CFP Fish Habitat & Ecosystem Health 3 — Questions and Answers
Question 1: Which process describes the colonization of disturbed habitat patches by fish species, followed by gradual community change over time?
- Ecological resilience
- Biological succession (Correct answer)
- Trophic cascade
- Source-sink dynamics
Correct answer: Biological succession
Biological succession describes the sequential replacement of species assemblages over time as habitat conditions change following disturbance.
Question 2: In a lake experiencing cultural eutrophication, which management technique uses aluminum sulfate applied to the water column?
- Biomanipulation
- Alum treatment (Correct answer)
- Hypolimnetic aeration
- Drawdown
Correct answer: Alum treatment
Alum (aluminum sulfate) treatment precipitates phosphorus from the water column and forms a floc layer on sediments that binds internal phosphorus loads.
Question 3: What is the primary function of a two-stage ditch design in agricultural drainage systems?
- Increase drainage velocity to prevent flooding
- Create bench features that reduce bank erosion and improve aquatic habitat (Correct answer)
- Eliminate riparian vegetation to improve channel maintenance access
- Increase channel depth to lower the water table further
Correct answer: Create bench features that reduce bank erosion and improve aquatic habitat
Two-stage ditches include bench features at bankfull elevation that dissipate energy, reduce erosion, and provide habitat and nutrient processing functions.
Question 4: Which spawning habitat characteristic is described by the term 'hydraulic head' in redd assessment?
- The water depth directly above the redd
- The pressure differential driving upwelling through spawning gravel (Correct answer)
- The velocity of water measured at the redd crest
- The turbulence index above the gravel surface
Correct answer: The pressure differential driving upwelling through spawning gravel
Hydraulic head in redd assessment refers to the pressure gradient that drives hyporheic upwelling through spawning gravel, supplying oxygen to developing embryos.
Question 5: The 'thermal guild' classification of fish species is primarily based on:
- Preferred feeding microhabitat
- Optimal and lethal water temperature ranges (Correct answer)
- Spawning substrate preferences
- Tolerance to dissolved oxygen variation
Correct answer: Optimal and lethal water temperature ranges
Thermal guilds group fish by their optimal temperature ranges and thermal tolerances, classifying species as cold-, cool-, or warm-water species.
Question 6: Which natural disturbance regime is ecologically important for maintaining diverse prairie pothole wetland complexes used by fish and waterfowl?
- Periodic drought cycles that concentrate and refill wetland basins (Correct answer)
- Annual flooding from snowmelt that maintains permanent inundation
- Frequent wildfire that removes emergent vegetation
- Beaver dam construction that creates permanent deep pools
Correct answer: Periodic drought cycles that concentrate and refill wetland basins
Boom-bust wet-dry cycles in prairie potholes create diverse hydrological conditions that maintain species diversity and ecosystem productivity across the wetland complex.
Question 7: Electroshocking (electrofishing) gear output is typically standardized for habitat assessments using which metric?
- Total voltage applied per survey reach
- Catch per unit effort (CPUE) adjusted for habitat area or stream length (Correct answer)
- Number of passes per sampling station
- Wattage-seconds per liter of water sampled
Correct answer: Catch per unit effort (CPUE) adjusted for habitat area or stream length
CPUE standardized by stream length, area, or time allows meaningful comparisons of fish community assessments across sites and sampling events.
CFP Fish Habitat & Ecosystem Health 3
Which process describes the colonization of disturbed habitat patches by fish species, followed by gradual community change over time?