Author: scbi@web

This article was first published on our Club’s sister, campaigning web site – Bluefin Tuna UK. 

In September 2000, the first Irish rod caught Atlantic Bluefin Tuna (ABFT), was taken out of Killybegs, in the Donegal Bay. Three fish were taken that season, including a new Irish record of 529lbs. This hugely significant event was the start of an amazing story, but the best was yet to come, by far….

What happened the following year set angling circles worldwide alight. Adrian Molloy, whose name would soon become synonymous with some of the best Atlantic Bluefin fishing in the world, achieved an incredible feat. From a small fishing boat out in the Donegal bay, he hooked, played and landed an incredible 968lb ABFT, below, setting a new European and Irish record that still stands in 2019.

Decline and fall, and rise…..
A number of fish were taken over the following 3 years but perhaps consistent with the huge decline occurring at that time in Bluefin numbers, after 2005 they pretty much disappeared from those Irish waters.

ICCAT, the species’ Global Management body, finally responded to this crisis and in 2007 enacted a 15 year recovery plan. From around 2010, the Stock Spawning Biomass troughed and began to recover, evidenced by multiple, wide ranging stock assessments since. Bluefin began to return to Irish waters from around 2012, aided perhaps by the then fledgling recovery in stocks, but also it seems by a major shift in a long term (typically 25-40 years) North Atlantic climatic cycle, the AMO, that entered a new phase early this century.

Whatever the reason, from 2013 on, ABFT have been regularly sighted and caught off of Donegal and indeed other parts of the Irish coast. Adrian Molloy was at the centre of efforts to persuade the Irish Government to lobby the EU to allow Ireland to set up a recreational catch and release fishery. ICCAT and EU rules deemed such a fishery illegal at that time for any country such as Ireland that did NOT hold a part of the EU’s huge share of the Global quota for Atlantic Bluefin. Adrian initiated and took part in a number of authorised research programs from 2016 involving the capture of ABFT and the application of high tech Satellite Tags that pop off after 9-12 months revealing great detail of the behaviour of that fish over the previous months. 

Despite the Irish Government’s lack of willingness or success in establishing a recreational fishery, multiple Irish skippers continued to operate charters to catch and release ABFT. In 2018, Adrian caught, tagged and released 228 Bluefin, including many under formal Research programs. With fish typically ranging from 250-500lbs, this feat is UNRIVALLED BY ANY CHARTER VESSEL OPERATOR IN THE WORLD. 

EU threats, a silver lining.
In August 2018, the EU audit office issued a formal warning to Dublin that Ireland was ‘operating an illegal recreational Bluefin Tuna fishery’, and that if it was not stopped, Dublin could face huge fines….

Faced with a PR disaster, with Brussels penalising Ireland for activities France, Spain and Italy amongst other carry out perfectly legally, in the midst of sensitive Brexit negotations with huge implications for Ireland, the EU found a temporary solution.

ICCAT rule changes in 2017 made it easier to establish authorised catch, tag and release programs in ‘non quota holding countries’. In early 2019 such a program was announced for Ireland, From mid August 2019 for 2 months, 15 charter vessels would be licensed to take paying recreational anglers to participate in a widespread EU/ICCAT authorised floy tagging program in Irish waters. At last, an opportunity existed for large numbers of anglers to experience this amazing angling opportunity free of concerns regarding the legality of those trips.

A fellow SCBI – Sportfishing Club of the British Isles – Club Member and I decided we wanted to get a piece of this action. The opportunity to fish with the ‘godfather’ of not just Irish but at the very least European Recreational ABFT fishing, Adrian Molloy, was just too good to ignore.

A trip to Donegal, this world renowned fishery, in the company of Adrian was no less than a pilgrimage for us, underpinned by the knowledge we might gain from our time with him.

The Pilgrimage.
In early October, Barry and I, along with renowned UK Charter skipper Jerry Rogers, touched down in Ireland at Knock airport, appropriately the centre for another pilgrimage, to the Sanctuary of our Lady of Knock.

Knock lies a good 100 miles South of Kilcar, our base on the North side of Donegal bay for the coming three days. A hire car was secured and a journey through some incredible scenery began. As you head North through Sligo, and hit the coast road, Donegal bay begins to appear on your left. The scale of it is breathtaking, At its widest point between, Malin Head and Ballyconnel, it is over twenty miles across, surround by imposing granite mountains that crash down to the sea, and many small inlets offering sheltered waters. 

The North side of the Bay is dominated by Killybegs, a largish fishing port home to dozens of huge pelagic offshore trawlers.

Kilcar is a small village containing everything a Bluefin fisherman could want. A great Bed and Breakfast, run by Adrian’s sister-in-law, two supermarkets, and three pubs….

Adrian runs an 11m BW Seacat Catamaran, a large, spacious boat with  great stability that we were to be grateful for in coming days.

Trying to subdue our ‘Molloy superfan’ urges, the three of us met Adrian aboard ‘Deep Blue’ the next morning and kicked off the adventure.

We knew conditions were tough before flying in and unusually for October the fish had thinned out recently, perhaps in response to multiple unpleasant weather fronts (which had curtailed fishing in the weeks before our arrival). Trolling without strikes is amongst the least exciting form of fishing in my view, but the chance to speak to Adrian at length was invaluable. Softly spoken, his knowledge of Bluefin biology, behaviour, fishing techniques, gear and regulations is incredible, and his willingness to share that was humbling.

We had been joined by an observer from Inland Fisheries Ireland who are overseeing the Tuna CHART (CatcH And Release Tagging) program in collaboration with other agencies. Far from being any hindrance on the first two days, it was really useful to talk with them at length about the background, objectives and operational framework for the program. We also completed a angler survey being carried out under CHART by Inland Fisheries Ireland to assess the socio-economic benefits of the program to the regions carrying it out.

Whilst at sea we were ‘intercepted’ by a couple of IFI Ribs. 15 Vessels are authorised in the program. IFI are tasked with inspecting authorised vessels and other vessels outside the program who they suspect of targeting Bluefin. The process may involve a caution, followed by confiscation of tackle for repeat offences, and ultimately prosecution. 

Whilst we were there, the two month program that should have ended 15th October was actually extended for another month given the poor weather that had curtailed fishing the previous month.

The Fishing.
Day one was grey, and wet, and cold, and a bit rough… We saw few signs of Bluefin on the sounder, little bird action and occasional Dolphin activity. Our expectations on day one were low, and we raised no fish, but as we moved further from the full moon and the forecast improved we were hopeful for day 2.

The killer technique for Donegal Bluefin is Trolling spreader bars. The bay itself is pretty featureless and unlike the SW UK waters does not appear to have many obvious areas where ABFT may aggregate. Covering ground, tapping into intel, and spotting birds and slicks is the key it seems to tracking down the quarry.

Day two saw the rain clear and sunnier skies. Large numbers of dolphin, several Minke whales and more bird action on baitfish fired up our hopes, and despite marking ABFT under working birds they declined throughout the day to play ball. Adrian worked ceaselessly scanning the skies, working numerous promising areas but it appeared Day 2 would end fishless. Two such days back to back is extremely unusual in this hugely productive fishery. Even given Adrian’s calm, measured composure, it was apparent he was very determined to not give up easily. 

By 4pm we were thinking of the Guinness when over Barry’s shoulder I saw a huge eruption on the back of the short bar. The 80W equivalent reel screamed as the fish tore off with the stinger. The response to a strike needs to be very measured. Jerry and I had discussed with Adrian our roles, and the team swiftly cleared lines, monitored and managed the hooked up rod/reel, whilst getting Barry harnessed and set up in the chair. CHART mandates that anglers must fight fish from a chair or a gunwhale rodholder. It is designed with non anglers in mind, or those of minimal experience, who want to access this fishing opportunity. ‘Deep Blue’ is well equipped with an adjustable fighting chair, and top quality Duel reels coupled with custom heavy trolling rods.

With over 250 yards of line out, Barry knuckled down to bring his first Bluefin to heel. It is an emotional and stressfull process, as Barry pointed out he was under the gaze of the Bluefin ‘godfather’ Adrian, an Irish Fisheries Board official, top UK skipper Jerry and me, who would rip him to pieces if he screwed it up……

The fish came up quickly and easily, too easily. Adrian refused an opportunity for a quick leadering and it was the right call. the fish was very green still and tore of nearly 100 yards on its next run from the boat. Lots of short, painful pumps and it was back alongside. 30 minutes from hookup to boatside. Expertly leadered by Adrian, the fish was floy tagged, had a fin clip taken by the IF official, was measured, revived and released within ten minutes, to kick away strongly. Barry’s first Bluefin, high fives all round, and much Guiness consumed that evening.

Day three saw just Barry and I out with Adrian. The swell was I’m sure the biggest I’ve ever been out fishing in, but ‘Deep Blue’ rode it amazingly well. Once again a frustrating day marking a few fish, working huge pods of feeding Dolphin and diving birds, more Minke whales but no strikes. At almost the same time as the previous day, 4.15, the long port rigger bar was hit twice by a large Bluefin before connecting with the stinger on the third attempt. An action replay of day 2 had me in the chair quickly, and this fish I had boat-side in around 20 minutes. Interestingly, this Bluefin measured out at 82″, exactly the same as Barry’s fish….

I cannot express how special it was to get Barry’s first Bluefin, and my first Irish Bluefin under Adrian’s tutelage. It was an absolute delight to spend time with an exemplary fisherman and gentleman. His knowledge of and respect for his quarry is immense and his commitment to establish a legal recreational Live Release Bluefin fishery is an inspiration as we attempt the same here in UK waters. 

If you’ve stuck with me this long, many thanks for taking the time. The Irish program now runs until 15/11/2019. Get out with Adrian if you can. 

An article originally published on the Club’s sister, campaigning web site, Bluefin Tuna UK in August 2019.

For several years now, we have seen increasing evidence of a significant change in the distribution of Atlantic Bluefin Tuna across the North East Atlantic. Reports from Ireland, Western UK waters, and from Norway down to the Skaggerak between Denmark and Sweden, indicate that these iconic giants are re-populating waters they have not been seen in for fifty years or more.

The reasons for this almost unprecedented shift are not fully known.

A recovery in the Stock over the last 10 years? (following an successful 15 year recovery plan by the species global management body, ICCAT).

Multi-decadal environmental cycles in North Atlantic currents, water temperatures and prey behaviour? (Distinct from simplistic conclusions about global warming related changes).

A combination of these and other, as yet unknown or unproven factors?

Scientists, and Anglers lead the search for answers.
What is clear, is that at the heart of understanding the What, Where and Why of this huge change, is a comprehensive, science based approach bringing scientists, anglers and fisheries managers together.

In collaboration with ICCAT, the species global management body, Governments and Universities have established research programs over the last three years to gather data to help further their knowledge of this important change.

Crucial to these programs are the co-operation of the recreational angling sector. Rod and line captures of large pelagic species like ABFT are acknowledged by scientists and conservation bodies as the most effective, low impact way of bringing the subject matter into the hands of scientists.

Just a few weeks ago, such programs kicked off in the UK, Ireland, Denmark and Sweden. Below is a brief summary of those programs and the early results.

Each take a slightly different approach to this research. However, to a greater or lesser degree they ALL recognise that recreational anglers have a key role to play in their programs.

IRELAND authorised 15 Recreational vessels for their ‘CHART’ program earlier this year, and they began operations on the 15th August. I cannot locate any centralised reporting of the numbers and size of fish captured, but from the FaceBook reports of participating vessels, you can see substantial numbers of ABFT already caught, tagged and released. This pilot scheme marks the first year allowing legal, widespread recreational angler involvement in Irish waters, (previous sanctioned tagging operations have been confined to just one or two vessels). My understanding is that the Irish CHART operations are applying only floy, or ‘dumb’ tags this year, in contrast to the archival, satellite tags (PSAT’s) applied in limited numbers in previous years.

The Irish Fisheries board webpage providing information on CHART can be found here, and includes links to the list of 15 skippers that anglers can charter up till mid October when the project closes.

DENMARK began its third year of Bluefin tagging on the 24th August, operating under the oversight of DTU Aqua, the highly respected Danish Marine focused University.

The Danish program has the widest level of authorised angler participation, with 70 Recreational vessels joining the first day of operations. In 5 1/2 days to the 28th August, 38 fish have been tagged. Mostly with Floy tags only, but some with PSAT’s, acoustic tags, or accelerometers. The home page of the Danish program can be found here with regular updates of their activities. In 2018 the Danes tagged a total of 91 fish.

SWEDEN The SLU Aqua University is overseeing further tagging operations this year following on from their joint operation 2 years ago with DTU Aqua. Their aim is to tag 26 fish with a variety of PSATs, Acoustic and Floy tags. They began operations on the 25th August with 23 teams of anglers participating in support of the scientists on the tagging vessels. Updates from this program are not as ‘live’ as the Danish program and require running through a translation tool, (unless you speak Swedish of course!) A number of fish have been tagged over the first few days and if you want to track this follow the SLU Aqua FB page or this webpage.

UNITED KINGDOM Our own research program, ThunnusUK, (a joint operation between Exeter University, CEFAS and DEFRA) began its second year of operations mid-August. After tagging 10 fish with PSAT’s in 2018, (a number of which have succesfully released already as planned and are providing data to the Exeter scientists already) , the program plans to tag between 30 and 40 fish this year, and as well as the PSATs used in 2018, a number of fish will be fitted with accelerometer tags.

In a change from 2018, four authorised ‘support’ vessels will be operating alongside the Tagging vessel this year, up to two at any one time, and experienced, authorised Recreational Anglers will be able to charter those vessels to assist in the capture for transfer to the scientists.

The program is off to a positive start with thirteen fish successfully tagged and released within the first nine days of operations. The program plans to spread the tag applications across the Autumn to obtain a wide ranging picture of the size, age and location of BFT in UK waters. In addition to the above operations taking place off of the Cornish coast, smaller scale tagging will also take place this year in Welsh and I understand Scottish waters.

The program’s home page can be found here with links to the pages detailing this years Tagging operations, and access to registration application forms for anglers keen to take part.

There are many sceptics about the merits of tagging, and critics of the participation of anglers in these programs.

The reality is that we still have huge gaps in our understanding of Atlantic Bluefin, and effective management of them to avoid another boom/bust cycle requires those gaps to be filled, something numerous scientists, conservation bodies and the species Global management body ICCAT frequently call for.

Large scale Floy tagging still has some merit, even with low recovery rates, the capture information itself can be of great value. Archival PSAT’s, Acoustic and accelerometer tags can provide very detailed information about migration and feeding patterns, stock mixing, use of spawning areas etc etc….

After several decades of programs, it has been shown beyond doubt that regulated rod and line capture of ABFT is the most effective way of bringing large Tuna into the arms of scientists to execute their tagging, measuring and DNA/Blood sampling.

Mortality of Bluefin in these programs is extremely low, consistently well below 5%, and this is despite the boarding and working upon them which can take 3-4 minutes.

These programs are an excellent example of ‘Citizen science’ at its best. Let’s hope for continued success the rest of this year and some interesting data to come out of them in coming months, supporting sustainable management of this iconic, still vulnerable species.

For several years a number of Charter skippers off of Donegal, on Ireland’s North West Coast, have been catching and releasing huge numbers of giant Atlantic Bluefin. The capture of some of those fish has been ‘covered’ by officially sanctioned tagging programs, from 2016 into 2018, but much has taken place in a rather ‘grey area’ shall we say.

Without any part of the EU 16,000 tonne quota, Ireland was unable to formally authorise a Recreational fishery, even a catch and release one. Indeed, in August 2018, the EU announced that it was launching an audit into various aspects of Irish Fisheries Management including an accusation that Ireland ‘was permitting the operation of an illegal recreational fishery for Atlantic Bluefin Tuna’. As recently as November, Irish Fisheries Minister Michael Creed said Ireland had no chance of persuading the EU to grant Ireland any form of quota.

Two month is a very long time in (Bluefin) politics….
So, like many we were taken completely by surprise today, 5th February, when the Irish Minister announced that the EU/ICCAT had agreed to endorse a wide ranging Tag and release Bluefin research program from this summer, to be operated by up to 15 Recreational vessels in Irish waters.

Note that this is not the establishment of a formal, ongoing Recreational fishery for Ireland, but rather a derogation as is required to operate a Scientific Tagging program with the data feeding back into ICCAT and possibly other Research teams ongoing studies of Atlantic Bluefin.

It is nonetheless a great success for Irish charter skippers, and recreational Anglers, in particular Ireland’s ‘godfather’ of Recreational Bluefin fishing, Adrian Molloy. Adrian persisted in the face of zero support from Dublin, continuing to show the reality and potential for a world class, sustainable Bluefin fishery off Donegal. Tagging and releasing 228 fish last Autumn, it seems that the Irish Government, the EU and Dublin were left with the only sensible choice. Bring it into a legal framework, and use the opportunity to carry out a large scale research program. Congratulations are very much warranted to Adrian for his persistence and skills in showing the way.

What does this development tell us more broadly about Bluefin, science and recreational fishing?
Well, once again it confirms that the organisations in charge of managing and researching vulnerable species such as Atlantic Bluefin view Recreational anglers as invaluable allies in executing their Research programs. This is because of their unique ability, proven time and time again, to capture, allow scientists to undertake valuable research, and then release unharmed these amazing fish. 

Mortality rates in such operations range between zero and 5% as proven multiple times.  Contrary to the charge of some anti angling groups, and even of some within the angling community that these programs are just a cover for anglers, Research programs have repeatedly drawn upon anglers to assist in carrying out this essential study.

So what of the UK?
Well, we have our own Research and tagging program under way, ThunnusUK, operating since last Autumn in waters off of Cornwall. The mandate for this program was established several years ago, and events regarding ‘UK Bluefin’ have rather overtaken them since then. We now know the presence of Bluefin in UK waters is much more widespread and of much greater abundance than we would have dreamed as recently as 2016.

Reports of fish all around the Western waters, from the Channel Islands, Cornwall, Wales, Scotland’s Western Isles and even sporadically in the NE North Sea have been coming in thick and fast for 2 -3 years years now.

We have been strong supporters of the ThunnusUK program since its announcement, but have also lobbied for changes that we felt were warranted.  

The program plans to tag 30 fish over two years, from a specific area off the Cornish South Coast. Last year it tagged 10 fish, utilising 3 vessels over 25 days.

We have argued that changes to the operational process would allow a larger number of fish to be tagged, transfer much of the financial burden from taxpayers to the private sector, (indeed GENERATING revenue for coastal communities), and bring in a much wider base of anglers with global experience of big game fish.

Ireland now joins Denmark, Sweden and Norway in embracing anglers in these programs. The last Danish program in 2018 utilised 30 vessels to capture, record and tag in various ways 91 fish over 10 days.

The latest developments underline again the value of such programs and the role recreational skippers and anglers can play in them. 

Recent meetings with senior UK officials have shown a collaborative, open minded approach to Recreational Fishermen and Bluefin, and we welcome that. We hope that will extend to a rethink on the scale and operational methods of the UK’s tagging programs. We are currently not making the most of this opportunity in so many ways, and would welcome another opportunity to put our case for change to DEFRA.

We’ve been working closely with the Angling Trust over the last few months to leverage their very useful media contacts as we roll out our Campaign.  I have been talking to David Mitchell, Head of Marine Environmental Campaigns, in some detail about the message we want to start to spread, and how we do it.

I am really pleased to report that the BBC Website today carries an extensive piece about the return of Atlantic Bluefin and asks ‘Could Big Game Fishing return to the UK?’  

We provided the background around Mortality Rates, Economic value etc… As always, any such article will be required to attempt balance, with responses from groups who do not share our view. 

There is a real danger we can be caricatured as fishermen “who just want to kill an endangered species”. Our arguments need to be evidence based, politely expressed, and specific. 

For example, the point about the endangered status. Yes, the IUCN DID list Atlantic Bluefin as Endangered in 2011.

They were absolutely right to do so. At that point, the scale of the danger facing ABFT had only just been recognised, stocks were heading towards possible extinction, and the Governing body ICCAT had only just, belatedly announced a 15 year ‘Recovery Plan’, that really only came into effect in 2010, slashed quotas and ramped up enforcement. Since then, there has been an undoubted recovery in the stock. There are however real questions about the extent of it, and whether ICCAT have gone too far in their latest 2018-2020 Quota increases which will see a near tripling of the Quota from the 2011 low to 36,000 Tonnes. We absolutely share those concerns and believe ICCAT need to monitor this extremely closely and be prepared to quickly reverse these increases if there is any evidence of a risk to the recovery. I also understand why organisations such as the IUCN and WWF do not wish to rush to reverse the Endangered listing they have applied. But that does not mean there has not been a real recovery, a ‘back from the brink’ moment in Atlantic Bluefin. However, with regard to what we are Campaigning for, we should stress the following points.

1) We are talking about an exclusively Catch and Release fishery. If we get it, (which will take several years), it will come 5-6 years after ABFT returned in numbers to UK waters. If it runs for 3-4 years on that basis, it would be only 8-10 years after their appearance that the UK would begin to consider any Commercial or Recreational ‘retained’ Quota for UK waters that would have to be justified by the evidence, some of which would have been obtained by the operation of a UK C+R fishery.

2) Scale. We are arguing for a mere 20 tonne ‘Mortality Quota’ to operate such a fishery. To compare, the EU Quota is soon to be over 20,000 Tonnes and the total Quota 36,000 Tonnes. Our efforts are a drop in the ocean in terms of the ‘risk’ ABFT may face from overfishing again.

3) Bear in mind also, when we talk about the risks, that these very same fish, in the majority of the year that they are NOT in UK waters, are being targeted by Commercial fishing fleets of multiple nations. The UK flatly refusing to consider some form of management of these fish does practically zero in terms of their prospects for survival longer term.

4) We are talking about a revolutionary approach. NOT blindly killing fish for the sushi market, but instead a licensed, monitored, well managed C+R fishery that would be in huge contrast to the vast majority of ICCAT member fisheries, and could set the World Standard for how fisheries for these iconic fish should be run. Early days, and a long road ahead but this BBC article is another big step in raising these arguments and getting a chance to make our case. You can find the BBC article on this link.

*Thunnus thynnus. Derived from the Latin “thyno”, “to rush, to dart”.
The return of Atlantic Bluefin Tuna (ABFT) to UK waters in the last few years has generated great interest in this iconic fish from anglers and non-anglers alike. Fishermen will spend thousands and travel across the globe for a chance to hook up to a Bluefin. They are one of the most desirable opponents in the angling world.
ABFT are the largest of all the Tuna and can grow to over 700kg, (1,500lbs), and live for up to fifty years. They can attain sppeds of 70kph and dive to depths of over 1000 metres.
They undertake great migrations each year, some on a par with those other great ocean travellers, Blue Whales.
Their flesh is prized around the world for the finest grades of Sushi, creating a huge global industry that can attach incredible price tags to the best quality fish.
Their unique physiology allows them to populate a very wide geographical range. In the Western Atlantic you can find them from the Gulf of Mexico, across the Caribbean, all along the Eastern seaboard of the US, and way up into the cold waters of Canada. In the East, they are found from Morocco, across all of the Mediterranean, and closer to home,
Ireland, Wales, Cornwall, Norway, Sweden and Denmark…..
Bluefin are almost unique in the geographical and water temperature range of waters they can operate in. Just how do they do this? Through a combination of physical characteristics that are unique in the fish world in their range and scale. Let’s have a look at this very special fish in a bit more detail.

Their Physiology

Atlantic Bluefin are one of the ‘True Tunas’, the Tribe ‘Thunnus’.
Perhaps the most important characteristic of the Thunnus tribe, and the one that most often surprises people, is that they are Warm Blooded.
Crucially, in addition to this, the “True Tunas” all have an ability to control their body temperature, a capability found in a very small number of fish, including some Billfish and Shark species. They are said to have an Endothermic capability.
Endothermic. “dependent on or capable of the internal generation of heat”.
This ability, most evident in the Bluefin sub-genus, allows them to travel and feed in a wide range of water temperatures. Atlantic Bluefin are the masters of this amongst all Tuna. They can vary their internal body
temperature between 25 and 33 degrees C, (subject to their age and size), and tolerate ambient water temperatures of up to 21 degrees cooler than their internal temperature, as
long as they have a source of energy rich food.
This trait allows them to be found in waters from 6 to 33 degrees Celsius, and explains their broad geographical presence.
How do they do this? Well it is a function of a combination of remarkable features. Those features also contribute to the Bluefin’s great speed and strength.

Internal Engineering

O2, the stuff of life….
It all starts with Oxygen, lots of it! Tunas do not ‘flap’ their gills, but in common with billfish
and some shark species, rely upon constant motion to pass water over their gills.
The gills of Bluefin are huge in relation to their size. TEN TIMES larger than those of Rainbow Trout (kg for kg). They are also incredibly thin. This huge surface area allows them to extract 50% of the Oxygen present in the water that flows across their gills, a phenomenal feat. Humans only extract 25% of the oxygen that is present in the air we
breathe.
This super-oxygenated blood, like hi-octane aviation fuel if you like, then needs to be delivered and utilised by the ‘engine’.
All heart….
Bluefin Tuna have big hearts, but being near their gills, close to the incoming cold water, it has to operate effectively at very low temperatures. Bluefin hearts have a super efficient intra-cellular trigger mechanism that allows them to continue pumping at very low temperatures. Their heart does slow markedly in colder water, but it continues to operate when most others would fail, and keeps that super-oxygenated blood flowing.

And a central heating system….
Perhaps the most impressive feature of Bluefin however, is the “Rete mirabille”, (“wonderful net”). The veins of a Bluefin, carrying warmer blood that has already circulated through the body, are intertwined with the arteries, carrying the fresh, cold, oxygenated blood from the heart. This intertwining allows residual heat from the veins to transfer to the arteries, pre-warming the arterial blood on its way to the muscles. There is also an intracellular transfer of some residual O2 in the veinous blood, to ‘top up’ the arterial flow.
So we have all this pre-warmed, super-oxygenated blood, pumped by their super efficient heart, but we need the right muscles to extract it and turn it into other forms of energy ed-danmark.com.

Nice guns….
Bluefin have a LOT of red muscle, deep into their bodies, unlike most fish which have only a narrow band below their lateral line. This red muscle is primarily for sustained motion, whilst their lesser amount of white muscle is used for high speed bursts. This extensive red muscle may also act as an oxygen reserve for when the blood flow slows at colder depths. They are also super efficient at utilising this oxygen in the ‘power cells’ or
mitochondria and converting it into muscle energy.
All of these features, coupled with the ability to raise and lower their body temperature give Bluefin this great flexibility and stamina that allow them to travel widely across the oceans, as well as dive to great depth in search of energy rich food.
In addition to these incredible internal features, Bluefin are also special on the outside.

External Engineering

All the ‘True Tunas’ have a super streamlined body shape that reduces drag. Their eyes are perfectly flush with their bodies, and their dorsal and pectoral fins can fold flat into grooves on their bodies, accentuating this streamlining.
They have an ability to tense their red muscles, stiffening their body. This accentuates the power transfer of their white muscle, designed for high speed bursts. This means that at anything over a low cruising speed their bodies do not move sinuously like most fish, but instead the large tail, or caudal fin oscillates at phenomenal speeds, providing great thrust.
It is generally accepted that Bluefin can attain speeds of up to 70/80kph (45/50mph). Studies of the small yellow caudal finlets on the rear end has shown how they move to direct water flow down around the sides of the body, and across the narrow caudal keels at the base of the tail. This effectively turbo boosts the water flow, providing more thrust.
The action of the finlets may also help reduce cavitation and turbulence in the water flow. The speed and pressure of this water flow is so great that some Tuna have been found with lesions over their tail area from it.
In additional, researchers at Stanford University in California, studying the bio-mechanics of various big tunas, have discovered another feature they believe unique amongst fish. It has been found that these tuna are able to alter the stiffness of their fins by the unique use of their lymphatic system. By controlling the flow of fluid into their fins, they can alter the resistance of their fins as required by the speed they are swimming at.
Inside and out, Atlantic Bluefin Tuna are incredible engineering feats of nature, and are truly a king amongst fishes.