bycatch

Shipping And The Endangered Whale Shark | Earth Wise

June 9, 2022 By EarthWise Leave a Comment

Whale sharks are the largest fish in the world. While they measure up to 60 feet long and weigh up to 15 tons – larger and heavier than a school bus – whale sharks are actually harmless. They are a graceful, slow-moving, filter-feeding carpet shark. They are found in marine environments around the world and play an important role in the marine food web and healthy ocean ecosystems.

Whale sharks are an endangered species. According to the International Union for Conservation of Nature, growing human pressures are putting whale sharks at an increased risk of extinction. The numbers of these gentle giants have declined by more than 50% over the last 75 years despite many international protections. Fishing bycatch, poaching, and collisions with ships are the main drivers of the population decline.

According to new research from marine biologists from the Marine Biological Association and the University of Southampton in the U.K., lethal collisions between whale sharks and large ships are vastly underestimated, and could be the reason why populations are continuing to fall. Whale sharks spend a large amount of time in surface waters in coastal regions, and the research team theorized that collisions with ships could be causing significant whale shark deaths.

In the study, researchers tracked the global movements of both ships and whale sharks, and then mapped so-called hotspots where their movements overlapped. The research team found that more than 90% of whale shark movements fell under the footprint of shipping activity.

While many conservation measures have been taken to protect whale sharks, no international regulations currently exist to protect them from ship collisions. The researchers say it’s time for that to change.

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Shipping poses significant threat to the endangered whale shark

Whale sharks (Rhincodon typus)

Global collision-risk hotspots of marine traffic and the world’s largest fish

Photo, posted July 8, 2010, courtesy of Marcel Ekker via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Assessing Human-Caused Wildlife Mortality | Earth Wise

May 31, 2022 By EarthWise Leave a Comment

Bycatch is the fishing industry term used to describe the deaths of non-target fish and ocean wildlife during the fishing process. Some bycatch species are thrown away because regulations prohibit them from being kept. Others are thrown out because they won’t fetch high enough prices. According to some estimates, global bycatch amounts to about 10% of the world’s total catch.

Approximately half of global bycatch is a result of trawling. Trawling is a method of commercial fishing that involves pulling or dragging a fishing net – called a trawl – through the water or across the seabed in hopes of catching fish. Commercial fishing companies favor towing trawl nets because large quantities of fish can be caught. But the method is destructive to the seafloor and leads to the indiscriminate catch of all sorts of species, including whales, dolphins, porpoises, sharks, seals, rays, turtles, and seabirds.

Researchers have developed a new method to assess the sustainable levels of human-caused wildlife mortality. When this method is applied to a trawl fishery in Australia, it shows that the dolphin capture is not sustainable. The study, led by scientists at the University of Bristol in the U.K. and United Arab Emirates University, modeled different levels of dolphin capture, including those reported in logbooks and those reported by independent observers. According to the findings, which were recently published in the journal Conservation Biology, even the lowest recorded dolphin capture rates are not sustainable.

The new approach is extremely adept at assessing human-caused mortality to wildlife, and can be applied to fisheries bycatch, hunting, lethal control measures, or even wind turbine collisions.

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Wasted Catch

Dolphin bycatch from fishing practices unsustainable, study finds

Photo, posted May 18, 2011, courtesy of Pete Markham via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Biodiversity And Trawling Bans | Earth Wise

June 7, 2021 By EarthWise Leave a Comment

Trawling is a method of commercial fishing that involves pulling or dragging a fishing net – called a trawl – through the water or across the seabed in hopes of catching fish. Commercial fishing companies favor towing trawl nets because large quantities of fish can be caught in one go.

However, the trouble with trawling is that it’s destructive to the seafloor and indiscriminate in what it catches. When towing these large trawl nets, the largest of which is reportedly big enough to catch thirteen 747 jets, everything that happens to be in the way gets caught. As a result, trawling results in lots of bycatch, a fishing industry term used to describe the deaths of non target species during the process.

In 2012, the Hong Kong government implemented a territory-wide trawling ban in its waters in hopes of rehabilitating the marine benthic habitat. The benthic zone refers to the ecological region at the bottom of the ocean.

Researchers from City University of Hong Kong collected sediment samples from 28 locations six months before the trawl ban and two and a half years after the trawl ban to see whether such interventions can facilitate ecosystem recovery.

According to the study, which was recently published in the journal Communications Biology, the ban on trawling significantly improved marine biodiversity. The researchers observed substantial increases in the richness of species and the abundance of benthic marine organisms following the trawling ban. And since small benthic organisms are the main source of food for large species like fish and crabs, the trawling ban actually helps support fisheries.

More governments should consider a trawl ban to promote sustainable fisheries and marine biodiversity conservation.

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Research confirms trawl ban substantially increases the abundance of marine organisms

Photo, posted December 4, 2018, courtesy of John via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

The Costs Of Mislabeled Seafood | Earth Wise

January 27, 2021 By EarthWise Leave a Comment

Seafood is the world’s most highly traded food commodity and reports of seafood mislabeling have become increasingly common over time. A new study by Arizona State University looked at the environmental effects of mislabeled seafood.

What is mislabeled seafood? Sometimes the snapper you were served was really Pacific Ocean Perch. Maybe grouper was really whitefin weakfish. Many times white leg shrimp are actually giant tiger prawns.

Approximately 190,000 to 250,000 tons of mislabeled seafood are sold in the U.S. each year, or 3.4 to 4.3% of consumed seafood. Previous studies focused on the economic aspects of getting cheaper fish when paying for more expensive fish. The new research looks at the environmental costs associated with mislabeled seafood.

Substituted seafood is 28% more likely to be imported from other countries, which may have weaker environmental laws than the U.S. In the United States, fishery management is pretty good. There is strong monitoring and enforcement to support limits on fishing. Metrics like fish abundance, fishing mortality, bycatch, and discards are all monitored. In many other places, this is not the case.

To really evaluate the overall effects of seafood mislabeling, one has to take into account both the rates of substitution and the levels of consumption.

Consuming fish from a well-managed fishery should not have a negative impact in terms of the population now or in the future. But even inadvertently consuming fish from poorly managed fisheries in not sustainable. It is good to get your seafood from a trusted source.

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ASU Study Looks At The Environmental Effects Of Purchasing, Consuming Mislabeled Fish

Photo, posted August 1, 2014, courtesy of Ralph Daily via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Sharks On The Decline | Earth Wise

September 4, 2020 By EarthWise Leave a Comment

During the past 70 years, global shark populations have been on the decline. Many species have become threatened or endangered. Conservation efforts have been underway in many places, but shark populations continue to be at risk because of over-fishing and habitat loss.

A comprehensive study by marine biologists at Texas A&M University deployed more than 15,000 baited remote underwater video stations on 371 coral reefs in 58 countries. The study included 59 different shark species in the Atlantic, Pacific and Indian Oceans. The researchers were surprised to find that no sharks at all were detected in almost 20% of the locations surveyed and were almost completely absent from coral reefs in several nations.

Scientists believe that demand for shark products, such as fins and meat, and bycatch (that is, sharks captured in nets by fisherman trapping other kinds of fish) are strong contributors to the widespread declines in shark numbers around the world.

The study shows that if corrective steps are not taken in regions where marine management is still ineffective, continued depletion of shark populations is highly likely.

Sharks have important roles in marine ecosystems. When their habitats deteriorate and their populations decrease, ecosystem stability and health is degraded because sharks help regulate prey populations.

Some countries, notably the Bahamas, are combating the problem by providing sanctuaries for sharks where fishing and harvesting is prohibited. Such places support some of the healthiest shark populations in the world. However, the decline of coral reefs is just another challenge facing shark populations around the world.

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Study Shows Alarming Decline In Shark Numbers Around The World

Photo, posted January 9, 2017, courtesy of Kris-Mikael Krister via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Keeping Lights On For Turtles

August 8, 2019 By EarthWise Leave a Comment

Gillnets are one of the most common types of fishing gear and are used extensively in most places where people fish for food. They operate by suspending a wall of netting in the water column.

Unfortunately, they are not selective in the species they catch. Sea turtles are one of the most common bycatch species that become entangled in these nets. When turtles are caught in gillnets, they can drown and die. Marine mammals, seabirds, and sharks are also frequently caught in gillnets.

Recently, researchers have been experimenting with illuminating the nets with LED lights to see if increasing net visibility reduces sea turtle bycatch.

Studies in Mexico show green sea turtle bycatch is reduced between 40-60% with no changes in target catch. Studies in Peru show green sea turtle bycatch is reduced between 65-80% with no changes in target catch. Studies in Indonesia show green olive ridley, and hawksbill sea turtle bycatch is reduced by 60% with increases in target catch and catch value.

Recent research shows that net illumination also reduces bycatch of other protected species such as seabirds, sharks and rays, as well as dolphins and porpoises.

The use of illuminated gillnets could prove beneficial to both sea turtles and fisherman by reducing the bycatch that can damage fishing gear.

Studies are now underway off the coast of North Carolina, where state gillnet fisheries are carefully managed to reduce turtle bycatch. Initial studies show that net illumination does not change target catch rates and may even decrease the bycatch of unwanted fish species. When it comes to protecting sea turtles, it looks like a good idea to keep the lights on.

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Illuminated Nets Could Provide A Brighter Future For Sea Turtles

Photo, posted June 2, 2016, courtesy of NOAA via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Is Sustainable Seafood Really Sustainable?

December 5, 2017 By EarthWise Leave a Comment

Tuna is perhaps the most popular seafood. We eat it out of a can, we splurge on high-end sushi, and we prepare it in many other ways. Some species of tuna are over-fished and some fishing methods are unsustainable. As concerned consumers, we would like to know what sort of tuna we are eating.

The State Of The Birds

June 6, 2016 By WAMC WEB

The North American Bird Conservation Initiative recently released its annual “State of the Birds’ report, which is a comprehensive analysis of North American birds. And as with many other things these days, we’re not doing well.