Similarities and differences: wild and farmed green-lipped mussels



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Similarities and differences: wild and farmed green-lipped mussels
In this activity, students use a paper-based Venn diagram to illustrate the key similarities and differences between how wild and farmed green-lipped mussels live.
By the end of this activity, students should be able to:

  • describe the key similarities and differences between farmed and wild green-lipped mussels

  • understand how to use a Venn diagram to graphically organise information.


Introduction/background

What you need

What to do

Discussion points

Extension activities

List of features

Venn diagram worksheet
Introduction
Wild green-lipped mussels grow abundantly in New Zealand’s coastal waters, and green-lipped mussels are also cultivated (farmed) here. At present, most farmed mussels begin their lives in the wild – they are grown from spat that has washed ashore on seaweed on Ninety Mile Beach and elsewhere. This means that wild and farmed mussels are not distinct populations. This differs from the traditional concept of ‘farming’, in which farmed animals or plants are isolated from their wild counterparts and bred in captivity over successive generations. (Note, though, that some green-lipped mussel larvae are raised in hatcheries, and mussel breeding programmes are under way.)

Although they arise from the same wild populations, there are some key differences between how wild and farmed mussels live during the adult phase of their life cycle. Exploring those similarities and differences can provide students with a framework for developing their knowledge of mussel biology and aquaculture.

The following table provides a summary of similarities and differences. Refer to the information sheets Life of a green-lipped mussel and New Zealand’s green-lipped mussel industry to find the information that is required to complete the activity.



Wild mussels only

Both wild and farmed mussels

Farmed mussels only

  • Grow up to 24 cm long

  • Can live for many years

  • May live on rocks and other mussels

  • Previously fished by dredging

  • Feed on phytoplankton

  • Filter feeders

  • Release eggs or sperm into the water

  • Can contain pea crab parasites

  • Larvae are free-swimming

  • Food source for fish and sea stars

  • Larvae settle onto seaweed

  • Spat may move from site to site

  • Mature females have orange flesh

  • Can accumulate toxins

  • Endemic to New Zealand

  • Harvested when about 10 cm long

  • Harvested after 18 months’ growth

  • Live on ropes in the water

  • Seeded onto ropes using mussock
  • Some spat is grown in hatcheries



Venn diagrams

Venn diagrams have been used for over a hundred years as a visual way to show the similarities and differences between two or more things (for example, concepts or products).


In a Venn diagram, two or more circles overlap – features present in only one thing appear in its circle, and features common to both appear in the overlapping area of the circles.
For example, farmed mussels (but not wild mussels) are grown on ropes suspended in the ocean, so this feature belongs in the ‘Farmed mussels only’ area, but both wild and farmed mussels feed on phytoplankton, so this feature belongs in the overlapping area (both wild and farmed mussels).
What you need


  • Access to the printed list of features and Venn diagram worksheet

  • Access to the information sheets Life of a green-lipped mussel and New Zealand’s green-lipped mussel industry

  • Access to the Mussel life cycle diagram


What to do


  1. Have the students read the information sheets Life of a green-lipped mussel and New Zealand’s green-lipped mussel industry


  2. Draw a sample Venn diagram on the board and discuss with the students what it can be used to show. It might be helpful to model how it works with another example, such as a lake and the sea.



  1. Allow the students sufficient time to complete the Venn diagram, either individually or in small groups. Provide the list of features either as a handout or put up on the board and ask students to complete the Venn diagram worksheet in pencil.





  1. Give individuals or groups the opportunity to feed back. Any disagreements can be resolved by referring to resources within the focus story Farming green-lipped mussels.


Discussion points


  • Are all mussels in New Zealand farmed using the same methods? Which stage in the farming process varies the most?

  • What constitutes ‘farming’? How does mussel farming differ from other species that are farmed on land in New Zealand (such as sheep or cattle)?


Extension activities


  • Annotate the Mussel life cycle diagram on an interactive whiteboard to demonstrate at which stages the lives of farmed and wild mussels differ (and how).

  • Write a first-person account of the life of a farmed and a wild mussel.

  • Research farming methods for other New Zealand aquaculture species and compare them with the methods used to farm mussels, for example, Pacific oysters are farmed in a similar manner to green-lipped mussels, whereas salmon are farmed using different methods. These Aquaculture in Action fact sheets provide a good starting point for independent research.

  • View the video series Mating mussels to learn about the mussel breeding programme at the Cawthron Institute in Nelson.

List of features

Can accumulate toxins



Larvae settle onto seaweed

Can contain pea crab parasites


Live on ropes in the water


Can live for many years



Mature females have orange flesh


Endemic to New Zealand



May live on rocks and other mussels


Feed on phytoplankton



Previously fished by dredging


Filter feeders



Release eggs or sperm into the water


Grow up to 24 cm long



Seeded onto ropes using ‘mussock’


Harvested after 18 months’ growth



Some spat grown in hatcheries


Harvested when about 10 cm long



Spat may move from site to site


Larvae are free-swimming







Venn diagram worksheet




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