How are humans causing extinction of species? (Secondary) - Lesson Three

Lesson 3 - What role are human activities playing?
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Slide 1: Tekstslide
Social StudiesHistory+311th,12th Grade

In deze les zitten 11 slides, met tekstslides en 1 video.

time-iconLesduur is: 45 min


Lesson Three – What role are human activities playing? This lesson covers the issues of overfishing, illegal fishing and by-catch and the role they are playing in reducing the number of species. Learning activities:  Discuss how students are contributing to overfishing.  Research one of the following topics and write a report – overfishing, illegal fishing or by-catch.


Time: 45 minutes

© Sea Shepherd 2022


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Lesson 3 - What role are human activities playing?

Slide 1 - Tekstslide

This lesson is provided by Sea Shepherd.  Sea Shepherd was founded in 1977 and is a marine conservation organisation working to protect the oceans and marine wildlife.  Sea Shepherd works globally on a range of issues impacting the oceans, running numerous direct action campaigns each year. 
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Watch  the video

Slide 2 - Tekstslide

During the lesson we will use these icons to identify the learning actions.
Introduction to IUU fishing and the impact of overfishing.
Human Impacts

Slide 3 - Tekstslide

This lesson we will be looking at some more reasons why extinction of species is occurring at increased rates, continuing to focus on ocean-based issues and species.

Ask students: “We have already discussed climate change and pollution, what other issues do you think there are?

Introduction to IUU fishing and the impact of overfishing.

Slide 4 - Tekstslide

The first issue we will discuss today is overfishing.

Ask students: “What do you think is meant by the term ‘overfishing?”

Overfishing – is the depletion of fish numbers by excessive fishing.
Overfished populations - depleted numbers of fish (in specific area) by excessive fishing, which could ultimately lead to the collapse of fisheries.

The result of commercial fishing activities is that over 90% of global fisheries have now been exploited or overexploited. Which means, according to UN data, that less than 10% of global fisheries are deemed to have healthy numbers. 90% of the predatory fish, including sharks, tuna, albacore, icefish, swordfish and grouper are already gone.

Fish is the largest trade commodity in the world, with over 100 million tonnes taken from the ocean each year.

Introduction to IUU fishing and the impact of overfishing.
Poaching of species

Slide 5 - Tekstslide

The next issue that contributes to overfishing and threatens species is poaching. Poaching is the illegal hunting or catching of marine mammals or fish, that is not one's own or in contravention of official protection.
We normally associate poaching with land-based species like elephants and rhinos, who are targeted as trophies or for their tusks and horns, but there are a number of marine species that are also heavily targeted by poachers.  Again, it is because they are protected species that can fetch high values.  
One species that has been heavily targeted is sharks, with over 100 million killed each year, mainly for their fins and liver oil.  Of the 400 plus species of shark, over one third are now endangered.
Another species targeted is sea turtles.  It is mainly the nesting females who are taken for their meat, eggs and the shells.  6 of the 7 species of sea turtle are either endangered or critically endangered.
Introduction to IUU fishing and the impact of overfishing.
Illegal fishing

Slide 6 - Tekstslide

Contributing to overfishing is Illegal, Unreported and Unregulated (IUU) fishing activity.  The United Nations estimates that an average 30% of the global fishing catch is considered to be from Illegal, Unreported and Unregulated (IUU) fishing. This amount varies by region from 15% to 40%.

The high demand for fish encourages illegal fishing operations.  Illegal fishing means that the fishermen enter the territorial waters of a country or regulated marine zone without permission or without a license for the fish they intend to catch. In basic terms they are stealing from these waters.

Introduction to IUU fishing and the impact of overfishing.

Slide 7 - Tekstslide

Another reason for overfishing is the waste created as a result of industrial fishing, both legal and illegal.  It is estimated that around 26% of the global fishing catch is by-catch, also known as ‘discards’.  But this is potentially being underreported

Ask students: “What do you think is meant by by-catch?  Can you give examples?”

By-catch is basically anything that is caught in fishing nets or on lines, that the fishermen don’t want or are not allowed to legally catch.   

Generally, they remove the by-catch from the nets and return it to the ocean.  However, many of these animals will have already died before they are freed. By-catch comprises other species of fish, turtles, dolphins, sharks or even whales.

It is estimated that over 300,000 whales and dolphins die as by-catch each year, as a result of commercial fishing activities.

Introduction to IUU fishing and the impact of overfishing.
Competition for food sources

Slide 8 - Tekstslide

Overfishing is directly leading to species becoming threatened with extinction, but it has another implication. It creates competition for food sources. With commercial fishing operations emptying entire ecosystems of fish, it leaves other species low on food sources.  This includes seals, whales, and dolphins.  Even worse, in areas where overfishing has resulted in the collapse of fish, fishermen are intentionally targeting these species, killing seals and dolphins, to protect what fish is left.   Not for the ecosystem but for themselves, so they have something to catch and sell.

Slide 9 - Video

This video explains purse seine fishing, which is contributing to overfishing, and the issue of by-catch:

Slide 10 - Tekstslide

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Slide 11 - Tekstslide

Refer Teachers Guide for Learning Activities.