Impact of Exploitation of the Oceans » Bycatch Issues and Impacts

What you'll learn this session

Study time: 30 minutes

Definition and types of bycatch in ocean exploitation
Environmental impacts of bycatch on marine ecosystems
Social and economic implications of bycatch
Bycatch reduction methods and technologies
Case studies of bycatch issues around the world
International policies and agreements addressing bycatch

Introduction to Bycatch

When fishing vessels set out to catch specific target species, they often unintentionally catch other marine creatures that weren't meant to be caught. This accidental capture is called 'bycatch' and it's one of the most serious problems affecting our oceans today.

Key Definitions:

Bycatch: The unintentional capture of non-target species during fishing operations.
Target species: The specific fish or marine organisms that fishing operations aim to catch.
Discards: Unwanted bycatch that is thrown back into the sea, often dead or dying.
Ghost fishing: Lost or abandoned fishing gear that continues to trap and kill marine life.

♥ Types of Bycatch

Bycatch can include:

Undersized individuals of the target species
Non-commercial fish species
Marine mammals like dolphins and whales
Sea turtles and seabirds
Sharks and rays
Corals and other bottom-dwelling organisms

! Bycatch Statistics

The scale of bycatch is enormous:

About 40% of global marine catch is bycatch
Over 300,000 small whales, dolphins and porpoises die from entanglement each year
Longline fisheries accidentally catch thousands of sea turtles annually
Some shrimp trawlers discard up to 10kg of bycatch for every 1kg of shrimp caught

Environmental Impacts of Bycatch

Bycatch has far-reaching consequences for marine ecosystems and biodiversity. When non-target species are caught and killed in large numbers, it can disrupt entire food webs and push vulnerable species toward extinction.

Impacts on Different Marine Groups

♦ Marine Mammals

Dolphins, whales and porpoises can get caught in fishing nets and drown because they need to surface to breathe. Some populations have declined by over 80% due to bycatch. The vaquita porpoise in Mexico is nearly extinct with fewer than 10 individuals remaining, largely due to gillnet bycatch.

♦ Sea Turtles

All seven species of sea turtles are threatened or endangered, with bycatch being a major cause. Turtles get caught on longline hooks or entangled in nets. They can drown if trapped underwater too long. Hundreds of thousands of sea turtles are accidentally caught each year.

♦ Seabirds

Albatrosses and other seabirds are attracted to baited hooks on longlines and can get hooked and drown. An estimated 300,000 seabirds die annually as bycatch. Some albatross populations have declined by more than 90% partly due to fishing activities.

Ecological Consequences

Bycatch doesn't just affect individual species it can disrupt entire marine ecosystems:

Food web disruption: Removing large numbers of predators or prey species can create imbalances in marine food webs.
Reduced biodiversity: High bycatch rates can reduce genetic diversity and push species toward extinction.
Habitat damage: Some fishing methods that cause high bycatch, like bottom trawling, also damage seafloor habitats.
Wasted resources: Discarded bycatch represents a huge waste of marine resources, especially when dead animals are thrown back.

Case Study Focus: Dolphin-Safe Tuna

In the 1950s-1980s, yellowfin tuna fisheries in the Eastern Pacific Ocean caused the deaths of millions of dolphins. Fishermen would locate tuna by spotting dolphins swimming above tuna schools, then encircle them with purse seine nets. This resulted in up to 100,000 dolphin deaths annually.

Public outcry led to the International Dolphin Conservation Program and "dolphin-safe" tuna labelling. These initiatives reduced dolphin mortality by over 99%. Today, dolphin-safe tuna must be caught using methods that don't intentionally encircle dolphins and independent observers monitor compliance on vessels.

This case demonstrates how consumer awareness, policy changes and fishing practice modifications can dramatically reduce bycatch impacts.

Social and Economic Impacts

Bycatch isn't just an environmental problem it has significant social and economic implications too:

£ Economic Costs

Wasted fishing effort and fuel when catching non-target species
Time spent sorting and discarding unwanted catch
Damage to fishing gear from large bycatch species
Lost future fishing opportunities when juvenile fish are caught before reproducing
Market access restrictions for fisheries with high bycatch rates

♣ Social Implications

Conflicts between different fishing sectors (e.g., commercial vs. recreational)
Impacts on coastal communities dependent on diverse marine resources
Cultural losses when traditional fishing practices must change
Ethical concerns about wasteful fishing practices
Reputational damage to fishing industries with high bycatch

Bycatch Reduction Methods

Fortunately, there are many ways to reduce bycatch through technological innovations, fishing practice changes and management approaches:

Technological Solutions

Turtle Excluder Devices (TEDs): Metal grids installed in trawl nets that allow shrimp to pass through but direct larger animals like sea turtles out through an escape hatch.
Circle hooks: Specially designed fishing hooks that reduce sea turtle bycatch in longline fisheries by up to 90% compared to traditional J-hooks.
Acoustic deterrents: "Pingers" that emit sounds to warn dolphins and porpoises away from gillnets.
LED lights: Attaching green LED lights to fishing nets can reduce sea turtle bycatch by 64% while maintaining target catch rates.
Bird-scaring lines: Streamers attached to longlines that scare away seabirds before they can take baited hooks.

Fishing Practice Changes

Time-area closures: Restricting fishing in certain areas during times when bycatch species are abundant.
Setting gear at night: Some species are less active at night, reducing their chances of being caught.
Deeper setting: Setting longlines deeper can avoid seabird bycatch.
Reduced soak time: Checking fishing gear more frequently allows for quicker release of bycatch species.

Case Study Focus: New Zealand Seabird Bycatch Reduction

New Zealand waters are home to more seabird species than anywhere else on Earth, including 36 albatross and petrel species. These birds were being caught at alarming rates by longline fisheries.

The country implemented a comprehensive approach including:

Mandatory use of bird-scaring lines (tori lines)
Night setting of longlines when birds are less active
Adding weights to lines so they sink quickly out of birds' reach
Strict rules about discarding offal that attracts birds
Observer programs to monitor compliance

These measures reduced seabird bycatch in New Zealand fisheries by over 80% while maintaining profitable fishing operations.

International Policies and Management

Addressing bycatch requires coordinated action at local, national and international levels:

UN Fish Stocks Agreement: Requires countries to minimize bycatch and impacts on associated species.
FAO Code of Conduct for Responsible Fisheries: Provides principles for reducing waste and bycatch.
Regional Fisheries Management Organizations (RFMOs): Develop specific measures for bycatch reduction in international waters.
Marine Stewardship Council certification: Requires fisheries to demonstrate minimal ecosystem impacts, including bycatch.
National bycatch reduction plans: Many countries have developed specific targets and measures to reduce bycatch in their waters.

What Can You Do?

Everyone can help reduce the impacts of bycatch:

Choose seafood from sustainable sources that use bycatch reduction methods
Look for eco-labels like Marine Stewardship Council (MSC) certification
Use seafood guides like the Good Fish Guide to make informed choices
Support organizations working on bycatch reduction
Learn about and raise awareness of bycatch issues

Summary

Bycatch represents one of the most significant impacts of ocean exploitation. It threatens marine biodiversity, wastes resources and creates economic inefficiencies. However, through technological innovation, changes in fishing practices and effective management, bycatch can be substantially reduced while maintaining viable fisheries.

The successful examples of dolphin-safe tuna and seabird bycatch reduction show that when there's sufficient will to address the problem, solutions can be found that benefit both marine ecosystems and the fishing industry.

As future decision-makers, your understanding of these issues will be crucial in developing more sustainable approaches to ocean resource use.

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