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

Nutrients (P and N) Large zooplankton Invertebrate Planktivore Vertebrate Planktivore

Nutrients (mg P/L) Lake Productivity

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 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 Population = ??? Sample 2 = 9 with 2 marked Sample 1 = 10 n 1 /N=m/n 2 Or N=n 1 n 2 /m n1n1 n2n2 N m n1n1

Population Density Density = fish/unit area Abundance = # fish in population CPUE can estimate density CPUA measures density directly

Population Change DENSITY Natality Emigration Mortality Immigration Stocking Angling There are a number of ways to measure growth rate and mortality.

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 Sample 1 = 20 Sample 2 = 10 Assume probability of capture is constant Then N = n 1 2 /(n 1 -n 2 ) Probability of capture = n 1 /N Probability of capture = n 2 /(N-n 1 ) n1n1 n2n2

Patterns of Mortality Eggs and larvae suffer the largest losses HATCH Recruit! 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

Density Dependence Population Density Rate of Change (per capita)

Density Dependence Stock (Parental Cohort) Recruitment

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 Largemouth bass Bluegill Green Sunfish Prey Weight (Relative) Temperature (Celsius)

Distribution in Lakes: Temperature C 4-20 C 4 C

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 Flowing Water Here be Floodwaters 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)

From Baltz et al. 1982

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 scales (Library Carp, Nerdus poindexterii) –Lateral line has 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 –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! Habitat Reach length Width Depths Velocity Substrate Canopy cover Land width Buffer width Undercut Fish Length Weight Species Number Sampling Effort Diet Method of Sampling Two teams everyone works on both teams!

How does habitat influence fish community?

Pool Riffle Run Undercut Bank Defining Geomorphic Stream Units 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

Electrofishing Workup Station 3 people 5 people Moving Block Nets 2 people Fish can be released down stream of electrofishing crew HOW TO SET UP

Stream habitat measurements

Flow Velocity Data Recorders- MOST IMPORTANT!!! 2 people 1 person Flagging transects 2 people Measure thalweg, depth, width 4 people

IBI= index of biotic integrity.