Lesson 07: Larval Drift

Sturgeon Lesson Plan #7

Lesson Title: Spawning of adults and dispersal of larval Lake Sturgeon in response to environmental cues


Adults have been captured over the period 2001-2012 using large trapezoid dip nets. Biological information including weight, length, location and date of spawning are recorded each year.  All adults are tagged using passive inducible transponder (PIT) tags and colored floy tags.   Lake Sturgeon larvae begin feeding and emerge from the substrate during evening hours (21:00 to 02:00) to disperse downstream in search nursery habitat.  Similar to peaks associated with adults spawning, drifting Lake Sturgeon also occurs in peaks and the entire drift period may last 30 to 40 nights.  Although it is not well documented, researchers believe that larval Lake Sturgeon inhabit natal rivers during this life period until they reach the first year or two of the juvenile period.  Mortality at this life period is significant due to the lack of habitat which provides cover for drifting larvae from predators.  Discharge is also a likely contributor to early mortality and may negatively affect year-class strength of lake sturgeon by either not providing enough water to, or pushing larvae beyond, critical nursery habitat areas.


Students will be able to develop questions based on data analysis from data provided.
Students will be able to write a hypothesis as a statement that answers a question or offers an explanation for an observed phenomenon.
Students will be able to make a prediction (the results if the hypothesis is supported) based on their hypothesis.
Students will be able to identify and explain data that; supports their hypothesis, refutes their hypothesis, is inconclusive regarding their hypothesis.

Subjects: Biology or Life Science

Grade Level(s): 7-12

Content Standards:

B1.1D Identify patterns in data and relate them to theoretical models.

B1.1E Describe a reason for a given conclusion using evidence from an investigation.

B1.1f Predict what would happen if the variables, methods, or timing of an investigation were changed.

B1.1h Design and conduct a systematic scientific investigation that tests a hypothesis. Draw conclusions from data presented in charts or tables.

Duration: 55 Min

Materials/What you Will Need:

Process of Science PP and/or additional background on the process of Science from the Understanding
Process of Science Worksheet
Data sets to be determined by the teacher.  Options: Adult and Larval Capture.xlsx


Video may require Adobe Flash Player

Larval and adult Lake Sturgeon (Acipenser fulvescens) have been captured over the period 2001-2012.  During annual census surveys, Michigan State University and Michigan Department of Natural Resources scientists capture adult Lake Sturgeon using large dip-nets.  These annual surveys begin when stream temperatures reach 11 degrees Celsius because this is approximately the temperature that initiates a long migration of Lake Sturgeon from the lake to their spawning grounds.  Lake sturgeon are “Lithophilic spawners” which means during spawning, eggs are broadcast on to rocks and in to crevices on the river bottom.  Once in contact with water, a sialic acid mediated chemical reaction hydrolyzes compounds on the egg surface creating an adhesive property, which allows eggs to become ‘sticky’ and adhere to rocks during incubation.   Spawning adults neither build a nest for egg cover, nor care for the developing offspring.  Hatching may take 5-12 days dependent upon water temperature.  Typically, eggs that incubate in colder temperatures take several days longer to hatch than those incubated in warmer temperatures.  As sturgeon hatch, the “free embryo” immediately burrows further into the substrate to find cover or refuge while utilizing yolk-sac reserves.   At this stage, lake sturgeon embryos are negatively phototaxic, which means that they avoid light sources by hiding in rocky stream substrate.  After their yolk-sac is absorbed, which usually takes up to 5 to 7 days depending upon temperature, the embryo begins exogenous feeding which is the onset of the larval period.  As Lake Sturgeon begin exogenous feeding, they emerge from the substrate as larvae and disperse at night, downstream to suitable larval rearing areas.


  1. Using a Larval and Adult Lake Sturgeon lecture, describe to students the process of capturing adult and larval Lake Sturgeon.  Describe the life history associated with Lake Sturgeon from the spawning to the larval period.
  2. Provide students with Excel spreadsheet “Adult and Larval Capture.xlsx”.  Discuss with the students the details associated with spawning and larval dispersal as well as the environmental cues that may trigger such biological processes.
  3. In groups of three or four, ask the students to discuss the data included in the Excel file and attempt to answer several questions.
    1. What environmental cues (discharge, temp, moon phase) may be a good predictor of Lake Sturgeon spawning (Indicated by number of captures)?
    2. What environmental cue (discharge, temp, moon phase) may be a good predictor of Lake Sturgeon larval or adult capture?
      1. Why might adult and larval sturgeon cue their activity around the phases of the moon?
    3. What patterns are visible when you compare the peaks in number of captures from the Adult Lake Sturgeon data versus those capture peaks graphed from the Larval Lake Sturgeon data?
  4. Give students a limited amount of time (10 minutes or less) to look at the teacher selected data and record questions they have on their process of science worksheet.
  5. Compile a list of questions on the whiteboard and give the students a few minutes to choose the question they’d like to pursue, while the teacher eliminates questions that time or the data will not support.
  6. Assign questions from the list to be answered by pairs of students or allow students to choose their own question and groups.
  7. Each group will need a process of science worksheet to guide the development of a hypothesis and prediction for their question.
  8. Allow time for students to analyze and compile data for their hypothesis.
  9. Students present their initial question, hypothesis, data, additional questions that arose and conclusion for peer review and discussion.  The teacher should keep a running list of the additional question that arose during the analysis.  This is a good reminder of the circular nature of science.

Extended Learning Opportunities:

Assessment and Evaluation:


Lesson Sources:

Sturgeon Research, Understanding Science Website

Data Sources:


Supporting Resources:

Background – www.understandingscience.org
Student Handouts – Process of Science Worksheet
Auer and Baker 2002. Duration of drift of larval lake sturgeon in the Sturgeon River, Michigan (PDF)