What does overfishing mean for the ocean? (Secondary) - Lesson Four
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Lesson duration is: 45 minIntroduction
Lesson 4 – Why and how does by-catch occur?
This lesson discusses the issue of by-catch/discards, and some methods used to reduce by-catch.
Learning activities:
Discuss several case studies, research the extent of by-catch in different fisheries.
Instructions
Time: 45 minutes
Contact: education@seashepherdglobal.org
© Sea Shepherd 2022
Items in this lesson
Slide 1 - Slide
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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During the lesson we will use these icons to identify the learning actions.
Slide 3 - Slide
Ask students what the term by-catch means?
Slide 4 - Slide
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 could be other species of fish, turtles, dolphins, sharks or even whales.
Also referred to as discards.
By-catch/discards are required to be recorded by fishing vessels.
By-catch / discards can be:
Undersized fish.
Catch over the quota limit.
A species they are not licensed to catch.
Threatened, endangered and protected species.
Excess catch over weight limit of the vessel.
Could be other species of fish, turtles, dolphins, sharks or even whales.
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 could be other species of fish, turtles, dolphins, sharks or even whales.
Also referred to as discards.
By-catch/discards are required to be recorded by fishing vessels.
By-catch / discards can be:
Undersized fish.
Catch over the quota limit.
A species they are not licensed to catch.
Threatened, endangered and protected species.
Excess catch over weight limit of the vessel.
Could be other species of fish, turtles, dolphins, sharks or even whales.
Slide 5 - Slide
It is estimated that around 26% of the global fishing catch is by-catch.
Commercial fishing operations for example are responsible for killing some 300,000 dolphins and whales as by-catch each year and 250,000+ loggerhead and leatherback turtles.
Commercial fishing operations for example are responsible for killing some 300,000 dolphins and whales as by-catch each year and 250,000+ loggerhead and leatherback turtles.
Slide 6 - Video
Let’s look at how by-catch occurs
The nets used for commercial fishing are so large that they capture everything in their wake and are down for long periods of time. So, while the fishermen may be targeting large schools of a particular fish species they will catch everything else in the area at the same time. It is simply a ‘by-product’ of bigger catches, which means more money in less time.
The purse seine tuna fishing industry has for many years had an issue with high by-catch levels. For example, yellowfin tuna will school with adult skipjack, meaning both will be caught in their nets. The survival of the tuna relies on fishermen processing and removing the unwanted tuna species from the nets. From the earlier lesson we discussed the issue of unreported fishing catches. By-catch is one area that is often underreported.
This video explains purse seine fishing and the issue of by-catch:
https://www.youtube.com/watch?v=TsmA0gX2qNk&list=PLx1pnhQVtbbBnH1BBXzQtknEROG73UNO9&index=13
The nets used for commercial fishing are so large that they capture everything in their wake and are down for long periods of time. So, while the fishermen may be targeting large schools of a particular fish species they will catch everything else in the area at the same time. It is simply a ‘by-product’ of bigger catches, which means more money in less time.
The purse seine tuna fishing industry has for many years had an issue with high by-catch levels. For example, yellowfin tuna will school with adult skipjack, meaning both will be caught in their nets. The survival of the tuna relies on fishermen processing and removing the unwanted tuna species from the nets. From the earlier lesson we discussed the issue of unreported fishing catches. By-catch is one area that is often underreported.
This video explains purse seine fishing and the issue of by-catch:
https://www.youtube.com/watch?v=TsmA0gX2qNk&list=PLx1pnhQVtbbBnH1BBXzQtknEROG73UNO9&index=13
Slide 7 - Slide
To help tackle the issue of by-catch a number of practices have been developed. If properly used these can help save the lives of marine wildlife. For instance:
Monitoring catch and releasing
Many countries require fishing operators to have crew that specifically look out for whales, dolphins, turtles and remove them from nets before they die.
Turtle Excluder Device (TED)
TED’s are grates attached to the mouths of shrimp trawler nets that keep sea turtles and other marine wildlife out of the nets. It is a requirement for some industries that these are fitted.
Fishing practices to deter marine birds
Many sea birds have been impacted by the growth of the long-liner fishing industry, where lines with hundreds of hooks are put out from the backs of fishing vessels. The birds are snared as they chase the baited hooks. With hundreds of sea birds were dying on each line action was required.
The Agreement on Conservation of Albatross and Petrels (ACAP) was established to coordinate international activity to reduce the threats to the species at risk, such as albatrosses and petrels.
The Agreement has been signed by 13 countries and covers 31 species of marine birds.
ACAP aims to reduce the impacts of fishing on seabirds and changing fishing practices. This has included:
Reducing the time the baited hooks are close to the surface and thus available to birds, before they sink into the water.
Using methods to deter birds coming close, such as streamers.
Setting lines at night-time, when birds are not around.
Monitoring catch and releasing
Many countries require fishing operators to have crew that specifically look out for whales, dolphins, turtles and remove them from nets before they die.
Turtle Excluder Device (TED)
TED’s are grates attached to the mouths of shrimp trawler nets that keep sea turtles and other marine wildlife out of the nets. It is a requirement for some industries that these are fitted.
Fishing practices to deter marine birds
Many sea birds have been impacted by the growth of the long-liner fishing industry, where lines with hundreds of hooks are put out from the backs of fishing vessels. The birds are snared as they chase the baited hooks. With hundreds of sea birds were dying on each line action was required.
The Agreement on Conservation of Albatross and Petrels (ACAP) was established to coordinate international activity to reduce the threats to the species at risk, such as albatrosses and petrels.
The Agreement has been signed by 13 countries and covers 31 species of marine birds.
ACAP aims to reduce the impacts of fishing on seabirds and changing fishing practices. This has included:
Reducing the time the baited hooks are close to the surface and thus available to birds, before they sink into the water.
Using methods to deter birds coming close, such as streamers.
Setting lines at night-time, when birds are not around.
While this has reduced the threat to sea birds it does not eliminate the risk completely.
Other methods
Other ways to reduce by-catch include the types of hooks used on longlines, and the bait used.
Other methods
Other ways to reduce by-catch include the types of hooks used on longlines, and the bait used.
Slide 8 - Video
While countries or regional fisheries management organisations may require these preventative devises to be fitted or the quick release of by-catch, fishing vessels do not always comply.
This video (1.02 min) from Sea Shepherd’s Operation Albacore shows the fishing crew refused to release two humpback whales until the catch had been brought in.
https://www.youtube.com/watch?v=JxzSZFbfF0U
This video (1.02 min) from Sea Shepherd’s Operation Albacore shows the fishing crew refused to release two humpback whales until the catch had been brought in.
https://www.youtube.com/watch?v=JxzSZFbfF0U
Slide 9 - Video
The level of by-catch can be higher in some specific sectors of the fishing industry.
This video (1.00min) from Sea Shepherd’s Operation Albacore shows the extent of by-catch on a shrimp trawler.
https://www.youtube.com/watch?v=pquriDgpt4o
This video (1.00min) from Sea Shepherd’s Operation Albacore shows the extent of by-catch on a shrimp trawler.
https://www.youtube.com/watch?v=pquriDgpt4o
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Refer Teachers Guide for Learning Activities.
