Copper Sulfate Toxicity to Various Fish: Role of Alkalinity/Hardness

Dave StrausHarry K. Dupree - Stuttgart National Aquaculture Research Center

Stuttgart, AR

2017 National Aquaculture Extension Conference

Our lab has done a lot of work with copper sulfate over the years.

Algae control

Snail control / trematodes

“ICH” / Whitespot

Egg fungus

Introduction

Introduction• Started working with copper sulfate when I started my career because it

was/is an inexpensive treatment for farmers.

• It is approved by the EPA as a general use material (algaecide, fungicide, insecticide, water treatment, molluscicide); it is not a restricted-use pesticide.

• Farmers had used it to control Ich on fish and fungus on fish eggs.

• It is the only economical product to treat ~20 acre ponds for Ich; the only FDA-approved compound to treat Ich is formalin.

• SNARC started a program in the mid-90s to gain FDA labels to:

• treat Ich on catfish in ponds

• control Saprolegniasis (fungus) on catfish eggs

• The only FDA-approved compounds for egg fungus control are formalin and hydrogen peroxide.

• Both are expensive and have human safety concerns/storage precautions.

• With most managers, $$ is the bottom line.

• Treating a catfish egg hatching trough (2016 prices):

• Hydrogen Peroxide (approved) - $0.89

• Formalin (approved) - $0.73

• Copper Sulfate (regulatory action deferred; allowed) - $0.02

• Eggs tested: channel catfish (10 ppm), hybrid striped bass (20 ppm), large-mouth bass (20 ppm), rainbow trout (10 ppm). Walleye?

Introduction

• Copper sulfate can be extremely toxic to fish under certain conditions.

• Typical water chemistry to measure:

• Alkalinity

• pH

• Hardness

• Dissolved Organic Carbon (can’t readily measure this)

• Treatment rate for Ich is alkalinity/100.

• Not recommended if alkalinities are below 50 ppm.

• Where did this come from??

• Temperature – no research, just observations (Drew Mitchell).

• Effectiveness limited below 45°F.

• When 45° - 50°F, effectiveness is questionable.

Introduction

• Earliest recorded use of copper sulfate was 1894 (for Ich; Mitchell 2001).

• 1933 – 1947, Frederick Forward Fish researched various fish health issues and included copper sulfate as a potential treatment.

• In the 1940s, researchers started associating toxicity of copper to water chemistry.

• In the late 1950s, most indications were that hardness was the key factor; but this might have been due to most of the research coming from Auburn University, where alkalinity and hardness were very similar (and very low).

• Fred P. Meyer

• 1960 – 1973 - Worked at the Stuttgart Lab.

• 1973 – 1990 - Director, National Fisheries Research Center, LaCrosse, WI.

Introduction

• Letter Fred Meyer to Billy Griffin.

• Fred recalled an informal meeting he was at in the late 1960’s to discuss standardizing copper sulfate treatment rates with water chemistry. Attendees: Thomas Welborn, Harry Bishop and several from Auburn University (Drs. Plumb, Rogers and Allison?).

• Not long after this meeting, extension pamphlets began to appear with the following table:

• MacMillan 1985 introduced the equation total alkalinity/100 = ppm CuSO4that is currently used.

• Need to find out more about where this came from!

Introduction

Alkalinity Copper sulfate<25 ppm Do not use50 ppm 0.5 ppm100 ppm 1.0 ppm

• There has been a lot of research on copper toxicity, but always in particular waters, not in standardized waters.

• Most of the older research, and even some current only report hardness.

• Our study determines 48 hr LC50 values in each of 5 reconstituted waters.

• More importantly to people in the field, we also determine the No Observed Effect Concentration (NOEC) and Lowest Observed Effect Concentration (LOEC).

• This information is a guideline for safe treatment rates.

• But, must be tailored to fit fish and site-specific water quality/chemistry.

Introduction

• 21 aquaria (5 gallon) with 10L of aerated water.

• 10 fish/aquaria, used 2 – 3” fingerlings.

• APHA Methods for 5 synthetic waters.

• Species of fish: bluegill, channel catfish, crappie, fathead minnow, golden shiner, goldfish, grass carp, hybrid striped bass, koi, large-mouth bass, rainbow trout, red-ear sunfish, striped bass, tilapia, walleye, white bass.

Methods

Water Type Hardness AlkalinityVery Soft 10-13 10-13Soft 40-48 30-35Moderately Hard 80-100 60-70Hard 160-180 110-120Very Hard 280-320 225-245

• 6 concentrations of CuSO4 and an un-treated control (3 reps).

• Treatments were randomized and CuSO4 solution added.

• Temperature and DO monitored daily.

• Fish observed for 48 hr; dead/moribund fish removed and recorded.

• LC50 values calculated by the Trimmed Spearman-Karber method.

• Why? Precision of the tests is most reproducible at the 50% level (straightest part of the dose-response curve).

Methods

• When high doses of copper sulfate are added to high alkalinity waters, a compound called tenorite (aka copper oxide) is formed.

• As expected, in some of our higher doses this was pretty severe.

Results

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.8 10 12 0.56 0.25 0.125Soft 7.4 30 44 2.83 2 1Moderately Hard 7.8 60 87 13.11 4 2Hard 8.1 120 185 70.70 64 32Very Hard 8.2 216 333 99.27 32 16

0

20

40

60

80

100

120

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Channel Catfish LC50 vs Alkalinity

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.7 11 12 0.41 0.50 0.25Soft 7.4 35 45 0.64 0.50 0.25Moderately Hard 7.7 55 80 0.72 0.50 0.25Hard 8.0 112 169 1.05 1.00 0.50Very Hard 8.4 217 335 1.52 0.50 0.25

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Golden Shiner LC50 vs Alkalinity

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.5 11 16 0.21 0.03125 0.016Soft 7.4 28 45 0.46 0.125 0.0625Moderately Hard 7.5 67 95 0.99 0.125 0.0625Hard 7.7 123 172 1.66 0.125 0.0625Very Hard 8.4 237 355 2.51 1.00 0.50

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Koi LC50 vs Alkalinity

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.6 11 11 3.65 4.0 2.0Soft 7.3 33 45 12.70 8.0 4.0Moderately Hard 7.6 69 95 34.30 32.0 16.0Hard 7.9 113 161 176.88 128.0 64.0Very Hard 8.3 241 318 322.54 256.0 128.0

0

50

100

150

200

250

300

350

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Largemouth Bass LC50 vs Alkalinity

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.6 10 11 0.07 0.016 0.008Soft 7.4 30 45 0.08 0.0625 0.03125Moderately Hard 7.8 60 90 0.06 0.0625 0.03125Hard 8.0 112 171 0.41 0.25 0.0125Very Hard 8.4 226 325 1.20 1.00 0.50

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Rainbow Trout LC50 vs Alkalinity

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.7 10 11 0.25 0.0625 0.03125Soft 7.6 30 39 0.42 0.25 0.125Moderately Hard 7.9 58 79 1.91 0.25 0.125Hard 8.1 117 154 2.3 4 2Very Hard ND ND ND ND ND ND

0.0

0.5

1.0

1.5

2.0

2.5

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Striped Bass LC50 vs Alkalinity

Results

Water pH Alkalinity Hardness LC50 (mg/L) LOEC (mg/L) NOEC (mg/L)Very Soft 6.5 10 10 0.17 0.03125 0.016Soft 7.2 28 42 1.04 0.125 0.0625Moderately Hard 7.3 58 81 1.45 1.00 0.50Hard 8.0 107 161 3.06 0.50 0.25Very Hard 8.1 220 283 1.18 0.25 0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

Alkalinity (mg/L)

Walleye LC50 vs Alkalinity

Results

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

0 50 100 150 200 250

LC50

Val

ue (m

g/L)

CuS

O4

Alkalinity (mg/L)

LC50 Values of 7 Species vs Alkalinity

RT

LB

CC

WE

KI

SB

GS

• Order of sensitivity to copper sulfate so far:

• Rainbow trout, koi, walleye, striped bass, channel catfish, largemouth bass.

• Channel catfish can tolerate 12.5X the recommended rate in very hard water and higher than recommended rates in all other waters except the Very Soft Synthetic, which remained at the recommended level.

• Striped bass tolerated ~ ½ the recommended disease rate based on alkalinity.

• Large-mouth bass tolerate 20 to 64X the recommended rate!

Discussion

• Still working on finishing other species.

• Interesting about largemouth bass tolerating such high concentrations.

• Thought we were missing something.

• Remembered an Aquaculture America presentation from KY State and looked it up to find our results were very similar to their results.

• They even showed that some of this tolerance of LMB gets passed to channel catfish when they are in the same water!

Conclusions

Peracetic Acid

Coming Soon

Questions?