Lesson 06: Larval Behavior

Sturgeon Lesson Plan #6

Lesson Title: Effects of current and previous environmental variables on embryo sturgeon behavior


After hatch, embryo sturgeon immediately burrow into stream substrate to evade predators.  For a period of several days to weeks, embryo sturgeon will remain in the substrate until they have absorbed their yolk sac food reserves and begin to feed on natural food sources in the stream.  At this point, the larvae will emerge and begin to disperse from the spawning areas downstream.  The timing of larval emergence can be important because emergence exposes larvae to predation.  We have observed a considerable amount of variation in the timing of dispersal.  Larvae produced from eggs that developed and hatched at the same time may disperse many days apart.  What causes this variability?  You are being provided data to find out.  In the background and in the excel spreadsheet provided you will find instructions and text that describe the variables to consider.  Your task is to develop hypotheses based on the text.  Estimate time to emergence as your dependent variable and try and find associations between emergence time and stream variables (temperature, food, predators, density, substrate characteristics, etc).


  1. Develop hypotheses of stream variables that could predict when a larvae emergence from the substrate.
  2. Develop summaries of data and show in figures or tables and statistical terms, what the significant associations might be.
  3. Discuss your findings.  What is your best explanation for your results?  What other possible variables may be involved?  What other variables could have been measured?  How can the results in this experiment be generalized to other situations or to natural stream environment?

Subjects: Science, Math, Statistics

Grade Level(s): 9-12

Content Standards:

Duration: 2 days

Materials/What you Will Need:

Review materials in web section on embryos
Background pdf file with figures of experimental design.
Excel spreadsheet with data and summary of variables measured along with time to dispersal.


Video may require Adobe Flash Player

See associated background pdf file.


The data in the excel spreadsheet consist of observations of individual larvae and their dispersal times.  Time to dispersal is measured in days and in CTU (cumulative thermal units).  CTUs may be as informative as time (days) because development time in cold-blooded animals like fish is highly temperature dependent.

Use basic Excel analytical tools (see Lesson one for excellent background) to estimate mean times to emergence over all individuals and by different groups based on discrete variables (treatments).  Make graphs of associations between emergence times (days and CTUs) as a function of the other stream variables that are measured along with each fish.

Determine appropriate statistical methods for comparing means among groups of fish (e.g., from the different treatments or as a function of continuous variables (substrate size, temperature, etc).

Extended Learning Opportunities:

What other behaviors may be similarly variable in fish?  How might emergence at different times (earlier or later) be adaptable?  What constraints to emergence may exist?  Under what situations would emergence early or later than ‘typical’ be detrimental?

Assessment and Evaluation:

Breadth of thought into causal relationships between emergence time (dependent variable) and other variables?  Thoroughness of written presentation of summaries of data in support of conclusions.