Well Skylab,
This is my take on it from the experience and knowledge that has been shared with me by many wholesaler's,and retailers.
They jump because they are freaked, period. Just like alot of fish in the ocean do when a pred
atory fish is closing in on them. Size of the holding tanks does play a role some what but a very small one. They are stressed from being caught up in a net and and whooshed out of thier home and in to a strange enviorment by what seems to them to be giants.
Thats why they make fish calmer for shipping and black out bags.
Thats also why you leave the lights off when adding new fish (most of the time). "Most" wholesaler's and retailer's do not cover thier tanks because they want to take atvantage of every available and least costly thing they can to help thier systems stay healthy. IE the gaseous exchange process.
"Fish arrive at the weekend" "most LFS receive their shipment on Monday or Tuesday" stick with one or the other.
Whosalers are usualy located directly at the source so there is NO shipping to them.
LFS I know of recieve thier shipments on tue. - fri. Not mon,and tues. If they recieved them on mon. or tues. that would mean they just spent possibly more than 48 hours in a bag in transit(friday,saturday,sunday, monday until tuesday delivery). If 30% loss was an aceptable standard
in retail standards then they would go belly up real quick.
If an LFS recieves two or more DOA fish specimens (and that depends GREATLY on what species of fish and its cost) they usualy call imediately to set up a free replacement with thier next order.
They also do not add them to the same tank, or one small system.
They have many tanks that are all linked (usualy) to two seperate systems. (usualy a california style plumbing set up with a huge sump and skimmer.)
With live rock and live sand in most of the holding tanks ( aka display tanks for retail) all linked together,combined with a huge sump and skimmer you essentialy have two big berlin filtration set ups that can handle just about anything if you keep good maitinance on them.
In fact I have seen several LFS set ups where two tanks side by side could by be bypassed from the main system ( or individualy isolated) by the turn of a ball valve, and the addition of a short section of pvc. Turning them into isolation tanks.
Wholesalers usualy use large holding tanks then transfer selected specimens to subdivided tanks for display or when getting ready to ship them off.
So assuming that most LFS just drop in huge bioloads in to $10,000-$20,000 systems that took months to set up with $1000's worth of live stock at steak as well, is pretty naive.
BTW "most" wholesalers I have seen have the cleanest systems I have ever
saw, with fresh seawater piped through them. Does it realy make any sense to threaten your own lively hood with filthy systems?