Spotted Dolphins and Spinner Dolphins

How are collections of dolphin tissues useful for scientists to learn more about dolphins? How did changes in fishing methods put dolphin populations at risk? What have scientists tried to do to reduce the risk?

This audio is part of the One Species at a Time series hosted by Ari Daniel and produced by Atlantic Public Media and the Encyclopedia of Life, with the support from the Harvard Museum of Comparative Zoology. Licensed under Creative Commons Attribution 3.0.

Story Length: 6:01

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  • Objectives

    Students will know and be able to…

    • Discuss how tissue samples collected from dolphins killed in tuna nets can be used to help scientists learn about dolphins.
    • Describe how changes in fishing techniques in the 1960s affected dolphin populations and how fishing techniques were changed to decrease this problem.
    • Answer questions about dolphin populations by producing and interpreting graphical information.
  • Student Background

    This lesson requires no additional information.  This could serve as the introduction to discussions of the effect of predator populations (in this case, fishing by humans) on prey population and discussions of how human activities can unexpectedly affect species.

    Vocabulary terms:

    Bycatch: species that are accidentally caught by attempts to capture other species (e.g., dolphins killed by tuna nets)

    Curator: a person who manages collections in a museum

    Dolphin morgue: a museum where tissue specimens of dolphins collected as bycatch are stored

    Parasites: organisms that use other organisms for food, but do not kill them

    Population: a group of individuals of the same species that lives in the same area

  • Materials

  • Lesson Plan

    One Species at a Time: 6:01

    1) Listening Guide

    Spotted dolphins and spinner dolphins are often found living with tuna.  When people started using large nets to capture tuna in the 1960s, many dolphins were killed as well.  Scientists responded by sending “observers” on tuna boats to keep track of the number of dolphins killed.  Scientists store samples of different parts of dolphins collected from dolphins killed by the tuna nets at the NOAA’s Southwest Fisheries Science Center in San Diego (a museum called “the dolphin morgue”).  Over time scientists have discovered uses for these tissues to try to learn more about these dolphins in order to help preserve dolphin populations

    2) Listening Prompts for Students

    a. How do fishermen locate tuna schools?

    b. What change in fishing technology occurred in the 1960s?  How did this change in fishing technique affect dolphins?  How did fisherman change their techniques to reduce the number of dolphins killed?

    c. What was the purpose of placing observers on tuna fishing boats?

    d. What is stored in the dolphin morgue?

    e. How have scientists used specimens stored in the dolphin morgue to learn about dolphins?

    f. How successful have changes in fishing technique been in allowing dolphin populations to get increase in size?

    3) Play the One Species at a Time Story

    4) Reading Guide

    Spinner dolphins and spotted dolphins are commonly found living with tuna. Spinner dolphins are named for their unique behavior of spinning several times when they leap out of the water.  Both spinner and spotted dolphins have been killed as bycatch of tuna fishing.

    5) Reading Prompts

    a. Which species do spinner dolphins and spotted dolphins tend to associate with?

    b. Why do spinner dolphins “spin”?

    c. How have spinner dolphin and spotted dolphin populations been affected by tuna fishing?

    6) Read the Encyclopedia of Earth Articles (sections on Behavior and Conservation Status and Threats)

    Atlantic Spotted Dolphins

    Pantropical Spotted Dolphins

    Spinner Dolphins

    7) Lesson

    Total lesson time: 45 minutes

    Listening time: 6:01

     

    Class Activities:

    1. Why do scientists collect samples of tissues from dolphins killed as bycatch of tuna fishing?  Where are these samples stored?

    Put students in small groups of 2 – 3.  Have each group discuss ways that scientists can use tissue samples stored in the “dolphin morgue” to learn about dolphins.

     

    2. Why do spinner dolphins “spin”?   Have small groups of students discuss the different ideas about why spinner dolphins “spin”.  Have the students write a paragraph describing the spinning behavior and discussing the possible reasons for this behavior.

     

    Extension:

    In order to monitor long term changes in the population sizes of spinner dolphins and spotted dolphins scientists conducted surveys of dolphin populations in the eastern tropical Pacific Ocean between 1979 and 2000.  Note: scientists did not conduct this survey every year.

    This data was taken from the article “Non-recover of two spotted dolphin and spinner dolphin populations in the eastern tropical Pacific Ocean.” By Tim Gerrodette and JaumeForcada.Published in 2005 in Marine Ecology Progress Series Volume 291, pages 1 – 21. https://swfsc.noaa.gov/uploadedFiles/Research/Legal_Mandates/International_Dolphin_Conservation_Program_Act_(IDCPA)/GerrodetteandForcada2005MEPS.pdf

     

    Year                 # spotted dolphins                  # spinner dolphins

     

    1979                            708,000                                   449,000

    1980                            740,000                                   271,000

    1982                            605,000                                   285,000

    1983                            548,000                                   619,000

    1986                            494,000                                   536,000

    1987                            501,000                                   443,000

    1988                            868,000                                   636,000

    1989                            954,000                                   734,000

    1990                            666,000                                   459,000

    1998                            676,000                                   557,000

    1999                            600,000                                   361,000

    2000                            647,000                                   428,000

     

    Thinking about the Data

    1.  The scientists are interested in conducting this survey to see whether the implementation of “dolphin safe” fishing techniques have caused dolphin populations to increase.

    Have the students discuss how they would graph this data to help the scientists answer this question.  Have them discuss what they would expect the graphs should look like under the following scenarios.  Assign a different scenario to each of the groups of students.  After they have determined their answer have them explain their answer to their classmates.

    a) If dolphin populations were steadily increasing over time.

    b) If dolphin populations were steadily decreasing over time.

    c) If dolphin populations remained constant over time.

    d) If there was no consistent pattern of change in dolphin populations over time.

     

    Looking at the Data

    1.  Which dolphin species has the largest populations?

    Have the students think about how they would use the data to answer this question.  How should they most effectively display the data that helps them answer this question using either a table or graph?

    2.  Assign each group of students to study either spinner dolphins or spotted dolphins.

    Draw the graph that shows how dolphin population size changes over time?

    Graph Interpretation Question:  Which of the graphs you thought about earlier best matches your graph?

    Biology Question:  How have dolphin populations changed over time?  Have students write a paragraph describing their answer to this question.

  • Homework Socrative Quiz

    Tell students to listen to the public radio story at home. Then assign a Socrative Assessment or written homework.

    socrative logo
    Short answer quiz: SOC-3939541

    Socrative.com allows you to give quizzes through any device or browser and get graded score reports immediately sent to you! To learn how to use Socrative shared quizzes, view this tutorial.

    Or tell students to listen to the Public Radio Story at home and answer the following questions:

    a. How do fishermen locate tuna schools?

    b. What change in fishing technology occurred in the 1960s?  How did this change in fishing technique affect dolphins?  How did fisherman change their techniques to reduce the number of dolphins killed?

    c. What was the purpose of placing observers on tuna fishing boats?

    d. What is stored in the dolphin morgue?

    e. How have scientists used specimens stored in the dolphin morgue to learn about dolphins?

    f. How successful have changes in fishing technique been in allowing dolphin populations to get increase in size?

  • Assessment Evidence

    Students’ written answers to questions and students’ participation in discussion.

  • Standards

    Common Core Standards: Speaking and Listening
    Grade 6

    CCSS.ELA-Literacy.SL.6.1 Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 6 topics, texts, and issues, building on others’ ideas and expressing their own clearly.

    CCSS.ELA-Literacy.SL.6.1a Come to discussions prepared, having read or studied required material; explicitly draw on that preparation by referring to evidence on the topic, text, or issue to probe and reflect on ideas under discussion.

    CCSS.ELA-Literacy.SL.6.1b Follow rules for collegial discussions, set specific goals and deadlines, and define individual roles as needed.

    CCSS.ELA-Literacy.SL.6.1c Pose and respond to specific questions with elaboration and detail by making comments that contribute to the topic, text, or issue under discussion.

    CCSS.ELA-Literacy.SL.6.1d Review the key ideas expressed and demonstrate understanding of multiple perspectives through reflection and paraphrasing.

    CCSS.ELA-Literacy.SL.6.2 Interpret information presented in diverse media and formats (e.g., visually, quantitatively, orally) and explain how it contributes to a topic, text, or issue under study.

     

    Grade 7

    CCSS.ELA-Literacy.SL.7.1 Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 7 topics, texts, and issues, building on others’ ideas and expressing their own clearly.

    CCSS.ELA-Literacy.SL.7.1a Come to discussions prepared, having read or researched material under study; explicitly draw on that preparation by referring to evidence on the topic, text, or issue to probe and reflect on ideas under discussion.

    CCSS.ELA-Literacy.SL.7.1b Follow rules for collegial discussions, track progress toward specific goals and deadlines, and define individual roles as needed.

    CCSS.ELA-Literacy.SL.7.1c Pose questions that elicit elaboration and respond to others’ questions and comments with relevant observations and ideas that bring the discussion back on topic as needed.

    CCSS.ELA-Literacy.SL.7.1d Acknowledge new information expressed by others and, when warranted, modify their own views.

    CCSS.ELA-Literacy.SL.7.2 Analyze the main ideas and supporting details presented in diverse media and formats (e.g., visually, quantitatively, orally) and explain how the ideas clarify a topic, text, or issue under study.

     

    Grade 8

    CCSS.ELA-Literacy.SL.8.1 Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 8 topics, texts, and issues, building on others’ ideas and expressing their own clearly.

    CCSS.ELA-Literacy.SL.8.1a Come to discussions prepared, having read or researched material under study; explicitly draw on that preparation by referring to evidence on the topic, text, or issue to probe and reflect on ideas under discussion.

    CCSS.ELA-Literacy.SL.8.1b Follow rules for collegial discussions and decision-making, track progress toward specific goals and deadlines, and define individual roles as needed.

    CCSS.ELA-Literacy.SL.8.1c Pose questions that connect the ideas of several speakers and respond to others’ questions and comments with relevant evidence, observations, and ideas.

    CCSS.ELA-Literacy.SL.8.1d Acknowledge new information expressed by others, and, when warranted, qualify or justify their own views in light of the evidence presented.

    CCSS.ELA-Literacy.SL.8.2 Analyze the purpose of information presented in diverse media and formats (e.g., visually, quantitatively, orally) and evaluate the motives (e.g., social, commercial, political) behind its presentation.

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