I use Shimano scales that weigh upto 50kg ,do this really quickly try too carm the fish down, put the little hook thing in there gob lift weigh and release.There is more than likely a better way maybe someone will post it.

I guess the best way is to use a dial scale with the hook set as normal, make a sling into which the fish is placed lift the scales up and bobs your uncle one fish weighed and ready to go back into the big blue. Practical????????????

All that dicking around will kill them,if you lift a 30kg kingi up by its lip and hang on the scales it will not feed again and die.The weight of the fish will do a huge amount of damage.Fish to be released  are hard to weigh.The best ive seen was a environet that the bloke netted the kingi then put the hook of the scales thru the ring of the net and lifted it out of the water by the net..he then deducted the weight of the wet net off the total and tipped the king out of the net unharmed.Another way is to measure by laying it on a wet towel and covering its eyes to calm it down.Personally i dont bother,on the charter boat i use alot they lift the fish out by its bottom jaw and lay it on a wet measure board ,tag and measure them release.In the ruff its hard to weigh a moving fish.. 

We use 100kg dial scales. Hang them from the boat hardtop. Used to weigh them through the bottom of the gills, didn't seem to hurt them. Now we use a tail rope, put it on the fish them hang it on the scale.

We have a set of 30kg lip grip scales but you have to be Arnie to get an accurate reading especially if the fish gives a kick.

If you don't have a roof then dial scales can be hung on a stick/rod.

We don't weigh all our fish usually just the heaviest ones for each angler, once you've weighed a few you get an idea of fish weights and can estimate them quite easily.

Weighing the odd one in competitions on proper scales also helps to get an idea of weight and also check your scales are reading properly.

Tape measure the ones for release and weigh the ones you keep.

Mozz is on to it if you intend to release a big king then measure it !!! Remember its just been exhausted and dicking around with it will stave it of oxygen it is already low on.Try running around a rugby field and then holding your breath straight away. No chance and not much chance for the kingi after being caught!!!    MEASURE AND RELEASE !!

Hanging a big fish by its mouth will no doubt do it some harm, i imagine it is going to stretch its vertabrate and do other damage as well. One idea i had but i am yet to try is hold the fish up in your arms as you would for a nice picture, once youve taken the pic step on a set of bathroom scales, release the fish then weigh yourself and deduct the weight. Not sure how the scales would work on a moving boat.

I've got a mate that I go rock fishing with that tried the bathroom scales thing but says if the scales aren't level they dont give a good reading. BUT he did say if you can keep it at the same pitch for BOTH readings, ie with and without the fish, you can usually still get a good idea.
Probably be hard on a boat on all but the calmest days but I guess if you've got them then why not give it a go.

sooshee wrote: I've read that holding a big fish by either ends will cause internal organs to tear off. Is this why some fish weighed at the docks have their mouths taped shut?

sooshee wrote: I've read that holding a big fish by either ends will cause internal organs to tear off. Is this why some fish weighed at the docks have their mouths taped shut?

with marlin it is to stop there guts coming out of their mouth.(looks bad in photos etc)