WEEK 3 (Feb 6,7): Population ecology, emphasis on WI stream habitats (MK)
- DUE: Assignment 1: Ecology of your fish
- Population ecology handout
- Population ecology powerpoint
Collect all assignments, check that all have sent in emails
Lecture:
Lab – How to ID fish
Count scales, find the lateral line, look at mouth parts, use google, use WISC.FISH
Use key forward and backward, use other keys
What metrics do we want to measure? Field methods (Specific to Black Earth Creek Trip), t
Population Ecology and
Habitat Use
(Autecology)
Announcements and Such
• Assignment 1 due today!
• Black Earth next week: Come prepared to
leave at XX:XX
• Readings/Lab Handout on side wall
• Other?
What is Population Ecology?
• “Ecology is the study of the interactions
that determine the distribution and
abundance of organisms” Charles Krebs
• Population represents one “level” on which
to approach ecology
– Other levels???
• Population level interactions
• Demographics
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
– “Stock” = population subject to fisheries
management
Gene Pools
• Distinct gene pools = distinct biological
populations.
• Several may be present in one area
• Gel Electrophoresis used to estimate
differences in allele frequency
• Morphology also used to distinguish
populations
Population Density
• On rare occasions, density can be
measured directly
– Small enclosed systems
– Migration
• Usually, density is assessed from samples
– Eggs estimated with quadrats
– Pelagic larvae sampled with modified
plankton nets
– Juvenile and adult fish with nets, 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 = ???
Catch per Unit Effort
• Density is reduced by fishing and natural
mortality while it is increased by stocking
and recruitment.
• 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)
Population Change
Stocking
Natality
Immigration
DENSITY
Mortality
Angling
There are a number of
ways to measure growth
rate and mortality.
Emigration
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
Fish Distribution in Rivers
• Headwaters are colder, faster, and have
limited primary producers (Trout, Sculpin)
• Transitional zones are generally variable,
and contain a smattering of species
(Variable)
• Deposition zones are warm, slow, and
often times 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, usually behind some large substrate or
debris
– 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
Black Earth Creek Trip!
• What metrics to measure?
– Habitat
– Fish
– Other?
• Field Methods
• Taking field notes
Metrics!
– Habitat
•
•
•
•
•
•
•
•
•
Reach length
Width
Depths
Velocity
Substrate
Canopy cover
Land width
Buffer width
Undercut
• Fish
–
–
–
–
–
–
–
Length
Weight
Species
Number
Effort
Diet
Method of Sampling
Lets talk Field Methods
Minnow Traps
Fish
goes in!
Habitat Sampling
• Primarily observational (see handout)
• Depth: Meter stick 101
• Flow Velocity: Flow meter vs. Pine cone
Taking Field Notes