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  • Electronic tagging of marine animals is common, but tagging marine invertebrates1 is very unusual! For example, in 1998, an estimated 11,800 marine animals were tagged electronically, and only 35 of these were invertebrates.

    Dr Miles Lamare and postgraduate2 research student Tracey Channon from the University of Otago, along with colleagues from the Cawthron Institute in Nelson, tested a new tagging technique to investigate the behaviour of Coscinasterias muricata, the New Zealand sea star.

    Rights: The University of Waikato Te Whare Wānanga o Waikato

    Downloading tag data

    Dr Miles Lamare has placed the tag in a special communication box (to the right of his laptop). Special software on the laptop retrieves and interprets information from the tag via infrared.

    Sea stars – a keystone species

    Sea stars are invertebrate3 animals that belong to the phylum4 Echinodermata. They are important marine predators and play a major role in keeping the numbers of other organisms down. As a result, they are often referred to as a keystone species5, as their impact on the community is greater than you would expect in relation to their abundance. The removal of a keystone species6 from an ecosystem7 results in a major change, in the same way that removing a keystone from an arch or bridge could cause the structure to collapse.

    Observing sea stars in their natural habitat

    A lot of the previous research into New Zealand sea stars relied on observations by scuba divers. This meant that it was really only possible to get an idea of what was happening over a short period of time. Sea stars don’t move very quickly and so this type of observation gave the impression that they are fairly static animals.

    Rights: The University of Waikato Te Whare Wānanga o Waikato

    Why tag a starfish?

    Tagging marine invertebrates is very unusual! Dr Miles Lamare, from the University of Otago, talks about why they decided to tag the New Zealand starfish and what they hoped to discover.

    Select here to view point of interest, video transcript and copyright information.

    By tagging individuals and monitoring their behaviour, the scientists hoped to gather information about how individual sea stars behave, what they feed on and how often they feed and get a better understanding of the role they play in structuring marine communities.

    The challenge of attaching the electronic tags

    Miles and his colleagues talked to a company in Iceland who make tags for large oceanic fish. This company had some very small tags that record variables such as depth, temperature8 and salinity9, but the challenge was how to attach them.

    Sea stars can shed their arms, and with the tags costing $500 each, the group didn’t want to attach a tag only to find it had dropped off with the arm somewhere on the seabed, so they tried out a few different techniques in the lab. One idea involved making a little backpack for the sea starwith 11 straps for all its arms, but the sea starin the lab managed to get out of the backpack overnight, like a little Houdini.

    As a last desperate measure, the group decided to try piercing one of the arms with stainless steel wire and attaching the tag this way. They were convinced that the sea star would just shed the arm with the tag – but luckily, it didn’t!

    Rights: The University of Waikato Te Whare Wānanga o Waikato

    How do you electronically tag a starfish?

    Dr Miles Lamare, from the University of Otago, talks about the challenges of attaching electronic tags to starfish.

    Select here to view point of interest, video transcript and copyright information.

    Testing whether the tag affected behaviour

    One of the aims of this research was to find out more about the behaviour of individual sea star, so the next important stage of the project was to test whether the tag affected the sea star’s behaviour. There would be no point in tagging an animal if its behaviour was totally different to an untagged animal.

    The scientists found that tagging had no effect on feeding rate, health or the way the sea star moved so they were confident that tagged animals could be used to accurately represent normal sea star behaviour.

    Nature of science

    Scientists often trial new methods in the laboratory before using them in the field. This allows them to test the methods under known conditions10 so that they can be more certain that effects seen in the field are real and not a result of the method.

    Tagging sea stars in the field

    The site for the research was Doubtful Sound in Fiordland. At any one time, the group tagged about 5 individuals in the population11 and left the tags on the animals for about 3 weeks. It was pretty easy to find the tagged individuals, as the water in the fiord is really clear and the sea stars didn’t move huge distances horizontally. A number of students helped in this aspect of the work.

    The tags used in this research are called ‘archival tags’ (different to ‘passive tags’ commonly used to identify an animal), which record and archive useful information over a set period of time, for example, these tags recorded water temperature and depth every 5 minutes for up to 2 weeks.

    After each tag was removed, it was placed into a communication box plugged into a computer. Using special software, the scientists downloaded the data12 from the tag and analysed it.

    The results of the study were really interesting and provided information about different sea stars’ behaviour, the amount of vertical movement and the influence of the physical environment (for example, salinity layers). Miles and his colleagues were really surprised to find out how dynamic13 sea star behaviour is. They do sometimes sit still for a couple of days but then suddenly they will quickly move to the freshwater layer, grab a mussel and move back down.

    Testing out the archival tags was the trial part of this research project. The next research question Miles and Tracey want to investigate in more detail is the impact of increased levels of freshwater, due to a nearby power plant, on the sea stars in the fiord.

    Related content

    Tiny transponder14 tags were used to help with the count of giant kōkopu, one of New Zealand’s most endangered15 species.

    Larger satellite16 tag were used to help track godwits.

    The Ministry of Education’s Connected series article On the move includes teacher support material about the technology used for monitoring migration of various animals.

    Activity idea

    Use the activity Tagging monarch butterflies for science with your students to explore why tagging is important for science research.

    1. invertebrates: An animal without a backbone, for example butterflies, worms, snails, insects, spiders and aquatic species such as crabs and jellyfish.
    2. postgraduate: A student who has obtained a first degree and is now working towards a higher degree such as master’s or PhD.
    3. invertebrates: An animal without a backbone, for example butterflies, worms, snails, insects, spiders and aquatic species such as crabs and jellyfish.
    4. phylum: A division used in the Linnean system of classification or taxonomy. It is a major division in animal classification (below Kingdom and above Class).
    5. keystone species: A species that has a greater impact on the community of organisms in an ecosystem than you would expect in relation to its abundance. The removal of a keystone species often has a dramatic effect on the ecosystem.
    6. species: (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.
    7. ecosystem: An interacting system including the biological, physical, and chemical relationships between a community of organisms and the environment they live in.
    8. temperature: A measure of the degree of hotness or coldness of an object or substance. Temperature is measured with a thermometer calibrated in one or more temperature scales. Kelvin scale temperature is a measure of the average energy of the molecules of a body.
    9. salinity: The amount of chemicals dissolved in water. In seawater, the main chemical is sodium chloride (salt), but there are many others in smaller quantities.
    10. condition: An existing state or situation; a mode or state of being.
    11. population: In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.
    12. data: The unprocessed information we analyse to gain knowledge.
    13. dynamic: In science, a process or system characterised by constant change.
    14. transponder: A device that receives a signal at one frequency and retransmits it at a different frequency.
    15. endangered: A species that is possibly going to become extinct soon due to limited numbers of individuals alive or not enough habitat to live in.
    16. satellite: Any object that orbits around another object.
    Published 8 October 2009 Referencing Hub articles
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        invertebrates

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      2. An animal without a backbone, for example butterflies, worms, snails, insects, spiders and aquatic species such as crabs and jellyfish.

        keystone species

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      4. A species that has a greater impact on the community of organisms in an ecosystem than you would expect in relation to its abundance. The removal of a keystone species often has a dramatic effect on the ecosystem.

        temperature

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      6. A measure of the degree of hotness or coldness of an object or substance. Temperature is measured with a thermometer calibrated in one or more temperature scales. Kelvin scale temperature is a measure of the average energy of the molecules of a body.

        population

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      8. In biology, a population is a group of organisms of a species that live in the same place at a same time and that can interbreed.

        transponder

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      10. A device that receives a signal at one frequency and retransmits it at a different frequency.

        postgraduate

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      12. A student who has obtained a first degree and is now working towards a higher degree such as master’s or PhD.

        species

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      14. (Abbreviation sp. or spp.) A division used in the Linnean system of classification or taxonomy. A group of living organisms that can interbreed to produce viable offspring.

        salinity

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      16. The amount of chemicals dissolved in water. In seawater, the main chemical is sodium chloride (salt), but there are many others in smaller quantities.

        data

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      18. The unprocessed information we analyse to gain knowledge.

        endangered

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      20. A species that is possibly going to become extinct soon due to limited numbers of individuals alive or not enough habitat to live in.

        phylum

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      22. A division used in the Linnean system of classification or taxonomy. It is a major division in animal classification (below Kingdom and above Class).

        ecosystem

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      24. An interacting system including the biological, physical, and chemical relationships between a community of organisms and the environment they live in.

        condition

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      26. An existing state or situation; a mode or state of being.

        dynamic

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      28. In science, a process or system characterised by constant change.

        satellite

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      30. Any object that orbits around another object.