What is marine mammal bycatch?

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what is the bycatch of marine mammals

Marine ecosystems constitute the lifeblood of our planet, playing a pivotal role in sustaining biodiversity and regulating global climate patterns. They harbor an unparalleled diversity of life, from marine microscopic organisms to majestic marine creatures.

These marine ecosystems provide essential services, including oxygen production, carbon sequestration, and nutrient cycling, which are vital for maintaining ecological balance. Unfortunately, human activities pose significant threats to these fragile environments, leading to detrimental consequences such as habitat destruction, pollution, and overfishing.

Among these challenges, the issue of bycatch of maritime mammals in the fishery emerges as a pressing concern. According to the Food and Agriculture Organization of the United Nations (FAO), statistics indicate that over 500,000 marine mammals, fall victim to bycatch across various fisheries every year.

Given the escalating threats posed by human activities, there’s an urgent need for conservation efforts to reduce bycatch and safeguard these invaluable marine ecosystems from irreversible damage.

Fishermen occasionally capture and discard unintended marine species they either don’t target, cannot market, or are prohibited from retaining. This phenomenon is commonly referred to as ‘bycatch,’ encompassing not only fish but also mammal creatures like dolphins, whales, sea turtles, and seabirds, which inadvertently get ensnared or hooked in fishing apparatus.

Bycatch of marine mammals indicates the incidental capture or confusion of marine species in fishing gear or other human activities targeting different marine varieties.

Different types of marine mammals

different types of marine mammals affected by bycatches

The concern happens because commercial maritime vessels and their gear are made to snare as many fish as possible using methods like gill netting or purse seining. More careful methods like pole and line fishing where one fish is caught at a time are not used by boats because they cost more and take longer. In addition, the longline fishery along the coast is notorious for its high rates of marine mammal bycatch, posing a significant threat to protected species.

Protected maritime mammals are categorized into four distinct taxonomic groups in the fisheries:

  • Cetaceans: encompass whales, dolphins, and porpoises.
  • Pinnipeds: including seals, sea lions, and walruses.
  • Sirenians: represented by manatees and dugongs.
  • Fissipeds: consists of polar bears and sea otters.

Which methods catch the most unintended marine mammals?

Large-scale fishing operations trap more unintended marine mammals compared to small-scale subsistence trawling. Numerous techniques are used, all of which capture marine creatures indiscriminately, whether they are alive or dead.

Gillnets: Due to their affordability and high trap rates, the fishing method gillnet ranks among the most prevalent options in fisheries worldwide. Gill netting is an international technique that permits only the fish’s head to pass through the net. As the fish attempts to flee, its gill cover becomes ensnared, trapping it in the net.

Purse seine: Another fishing practice is purse seining, a large fishing net used to encircle schools in open waters. The net is deployed in a circular manner around the fish, and then its bottom is drawn closed, resembling a purse, hence the name “purse seine.”

Importance of marine mammals in marine ecosystems

Although there are fewer marine mammals than land animals, these animals have key roles in marine ecosystems, like controlling prey numbers. This is worrying because 23% of these protected animals are in danger, and they are crucial for keeping the oceans healthy.

Marine mammals’ roles in the ecosystem

Marine mammals play integral roles in maintaining the balance and health of marine ecosystems worldwide. As apex predators, marine species like dolphins and whales help the management of prey marine populations, preventing ecological imbalances. Their movements and migrations facilitate nutrient cycling and ocean mixing, contributing to the overall health of marine habitats.

Additionally, marine creatures serve as indicators of marine health, reflecting changes in marine ecosystem dynamics and environmental conditions. For example, the decline of certain aquatic habitats may signal overfishing or marine habitat degradation.

Furthermore, their carcasses provide sustenance to deep-sea communities, fostering biodiversity in ocean depths. When protecting these marine animals, ensuring the resilience and sustainability of ecosystems for future generations is guaranteed.

Conserving the vulnerable marine species

The issue gained attention when biologist Sam LaBudde assumed an undercover role as a cook on a Panamanian tuna fishing vessel in 1987. Over his four-month stint, he meticulously documented the tragic reality: hundreds of dolphins perished as bycatch during the tuna harvesting process.

These animals play vital roles in food webs and the management of marine populations of prey species.

For example, large whales play a significant role in bolstering primary productivity within marine ecosystems by releasing nitrogen and other nutrients into the ocean surface through their excretions, a process commonly termed the “whale pump.”

By conserving marine species, biodiversity is safeguarded and the delicate balance of marine habitats is preserved. Additionally, marine mammals serve as indicators of ocean health, signaling changes in environmental conditions and human impacts. Their conservation not only ensures the survival of these protected mammals but also benefits coastal communities reliant on marine resources for livelihoods and sustenance.

Types of marine mammals affected by bycatch

Marine mammals encompass a wide array of animals reliant on the sea for sustenance. While classified as mammals, they do not necessarily share a recent common ancestor but have independently evolved to thrive in environments. Their primary criterion for inclusion is dependence on the sea for sustenance. Some, like dolphins, have fully adapted to aquatic life, while others, such as polar bears, seals, and otters, navigate between land and sea.

Overview of different vulnerable marine species

The unintended capture of non-target marine species in fishing gear poses a significant threat to various types of marine life. Among animals commonly affected by mortality due to bycatch in fisheries are

  • Cetaceans: whales, dolphins, and porpoises.

Fishing nets or longlines intended for other animals often entangle these highly intelligent and social marine creatures or hook them.

  • Pinnipeds: seals, sea lions, and walruses.

These protected marine animals are susceptible to marine bycatch, particularly in gillnets and trawls.

  • Sirenians: manatees and dugongs

The indiscriminate nature of tools also affects sirenians, who may inadvertently fall victim to bycatch practices in the fishery. These vulnerable marine mammals face severe injuries or death when they are caught in accidental entanglement through hooks or other fishing methods.

Long-term consequences for marine mammal populations

Long-term consequences for aquatic populations can be profound, influenced by various factors including overharvesting and bycatch.

  • Marine habitat degradation, pollution, and climate change
  • The stressors can disrupt marine ecosystems, fragment habitats, and deplete prey populations, which will reduce reproductive success and diminish marine genetic diversity.
  • Increased susceptibility to diseases among marine creatures.
  • Alterations in oceanic conditions


For example, ocean acidification in the Canary Current in the Atlantic Ocean, resulting from increased carbon dioxide levels, inhibits the ability of corals to build their calcium carbonate skeletons, essential for their structure and growth.

Ecological implications of marine mammals’ bycatch

The issue carries profound ecological implications, imperiling biodiversity and disrupting marine ecosystems. According to the International Whaling Commission, fishing gear claims the lives of at least 300,000 cetaceans annually, resulting in an estimated 800 whales, dolphins, or porpoises per day. This indiscriminate loss affects not only target marine fauna but also the delicate balance of marine habitats.

Bycatch of marine mammals depletes marine populations of vulnerable species, destabilizes food webs, and hampers ecosystem resilience. Moreover, by disrupting trophic interactions, it triggers cascading effects throughout the marine environment. An urgent program should be released to reduce the practice through improved practices, technological innovations, and a robust program, safeguarding marine populations and preserving ecosystems for future generations.

Efforts to mitigate the bycatch of marine mammals

Throughout history, fishing has been a fundamental source of sustenance for human communities, woven into the fabric of civilizations for thousands of years. Nevertheless, over the past five decades, seafood consumption has more than doubled, driven by advancements in more efficient fishing techniques.

efforts to mitigate the bycatch of marine mammals

Overview of existing innovations

Existing regulations and policies on bycatch aim to reduce its adverse impacts on marine ecosystems and non-target marine animals. These measures typically involve the establishment of bycatch reduction targets, the implementation of new tools, and the adoption of time-area closures to protect marine-sensitive habitats. International regulations should work on the adoption of alternative tackle, monitoring programs, and technologies such as:

  • Turtle Excluder Devices: designed to enhance turtle conservation efforts, turtle excluder devices, commonly known as TEDs, play a pivotal role in minimizing entangled turtles with trawl fishing supplies. Comprising sturdy metal bars and mesh, the devices are inserted into the throat of trawl nets. As shrimps traverse through the bars to the posterior end of the net, larger creatures encounter the metal structure and are guided out through a mesh opening, preventing accidental capture.


  • Acoustic deterrent devices (ADDs): known as, acoustic alerting devices or ‘pingers,’ the innovations are electronic or mechanical gadgets designed to emit specific sounds. Typically, these devices are compact, cylindrical units resembling the size of a standard soda can. Attached to angling gear, they emit acoustic signals for detection or prompting cetaceans. This proactive measure was released to prevent marine mammals’ entanglements and accidental drownings.


  • NOAA: The commitment and assessment of NOAA (National Oceanic and Atmospheric Administration), also known as the NMFS (National Marine Fisheries Service), to advancing marine mammal science have resulted in the development of innovative technologies to reduce bycatch in sensitive fisheries.


  • Obsmer Program: Obsmer is a program for observing professional fishing vessels at sea, implemented nationally (in France), since 2009 by the DGAMPA – Directorate General of Maritime Affairs, Fisheries, and Aquaculture. The observations conducted at sea enable the measurement of fishing activity and the sampling of bycatches.


  • OBSCAMe Program:
    It’s a project studying bycatches of marine mammals by fishermen using onboard cameras. The goal is to gain a deeper understanding of the circumstances surrounding these catches to prevent them more effectively. This program is the first in a list of different programs (OBSCAMe IV, OSBCAMe +).

Protecting the marine mammals using AI

Using AI technology is a better way to protect marine mammals from accidental capture in fishing gear. By analyzing data and spotting trends, AI helps to create smarter solutions to prevent harm to marine mammal populations and keep them safe in the oceans.

Sinay is the top innovator in the maritime sector that helps maritime-based businesses around the world with data management related to operations and environmental impacts. The tech company was released to emphasize the importance of leveraging Artificial Intelligence (AI) and data analytics to address marine environmental challenges, including the bycatch of marine mammals.

Sinay uses advanced AI algorithms and real-time data analysis to develop selective fishing gear aimed at reducing the unintentional capture of maritime mammals, such as dolphins and whales. By leveraging machine-learning technology, the company’s initiatives focus on creating solutions that significantly decrease the incidental capture of non-target species during maritime activities. This assessment and approach align with its commitment to sustainability and its efforts to reduce the environmental impact of maritime operations on marine ecosystems.

Regulations and collaborative efforts among stakeholders

Regulatory frameworks, established by governmental commissions, and national and international organizations, set standards and guidelines to reduce the bycatch of marine mammals. These regulations often include the implementation of the issue’s reduction devices, supply modifications, and area closures to protect vulnerable marine species and sensitive habitats.

Through collective action and shared responsibility, diverse parties contribute to the development of strategies fostering sustainable practices in the fisheries. Collaborative initiatives encompass research, policy development, and the promotion of innovative technologies to reduce the practices. These efforts prioritize marine ecosystem health, marine species preservation, and the long-term viability of marine ecosystems.

Code of Conduct for Responsible Fisheries

The Food and Agriculture Organization (FAO) Code of Conduct for Responsible Fisheries serves as a comprehensive framework for promoting sustainable fisheries management worldwide. Adopted in 1995, it aims to ensure the long-term viability of fish stocks and marine ecosystems while supporting the livelihoods of marine communities.

The bottom line

The inadvertent capture of non-target marine species in fishing equipment remains a pressing concern with significant ecological implications. The bycatch of marine mammals in the fishery threatens the survival of oceanic populations, leading to declines in biodiversity and destabilizing ecosystems. The devastating consequences underscore the urgent need for concerted action from stakeholders and the commission. It is imperative to learn and implement effective mitigation measures, including the use of Artificial Intelligence, acoustic deterrent devices, and improved practices. Safeguarding marine mammals and preserving biodiversity for future generations is a collective responsibility.

Also, it’s important to remember that fishermen don’t enjoy accidentally catching marine mammals! This is why direct collaboration with fishermen is essential to reduce catches and find suitable methods.

Frequently Asked Questions About Byctach of Marine Mammals

Bycatch of marine mammals refers to the unintentional capture or entanglement of species like dolphins, whales, sea turtles, and seabirds in fishing gear meant for other species.

This phenomenon occurs across various fishing methods and poses a significant threat to marine biodiversity.

Large-scale fishing operations, particularly those using gillnets and purse seines, are known to catch the most unintended marine mammals due to their indiscriminate nature.

Gillnets, for example, trap marine creatures by their gills, while purse seines encircle schools of fish, often resulting in bycatch of non-target species.

Long-term consequences of marine mammal bycatch include habitat degradation, pollution, climate change, and increased susceptibility to diseases.

These stressors disrupt marine ecosystems, fragment habitats, deplete prey populations, and diminish genetic diversity, ultimately threatening the survival of marine mammal populations.

Efforts to mitigate marine mammal bycatch include the use of innovative technologies like Turtle Excluder Devices and Acoustic Deterrent Devices, as well as regulatory frameworks and collaborative initiatives among stakeholders.

Additionally, leveraging Artificial Intelligence (AI) for data analysis and developing selective fishing gear can help reduce unintentional captures and preserve marine mammal populations.

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