Tag Archives: tuna

How warm-bodied tuna hearts keep pumping in killer cold

Pacific bluefin tuna are unique amongst bony fish as they are warm bodied (endothermic) and are capable of elevating their core body temperature up to 20°C above that of the surrounding water. They can also down below 1000 m into much colder water that would stop a human heart.

Scientists at The University of Manchester, working with colleagues at Stanford University in America, have discovered how these tuna keep their hearts pumping during these extreme temperature changes.

The research helps to answer important questions about how animals react to rapid temperature changes, knowledge that’s becoming more essential as the earth warms.

Dr Holly Shiels at the Manchester University’s Faculty of Life Sciences says: “When tunas dive down to cold depths their body temperature stays warm but their heart temperature can fall by 15°C within minutes. The heart is chilled because it receives blood directly from the gills which mirrors water temperature. This clearly imposes stress upon the heart but it keeps beating, despite the temperature change. In most other animals the heart would stop.”

The mis-match between oxygen demands of the tunas’ warm swimming muscles and the cardiac system that operates at water temperature is a puzzle the team has long been trying to solve.

“Tunas are at a unique place in bony fish evolution” says Professor Barbara Block at Stanford. “Their bodies are almost like ours – endothermic, but their heart is running as all fish at ambient temperatures. How the heart keeps pumping as the fish moves into the colder water is the key to their expanded global range.”

To study the problem the team, including Dr Gina Galli from Manchester’s Medical and Human Sciences Faculty, worked at the Tuna Research and Conservation Center at Stanford University one of the only places on the planet with live tuna for research.

Professor Block’s team used electronic tags to monitor bluefin tuna in the wild: “These fish are born in the waters off Japan and will swim across the ocean in their first year of life to California. Here we tag the tunas and follow their migrations for years. The data reveals the tuna are very broad ranging in their thermal tolerances and the team from Manchester and Stanford University have worked together for nearly two decades to reveal how the heart of this unique fish is specialised for meeting these temperature changes.”

Tracking bluefin tuna in the wild using archival tags, the researchers were able to measure three things: the depth of the fish; its internal body temperature and the ambient water temperature. They then used the wild data to set the experimental conditions in the lab with single tuna heart cells to see how they beat. The results have been published in Proceedings of the Royal Society B.

Dr Shiels explains their findings: “We discovered that changes in the heart beat due to the temperate, coupled with the stimulation of adrenalin by diving adjusts the electrical activity of the heart cells to maintain the constant calcium cycling needed to keep pumping. If we went through this temperature change our calcium cycling would be disrupted, our hearts would stop beating and we would die.”

Professor Block says that the discovery may explain some strange behaviour they’d monitored in the tagged tuna: “We were recording the fish swimming down into colder depths only to resurface quickly into the warmer surface waters, a so-called “bounce” dive. From work at sea and in the lab we now know the fish hearts slow as they cool and as they resurfaced it sped up. Our findings suggest adrenalin, activated by the stress of diving, plays a key role in maintaining the heart’s capacity to supply the body with oxygen.”

Dr Shiels concludes: “This research was about understanding how animals perform under dramatic environmental changes. This gives us a clear insight into how one species maintains its heart function over varying temperatures, something we will need to study further given recorded changes in the earth’s temperature.”

Further Reading
Cardiac function in an endothermic fish: cellular mechanisms for overcoming acute thermal challenges during diving. H. A. Shiels, G. L. J. Galli, B. A. Block Proc. R. Soc. B: 2015 282 20141989; DOI: 10.1098/rspb.2014.1989. Published 24 December 2014

Fiji achieves her first certified sustainable tuna fishery

The Marine Stewardship Council (MSC) has awarded the Fiji Albacore Tuna Long Line fishery its sustainability certification, the fourth tuna fishery in the South Pacific to achieve this. This follows an independent assessment against the MSC’s standard for sustainable and well-managed fisheries.

MSC manager for Australia, New Zealand and the Pacific, Patrick Caleo, is pleased to recognise another tuna fishery with MSC certification.

“The Fiji albacore tuna fishery is the first albacore long line fishery to demonstrate its sustainability credentials with an MSC certification. Tuna is one of the most popular species of fish and now consumers can enjoy verified sustainable albacore from this Fiji fishery,” he said.
Assessment against the MSC standard, which took 18 months to complete, was conducted by the independent, third party certifier, Intertek Moody Marine. In scoring the fishery the assessment team took into consideration overall stock health and management of albacore in the South Pacific, as well as all potential ecosystem impacts attributed to the Fiji fishery. The assessment found the albacore stock to be in a healthy state and the fishery adhering to good management principles, with marginal impact on habitats and non-target species.

The current certificate is valid for five years, during which progress against the conditions set out in the certification requirements will be tracked and available for public review in annual surveillance audits.

The fishery has committed to take action to meet eight conditions to improve some aspects of the fishery up to the international best practice level. This includes ensuring that management of the fishery is improved to establish reference points and a harvest strategy including harvest control rules. The fishery has also implemented a management strategy that ensures the fishery does not slow down the recovery and rebuilding of retained species.

The assessment has been strongly supported by the Fiji Government through the Fisheries Division, especially in ensure appropriate fishery management conditions are in place.

Further Reading:
Marine Stewardship Council

‘Electronic Eyes’ Watch Tuna Fishing

A Spanish ship is the first tropical tuna vessel to test the latest in electronic monitoring technology, designed for when an onboard human observer is not a practical option. The observation of fishing activities provides validation of critical catch and operational data, integral to scientific analyses and market transparency.

Experts from Archipelago Marine Research Ltd, working on behalf of the International Seafood Sustainability Foundation, outfitted the vessel with a video-based electronic monitoring system. The system uses an array of sensors to monitor key fishing gear, and trigger the video cameras when it detects fishing activity. An onboard control centre manages the system and logs the data, along with boat location, speed and heading information provided by the system’s GPS receiver. Throughout the trip, the system also delivers hourly updates via satellite, reporting vessel position, fishing activity, and other relevant information. Once the vessel returns to port, any portion of the logged data can be reviewed to help evaluate fishing activity.

Borja Soroa, Managing Director of fishing fleet involved said, “The success of this monitoring technology means that even in regions where safety is a chief concern, like it is in the Indian Ocean, observer coverage is not optional. This will become a standard for doing business and we’re committed to doing our part to help make it work.”

The International Seafood Sustainability Foundation (ISSF) is a global coalition of scientists, the tuna industry and World Wildlife Fund (WWF), promoting science-based initiatives for the long-term conservation and sustainable use of tuna stocks, reducing bycatch and promoting ecosystem health.

Further Reading: International Seafood Sustainability Foundation

Mantas and Tuna on Red List of Endangered Species

The latest update of The IUCN Red List of Threatened Species reveals two species of Manta Ray are vulnerable, and the situation is particularly serious for tunas.

Until recently only one species of Manta Ray was known, but new comparisons of field observations now reveal that there are actually two species of ‘manta’: the Reef Manta Ray (Manta alfredi) and the Giant Manta Ray (Manta birostris), both of which are now classified as Vulnerable. The Giant Manta Ray is the largest living ray, which can grow to more than seven meters across. Manta Ray products have a high value in international trade markets and targeted fisheries hunt them for their valuable gill rakers used in traditional Chinese medicine. Monitoring and regulation of the exploitation and trade of both manta ray species is urgently needed, as well as protection of key habitats.

The situation is also particularly serious for tunas. Five of the eight species of tuna are in the threatened or Near Threatened categories. These include: Southern Bluefin (Thunnus maccoyii), Critically Endangered; Atlantic Bluefin (T. thynnus), Endangered; Bigeye (T. obesus), Vulnerable; Yellowfin (T. albacares), Near Threatened; and Albacore (T. alalunga), Near Threatened. The IUCN declare that this information will be invaluable in helping governments make decisions which will safeguard the future of these species, many of which are of extremely high economic value.

“The IUCN Red List is critical as an indicator of the health of biodiversity, in identifying conservation needs and informing necessary changes in policy and legislation to drive conservation forward,” says Jean-Christophe Vié, Deputy Director of IUCN’s Global Species Programme. “The world is full of marvelous species that are rapidly moving towards becoming things of myth and legend if conservation efforts are not more successfully implemented.

Among the marine species classified as critically endangered – the most serious risk category – are staghorn and elkhorn coral, the hawksbill turtle and the Mediterranean Monk Seal. At the moment, though, the marine realm is very poorly covered in the IUCN Red List, comprising less than 5% of the species included. The IUCN has thus identified priority taxonomic groups of marine fish, invertebrates, plants and seaweeds. If these priority groups can be assessed, the number of marine species on the IUCN Red List will be increased more than six-fold, giving a much more accurate picture

Further Reading:
IUCN: Another leap towards the Barometer of Life
IUCN Red List of Threatened Species
More sealife news…

Greenpeace confronts Mediterranean Tuna Fishermen

The Greenpeace flagship Rainbow Warrior has headed off to sea on a campaign to defend the Mediterranean and halt destructive bluefin tuna fishing operations.

Mediterranean bluefin tuna fishing has brought the species to the brink of extinction and is the most visible example of how oceans and fishery management are leading to disaster, says Greenpeace. Scientists have warned of the imminent collapse of the bluefin tuna fishery if fishing continues. The species must be allowed time to recover.

“Politics and fishery management have failed our oceans and set the bluefin tuna on a one-way path to extinction,” said Oliver Knowles, Greenpeace International oceans campaigner. “Others have failed our oceans, so Greenpeace will act. The Rainbow Warrior is now heading to sea to take action against one of the most irresponsible and destructive fishing operations in the world, to demand that the Mediterranean bluefin fishery be closed immediately. We will enforce the repeated recommendations of scientists. If we want bluefin tuna and healthy oceans tomorrow, we need marine reserves today.”

Governments gathered at the meeting of the Convention on International Trade in Endangered Species (CITES) in March failed to approve a ban on the lucrative trade in Atlantic bluefin meat, a measure which could have helped avert rapid bluefin tuna extinction.

“Time and tuna are running out and urgent action to save our oceans is needed now from governments and the public. Consumers must not buy or eat bluefin tuna and governments should put healthy oceans ahead of short-term profits by changing fishing policies and creating marine reserves,” added Knowles.

On Wednesday, Greenpeace activists delayed the departure of three bluefin tuna fishing vessels from the port of Frontignan, France. The vessels were among those with the highest quotas in the French bluefin tuna fishing fleet.

Northern Atlantic Bluefin tuna is fished in the Mediterranean using purse-seine nets, long-liners and other destructive fishing methods. The fishing season this year runs from 16 May until 15 June 2010.

Further Reading:
Greenpeace International

Mediterranean tuna management an “international disgrace”

According to environmental groups, an independent review panel of international fisheries experts has branded the management of the Mediterranean bluefin tuna fishery an “international disgrace” in its conclusions, published this week.

The body responsible for the conservation of tunas and tuna-like species in the Atlantic Ocean and adjacent seas is the International Commission for the Conservation of Atlantic Tunas (ICCAT). The independent panel was commissioned by this very organisation to review its performance following concerns raised by the international community about the management of tuna fisheries resources.

In a very strong and direct recommendation, the Panel asks for “the suspension of fishing of bluefin tuna in the eastern Atlantic and Mediterranean until countries fully comply with ICCAT’s recommendations on bluefin“. Such a closure is seen by the Panel as “the only way to stop the continuation of what is seen by observers and by other contracting party countries as a travesty in fisheries management“.

The Panel found that the management of the Mediterranean bluefin tuna fisheries was “unacceptable and not consistent with the objectives of ICCAT“, such as the objective of guaranteeing that fish populations do not dwindle to unsustainable levels.

In addition to immediate suspension of the fishery, the Panel also recommended the immediate closure of all known bluefin tuna spawning grounds, at least during known spawning periods. This is in line with Greenpeace demands for the closure of the fishery and the creation of no-take marine reserves to protect crucial breeding areas in the Mediterranean Sea. Also needed are minimum size limits to allow the species to breed before being caught, fishing and farming capacities scaled back to sustainable quota levels, and the elimination of pirate fishing.

The Panel attributed the failure of ICCAT management largely due to the lack of implementation of existing regulations by its contracting party countries. However, some problems lie deeper than enforcement of rules. The review drew attention not only to the illegal catch, but also to the fact that the quota set by ICCAT was 29,500 tonnes – almost twice the 15,000 limit recommended by its own scientific committee. As the Panel put it, “it is difficult to describe this as responsible fisheries management and it reflects negatively not only on ICCAT but on all tuna RFMOs“(3).

In November, ICCAT members will review the current bluefin tuna management plan. Pressure groups Greenpeace and the WWF are demanding that they follow the recommendations of the Panel and close the fishery until capacity is decreased, spawning grounds protected and compliance guaranteed.

“Such staggering conclusions from independent experts only reinforce what WWF has been saying for years – this is a fishery grossly out of control, and if the fishery is not closed now pending radical management overhaul, this majestic species may be confined to the history books,” says Dr Sergi Tudela, Head of Fisheries at WWF Mediterranean.

“Fisheries Ministers are failing to protect single species, let alone marine ecosystems. What kind of management organisation ignores the advice of its own scientists and set quotas that condemn the very species it is responsible for??” asked Sebastian Losada, Greenpeace Spain oceans campaigner. “This report signals that it is time for ICCAT members to take responsibility for the fishery that has brought tuna to near-collapse or be relieved of its management altogether.

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Mediterranean leaders urged to save tuna

Bluefin tuna populations have declined alarmingly over the past few decades due to overfishing fuelled by an increasingly expensive industry.

A new WWF report shows that the international fleets hunting this species to extinction have twice the fishing capacity of current quotas and are netting more than three and a half times the catch levels recommended by scientists to avoid stock collapse.

“WWF’s new report uncovers the absurdity of a system long out of control, where hundreds of hi-tech boats are racing to catch a handful of fish,” says Dr Sergi Tudela, Head of Fisheries at WWF Mediterranean.

“It is crazy – the numerous new fleets are so modern and costly that fishermen are forced to fish illegally just to survive – and worse still they are fishing themselves out of a job,” added Tudela.

To keep fishing capacity within the 2008 legal catch limits imposed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), the Mediterranean fleet would need to shed 229 vessels – almost a third of the current 617-vessel fleet. Reducing fishing effort to scientifically recommended levels would require the decommissioning of 283 vessels.

WWF is calling on concerned countries to dramatically reduce capacity in this fishery as a matter of urgency ahead of the 2008 fishing season that starts at the end of April.

WWF also urges ICCAT, the body tasked with sustainably managing the fishery, to take a lead in proposing radical solutions. Until the fishery is under control and sustainably managed, WWF continues to advocate a fishing ban – and to applaud responsible retailers, restaurants, chefs and consumer groups who are boycotting Mediterranean bluefin in increasing numbers.

“The fishery is unsustainable in every way – economically, socially, and ecologically. When will the situation be brought under control? The time to act is now – while there are still bluefin tuna to save in the Mediterranean,” Tudela concluded.

What can you do? If you want to buy a tin of tuna off the supermarket shelf don’t worry – you almost never find bluefin tuna in a tin. Most tinned tuna is yellowfin or skipjack. If you buy fresh tuna ask your fishmonger whether the tuna is Atlantic bluefin, and whether it comes from the Mediterranean. If it does come from the Med, don’t buy it. And at the Japanese restaurant check where they source the Atlantic bluefin tuna. If it is from the Mediterranean, avoid it.

Note: the tuna caught in the Med is called “Atlantic Bluefin Tuna” (Thunnus thynnus). Don’t think that because it has the word Atlantic in the name that means it was caught there.

Further Reading:
Bluefin tuna in crisis
Race for the last bluefin: Capacity of the purse seine fleet targeting bluefin tuna in the Mediterranean

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