined.
INTRODUCTION
Simazine is widely used for aquatic macrophyte control in fish ponds (Snow, 1964; Mauck, 1974). Results of a number of studies have led to the recommendation of one or more small applications of simazine (0.80 mg/l or less) to reduce phytoplankton growth throughout the growing season in fish ponds (Grigsby, 1958; Snow, 1963; Walker, 1964; Norton and Ellis, 1975). However, applications of simazine to channel catfish (Ictulurus punctatus) production ponds for the purpose of phytoplankton control resulted in extended periods of low dissolved oxygen and decreased fish yields (Tucker and Boyd, 1978). A possible alternative to periodic applications of simazine to pond water is a preflooding treatment of the pond bottom with 11.2 to 16.8 kg/ha of simazine. Snow (1964) points out several advantages to this method of herbicide application including effective rooted weed control, predictability of herbicidal activity and minimization of the possibility of oxygen depletion caused by decaying weeds or phytoplankton. One objective of the present study was to determine if a single preflooding treatment of simazine controlled algae in channel catfish ponds without resulting in a reduction in fish yields.
346
Ponds used to produce bluegill (Lepomis macrochirus) often develop dense mats of macroscopic, filamentous algae and rooted aquatic plants (Boyd, 1973). Excessive growth of these macrophytes competes with phytoplankton for nutrients (Boyd, 1973), and may restrict fishing or interfere with observation and harvest of fish in hatchery ponds (Snow, 1964). Simazine is used at a rate of 1.5 mg/l for control of certain filamentous algae in fish ponds (Mauck, 1974). Since the use of simazine at concentrations less than this resulted in decreased growth of catfish (Tucker and Boyd, 1978), another objective of the present study was to determine if bluegill production decreased following application of simazine to ponds at concentrations used to control filamentous algae. MATERIALS AND METHODS
Fourteen earthen ponds (0.04---0.06 ha) were used in the present study. Ponds were similar in design and morphometry to those described by Dobbins and Boyd (1976). Six ponds were stocked with 7400 fingerling channel catfish per ha on March 10, 1977. The average weight of individual catfish stocked was 18.5 g. Fish were fed daily at 3% of body weight with feeding rate adjusted periodically for weight gain. A total of 5596 kg/ha of feed was applied to each pond during the 209 day experimental period. Catfish were harvested and weighed on October 4,1977. Eight ponds were stocked with 5000 bluegill per ha on December 7, 1976. The average weight of individual bluegill stocked was 1.2 g. Bluegill ponds were fertilized 11 times during the season with 45 kg/ha per application of 20-20-5 fertilizer. Ponds were fertilized according to the schedule outlined by Boyd and Snow (1975). Fish were harvested and weighed November 14,1977. One day prior to filling with water, the bottoms of three of the six catfish ponds were treated with simazine at a rate of 13.4 kg/ha (16.8 kg/ha of of the 80% active ingredient preparation Aquazinem, Ciba-Geigy Corp., Greensboro, N.C.). The chemical was prepared as a suspension in water and applied evenly over the entire pond bottom. Three ponds remained untreated and served as controls. After filling completely with water, fish were stocked. At 0.5, 1, 2, 3, 4, 5, and 6 months after treatment, water samples were collected from each treated pond at a depth of 0.5 m with a Kemmerer water sampler. Samples from the three control ponds were cornposited into a single sample. Samples were sent to the Alabama State Pesticide Residue Laboratory for analysis of simazine by’ gas chromatography using an electron capture detector. Four of the eight bluegill ponds were treated on March 9, 1977, with 1.5 mg/l simazine (1.88 mg/l Aquazine 80 W). A thin slurry of the chemical was evenly dispersed over the pond surface. At 4, 8, 16, 32, 64, and 128 days after treatment water samples were collected and analyzed for simazine as above. Water samples were collected weekly from 14 ponds with a 90-cm column
341
sampler (Boyd, 1973) for determination of chlorophyll a (Golterman and Clymo, 1969). Dissolved oxygen concentrations were determined every 3rd day during the growing season with a polarographic oxygen meter. Readings were taken between 08.00 and 09.00 h at a depth of 10 cm. The percentages of the pond bottoms covered by macrophytes were established twice a month between March and September. Weed cover was determined visually or indirectly in deeper water with the aid of a garden rake (Dobbins and Boyd, 1976). RESULTS
AND DISCUSSION
Catfish ponds In catfish ponds where pond bottoms were treated prior to flooding the concentration of simazine in the water remained above 0.2 mg/l for more than 4 months (Fig.1). This prolonged persistence resulted in a lower average
Fig.1. Average concentrations of simazine in the water of three catfish ponds that received a preflooding application of 13.4 kg/ha simazine.
chlorophyll a concentration in treated ponds (P < 0.1) and the magnitude of chlorophyll a values were lower in treated ponds than control ponds throughout the growing season (Fig.2). The average percentage of pond bottoms covered by macrophytes was less (P < 0.05) in treated ponds (Table I). Two control ponds had considerable proportions of their bottoms covered by a Chum species, but by mid-July both ponds were free of macrophytes. The above results are in agreement with those of Snow (1964) who found the preflooding simazine treatment to be an effective weed management procedure in catfish ponds. As found in a previous study (Tucker and Boyd, 1978), use of simazine in catfish ponds resulted in an extended period of decreased concentrations of dissolved oxygen when compared to those in control ponds (Fig.3). The yield of catfish from treated ponds was 19% less (P < 0.01) than that from control ponds (Table II). Feed conversion efficiency of fish from treated ponds was poorer (P < 0.01) than the controls. Tucker and Boyd (1978) discussed the possible causes of decreased catfish growth in ponds treated
348
TABLE I Average percentage of pond bottoms covered by macrophytes in simazine treated and untreated control ponds. Each value is the average of estimations in three ponds on each date. Catfish ponds were treated on March 3 with 13.4 kg/ha simazine applied to pond bottoms prior to flooding. Bluegill ponds were treated with 1.5 mg/l of simazine applied to the water on March 9 Date
Average percent of macrophyte Catfish ponds Control
8 15 5 5 21 12 28 6 13 4 30 15 30
March March April May May June June July July August August September September
0,
, MAR
0
0 0 0
I
APRIL
_
0 0 0 0 0
5 0 0 0 0
I
MAY
Bluegill ponds
Treated
10 5 10 15 10 15 5 5 0 0 5 0
Control
Treated
40 40 65 70 70 75 75 55 55 50 65 60 65
100 100 25 20 15 20 25 30 45 45 50 40 55
I
I
JUNE
infestation
JULY
t
AUGUST
SEPT
Fig.2. Chlorophyll a concentrations in control and preflooding simazine treated catfish ponds. Simazine was applied at a rate of 13.4 kg/ha. Each point represents the average of three replicates.
with simazine and suggested that exposure to prolonged periods of lowered dissolved oxygen concentrations was possibly responsible. The fact that dissolved oxygen concentrations were depressed throughout the growing season in the previous and present study indicates that this may be at least partly responsible for the poorer growth observed in both studies. However, the possibility of chronic simazine toxicity cannot be ignored.
349
GIHA:INE
0,
, MAR
W’REFLOODING)
1
MAY
APRIL
JUNE
v
I
JULY
AUGUST
8
SEPT
Fig.3. Percentage saturation values for dissolved oxygen in control and preflooding simazine treated ponds. Simazine was applied at a rate of 13.4 kg/ha. Each value represents the average of three replicates. TABLE II Yield of catfish and bluegill and feed conversion efficiency for catfish in control and simazine treated ponds. Each value represents the average ?: one standard deviation for three ponds Experiment
Treatment
Yield (kg/ha)
Feed conversion efficiency
Control Simazine
3495 f 68 2832 + 163
1.60 ?: 0.03 1.97 f 0.12
Catfish ponds
Bluegill ponds Control Simazine
BLUEGILL
192 f 171 f
49 22
PONDS
In bluegill ponds treated by adding 1.5 mg/l simazine to the water, the concentration of simazine quickly declined with less than 0.3 mg/l remaining 2 months after application (Fig.4). The half-life of simazine in this study was 18.5 days, approximately the same rate of dissipation found by Tucker and Boyd (1978) and Sutton et al. (1966). Average chlorophyll a concentration did not differ (P > 0.1) in treated and control ponds but the magnitude of chlorophyll a concentrations was generally lower in treated ponds during the growing season. All treated ponds were infested primary with species of Spirogyra and Rhizoclonium before simazine was added. Treatment soon reduced macrophyte coverage to less than 20% in all treated ponds (Table I). By late July, simazine concentrations had decreased to less than 0.1 mg/l and
350
0
4
S
16 DAY.3
32
64
128
Fig.4. Average concentration of simazine in water of three fertilized bluegill ponds. On day 0, ponds were treated with 1.50 mg/l simazine.
species of Spirogyra, Rhizoclonium and Pithophora reinfested treated ponds and macrophytes spread to cover 40 to 60% of the pond bottoms. These levels of infestation were similar to those in untreated ponds. Since certain filamentous green algae are less sensitive to simazine than many planktonic algae (Norton and Ellis, 1975), the occurrence of these forms several months after treatment is not surprising. Walker (1964) also found that filamentous algae such as Spirogyra and Pithophora were the first plants to recolonize ponds previously treated with simazine. Dissolved oxygen concentrations in bluegill ponds decreased rapidly following application of simazine (Fig.6). Within 2 months, concentrations had increased to levels comparable to those in control ponds. The average yield of bluegills from simazine treated ponds was 11% less than from controls (Table II), but means did not differ (P > 0.1). Snow (1964) and Gilderhaus (1964) also noted decreased bluegill production in Simazine treated waters, although in neither case was the decrease significant. 5or
0
,
I
WAR
API?
MAY
JUNE
J”LI
A”0
SEPT
Fig.5. Concentrations of chlorophyll a in control and simazine treated bluegill ponds. Simazine was added at a rate of 1.50 mg/l on March 9, 1977. Each point is the average of three replicates.
351
0
,
MAR
4
APR
MAY
JUNE
JULY
AU0
SEPT
Fig.6. Percentage saturation values for dissolved oxygen in control and slmazine treated bluegill ponds. On March 9, 1977, 1.50 mg/l of simazine was added to treated ponds. Each point represents the average of three replicates.
The results of this and a previous study (Tucker and Boyd, 1978) indicate that,while simazine is a powerful algicide, its use in catfish ponds stocked and managed for maximum production is accompanied by a decrease in yield of up to 20%. This applies whether simazine is added to the pond water or to the pond bottom prior to flooding. Bluegill production was not reduced as much as catfish production by treatment with simazine. However, the single application of simazine to the water of bluegill ponds did not result in season-long control of macrophytes. To affect weed control throughout the growing season, reapplication of simazine would have been necessary which may have had a more profound effect on fish yield. REFERENCES Boyd, C.E., 1973. Summer algal communities and primary productivity in fish ponds. Hydrobiologia, 40: 357-390. Boyd, C.E. and Snow, J.R., 1975. Fertilizing Farm Fish Ponds. Auburn Univ. Agric. Exp. Sta., Leaflet 88, 6 pp. Dobbins, D.A. and Boyd, C.E., 1976. Phosphorus and potassium fertilization of sunfish ponds. Trans. Am. Fish. Sot., 105: 536-540. Gilderhaus, P.A., 1969. Some Effects of Long Term Exposure to Simazine on Goldfish, Bluegills and Aquatic Invertebrates. Research Report, U.S. Department of the Interior Bureau of Sport Fisheries and Wildlife, 16 pp. Golterman, H.L. and Clymo, R.S., 1969. Methods for Chemical Analysis of Freshwaters. IBP Handbook No. 8. Blackwell Sci. Publ., Oxford, 172 pp. Grigsby, B.H., 1958. Response of certain unicellular green algae to several herbicides. Proc. Northcentral Weed Conf., 19: 29-34. Mauck, W.L., 1974. A review of the literature on the use of simazine in Fisheries. U.S. Fish. Wild. Serv. Rep. FWS-LR-74-16, 46 pp. Norton, J. and Ellis, J., 1975. Management of Aquatic Vegetation with Simazine. CibaGeigy Corp., Greensboro, N.C., 6 pp.
352
Snow, J.R., 1963. Simazine as an algicide for bass ponds. Prog. Fish Cult., 25: 34-36. Snow, J.R., 1964. Simazine as a preflooding treatment for weed control in hatchery ponds. Proc. Annu. Conf. Southeast Assoc. Game Fish Comm., 18: 441-447. Sutton, D.L., Evrard, T.O. and Bingham, S.W., 1966. The effects of repeated treatments of simazine on certain aquatic plants and residue in water. Proc. NE Weed Control Conf., 20: 464-468. Tucker, C.S. and Boyd, C.E., 1978. Consequences of periodic applications of copper sulfate and simazine for phytoplankton control in catfish ponds. Trans. Am. Fish. Sot., 10 107: 316-320. Walker, C.R., 1964, Simazine and other S-triazine compounds as aquatic herbicides in fish habitats. Weeds, 12: 134-139.
345
EFFECTS OF SIMAZINE TREATMENT ON CHANNEL CATFISH AND BLUEGILL PRODUCTION IN PONDS
CRAIG S. TUCKER and CLAUDE E. BOYD Department of Fisheries and Allied Aquacultures, University, Auburn, Ala. (U.S.A.) Research supported by U.S.A.I.D.
Agricultural Experiment
Station, Auburn
Contract 211-d
(Received 22 May 1973; revised 29 August 1978)
ABSTRACT Tucker, C.S. and Boyd, C.E., 1978. Effects of simazine treatment on channel catfish and bluegill production in ponds. Aquaculture, 15: 345-352. Application of 13.4 kg/ha of simazine to the bottom of channel catfish (Zctalurus punctatus) ponds before flooding resulted in an extended period of low dissolved oxygen, a 19% reduction (P < 0.01) in channel catfish yield, and poorer feed conversion by fish when compared to control ponds. A single application of 1.6 mg/l of simazine to the water of fertilized bluegill (Lepomis macrochirus) ponds also decreased dissolved oxygen. The 11% reduction in bluegill yield was not statistically significant (P > 0.05). Simazine treatment caused an initial reduction in macrophyte coverage in bluegill ponds, but macrophyte coverage increased as simazine concentrations in the pond water declined.
INTRODUCTION
Simazine is widely used for aquatic macrophyte control in fish ponds (Snow, 1964; Mauck, 1974). Results of a number of studies have led to the recommendation of one or more small applications of simazine (0.80 mg/l or less) to reduce phytoplankton growth throughout the growing season in fish ponds (Grigsby, 1958; Snow, 1963; Walker, 1964; Norton and Ellis, 1975). However, applications of simazine to channel catfish (Ictulurus punctatus) production ponds for the purpose of phytoplankton control resulted in extended periods of low dissolved oxygen and decreased fish yields (Tucker and Boyd, 1978). A possible alternative to periodic applications of simazine to pond water is a preflooding treatment of the pond bottom with 11.2 to 16.8 kg/ha of simazine. Snow (1964) points out several advantages to this method of herbicide application including effective rooted weed control, predictability of herbicidal activity and minimization of the possibility of oxygen depletion caused by decaying weeds or phytoplankton. One objective of the present study was to determine if a single preflooding treatment of simazine controlled algae in channel catfish ponds without resulting in a reduction in fish yields.
346
Ponds used to produce bluegill (Lepomis macrochirus) often develop dense mats of macroscopic, filamentous algae and rooted aquatic plants (Boyd, 1973). Excessive growth of these macrophytes competes with phytoplankton for nutrients (Boyd, 1973), and may restrict fishing or interfere with observation and harvest of fish in hatchery ponds (Snow, 1964). Simazine is used at a rate of 1.5 mg/l for control of certain filamentous algae in fish ponds (Mauck, 1974). Since the use of simazine at concentrations less than this resulted in decreased growth of catfish (Tucker and Boyd, 1978), another objective of the present study was to determine if bluegill production decreased following application of simazine to ponds at concentrations used to control filamentous algae. MATERIALS AND METHODS
Fourteen earthen ponds (0.04---0.06 ha) were used in the present study. Ponds were similar in design and morphometry to those described by Dobbins and Boyd (1976). Six ponds were stocked with 7400 fingerling channel catfish per ha on March 10, 1977. The average weight of individual catfish stocked was 18.5 g. Fish were fed daily at 3% of body weight with feeding rate adjusted periodically for weight gain. A total of 5596 kg/ha of feed was applied to each pond during the 209 day experimental period. Catfish were harvested and weighed on October 4,1977. Eight ponds were stocked with 5000 bluegill per ha on December 7, 1976. The average weight of individual bluegill stocked was 1.2 g. Bluegill ponds were fertilized 11 times during the season with 45 kg/ha per application of 20-20-5 fertilizer. Ponds were fertilized according to the schedule outlined by Boyd and Snow (1975). Fish were harvested and weighed November 14,1977. One day prior to filling with water, the bottoms of three of the six catfish ponds were treated with simazine at a rate of 13.4 kg/ha (16.8 kg/ha of of the 80% active ingredient preparation Aquazinem, Ciba-Geigy Corp., Greensboro, N.C.). The chemical was prepared as a suspension in water and applied evenly over the entire pond bottom. Three ponds remained untreated and served as controls. After filling completely with water, fish were stocked. At 0.5, 1, 2, 3, 4, 5, and 6 months after treatment, water samples were collected from each treated pond at a depth of 0.5 m with a Kemmerer water sampler. Samples from the three control ponds were cornposited into a single sample. Samples were sent to the Alabama State Pesticide Residue Laboratory for analysis of simazine by’ gas chromatography using an electron capture detector. Four of the eight bluegill ponds were treated on March 9, 1977, with 1.5 mg/l simazine (1.88 mg/l Aquazine 80 W). A thin slurry of the chemical was evenly dispersed over the pond surface. At 4, 8, 16, 32, 64, and 128 days after treatment water samples were collected and analyzed for simazine as above. Water samples were collected weekly from 14 ponds with a 90-cm column
341
sampler (Boyd, 1973) for determination of chlorophyll a (Golterman and Clymo, 1969). Dissolved oxygen concentrations were determined every 3rd day during the growing season with a polarographic oxygen meter. Readings were taken between 08.00 and 09.00 h at a depth of 10 cm. The percentages of the pond bottoms covered by macrophytes were established twice a month between March and September. Weed cover was determined visually or indirectly in deeper water with the aid of a garden rake (Dobbins and Boyd, 1976). RESULTS
AND DISCUSSION
Catfish ponds In catfish ponds where pond bottoms were treated prior to flooding the concentration of simazine in the water remained above 0.2 mg/l for more than 4 months (Fig.1). This prolonged persistence resulted in a lower average
Fig.1. Average concentrations of simazine in the water of three catfish ponds that received a preflooding application of 13.4 kg/ha simazine.
chlorophyll a concentration in treated ponds (P < 0.1) and the magnitude of chlorophyll a values were lower in treated ponds than control ponds throughout the growing season (Fig.2). The average percentage of pond bottoms covered by macrophytes was less (P < 0.05) in treated ponds (Table I). Two control ponds had considerable proportions of their bottoms covered by a Chum species, but by mid-July both ponds were free of macrophytes. The above results are in agreement with those of Snow (1964) who found the preflooding simazine treatment to be an effective weed management procedure in catfish ponds. As found in a previous study (Tucker and Boyd, 1978), use of simazine in catfish ponds resulted in an extended period of decreased concentrations of dissolved oxygen when compared to those in control ponds (Fig.3). The yield of catfish from treated ponds was 19% less (P < 0.01) than that from control ponds (Table II). Feed conversion efficiency of fish from treated ponds was poorer (P < 0.01) than the controls. Tucker and Boyd (1978) discussed the possible causes of decreased catfish growth in ponds treated
348
TABLE I Average percentage of pond bottoms covered by macrophytes in simazine treated and untreated control ponds. Each value is the average of estimations in three ponds on each date. Catfish ponds were treated on March 3 with 13.4 kg/ha simazine applied to pond bottoms prior to flooding. Bluegill ponds were treated with 1.5 mg/l of simazine applied to the water on March 9 Date
Average percent of macrophyte Catfish ponds Control
8 15 5 5 21 12 28 6 13 4 30 15 30
March March April May May June June July July August August September September
0,
, MAR
0
0 0 0
I
APRIL
_
0 0 0 0 0
5 0 0 0 0
I
MAY
Bluegill ponds
Treated
10 5 10 15 10 15 5 5 0 0 5 0
Control
Treated
40 40 65 70 70 75 75 55 55 50 65 60 65
100 100 25 20 15 20 25 30 45 45 50 40 55
I
I
JUNE
infestation
JULY
t
AUGUST
SEPT
Fig.2. Chlorophyll a concentrations in control and preflooding simazine treated catfish ponds. Simazine was applied at a rate of 13.4 kg/ha. Each point represents the average of three replicates.
with simazine and suggested that exposure to prolonged periods of lowered dissolved oxygen concentrations was possibly responsible. The fact that dissolved oxygen concentrations were depressed throughout the growing season in the previous and present study indicates that this may be at least partly responsible for the poorer growth observed in both studies. However, the possibility of chronic simazine toxicity cannot be ignored.
349
GIHA:INE
0,
, MAR
W’REFLOODING)
1
MAY
APRIL
JUNE
v
I
JULY
AUGUST
8
SEPT
Fig.3. Percentage saturation values for dissolved oxygen in control and preflooding simazine treated ponds. Simazine was applied at a rate of 13.4 kg/ha. Each value represents the average of three replicates. TABLE II Yield of catfish and bluegill and feed conversion efficiency for catfish in control and simazine treated ponds. Each value represents the average ?: one standard deviation for three ponds Experiment
Treatment
Yield (kg/ha)
Feed conversion efficiency
Control Simazine
3495 f 68 2832 + 163
1.60 ?: 0.03 1.97 f 0.12
Catfish ponds
Bluegill ponds Control Simazine
BLUEGILL
192 f 171 f
49 22
PONDS
In bluegill ponds treated by adding 1.5 mg/l simazine to the water, the concentration of simazine quickly declined with less than 0.3 mg/l remaining 2 months after application (Fig.4). The half-life of simazine in this study was 18.5 days, approximately the same rate of dissipation found by Tucker and Boyd (1978) and Sutton et al. (1966). Average chlorophyll a concentration did not differ (P > 0.1) in treated and control ponds but the magnitude of chlorophyll a concentrations was generally lower in treated ponds during the growing season. All treated ponds were infested primary with species of Spirogyra and Rhizoclonium before simazine was added. Treatment soon reduced macrophyte coverage to less than 20% in all treated ponds (Table I). By late July, simazine concentrations had decreased to less than 0.1 mg/l and
350
0
4
S
16 DAY.3
32
64
128
Fig.4. Average concentration of simazine in water of three fertilized bluegill ponds. On day 0, ponds were treated with 1.50 mg/l simazine.
species of Spirogyra, Rhizoclonium and Pithophora reinfested treated ponds and macrophytes spread to cover 40 to 60% of the pond bottoms. These levels of infestation were similar to those in untreated ponds. Since certain filamentous green algae are less sensitive to simazine than many planktonic algae (Norton and Ellis, 1975), the occurrence of these forms several months after treatment is not surprising. Walker (1964) also found that filamentous algae such as Spirogyra and Pithophora were the first plants to recolonize ponds previously treated with simazine. Dissolved oxygen concentrations in bluegill ponds decreased rapidly following application of simazine (Fig.6). Within 2 months, concentrations had increased to levels comparable to those in control ponds. The average yield of bluegills from simazine treated ponds was 11% less than from controls (Table II), but means did not differ (P > 0.1). Snow (1964) and Gilderhaus (1964) also noted decreased bluegill production in Simazine treated waters, although in neither case was the decrease significant. 5or
0
,
I
WAR
API?
MAY
JUNE
J”LI
A”0
SEPT
Fig.5. Concentrations of chlorophyll a in control and simazine treated bluegill ponds. Simazine was added at a rate of 1.50 mg/l on March 9, 1977. Each point is the average of three replicates.
351
0
,
MAR
4
APR
MAY
JUNE
JULY
AU0
SEPT
Fig.6. Percentage saturation values for dissolved oxygen in control and slmazine treated bluegill ponds. On March 9, 1977, 1.50 mg/l of simazine was added to treated ponds. Each point represents the average of three replicates.
The results of this and a previous study (Tucker and Boyd, 1978) indicate that,while simazine is a powerful algicide, its use in catfish ponds stocked and managed for maximum production is accompanied by a decrease in yield of up to 20%. This applies whether simazine is added to the pond water or to the pond bottom prior to flooding. Bluegill production was not reduced as much as catfish production by treatment with simazine. However, the single application of simazine to the water of bluegill ponds did not result in season-long control of macrophytes. To affect weed control throughout the growing season, reapplication of simazine would have been necessary which may have had a more profound effect on fish yield. REFERENCES Boyd, C.E., 1973. Summer algal communities and primary productivity in fish ponds. Hydrobiologia, 40: 357-390. Boyd, C.E. and Snow, J.R., 1975. Fertilizing Farm Fish Ponds. Auburn Univ. Agric. Exp. Sta., Leaflet 88, 6 pp. Dobbins, D.A. and Boyd, C.E., 1976. Phosphorus and potassium fertilization of sunfish ponds. Trans. Am. Fish. Sot., 105: 536-540. Gilderhaus, P.A., 1969. Some Effects of Long Term Exposure to Simazine on Goldfish, Bluegills and Aquatic Invertebrates. Research Report, U.S. Department of the Interior Bureau of Sport Fisheries and Wildlife, 16 pp. Golterman, H.L. and Clymo, R.S., 1969. Methods for Chemical Analysis of Freshwaters. IBP Handbook No. 8. Blackwell Sci. Publ., Oxford, 172 pp. Grigsby, B.H., 1958. Response of certain unicellular green algae to several herbicides. Proc. Northcentral Weed Conf., 19: 29-34. Mauck, W.L., 1974. A review of the literature on the use of simazine in Fisheries. U.S. Fish. Wild. Serv. Rep. FWS-LR-74-16, 46 pp. Norton, J. and Ellis, J., 1975. Management of Aquatic Vegetation with Simazine. CibaGeigy Corp., Greensboro, N.C., 6 pp.
352
Snow, J.R., 1963. Simazine as an algicide for bass ponds. Prog. Fish Cult., 25: 34-36. Snow, J.R., 1964. Simazine as a preflooding treatment for weed control in hatchery ponds. Proc. Annu. Conf. Southeast Assoc. Game Fish Comm., 18: 441-447. Sutton, D.L., Evrard, T.O. and Bingham, S.W., 1966. The effects of repeated treatments of simazine on certain aquatic plants and residue in water. Proc. NE Weed Control Conf., 20: 464-468. Tucker, C.S. and Boyd, C.E., 1978. Consequences of periodic applications of copper sulfate and simazine for phytoplankton control in catfish ponds. Trans. Am. Fish. Sot., 10 107: 316-320. Walker, C.R., 1964, Simazine and other S-triazine compounds as aquatic herbicides in fish habitats. Weeds, 12: 134-139.