Absolutely fool proof method? Try fishing ABOVE the tide line!1 Very little crab 'damage' but also very low fish-catch rate! Seriously they are both the worst problem and the absolute brilliant bait! So if fish are feeding well the more crabs you attract to your baits the more fish will be attracted to all the 'cuffufle' (technical term) they make fighting for food.
Big baits keeps them occupied for longer 'cos you've got to grin and bear it, and feel them eating away!
You can float your rig up off the bottom with an 'underwater' float placed at the top of the rig - I still use the old 'peg' floats because you can decide to put one on and not have to untie anything. The float will only lift the hooks and snoods off the botttom and will still be tethered by the weight at the bottom. Yes this does preserve the top two hook baits on a three hooker but crabs can swim and they'll find the bait. Also you have to decide whether or not the fish you have targeted are after swimming up into the vulnerable spots above the sea bed (all fish are predators remember) Autumn and Winter Cod will be in that 4' region anyway so try it if you haven't much bait. The biggest problem though with a bigish float is the anti-aerodynamic nature of your rig, so don't try to get too much distance.
If you're using small hook baits/hooks then try small individual cork balls on each snood (I get mine from the carp shop!!) Frankly I try them more as a novelty but others may have more success.
Use a hard bait - squid, limpet mixed with others in a cocktail that again will slow them down.
I'll tell you my secret method if you promise not to tell anyone else! I was experimenting with groundbait and using a method feeder (weight attached to a frame around with the hook length running through it. You make up the groundbait and 'mould' it around the cage. You bait your hook and cast out. NOW the carp boys are far more subtle than me (not hard to be!) and after a little while having allowed for the softening effects of water on groundbait they pull in their line JUST ENOUGH to pull the hook bait into the 'pile' of groundbait. Clever lot! Lacking their subtlety I just let it lie! However the crabs seem to be drawn to the mass of groundbait and the hook bait is preserved for longer than it would otherwise!!
This game is a good one but as I said to begin with, you have to put up with nature's best fish attractants in my opinion.
I would like to point out that I read in an article in Sea Angler several years ago that it stated that 'wherever you find spider crabs that the Cod will not be present' Aparently the scent of the spider crabs deters Cod. Dunno how much truth is in this.
Am I right in thinking that big crabs would have a go with a reasonable sized codling or similar?
Having worked on a fishing boat fishing some 200 fathoms deep, the depth of water doesnt affect where the spider crabs are. They only get bigger the deeper the water is.
What interesting ideas Scirro, thanks.
I've found the following, so far: http://www2.hawaii.edu/~carlm/spider.html Interesting, if heavy, but had the incredible point, "...is able to copulate while the female is hard" Never did like overly aggressive women! But the best site so far was: http://www.newquay-westwales.co.uk/spider.htm which details an invasion of Cardiganshire, by Spider crabs! (Doctor Who??) It also has an overview generally of the species. Havn't found anything yet about their ability to put Cod off, but still looking!
However there was a mention of: "moult-inducing hormone, 20-hydroxy ecdysone ", now if we could get hold of some of that we could produce peelers at will!
there has been some experiments using hydroxy ecdysone with limited success.
There is also a secondary inhibitor hormone GIH (gonadatrophin inhibiting hormone)at play. This is produced in the eyestalks and there has also been some experimentation whereby the eyes and eyestalks are cut out to prevent the release of GIH, this has had a little more success but has been far from reliable.
If your interested in the science I could post some links to other papers on the subject.Most of the work is on spider and Alaskan snow crabs.