Pregnant rays tangled in trawler nets have small, sickly babies

16 May 2017

By Alice Klein

The accidental capture of pregnant rays in fishing trawls harms their unborn babies.

Rays often get tangled up in trawling nets dragged behind boats to catch large volumes of fish. They are usually thrown back into the sea, but being trapped and brought up to the surface can be traumatic — and sometimes fatal.

Those that survive can experience ongoing health problems and have undersized, sickly babies, found Leonardo Guida at Monash University in Melbourne, Australia, and his colleagues.

The researchers collected 19 pregnant southern fiddler rays (Trygonorrhina dumerilii) from Swan Bay in Victoria off the south coast of Australia, and divided them into two groups.

One group was subjected to 8 hours of being dragged in a trawl net, followed by 30 minutes of air exposure in a crate to simulate commercial fishing. The other group served as a control.
Stunted growth

The trawled mothers lost weight and showed signs of stress, and their offspring were born 27 per cent lighter and 12 per cent shorter in length. Examinations of the babies’ blood also indicated that their immunity was reduced.

These effects could have been caused by the release of stress hormones during trawling, says Guida. These hormones may hamper the growth and impair the immune system of a developing fetus, he says.

The findings may have implications for the long-term survival of ray species, many of which are already listed as vulnerable or endangered, adds Guida. Undersized babies with compromised immunity are more vulnerable to predators and pathogens, and may have impaired fertility.

Trawl fishing could also have adverse effects on the offspring of other species unintentionally swept up in nets, such as sharks, says Guida. 

 

Continued

Identifying Danger Zones Could Help Prevent Sea-Turtle Deaths

By Wynne Parry, LiveScience Contributor | January 18, 2014 09:44am ET

When ocean-dwelling leatherback turtles encounter fishing lines or nets, the results can be deadly for the large marine animals. To help protect these turtles, researchers have identified "hotspots" where some of these deadly encounters are likely occur in the Pacific Ocean.

Leatherback turtles, which weigh up to 2,000 lbs. (900 kilograms), don't have a solid shell. Instead, their shell is made of bones connected by cartilage and covered by leathery skin (hence their name), said James R. Spotila, a study researcher and an ecologist at Drexel University in Philadelphia who studies these and other sea turtles.

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Making Time: How to rescue whales tangled in nets

The Campobello Island Whale Rescue team disentangles whales caught in fishermen's gear and nets around the Bay of Fundy off the east coast of Canada.

To free a trapped whale, you have to tire it out. When writhing around in the water, they can be impossible to cut loose, so volunteer Mackie Greene ties polyurethane balloons to the fishing nets wrapped around their fins.

These make it harder for the giant mammals to dive back beneath the surface, and allow his team to start severing the ropes.

In the early 1990s, Greene had wanted to become a fisherman, but years of overfishing in the Bay of Fundy had left cod stocks heavily depleted.

"I still wanted to be on the water though," he says, "so I started a little whale watching business back in 1995."

The bay is a rich feeding ground for a variety of sea life, attracted to the coast in search of food. The densely populated waters are a similar draw for fishermen, whose nets can prove fatal for the whales.

Greene got to know a team of marine scientists stationed in the bay, and when a whale became wrapped up in a fishing net he helped them untangle the cords and set it free. "I helped them out and I fell in love with it," he says.

Read on

Will nets halt South Africa's shark attacks?

By Karen Allen, BBC News, Cape Town 

You can smell them before you see them: a 20-minute boat ride out to sea from South Africa's coast takes you to False Bay, home to a huge colony of seals. 

It is one of the key attractions for visitors to the Western Cape - a quarter of a million British visitors holiday here every year. 

But the region is also important territory for one of the most feared predators of the deep - the great white shark. 

Within minutes of our boat coming to rest, a 3.5m beast emerges from the depths below and picks off an injured seal. 

This is nature: raw and real. 

It feels even more raw and real being hoisted down in a small metal cage to take a closer look. 

These vast creatures demand respect and, despite their serrated teeth, which are replenished at an astonishingly efficient rate, they are also misunderstood. 

Continued: http://www.bbc.co.uk/news/world-africa-22387564

Humpback whale freed from Queensland shark nets - But hundreds of sharks, dolphins and turtles not so lucky

Indiscrinate nets kill hundreds of sharks, turtles, dolphins and rays
August. 2012. The Queensland Boating and Fisheries Patrol's Marine Animal Release Team has successfully freed a juvenile whale from shark nets off the Gold Coast. Shark Control Program Manager Jeff Krause, from the Queensland Boating and Fisheries Patrol, said the 8 metre long animal was moderately entangled in the nets.

"The Marine Animal Release Team was activated immediately once reports were received of the whale, and quickly assessed the best strategy to release the whale. Seaworld also assisted with the release," Mr Krause said.

"The release was complicated by the whale diving repeatedly under water, and the presence of two adult whales nearby. Throughout the situation the whale was relatively calm and was near the surface, which meant it could breathe easily. It appears the animal was a juvenile, and we often find it is these younger whales that can get caught up. This is mainly due to their inexperience in identifying obstructions in the water such as shark nets."  

Non target species
A Fisheries Queensland spokesperson said "Over the past three years, only one whale each year was caught in shark control equipment and they were all successfully freed."

"The Queensland Government is committed to the Shark Control Program because human safety must come first, but we do strive to get the balance right through the use of a number of measures to reduce entanglements of non-target species."

Continued:  http://www.wildlifeextra.com/go/news/humpback-shark-nets.html

New ‘pingers’ could help save Cornwall’s dolphins

Pingers have been around for a while, but with problems
July 2012. Cornwall Wildlife Trust has found a potential solution to the biggest threat facing Cornwall's dolphins and porpoises - getting tangled in fishing nets. Known as ‘pingers', these devices are fitted to the nets and emit a regular sonic noise to highlight the presence of a net to the animals, thereby reducing their chances of becoming entangled.

Pinger problems
In the past, there have been problems associated with the practicalities and safety of using pingers when previously trialled on larger offshore fishing vessels. This also raised the question as to whether pingers would be practical on smaller vessels, which make up a large proportion of our Cornish inshore static net fishing fleet.

To tackle this problem, Cornwall Wildlife Trust, which has 14,000 members and 90 Business Members, has been working in partnership with Cornish inshore fishermen to trial a suitable pinger that will stop dolphins and porpoises getting caught in nets, without causing major practical problems for usual fishing activity.

Hydrophones
The Trust's pinger trial used hydrophones to monitor porpoise and dolphin activity around nets with and without pingers. The results were positive and showed a 48% reduction in harbour porpoise activity around nets with pingers.

The methodology used by the Trust in this work has been accepted by the scientific community and results have recently been published in the prominent ‘Journal of Cetacean Research and Management'.

Ruth Williams, Marine Conservation Manager for Cornwall Wildlife Trust says, "We are delighted that the trials proved such a success, not only in testing what could be an essential tool in protecting our enigmatic and precious inshore dolphins and porpoises, but also in building good relationships with the fishing industry in this county. The fact that this work has been recognised by the scientific community and published is an additional feather in our cap and we hope we can further progress this vital area of work to help protect our dolphins for the future."

Continued:  http://www.wildlifeextra.com/go/news/cornwall-pinger.html