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Monster crab invasion

  • Key Stage 3
  • Popular Activity
  • Topical

Type: Activity
Learning Strategy: Modelling
Topic: Feeding relationships

Red king crabs have arrived in Europe. Huge, and with no natural predators, they compete with cod for food and have a massive impact on ocean food webs. In this activity students build up ocean food webs before and after the monster crab invasion. If you wish, they then take the role of a fish company manager who must decide how to react to the invasion.

This activity is truly a teacher effort:
It launches with an inventive and amusing video starter, featuring talking crabs and cods as boxers in the ring. Thank you to Henry Cordy-McKenna, of Honywood Community Science School!

The original activity was written by a teacher after our new Professional Development course. UPD8 Live! provides the tools and techniques so you can develop your own UPD8-style activities. Tony Stevens, of Trinity School: "decided to build an activity around the new headlines "hordes of gigantic crabs on their way to invade Europe." We liked the activity and hope you will.

Published: 22nd January 2005
Reviews & Comments: 31

Learning objectives

Students will build up an ocean food web and look at the impact of invading red king crabs on this.

Try the activity

You will need Acrobat Reader installed to open the activity sheets.

11 - 14 (KS3)
Environment and feeding relationships QCA 7c - combine food chains into food webs
Ecological relationships QCA 8d - relate abundance and distribution of organisms to the resources available in a habitat.

Running the activity

Suggested time: 15 minutes for the food web activity, a further 10 minutes for the decision-making activity.

Suggested starter: Show students page 1 - either projected or on transparency. (For maximum impact on a projector/whiteboard, display the activity 'full screen'. This option is under the 'view menu ', and it removes the distracting toolbars and menus). Ask students to think about the possible impacts of invading red king crabs on ocean food webs and on the fishing industry.

Main activities: Groups create a food web without the red king crab using the cards on page 2. They could spread the pictures on scrap A3 paper or on individual whiteboards and draw arrows between the pictures. They then introduce the red king crab to the food web and discuss its impact, particularly on cod. Each group will need their own copy of page 2, photocopied in colour or black and white.
Groups then tackle task 3, set at the top of page 2. They need to be able to see page 1.

Possible plenary:
groups state which option they choose in response to option 3, giving reasons for their choices.

News links

News reports of the red king crab invasion
Daily Telegraph
More on the invasion

Media links

Video starter - try this!
What better way to set up the activity than to hear from the King Crab and cod themselves. Watch them put their own case, thanks to some clever animation.

Reviews & Comments

Write your online review to share your feedback and classroom tips with other teachers. How well does it work, how engaging is it, how did you use it, and how could it be improved?

King Crab invasion is useful

Mar 2nd, 2014

4 Star

A dencent idea especially for higher ability pupils. I would use this resource again.

Reviewer: Ben Golden


Apr 27th, 2013

4 Star


Reviewer: Racahel Scullion


Mar 27th, 2013

5 Star

Easy to follow. Kids on task :)

Reviewer: Ben Ford

Good activity

Sep 2nd, 2012

4 Star

Super video starter is quite funny. I found that taking out a few part of the food chain for weaker groups may be benefiical

Reviewer: Louise Steel

Monster crab invasion review

Jun 7th, 2011

4 Star

Very smart lesson plan, and it clearly works because I used it for an interview and got the job! I added a few more species to the food web as the students completed it a little quickly, but a great well rounded lesson covering key terms, subject content and HSW. Thanks!

Reviewer: Ben Davis


May 18th, 2011

5 Star

Fantastic teaching feeding relationships as well as developing different skills such as leadership, communication and problem solving. Thanks.

Reviewer: Xue Han

Monster crab invasion review

Jul 8th, 2010

4 Star

This activity fitted in well with my lesson on food webs, the pupils were really enthusiastic about having a debate.

Reviewer: Samantha Lyskava

monster crab invasion

May 27th, 2010

5 Star

Did this activity today with my year 8s in an observed OFSTED lesson and achieved an outstanding! Thanks so much to the people that wrote it - the kids loved it and the video on you tube is perfect. Thanks again!

Reviewer: Emma Dean

Monster Crab Invasion

Mar 28th, 2010

5 Star

I have now used this excellent activity about 3 times in successive years with Yr7 mixed ability pupils. The video starter is really good and engages pupils well. Each time I have modified the activity to make it run more smoothly. The main change I made was to dispense with the cutting and pasting of cards to save time - pupils draw their food webs on A3 paper and write in the names of the organisms. They add arrows to make the food chains. I have made differentiated versions of the organism cards, and produced a learning ladder to go with the task which has now become a nice APP assessment.

Reviewer: John Eaden

Monster crab invasion review

Jan 6th, 2010

5 Star

used this in a y7 competition/adaptation lesson - they loved the animation on the link and the lesson was great

Reviewer: Rob Loveridge

Nice one

Nov 24th, 2009

4 Star

A really nice activity to engage pupils in food webs and looking at the effects of changes to populations.

Had difficulty with the video for the starter - we can't have utube at school!

Reviewer: Audrey McCafferty


Nov 22nd, 2009

4 Star

This is a very good resource and has been a fun way to show the impact of introducing new organisms to a food web.

I used a resource from you tube that actually had a cod and a king crab talking about their problems and then gave the children a large sheet of sugar paper for them to do the food web in groups of 2.

The plenary consisted of a spokesperson from each group stating reasons for the option that they had chosen

Reviewer: lavkesh lal

Monster crabs

Jul 8th, 2009

5 Star

Used this with my yr8 top sets with a prize for the best team - worked really well especially highlighting the complexity of the food web

Reviewer: Rachel Causey

King Crab!

Jun 15th, 2009

4 Star

This activity was very well received by my mixed ability year 7 group! The video clip really helped to set the scene and enthused students about the task!

Reviewer: Catherine Sheffield-Kelly

Monster crab invasion review

Apr 28th, 2009

5 Star

It was wonderful with mixed ability students.

Reviewer: Friday Akpa

monster crabs

Mar 26th, 2009

5 Star

This was a brilliant activity done with a middle ability year 8 class - they loved it. Thanks

Reviewer: Melissa Baines

Monster crab invasion review

Jul 9th, 2008

4 Star

Good activity, size of king crabs attracts intrest. Reinforces drawing and interpreting food chains and webs. Discussions need to planned with good level of questioning, can take most of a 50 minuite lesson.

Reviewer: sreeja bhaskaran

Monster Crab Lesson

May 19th, 2008

4 Star

I ran this activity with a Year 8 class as part of Ecological Relationships.
I was surprised at how many pupils had forgotten how to construct a food web (so it was good revision for them).
The lesson served both as revision and as a thought provoking activity about the bigger picture and environmental responsibility.
I will definitely use it again.

Reviewer: Stephen Clark

Year 7 were engaged and debated with one another!

Apr 24th, 2008

4 Star

I ran this activity with my Year 7 while doing food webs and interdependence. They usually work quite well, all were engaged. The G&Ts really enjoyed debating the issues and even were responding to each other's comments without much prompts from me.
For the less able, constructing the food web was a good way for me to reinforce ideas about direction of arrows to show energy flow in food webs. I loved it and they did too, I think. I had to force them to stop discussing and move on to next task.
One thing I would say is to think of ways to make sure that discussions don't just focus on the economic issues but discuss the science too.

Reviewer: Ogechi Okoli

An excellent activity

Jul 3rd, 2007

5 Star

I ran this activity twice on one day with two bright year 7 groups and had very good engagement from the pupils. Lots of "crab experiences" at the start that our (admittedly coastal) pupils wanted to share - leading to a great discussion of "why would a crab spend energy chasing you? (protection or potential food source)

As with a previous reviewer I found that the activity plus some extra questions along the way e.g. "What would happen if you took the zooplankton and the small crustaceans out" gave a very active 50 minute lesson. It would work as a useful revision exercise also.

The activity leaves a great deal of flexibiity as to the level of language you want to use. I am sure this can work in many year groups with small changes of that type.

In essence I did what it said on the tin (definitely use the A3 paper) and it worked. Thanks.

Reviewer: Philip Blair

Monster crabs

Jun 18th, 2007

3 Star

Tried this today with some low ability year 8 as a discussion piece. The visuals worked really well with the crab facts grabbing their attention. most were able to put together a food web and once that done they were much more able to see the affect of changes brought about by the crabs. Best to use white boards so that they can change there arrows etc, Nice topic.

Reviewer: w woodburn

Monster crabs

Jun 4th, 2007

5 Star

I have used this activity twice now, each time it has been great. The great size of the crab captured and maintained interest. It was easy to extent for the more able with further discusion about sustainable fishing, the influence of the consumer and how invasive species arrive in our seas. Pupils enjoyed the activity and it did improve their understsnding of interdependent food webs.

Reviewer: sarah janman

Monster crab invasion review

May 17th, 2007

5 Star

I used this with middle attainment Year 10 as a plenary to competition in animals. I used laminated A3 pages so they could make their food webs and this made it very easy for the pupils to change their minds. It worked really well and had lots of pupils wanting to have their say. Would definitely use again. Thank you for a great resource.

Reviewer: Michele Morris

Monster Crabs

Sep 12th, 2006

5 Star

Year 7 mixed ability group loved this activity and it led to a good discussion

Reviewer: Tracy Page

Monster crabs rule

Jul 13th, 2006

5 Star

I did this with top set year 7. So simple, sheets, exercise books, scissors glue. It stimulated intense discussion and it was probably the best lesson I did all year. Thanks

Reviewer: David Hammond

Monster crabs

Mar 30th, 2006

5 Star

Excellent activity. I used it as a plenary with my mixed ability year 7. Everyone was able to engage with the activity and explain why they chose either option A or B.

Reviewer: Amrat Johal

Monster crab invasion

Oct 15th, 2005

4 Star

I've tried this with both year 7 & 9, the senario is engaging and constructing the food web is a good activity. Most students identify the correct consequences of adding the King Crab to the wood web. This ten provoked some good discussion on what should be done. This gives a good opportunity for the students to practise thier debating skills to get their point of view across.
The PDF format colours don't photocopy very well into black and white is my only constructive comment.

Reviewer: Ian Platten

Great for revision

Jun 27th, 2005

5 Star

I used this activity with a Set 1 single award GCSE group as revision on food webs and a way at looking at the interdependance of species. The students did the activity as independant learners during a period disrupted by work experience. They all enjoyed the activity and seem to have improved their understanding of how a food web works. A great activity

Reviewer: Scott Jones

Year 7 debate

Jun 23rd, 2005

5 Star

Great lesson, but it did take the whole lesson. The year 7 class just wouldn't stop talking - about the crabs.
Some great debate and argument coming through, along with some good ideas about how to have both the cod and the crabs in the same habitat - including selective breeding to make the cod larger and a predator! Other just wanted to keep the crabs as they didn't like fish!

Reviewer: Stacey Whitehead

Monster crab invasion review

Jun 11th, 2005

4 Star

Most of the students I used this with enjoyed this, especially as it related to their beloved fish and chips. It took longer than I thought although it was with a very mixed class which I hadn't previously taught.
In future rather than getting the students to cut out the sheets I would have the cards pre cut and laminated. Many of the students also did not know what all the organisms were (this was at an inner city school where many of the students had not seen a fish outside the fishmongers).

Reviewer: Stephen Goodall

Monster Crabs

Mar 10th, 2005

5 Star

I was trying to think how I could use the Upd8 activities with my EBD pupils, who find discussion within science a turn off , and I thought up the idea of using a small display board as a Science 'chat board'. I constructed the display from the Monster crab invasion activity and put up a voting sheet whether to eat the crabs or kill off the problem. Encouraged by staff participation the pupils showed a positive interest and enjoyed the idea of signing their name on the display. The interest was maintained because it led to discussion about the problems faced in cooking/ killing such whoppers. It struck me that the pupils probably had little idea of the scale of the crabs and this led to a cross curricular display of a model crab (art)and additional input from the ICT, Hums and Literacy support.. What's more this spark of interest took place outside of the lab in the pupils own time at break or lunch! A successful acitivity all round.
I intend to try out other Upd8 activities in a similar way.

Reviewer: Jane Demet