Lesson 03: Egg Survival

Sturgeon Lesson Plan #3

Lesson Title:   Modeling Sturgeon Egg Survival Rates

Summary:

One of the greatest challenges for the survival of lake sturgeon populations is the survival of individuals during the egg period.  During the egg period, developing lake sturgeon are vulnerable to a host of potential predators that inhabit Great Lakes tributaries where sturgeon eggs are laid.  In this activity, students will analyze a data set, graph changes in a population growth, and explain influences that affect the growth of sturgeon egg populations.

Objectives:

Students will be able to graph changes in population growth of sturgeon eggs in the Black River.
Students will be able to explain the influence of aquatic exotic species on the survival of lake sturgeon in the Black River.
Students will be able to graph changes in population growth of sturgeon eggs in the Black River.
Students will be able to explain the influence of aquatic exotic species on the survival of lake sturgeon in the Black River.
Students will be able to model sampling procedures for collecting macroinvetebrates and sturgeon eggs in a river system. Students will be able to model sampling procedures for collecting macroinvetebrates and sturgeon eggs in a river system.

Background:

Lake sturgeon are the longest lived Great Lakes fish species and can attain ages up to 100 years old.  They can grow to over 8 feet and weigh up to 300 pounds.  Lake sturgeon have no scales but are covered by five rows of bony scutes on its back, sides, and stomach.  Lake sturgeon have a low reproductive rate and may not begin to spawn until they are 15-25 years old.  Male lake sturgeon reach sexual maturity at 15-20 years of age, and then spawn only every other year.  Once females mature at about 20-25 years of age, they spawn on average every four years.  These characteristics have prevented the recovery of the lake sturgeon, which has been designated as a protected species throughout much of their native range.  Lake sturgeon prefer large shallow lakes and rivers and the Great Lakes shorelines.  They feed by using their protruding mouth to suction up bottom dwelling organisms like crayfish and other crustaceans as well as insect larvae.

SPAWNING HABITS
Lake sturgeon are “Lithophilic spawners” which means during spawning, eggs are broadcast into rock crevices on the river bottom.  Once in contact with water, a sialic acid chemical reaction creates an adhesive property, which allows eggs to become ‘sticky’ and adhere to rocks during incubation.
Spawning adults neither build a nest for cover, nor care for the developing offspring during this life period.  Hatching may take 5-10 days dependent upon water temperature.  Typically, eggs that incubate in colder temperatures take several days longer to hatch than those incubated in warmer temperatures.
During the egg period, developing lake sturgeon are vulnerable to a host of potential predators that inhabit Great Lakes tributaries where sturgeon eggs are laid.  Recent studies have shown that predators such as Rusty Crayfish (O. rusticus), Round Goby (N. melanostomus) prey on lake sturgeon eggs.   Also, there are microbes and fungi that attack developing embryos and feed off of dead or decaying lake sturgeon eggs.
See “Morphology of Embryonic Larval Lake Sturgeon” pdf document for further information regarding embryonic development of sturgeon eggs.

Procedure:

PART #1
Day 1:

1. Begin with “Egg Period Ecology Lecture” and facilitate a discussion with students.  Ask students to take notes on key points of lecture slides.
2. Pass out copies of “Morphology of Embryonic and Larval Lake Sturgeon” and discuss sturgeon egg development with students.  Ask students to answer the following questions:
   1. How long (in days) after fertilization would you expect a sturgeon egg to develop before hatching?
   2. List two environmental factors you predict might alter the number of developmental days necessary for a sturgeon egg to hatch.
   3. In the Black River, what percent of sturgeon eggs do you think will survive long enough to hatch?

Day 2

1. Pass out a copy of “Spawning Site Transect Data” to each of the students.  Split students into groups of three and ask them to review the data set as a group.  Ask each group to answer the following questions:
   1. What is a stream’s velocity?
   2. Why would the depth of the stream be an important variable to record along with sturgeon egg numbers in the Black River?
   3. What is a macroinvetebrate?
   4. What do you think macroinvetebrates feed on?
2. Using Microsoft Excel, have students enter data and create 2 graphs:
   1. Graph #1
      1. Transect number compared to
         1. Stream velocity
         2. Sturgeon egg numbers
   2. Graph #2
      1. Transect number compared to
         1. Sturgeon egg numbers
         2. Macroinvetebrate numbers
3. Split students into groups of 3 and ask students analyze their graphs by responding to the following questions:
   1. Do you think there is a correlation between stream velocity and sturgeon egg numbers?
   2. Do you think there is a correlation between sturgeon egg numbers and macroinvetebrate numbers present?
   3. What piece of additional data would you like to compare sturgeon egg numbers to in the Black River (what other causes of sturgeon egg mortality do you think would be important to study)?
4. Ask each group to share their responses with the rest of the class.

PART #2
Teacher’s Note: Part #2 is intended for teachers who have access to a local stream or river and are able to complete a stream monitoring unit with their class.

1. Using Michigan Clean Water Corps “Streams_Powerpoint_Development_Tool.ppt” explore and discuss with students the importance of completing stream monitoring projects.
2. Teachers should use the “MiCorps Stream Monitoring Procedures.pdf” as a guide for establishing and setting up a stream monitoring program.

Teacher’s Note:
It is intended for your stream monitoring program to also provide an opportunity for students to model a sampling and data collection set similar to those used to collect sturgeon eggs on the Black River.  In order to accomplish this, teachers will need to place “sturgeon eggs” (airsoft biodegradable bb’s) in the stream sampling location prior to the students sampling.  Airsoft bb’s can be purchased from a number of different companies.  Teachers should spread the bb’s or “sturgeon eggs” out within the sampling location so that students will collect eggs along with their macroinvetebrate sampling.  Students should record sturgeon eggs along with their macroinvetebrate collection data.

Following your stream monitoring, students can reference their graphs that were developed in Part #1 of this activity and use it as a comparison with their collection data.

Extended Learning Opportunities:

Assessment and Evaluation:

See student sharing in Part #1 of this activity.