Overview for Week 3
• Announcements and Lingering Questions
• Reading Quiz
• Reading Discussion
• Lecture on population ecology and fish assemblages in
streams
• Becker key lab activity
• Lecture: Background to Badger Mill Creek
• Free time to work on “make your own key” assignment
Announcements and Lingering Questions
• Field trip next week barring massive conspiracy
• Meet at 1pm, arrive back at 5pm
• Wader sizes
• You need: weather appropriate layers (hats, gloves, etc.), a
pencil, positive attitude
• Questions from week two:
• Brown, brook, and rainbow trout
• Gape limitation
• Sculpin fin typo
• Not responsible for distributions, only major trends
Announcements and Lingering Questions
• Assignments 1 and 2 due next week!
Reading Quiz
1. Name one of the authors of this
paper. (1pt)
2. If the population of piscivores
increases in a lake, what happens to
the density of phytoplankton? (2pts)
3. How does “time lag” apply to
trophic cascades? (1pt)
Reading Discussion
Vertebrate Planktivore
Invertebrate Planktivore
Large zooplankton
Nutrients (P and N)
Lake
Productivity
Nutrients (mg P/L)
How do you interpret this
figure?
What piece of information
does it convey?
How pervasive are trophic cascades in reality?
Can you think of other examples of trophic cascades?
Any examples of systems where they do not exist?
What is a model?
Population Ecology and
Habitat Use
(Autecology)
What is Population Ecology?
• Ecology is the study of the distribution and
abundance of living organisms and how
the distribution and abundance are
affected by interactions between the
organisms and their environment (Krebs).
• Population represents one “level” on which
to approach ecology
– Other levels???
What is a Population?
• “A population is a group of fish of the same
species that are alive in a defined area at
a given time” (Wootton 1990)
– Area can be arbitrary, physical, or genetic
• Give examples on chalkboard
– “Stock” = population subject to fisheries
management
Population Abundance
• On rare occasions, abundance can be
measured directly
– Small enclosed systems
– Migration
http://www.acoustics.org/press/149t
h/holmes.htm
Population Abundance
• Usually, abundance is assessed from
samples
– Eggs estimated with quadrats
– Pelagic larvae sampled with modified
plankton nets
– Juvenile and adult fish with nets, traps, hook
and line, or electrofishing
Mark/Recapture
n2
n1
m
Sample 1 = 10
Sample 2 = 9 with 2 marked
N
n1/N=m/n2
Or
N=n1n2/m
Population = ???
Population Density
Density = fish/unit area
Abundance = # fish in population
CPUE can estimate density
CPUA measures density directly
Population Change
Stocking
Natality
Immigration
DENSITY
Mortality
Angling
There are a number of
ways to measure growth
rate and mortality.
Emigration
Catch per Unit Effort
If two samples are taken with the same
fishing effort over a short time period,
mortality, stocking, and recruitment are
negligible
Catch per Unit Effort
n2
n1
Sample 1 = 20
Probability of capture = n1/N
Sample 2 = 10
Probability of capture = n2/(N-n1)
Assume probability of capture is constant
Then N = n12/(n1-n2)
Patterns of Mortality
• Eggs and larvae suffer the largest losses
HATCH
Egg
Larva Viable & Competent
Not Fertile
Starvation
Inviable
Eaten
Eaten
Other
2 cohorts each produce 10,000,000 eggs
90.5% survivorship/day yields 24,787 survivors at 60 days
95.1% survivorship/day yields 497,871 survivors at 60 days
Recruit!
Density Dependence
45
Death Rate
Birth Rate
40
35
30
Rate of
Change
(per capita)
25
20
15
10
5
0
0
5
10
Population Density
15
20
Density Dependence
60
Density Independent
Beverton-Holt
Ricker
50
40
Recruitment
30
20
10
0
0
5
10
Stock (Parental Cohort)
15
20
Fish Populations in Wisconsin
• Populations of fish are
distributed based primarily on:
– Type and amount of food available
– Temperature
– Oxygen demand
– Flow velocity
– Tolerance of pollution
Food and Thermal Niches
4
3.5
Largemouth bass
3
2.5
Prey Weight
(Relative)
2
1.5
1
Green Sunfish
0.5
Bluegill
0
25
26
27
28
29
30
31
Temperature (Celsius)
32
33
34
Distribution in Lakes: Temperature
20-30 C
4-20 C
4C
Distribution in Lakes: Temperature
• Habitat separated and competition
reduced by stratification
– Bass and Bluegill (eurytherms) in the
epilimnion
– Pike, Perch, and walley (mesotherms) in the
metalimnion
– Lake Trout (stenotherms) in the hypolimnion
• Competition in winter more intense
Movement
• Fishes may move about the water column
or around various depths for
– Foraging: shallow water cooler at night;
plankton moves about at night
– Spawning: nest sites often in shallows
Oxygen Demand
• Eutrophic lakes can have anoxic
hypolimnions in the summer
• Primarily affects coldwater species (i.e.
trout)
Lotic Systems
Here be Floodwaters
Flowing Water
Watershed Boundry
Distribution in Rivers
• Systems zone
longitudinally
– Chalk Talk
Fish Distribution in Rivers
• Headwaters are colder, faster, and have
limited primary producers (Trout, Sculpin)
• Transitional zones variable
(cold/cool/warm)
• Deposition zones are warm, slow, turbid
(from sediment load) and polluted (from
proximity to agriculture and urban areas)
(Carp, Centrachids)
100
90
80
Fish Abundance
70
60
Sculpin
50
Dace
40
30
20
10
0
1
2
3
4
5
6
7
8
9
Station (1=downstream)
From Baltz et al. 1982
10
11
12
Diversity Within A Reach
• Riffles (scuplins, stonerollers, darters – smaller
fish)
–
–
–
–
High flow velocity
Well oxygenated
Rocky substrate
Generally shallow
• Eddies/pools (trout, larger fish)
–
–
–
–
Low flow velocity
Also well oxygenated
More cover
Generally deep
Lab: Identifying Fish
• Dichotomous keys
– Will always present you with two choices, e.g.:
• Body noticeably covered with scales: Go to 2
• Scales not covering body or too small to be seen:
Go to 12
– Follow the choices until you have reached a
species!
– Becker’s “Fishes of Wisconsin” tome provides
our class with our keys
Things to keep in mind
• Some choices are obvious (i.e. jaws vs.
jawless).
• Many others require careful scrutiny:
– Lateral line has 45-48 scales (Library Carp,
Nerdus poindexterii)
– Lateral line has 50-56 scales (Northern
Shiteater, Carpus stinkostomus)
• Finding the lateral line, counting scales,
identifying mouth parts…struggling through
the keys now will save you strife later
Secondary Keys
• www.wiscfish.org
– Non-dichotomous: harder to narrow down to
species, easier to get to a few choices
– Actual photos, detailed attribute descriptions
help identify species
– Requires a computer, not good for field IDs
• Google.com
– There’s bound to be something there
Badger Mill Creek Field Trip
Goals
- Illustrate aspects of fish ecology in a Wisconsin trout
stream
- Collect fish and stream habitat data to use in research
paper
- Demonstrate various field methods for fish collection
- Experience the field portion of research
Quick Question: How many people have waders?
What’s Ecology -is the study of the distribution
and abundance of living organisms and how the
distribution and abundance are affected by
interactions between the organisms and their
environment (Krebs).
Metrics!
Fish
•
•
•
•
•
•
•
Length
Weight
Species
Number
Sampling Effort
Diet
Method of Sampling
Habitat
•
•
•
•
•
•
•
•
•
Reach length
Width
Depths
Velocity
Substrate
Canopy cover
Land width
Buffer width
Undercut
Two teams everyone works on both teams!
How does habitat influence fish
community?
Defining Geomorphic Stream Units
Undercut
Bank
Riffle
Pool
Run
Goal is to sample at least 6 different units!
Notice how they are positioned
ANODE (business end)
Use the current(s) to your advantage!!
Lead fish
right to
your
netters
Moving Block Nets
2 people
Electrofishing
5 people
Fish can be
released down
stream of
electrofishing
crew
Workup Station
3 people
HOW TO
SET UP
Stream habitat
measurements
Flagging transects
2 people
Flow Velocity
1 person
Measure
thalweg, depth,
width
4 people
Data Recorders- MOST IMPORTANT!!!
2 people
IBI= index
of biotic
integrity.