Debate kit Grade 9 Science
Stock Trout or Plant Shade Along Tessleton Brook
A grade 9 science debate kit on whether a fictional county should spend its stream grant on stocking trout each spring or on shade trees and floodplain reconnection.
Objectives
- Students will explain how shade and floodplain connection affect stream temperature and dissolved oxygen.
- Students will compare a yearly stocking program with a long-term habitat project as competing solutions.
- Students will deliver a rebuttal supported by a named piece of evidence.
Vocabulary
- Floodplain
- A floodplain is the flat land next to a river that the river spills onto when it floods. Floodplains are natural storage areas that give floodwater a safe place to spread out.
- Dissolved oxygen
- Dissolved oxygen is the oxygen gas mixed into water that fish and other underwater animals breathe. Cold, moving water holds more oxygen than warm, still water.
Also: riparian, thermal refuge, stocking, biodiversity
Teacher overview
This kit is a two-team structured debate that runs across two class periods, with the first used for evidence study and the second for the rounds. A fictional county has one grant and two ways to spend it on the same stream, and both have real support among biologists and among the people who fish the stream. The debate asks students to weigh a benefit that arrives this spring against a benefit that arrives in fifteen years.
Resolution & Background
Resolution: "Thurlbeck County should spend its stream grant on stocking trout in Tessleton Brook each spring, rather than on planting streamside trees and reconnecting the brook to its floodplain."
Background: Tessleton Brook is a fictional stream that runs through pasture and small farms in a fictional county. A century ago the brook was straightened and its banks were cleared to the water's edge. Today most of the channel sits in open sun, and it is cut about four feet below the surrounding fields, so high water stays in the channel instead of spreading onto the floodplain.
Trout need cold water. Cold water also holds more dissolved oxygen than warm water, and most fish need dissolved oxygen above 5 mg/L. Shade from streamside trees keeps summer water temperatures down. A brook connected to its floodplain spreads out during storms, which slows the water and lets some of it soak in, and that stored water seeps back during dry weather.
Stocking means raising trout in a hatchery and releasing them into the stream, usually in spring. Stocked fish give anglers something to catch right away. Whether they survive the summer depends on how warm the stream gets.
The county has a fictional grant of $400,000. It can fund about ten years of spring stocking, or it can fund tree planting and floodplain work along roughly two miles of the brook. It cannot fund both.
Roles. Divide the class into two teams. The affirmative argues for stocking. The negative argues for habitat restoration. Each team names an opening speaker, two cross-examination speakers, and a closing speaker. Two students serve as judges and score with the rubric, and one keeps time. Suggested rounds are four minutes per opening, three minutes per cross-examination, and three minutes per closing.
Evidence File
Case for spring stocking:
- People use the stream now. A fictional county parks survey prepared for this debate reports that visits to the Tessleton Brook access points more than doubled in stocking years. Public use builds support for future stream funding. (Illustrative survey created for this debate.)
- Restoration is slow. A fictional restoration contractor testifies for this debate that newly planted trees take fifteen to twenty years to shade a channel this wide. Students in school today would be well into their working lives before the shade arrived. (Illustrative testimony created for this debate.)
- Part of the brook is already cold enough. A fictional temperature study for this debate found that the upper mile, fed by springs, stays cool through August, so trout stocked there can survive the summer. (Illustrative study created for this debate.)
- Stocking is flexible. A fictional fisheries manager testifies for this debate that the county can stop, expand, or move a stocking program from one year to the next, while a planted floodplain is a one-time commitment of the whole grant. (Illustrative testimony created for this debate.)
Case for habitat restoration:
- Warm water undoes stocking. In the same fictional temperature study, the lower two miles of the brook rise well above what trout tolerate by late July, and most stocked fish there do not survive to fall. Money spent stocking those reaches buys one season of fishing and nothing beyond it. (Illustrative study created for this debate.)
- Shade is the direct fix for the limiting problem. Cold water holds more oxygen than warm water, and most fish need dissolved oxygen above 5 mg/L, so lowering summer temperature raises the oxygen available to every fish in the brook. (Source: standard water-quality benchmark, EPA and USGS.)
- Floodplain reconnection helps in both directions. A fictional county engineer testifies for this debate that letting high water spread onto the floodplain would lower flood peaks at the road crossings, and that water stored in the floodplain seeps back to the brook during dry weeks. (Illustrative testimony created for this debate.)
- Restoration serves more than one species. A fictional stream survey for this debate counted more kinds of insects and native minnows in a shaded, reconnected reach upstream than in the open reach, which suggests the benefits reach the whole community rather than one stocked species. (Illustrative survey created for this debate.)
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Use of evidence | Argues from opinion without citing the file | Cites one point without explaining its relevance | Cites at least two points and explains how each supports the position | Cites several points, explains them, and separates illustrative material created for this debate from sourced benchmarks |
| Scientific reasoning | Does not connect temperature, oxygen, or habitat to fish survival | Mentions a connection but states it inaccurately | States the temperature and oxygen connection correctly and applies it to the brook | Traces the full chain from shade to temperature to oxygen to survival, and applies it to specific reaches of the brook |
| Rebuttal quality | Does not respond to the opposing case | Responds without naming evidence | Answers a specific opposing point with a named piece of evidence | Answers several opposing points and explains why its own evidence should count for more |
| Delivery and organization | Difficult to follow | Structure present but unclear transitions | Clear claim, evidence, and conclusion delivered within time | Clear structure, controlled timing, and direct engagement with the other team's strongest point |
Differentiation
Support
Provide a shortened evidence card carrying the two strongest points for the assigned side, each written as one sentence, plus a rebuttal frame: "The other team says ___, but our evidence shows ___." Allow these students to read from notes and to speak for two minutes rather than four.
Extension
Ask these students to design a split proposal that spends part of the fictional grant on each option, then defend a specific split with evidence from the file. They should state which reach of the brook they would stock, which reach they would plant, and what measurement would tell the county in five years whether the split worked.
ELL supports
Pre-teach "riparian," "floodplain," "stocking," and "dissolved oxygen" with a labeled drawing showing a shaded reach and an open reach of the same stream. Give a glossary card at each seat, and allow students to plan their opening statement in their first language before writing the final version in English.
Extensions
Have students write a short letter to the fictional county board naming the option they support, the single strongest piece of evidence for it, and one measurement the county should collect each summer to check whether the decision worked. Compare letters across the class and discuss how often students who disagreed still asked for the same measurement.