404 Final Fish Kills Flashcards
(22 cards)
Discuss 3 reasons it is important to investigate and diagnosis fish kill
- Indicator of environmental change
- Potential risk to humans
- May predict downstream events
T/F Fish kills can occur naturally
True
What fish symptoms, and environmental conditions are typically
associated with a winter kill (oxygen related)
-Little production of oxygen due to ice cover
-Lack of light reduces photosynthesis
-Biological oxygen demand (BOD) exceeds available oxygen
-Dissolved oxygen drops to anoxic levels until spring turnover
What fish symptoms, and environmental conditions are typically
associated with a summer kill (oxygen related)
-Caused by heat and dissolved oxygen depletion
-Algal toxins maybe involved
-Rapid decomposition of organic matter
-Associated with lakes with heavy algal blooms
Why might we see die offs of Walleye, Northern Pike, and other spring
spawners during the spring?
Crowding leads to disease and parasites transmission
Why might oxygen become limited in the winter and summer in a
stratified lake
Winter: Lack of mixing and ice cover
Summer: Oxygen level depletes through increase of decaying organic matter and eutrophication
Can an oxygen kill occur during fall or spring turnover? Why?
Yes lake turnover can deplete overall oxygen levels.
Can cause the water column to have temporarily low DO concentrations
Why might oxygen become limited after a big algal bloom?
-Algae consume oxygen at night
-Algal blooms block sunlight, impacting oxygen production
T/F toxin related kills are more gradual than oxygen related kills
False
T/F sudden changes in temperature can cause a fish kill
True
T/F fish are immune to algal toxins
False
T/F Algal toxins are more likely to peak during the night period
False
T/F Toxins tend to kill small fish, while DO depletion impacts large fish
True
Why might we see fish kills after a heavy rain?
Related to pesticide runoff into waterbodies
T/F Neonicotinoids is a type of herbicide that can kill fish and
other aquatic animals
False
T/F Fertilizers typically lead to an influx of Nitrogen and Ammonia
in the water
False
T/F Acid waste from mining can mobilize heavy metals into the
environment
True
Where do heavy metals typically accumulate in fish?
Liver and fat
T/F Septic systems can cause toxic levels of ammonia in
downstream waterbodies
True
Explain the difference between impingement and entrainment
-Impingement: stuck on screen
-Entrainment: Stuck inside of dam or structure
Branding” is a symptom of what type of fish kill?
Electro fishing
