Here a Fish  There a Fish - Deep Dive


Deep Dive Research Question: How does the diversity of nearshore fish populations vary along the Poquonnock River?

Part A: Read the background information

Biodiversity is a measure of the variety of living organisms present in a particular habitat.  There are many factors that influence biodiversity, but many habitats with high biodiversity share one or more of the following characteristics:

  • Abundant resources (resources can include food, space, etc)

  • Complex food webs

  • A variety of ecological roles/niches

  • Large populations

The simplest and most common way to measure biodiversity is to measure species richness: count the number of species present in the habitat.  The more species are present, the higher the biodiversity!  However, species richness does not always capture everything about biodiversity.  Consider the two communities illustrated below: 

In your opinion, which of these communities looks more diverse?

Each of the communities has a species richness of three (silversides, cunners, and pipefish), but they are clearly not the same!  Community 1 has an even mix of species, but Community 2 is almost entirely made up of silversides.  Scientists have developed some alternative measures of biodiversity that we can use in this situation, that take into account both species richness AND the distribution of those species. 

The biodiversity measure we will use today is one of the most common measures used by scientists, known as the Shannon Index.  The formula for the Shannon index is included below - you may use this formula to calculate it, or you may use an online calculator (see link below in the data section).  The higher the Shannon Index, the higher the biodiversity.

Calculating the Shannon Index​ (Optional):

H’ is the Shannon Index, and p  is the proportion of all the organisms captured that are from that particular species. For example, if you captured 12 organisms, and two of them were shrimp, p   for shrimp would be 2/12 = 0.17  

To calculate the Shannon index, first calculate p  for each species in your dataset.  Next, multiply each p   by the natural log (ln) of that same p  ,  add them all up, and then multiply by negative one.






Part B: Prediction and Reasoning

Study the background information provided on the physical and biological factors that influence biodiversity (above), and take the virtual tour of the Poquonnock River, paying close attention to habitat descriptions.  Write answers to the following prompts on your sheet of paper.

  1. Make a prediction:  Where along the Poquonnock River would you expect to see the highest biodiversity?

  2. Explain your reasoning:  WHY do you think biodiversity would be high in this location?

Part C: Analyze the Data

This table shows the number captured for each species while seining at each location, on a single day in July 2019.  Study the table, and then use the number in it for your calculations (below).

For each of the six locations, you will make two calculations:

  1. First, calculate the species richness simply by counting the number of different types of organisms captured at each location.  Record these numbers in a table on your sheet of paper.

  2. Second, calculate the Shannon Index.  If you have sufficient math background you can do this yourself using the formula in the section above, or you can use this online calculator.  Remember, the higher the Shannon Index, the higher the biodiversity.  When using the online calculator, follow these directions:

    1. Enter the species richness in the box for “number of species/taxa in sample’ and hit ‘submit’

    2. Enter the numbers of each taxa in the red-outlined boxes.  It is not necessary to type in the names of the species. You should enter a number for each box (no zeroes) and hit ‘submit’

    3. The output includes a TON of diversity measures.  There are three entries for the Shannon Index; you want the one that matches the formula above (the middle one in the left hand column).

    4. Record the Shannon Index in a table on your piece of paper.

Next, illustrate the data by making two graphs - one for species richness, and one for Shannon Index.  Your graphs should have clear labels on both the x-axis and the y-axis.  The type of graph (scatterplot, column graph, etc) is up to you.

 Part D: Interpret the Results and Make Arguments from Evidence

On your sheet of paper, answer the following questions:

  1. Which locations had the highest and lowest biodiversity?  Did you get different results using species richness vs. the Shannon Index to measure biodiversity?  If you found any differences, explain why the two different measures gave you different results:

  2. Which measure of biodiversity do you think is the most accurate?  Explain your reasoning.

  3. Make a claim that answers the research question from the beginning of this section (one sentence).

  4. What evidence was used to write your claim?  Reference specific parts of your graph(s).

  5. Explain your reasoning.   Make sure to connect your answer to what you have learned about biodiversity.

  6. Was your prediction supported by the results? Use evidence to explain why or why not.

  7. How would you follow up?  Describe a new question that should be investigated to build on these results, and what future data should be collected to answer your question.

Congratulations!  Your final analysis should include the following components:

  • A statement of the research question that you chose/were assigned

  • Your prediction and your reasoning

  • A table of your species richness and Shannon Index results

  • Your labelled graphs (2)

  • Your answers to the results questions

Share your results with your teacher, and/or by emailing it to Project O:, attn: Dr. Molly

**Educators and/or homeschool parents: educator guides are available for all research projects. 

Email to request an educator guide**

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