Keeping yellowfin...

Discussion in 'Fish Species and Techniques' started by bnz, Aug 19, 2017.

  1. lite-liner

    lite-liner troll enforcement Staff Member

    just about every good deckhand & mate on every tuna charter I've taken has known our
    expectations ahead of time. They have the pith/bleed/slurry thing down pat.
    Including the fine gentleman posting before me, when he was coming up on the "E".....:)
    I will say that I think Hyperman kinda set the bar a little higher with the pith/brain spike thing,
    but it caught on & now every good deckhand on a tuna trip knows the deal.
    .....At least here in Texas......;)
  2. Capt.matt

    Capt.matt Well-Known Member

    Every single Yellowfin we catch is gutted and put into a ice slurry immediately. Once fish is chilled it goes into the fish box.
    The fight has a lot to do with the quality of the meat also. A fish that is landed promptly will have much better quality than a fish that fought for half an hour.
    lite-liner likes this.

  3. DenisB

    DenisB Senior Member

    Just Say'in.............needs to be more than just gutting " & put into ice slurry immediately".
    Maybe what you wrote was just shorthand for "gutting & pithing".
    If you are not spinal coring / need to let the fish go into rigor while cooling with seawater on towels etc before icing/ice slurry............this prevents the yellowfin/any tuna from shivering autogenously when it feels the cold ice & heating up its core.......
    known in the sashimi world as "burning" the flesh in the core of a tuna.

    Out of the water & into ice slurry works great for the myriad of snappers & other whitefish...........but tunas have different physiology, as they can elevate their body temperature , & require a different technique to get the best out of them on the plate.
    Last edited: Apr 14, 2018
  4. scubaarchery

    scubaarchery Senior Member

    What about smaller tuna? This process looks to be for tuna less than 30k. By far the majority of tuna we catch are blackfin or yellows smaller than that...
  5. DenisB

    DenisB Senior Member

    Still works big or small.
    the smaller fish chill the core in less time than a big fish, but the shivering reaction due to cold still occurs without spinal reaming............the penalty is simply less for smaller fish than for big.
    small fish have the difficulty ( sort of ) in having a reamer cable small enough for the job.
    without a suitable reamer cable its advisable for best quality on the table , to cool with seawater on wet towel etc till in rigor before adding to ice slurry............ at least for any tuna >10#.
  6. scubaarchery

    scubaarchery Senior Member

    Is there a specific reaming device to use? I don’t need to keep mono in the fish to prove to the buyer it was reamed so is there a device sold to do that? Thanks!
  7. Kim

    Kim Senior Member Supporting Member

    This is a pretty all inclusive on "how to" when it comes to tuna once it's in the boat.

    I just use an ARC dehooker with the dehooker coil cut off and the tip sharpened. After you stick a few you will get the "feel" of hitting the right spot. I'll spike a real big fish but normally just bleed them and into the fish box.

    Black Fin get the gills ripped with a dehooker and head down into the bucket, the real tall chlorine buckets work great (no water).

    Last edited: Apr 15, 2018 at 12:13 PM
  8. Capt.matt

    Capt.matt Well-Known Member

    I honestly don't see how our fish could be in any better shape than how they are. I'm sure if I were commercially fishing tuna I would spine them, I have done it with 300 lb mono and haven't seen any difference in the quality. With our 60-100lb fish I do not see the need in wasting any time that doesn't need to be wasted. With 38 people fishing there is always something that needs to be done and we try to do everything as time efficient as possible.
    I have had this conversation with a few longliners and it seems like everyone has a different theory. Some like to let the fish settle down on deck before chilling while others like to throw them straight in the chill.
    Either way if your fish are in primo condition once you get to the dock I'd say you have a decent system.
    Kim likes this.
  9. Capt.matt

    Capt.matt Well-Known Member

    That's a good idea. I have a customer that uses a tool that looks like a hammer with a spike and he is really good with it. Unfortunately I am not.
  10. DenisB

    DenisB Senior Member

    Ha Ha...............the SPC doc...............I published the base document this is based on in Australia...........a japanese to english translation of Professor Tanaguichi's work on the physiology of tunas & the appropriate prep technique for them. The english translation of Prof Tanaguichi's work is the reference material for tuna handling in the western world.
    A very good friend who sadly passed long before he should have , Kuni Yamamoto, the original importer of Jinkai into Oz did the translation for me...............Kuni also organised the export of my sashimi grade tuna into LA before you yanks woke up to the value of properly handled tuna in the marketplace.
    Ha Ha .........sorry guys & gals couldn't resist the dig.

    There's myths & there is real science.
    what works best for a snapper is definitely not best for a tuna.
    Like a lot of things in life you can get away with cutting a few corners some of the time .
    If you want consistently the best results from the tuna you have caught onto the plate ............spinal reaming / pithing is the required technique.
    A quick repeat of the biology.
    Tuna are warm blooded fish............the myriad of snappers & other whitefish are cold blooded.
    tuna can elevate their body temp above ambient water temps , this is achieved by 2 mechanisms
    countercurrent blood flow in the "lateral line" of the fish
    ............oxygen rich blood from the gills is at water temp...... blood flowing back towards the heart from the body is at body temp...........counter current heat exchange flow in the lateral line warms the cold blood from the gills before it circulates in the rest of the body.. enabling elevated blood temps above ambient water temp.
    shivering generates heat in the body .............just like us humans do.
    shivering is generated by pulsing opposing muscle groups..........just like us humans do.
    shivering is an autogenous reaction to cold it is independent of brain function (ie it is not a voluntary directed & controlled action ) merely requires nerve pathway between opposing muscle groups.
    spiking the brain to cause a brain dead fish...........DOES NOT STOP THE SHIVERING REACTION until all of the stored energy in the muscles is exhausted.
    Read & weep.............
    putting a tuna into ice slurry etc before either :-
    nerve connections between adjacent opposing muscle groups is destroyed
    stored energy in the muscle groups is depleted ( ie fish goes into rigor & cannot shiver ).... causes shivering.
    Shivering generates slurry etc cools from the outside of the fish ( yes from the gut cavity too , but that is a small part of a tuna ). shivering generates heat from the inside.
    How much distance between outside & inside of the body determines whether the heated flesh starts to deteriorate faster than it can be cooled.
    Take it from +10 # the heat is winning in a tuna that is not spinal cored or has been kept at water temp until it is in rigor.
    From HJ's kind image of prep eqpt.
    The wooden handled one is a bleeding knife
    on its left is an ike-jima spike .
    left of that is a wad-punch........used to expose the brain cavity when spinal reaming
    ( it is used on the front half of the brain leaving the rear of the cavity intact to act as a perfect funnel for the spinal reamer ( top right ).............good luck with finding the spinal cord channel when you destroy the entire brain cavity.
    NB the spinal cord in a tuna runs ON TOP of THE SPINE between the bifurcated base of the dorsal spines.

    The best spinal reamer is a piece of 1 x 19 stainless wire ( sailboat rigging wire ) because it is stiff but has some flexibility
    larger tunas ( + 40# ) 3mm dia ( 1/8 ins dia)...... length to suit the largest tuna you hope to encounter.
    smaller tunas 2mm or 2.5mm dia
    NB both ends of this wire needs to be sealed with silver solder , so the wire does not fray & has a rounded end rather than a flat end.............ditto for mono if you are desperate.......melt the ends round.

    Greenies & animal husbandry freakes need to note that in the following ......THE FISH IS ALREADY BRAIN DEAD & CANNOT FEEL PAIN..........
    as the spinal reamer passes down the spinal cord towards the tail you will see the finlets ( top & bottom ) wriggle as the end of the spinal reamer passes down adjacent to them.
    This is how you can tell how far the reamer has reached ( without measuring penetration ) & whether you need a smaller reamer wire for the size of tuna you are catching.... to destroy the spinal cord down to the wrist of the tail ( or near to )

    Enough of the techie stuff

    Your palate will appreciate your efforts more if you do it right.

    You maybe think all this stuff is too much to worry about
    All the cattle, sheep & pigs handled in a modern abattoir deals with this shivering stuff before chilling , by repetitive electric shocking of freshly killed carcasses to make the muscles work & deplete the muscle energy sources so the animal cannot shiver & reduces rigor time to produce more tender meat on the plate. Even Chickens & other birds are being treated this way in some abattoirs too.

    If its good enough for the red meat on your plate ...........its good enough for your tuna.

    This stuff was dealt with on 360 T years ago & was a "sticky" it seems like so many other good things that had been posted as "stickies" it has been lost in ownership changes of the site...............sadly
    HungryJack, iyaman and jiggingnut like this.
  11. DenisB

    DenisB Senior Member

    While we are at it.........
    Bluefin have the greatest ability to elevate their body temp above ambient water temp
    then Big eye
    followed by the smaller tunas.

    Why is warmer body important
    its actually warmer brain & blood in the brain thats important
    warmer brain & more oxygen mobility in the brain generates faster & better decisions............for a tuna that means more successful predatory attacks,........more food means you get bigger quicker & become less of a prey yourself..............nature is amazing , Hey...........
    iyaman and jiggingnut like this.
  12. DenisB

    DenisB Senior Member

    Ohhh........... best wad punch
    A piece of thin wall stainless tubing 3/4" - 1" dia ( 20-25mm ) with a tapered wooden handle 3-4" dia at the top looking like a giant oversized golf tee........strike with the heel of your palm & its like a hot knife thru butter.
    Make sure you have a 3/8" hole down thru the centre of the handle to allow you to push the skull pieces out & clean the punch .
    HungryJack and jiggingnut like this.
  13. scubaarchery

    scubaarchery Senior Member

    Thanks this a great thread. I will see if I can assemble the gear and use it on the next trip. Not sure my pallet or cooking skills are sophisticated enough to discern the difference but there is only one way to find out for sure!
    iyaman and jiggingnut like this.
  14. Kim

    Kim Senior Member Supporting Member

    Below is from another site but the info is as detailed as it gets...if you care.

    Tuna should NOT be iced before they go into rigor UNLESS they have been spiked and spinal reamed.
    to understand this we need to go into some basic tuna physiology.

    Gunna be a longish post, so bear with me ,the detail is important.
    There are 2 types of fish.
    Cold blooded fish & 'warm' blooded fish
    Tuna are 'warm' blooded fish........... not so warm as you & me but none the less.
    Tuna have the ability to generate a body temperature higher than the water they are in............ this is achieved by a heat exchange in the bloodflow between the blood flowing back to the heart from the body and the blood flowing from the heart thru the gills & into the body...........this is that mass of blood vessels in the lateral line ( the dark red "meat" ).
    Now to the nervous system:
    There are voluntary muscle movements & autogenous muscle movements
    The voluntary ones are go fast/slow swim right or left etc
    The autogenous ones are heartbeat & shiver etc
    Yep SHIVER...........same as you & me ........when experiencing cold.........shiver to generate heat & warm up.
    Now to nerves & muscles & rigor Simple version )
    muscles work from the action of stored energy compounds held in the muscle cells & released by the nerves attached to them ( either voluntary signal or autogenous ).
    In the living fish ( and you & me ) these compounds are regenerated from the blood
    The muscles when working create lactic acid which is taken away by blood flow & disposed of by body organs.
    We will not go into the scientific details of what compounds or how they are regenerated or the chemistry of muscle contractions & relaxation ( another 1000 words to do that )
    I'm sure you understand the term " brain dead"
    brain is dead but body functions are still alive.
    When the fish is brain dead the energy compounds in the muscle cells are still available and controlled by the nerves. The nerves are still working for quite a while after the brain is dead.
    The muscles can & do work autogenously to shiver even when the brain is dead ( if the tuna is exposed to cold ).
    The muscles will work until the stored energy compounds are used up.
    fish (& every other animal with muscles) go into rigor when the muscles have depleted the compound required to relax the muscles.
    In death the energy compounds leak away and the last muscle action is contraction of every muscle cell in the body & the fish goes hard ( its in rigor ).
    Fish stays in rigor until biological enzyme actions start to break down the muscle tissue itself.( ie the fish flesh is starting to deteriorate - not rotten........just starting the process ).

    OK the answer to what should be done with the tuna on the deck:
    every fish to be kept should be humanely dispatched immediately on capture as death starts the process of getting into rigor, and it stops the fish from thrashing about and bruising the flesh ( and maybe you ).
    Brain spike or clubbed.
    The tuna should then be bled. Minimum action is to sever the gills. The best practice is to stab the fish immediately behind the pectoral fin on the lateral line on both sides & slash the lateral line at the tail on the lateral line on both sides.
    Why ???
    The tuna has been fighting you hard & has a high level of lactic acid in its blood from the muscle effort.
    If left there it will eat thru the blood vessels and into the flesh.........this results in sour flesh exposed to the lactic acid.
    Severing the gills is better than nothing , but the blood in the heat exchanger vessels is still trapped there ......... so severing the lateral line front & back & both sides drains these organs.
    This should be done as soon as the fish is on the deck & killed, but the heart is still beating, to pump it out.
    Gutting: ( added in edit )
    Gutting should not take place until the fish has fully bled out.
    You want the heart to pump as much of the blood out as possible , as it will continue to function autogenously after brain death until it no longer has any energy compounds in its muscle mass to keep functioning.( the heart will be the first muscle mass to go into rigor).
    Only the gut & gills should be removed , leaving the membrane between the gut & the rest of the body intact as this is a natural barrier to gut enzymes and bacteria entering the flesh of the fish.
    That really dark red stuff under the fishes spine in the gut cavity is the fishes kidney
    No need to remove it in the gutting process and strip the gut cavity membrane away to get at it. Leave it there & deal with it in the filleting process down the line
    This applies to ALL fish not just tuna.
    When whole fish or cutlets are being cooked, the time to remove the kidney by scraping & brushing is in the prep immediately before cutting the cutlets or cooking whole.
    Now to chilling practice:
    2 choices;
    best practice is to use a wad punch ( stainless tube ) instead of using just a spike and then running a flexible rod down the spinal cord as far as you can to destroy the nerve links between adjacent muscle groups in either side of the fish to prevent shivering
    then straight into RSW or ice ( preferably as a slurry with water ).
    The spinal cord runs from the brain cavity down along the top of the spine ( not in it ).
    it runs in the bifurcated legs of the top spines of the backbone & whilst tricky to learn is easy once you have done it a couple of times. The big trick is to cut into the front of the brain cavity with the wad punch leaving the back of the cavity as a nice little funnel into the spinal cord track, to run the reamer into.
    If you can't , don't, or don't have time to do this DO NOT PUT THE TUNA STRAIGHT INTO RSW or ICE.
    the tuna will shiver and generate heat & cook in its core. The RSW / ICE cannot cool the insides of the fish fast enough & has no effect on counteracting the heat generated as the cold will not reach that area & depth of the fish for a couple of hours.
    Yes HOURS.
    IF you dont destroy the spinal cord , tuna should be left in a cool place with a wet rag over it or in a killbox with seawater ( not RSW ) running over it until the fish starts to go into rigor ( ie the fish is telling you the muscles have run out of energy compounds )
    Then Chill.
    If you take shortcuts to the above you are giving yourself a substandard product.
    Hope that helps understand the what & why of tuna flesh care.
    Your choice as to what you do & there are a lot of myths out there.........especially the one about chilling tuna ASAP.
    I know what good tuna flesh looks & tastes like.

    Chilling most fish ASAP is correct ( the cold blooded ones )............chilling tuna ASAP without the correct preparation is WRONG.
    in decending order the fish with the highest ability to elevate their body temp , is :-
    Blue Fin Tuna
    Yellow Fin Tuna
  15. jiggingnut

    jiggingnut Junior member


    DenisB, thank you very much for taking the time in explaining this...really makes for an educational and enjoyable reading especially to those who find anatomy interesting. I have not had a top grade sashimi, but is looking forward to trying this on my next Tuna.
  16. Kim

    Kim Senior Member Supporting Member

  17. bnz

    bnz Just a guy who likes to fish

    Hey guys, I originally started this post to figure out the best way to keep my tuna on a smaller boat (23'). I have since found something a couple of months back that works. But you guys keep having fun with this. :D

    As we all know, I have the palate of cat food so none of this makes any difference to me whatsoever. :cool::p
    ReelMe likes this.
  18. Kim

    Kim Senior Member Supporting Member

    So Bnz, what did you settle on for your boat?
  19. DenisB

    DenisB Senior Member

    Interesting paper in what it doesn't do & doesn't say.
    the paper proposes a THEORY on what causes burnt tuna.
    The biochemical relationships examined are no time are they identified & proven as causative.
    The biggest problem in modern day analysis using computer techniques is that there is an assumption that because "A" happens with "B" it must be causative of what happens with "B".
    This is a fallacy..............the only proven thing is that "A" & "B" occur together & often are both caused by another "C" that hasn't been yet identified.
    Most of the reference materials used in this paper are also correllative theories.
    This is bad science.

    The project itself does not identify the isolation of other potential variables in its analysis.
    ie was the temp regime of all the samples consistent.
    Was the bleeding technique consistent ( bleeding being terribly important in venting the waste biochemical products of muscle exertion during the fight from the fish prior to chilling & storage
    ie what is the analysis of all of the samples with fixed prep technique.
    ie what is the analysis of all of the samples with the same "at capture" biochemical content , such as lactic acid or C,D,E.F,G etc.
    The discussion about Calcium interactions is grossly inadequate............. Calcium leaching across intracellular boundaries in muscle tissue in the presence of ATP ( Adenosine TriPhosphate ) causes muscle contraction into Rigor.
    ATP is an interesting biochemical compound as its presence is required to both cause muscle contraction & cause muscle relaxation.
    Many of the biochemicals in muscle function are not destroyed permanently in muscle movement .....they change from one biochemical into another & in many cases are recycled by enzyme action in other organs in blood flow back to their original form. This includes muscle activity products like lactic acid which is broken down in the flow of blood around the body organs & reabsorbed into muscle tissue as another biochemical ready to participate in muscle movement & be converted back again into lactic acid as a result of the biochemical action of muscle cellular contraction & ultimately go around the circuit again.

    Nature is not so wasteful as to use & destroy or vent the basic biochemicals necessary for function on a single use system , its much more efficient to use a part of a biochemical construct to do something contributing to life , leaving a depleted bi-product & recycle & reconstruct that part of the construct back into the original biochemicals necessary for life

    The analysis in this paper takes a far too broad basis for its THEORY...........largely based on correllative relationships between biochemicals examined by other scientists.......and the author(s) theory of additional relationships that MIGHT improve the understanding of the issue in future directed studies.

    What the paper does identify is that one fisherman in 14 dramatically improved his occurrence of burnt tuna by spinal reaming prior to chilling ..........compared to 14 other fisherman in adjacent activity........ the only one spinal reaming in this sample of fishers.
    Sooooo.......... properly bled & spinal reamed tuna can't shiver their muscles & generate MORE muscle exertion bi-products like lactic acid so the bitter taste of lactic acid & its effect on flesh/muscle is not increased & the heat generated by muscle shivering does not affect the flesh in the core & promote other heat related reactions in the biochemicals of flesh & muscle tissue.
    Makes sense ....HEY......... absolute proof worked.
    All the theoretical correlations did "Diddly Squat" for the other 14 fishers explaining why they had more trouble.

    Thanks Kim for several good posts relevant to the subject .
    HungryJack likes this.