This is a great description of what happens and why fish die in transit. Thank you for taking the time to give a detailed explanation.Its really not where you live that matters.
1st thing Fish travels at night. I get email after email saying weather tomorrow at my location is 80F (or warm) so should'nt be a problem. Well they forget fish travels at night. when temp are at the lowest.
We pack our fish in the morning and by evening they are picked up by UPS around 6-7PM central.
temps are starting to drop as suns coming down.
They sit at Tulsa airport in a metal case/trolly made to transport cargo into the belly of the plane from roughly from 8pm to 10pm. UPS flies out of Tulsa at 1030pm daily. (only 1 overnight flight out of Tulsa). If there is something wrong wuth the plane they sit addition 24 hrs before flying out.
They fly to Louisville Kentucky. Arriving at 1130 to midnight. They get unloaded and travel on a chain on conveyor belts from 12am to 5-6am getting sorted through open warhouse. That sorting facility has a thousand garage doors open in front and back with trucks constantly driving in from front and out the back.
This is the critical part of the shipping from 9pm onwards boxes has been subjected to nothin but cold temps.
In midwest nights are ranging about 0-30F on the coldest and about 20-40F currently.
Boxes are subjected to these low temps for 8-9 hours.
They fly out to respective states and are normally at their hubs by 7am and then loaded on to truck to delivery by 10-11am.
So even if you live in the hottest part of USA, temp at that point does not matter as the damage was done in the previous 8-9 hours they were sitting in cages or on convayer belts getting sorted.
I have dont many studies on these boxes and temp inside the box will remain between 72F to 84F for over 30 hrs if they are left outside on a normal day that has a low of 60F and high on 90F.
In the winter same box will only remain in good range for 6 hrs without any heat pack. 1 single heat pack will increase the temp inside the box by about 20 degree compared to ambient temp. If temp is constantly between 30-40F throught the night, single heat pack by the time you recieve the fish will register temps of 60-65F inside the box.
Double heat pack will register about 72-76F for the same box.
Cant put 3 because at some point heat packs will glow so hot (they glow at 120F at max within 2-3 hrs of activation)
that they will produce more than 90F in the box will will likely kill the fish.
Thats what happens sometimes when fish arrives dead in a bag. either due to excessive heat or heat pack near the bag or too many heat packs.
I hope that helps.