59. The most common cause of fish kills in Ohio is:
A. Pesticides which accidently enter the pond
B. Natural mortality
C. Suffocation due to a lack of oxygen
D. Runoff from barnyards, cropland, and septic tanks
60. An inversion or turnover may result when:
A. A strong wind occurs during late spring or early summer
B. A large rain creates an inflow
C. A rapid temperature change occurs
D. All of the above
61. Agricultural pesticides cause only a small percentage of fish kills. Which class of pesticides are considered most toxic to fish and other aquatic organisms?
A. Herbicides
B. Miticides
C. Fungicides
D. Insecticides
62. The cooler layer of water in the bottom of the pond has less potential to hold more oxygen because it is denser.
A. True
B. False
63. Which of the following would prevent oxygen depletion?
A. Using an aerator
B. Utilizing a good aquatic weed control program
C. Keeping portions of the ice free of snow in the winter
D. All of the above
64. Oxygen levels in a pond would be highest at:
A. Sunrise
B. Noon
C. Midday
D. Midnight
65. Cloudy, cool, or rainy weather can cause some algae scums to die.
A. True
B. False
66. Once a fish kill is in process, little can be done to stop it.
A. True
B. False
59. Correct Answer: C, OPM
Explanation: The most common cause of fish kills in Ohio is suffocation due to lack of oxygen.
60. Correct Answer: D, OPM
Explanation: A turnover results when a strong wind, rapid temperature change, or inflow of a large volume of cold water causes the upper layer of water to be replaced by the lower layer of oxygen -deficient water.
61. Correct Answer: D, OPM
Explanation: Agricultural pesticides, particularly insecticides, may be toxic to fish and other aquatic organisms if they enter a pond in aufficient quantities.
62. Correct Answer: B, OPM
Explanation: The bottom, cooler layer of water in the pond has the potential to hold more oxygen than the top layer because it is denser. However, the lack of photosynthesis and the decomposition of organic matter actually results in a lower level of dissolved oxygen compared to the top layer.
63. Correct Answer: D, ILL
Explanation: Using an aerator, controlling weeds so they don't decompose, and keeping snow off the ice in the winter are all ways to prevent oxygen depletion.
64. Correct Answer: B, ILL
Explanation: Plants cease photosynthesizing at night but continue to utilize oxygen for respiration. Thus, oxygen levels are lowest just before sunrise and highest at midday.
65. Correct Answer: A, ILL
Explanation: In some cases, cloudy, cool, or rainy weather can cause algae scums to die. The death and rapid decomposition of these algae can reduce dissolved oxygen content from 8 to 0 parts per million within 24 hours.
66. Correct Answer: A, ILL
Explanation: Once a fish kill is in progress, little can be done to stop it. Aeration should be provided, but sometimes even aeration cannot overcome the oxygen deficit.