You are better off transporting live crab in at temperatures between 45-50F. And, yes periodically open that cooler! Out of water they will live for quite a few hours, actually up to about fifteen! In un-oxygenated water they will DIE, just as soon as they use up that oxygen!
1)
LACKOF OXYGEN
While in water crabs are able to use about 20% of the oxygen available. That is efficient enough to use up all of the oxygen faster than you would like, were a pump or aerator to fail. In open/flow-through systems of sufficient flow the naturally occurring dissolved oxygen (D.O.) is sufficient to maintain good blood chemistry. [e.g. any type of open mesh nets] In closed/recirculating systems that are usually operating at lower temperatures it is easier to achieve, through mechanical means, levels of D.O. that are superior to that occurring in nature but if an oxygenation component fails that superiority is relatively quickly used up.
Out of water, the crabs gills are no longer held buoyant. In that situation the gills collapse dramatically reducing their ability to assimilate oxygen from the air. Now add to that, debris in the form of silt or other suspended particulates deposited on the already reduced gill surface further impairing oxygen uptake. Remember the crab is already literally out of its element during shipping. Putting all of these obstacles together might be something like you or I running the Boston Marathon with a bag overour heads. Not a pretty picture in any ones book.
ACTION TO TAKE: IN AN OPEN/FLOW-THROUGH SYSTEMTHE BEST WAY TO INCREASE D.O. IS TO DECREASE THE BIO-LOAD OR INCREASE THE FLOWRATE THROUGH THE TANKS. IN A CLOSED SYSTEM DECREASE BIO-LOAD OR INCREASE CASCADING OR OTHER AGITATION AND MIXING SUCH AS WITH VENTURIES OR SKIMMER SWHICH INCORPORATE VENTURIES. IN ALL TYPES OF SYSTEMS ALLOW FOR MECHANICAL FILTRATION AND APPROPRIATE SOAK TIME PRIOR TO SHIPPING TO ALLOW FOR DEBRIS TO CLEAR FROM GILLS.
Have you ever put live crabs in a live well and noticed after awhile you will start seeing some legs floating around in the bottom? They fight! You are much better off putting them in a net (yes, even stacking them) then letting them swim around free in a live well, and fighting!
BLEEDING
Crabs have blood and, yes, they can bleed to death. Crabs are so vulnerable to bleeding that they have evolved a fascinating ability. If a crab is injured in a fight with another crab and is bleeding through a puncture in a leg and the injury is life threatening they can actually voluntarily “throw” the injured leg. There is a muscle attached to a valve sort of apparatus on the joint of each leg closest to the carapace. By contracting that muscle the leg is severed at the joint losing the leg and saving the life. If a crab is in a weakened state or is otherwise stressed it may be incapable of accomplishing this life saving feat and die from loss of blood. That is why proper and gentle handling when loading tanks is so important. Crab handled by fishermen and first receivers are usually handling “hot” crab in warmer (40 degrees and above) water making the crabs especially susceptible to puncture wounds inflicted by other crabs. Crabs are also very territorial, so when they are crowded in a tank they tend to fight. That is when puncture wounds can occur, and cause bleeding or even death. Another puncture danger is from rough handling, like tossing one on top of the other instead of setting the crab in the water. The points on the sides of the shell are capable of actually puncturing the crab it lands on.
ACTIONTO TAKE: FIRST RECEIVERS ALWAYS TRANSFER WATER TO WATER OR AT LEAST DRY TO WATER. NEVER TRANSFER WET TO DRY OR DRY TO DRY. A BANDING PROGRAM WOULD BE A GOOD IDEA TOO. WHEN LOADING TANKS TRY TO DISTRIBUTE THE CRAB AROUND THE TANK SO THAT YOU ARE NOT PUTTING CRAB ON TOP OF CRAB ON TOP OF CRAB ETC.. THAT CAN REALLY **** THEM OFF AND WHEN CRAB ARE PISSED OF SOME ONE IS GOING TO BLEED.
3)
MECHANICAL SHOCK
To my knowledge no definitive research on mechanical shock damage has ever been done. It remains just one of the many areas needing to be studied to further our understanding of why crabs die. We do know, experientially, that Dungeness are far more susceptible to mechanical shock than are East Coast Lobster. Internally Dungeness crab have, proportionally, much larger sinus areas than that of the lobster and I believe that is the principle reason for this lethal vulnerability to mechanical shock.
It has been observed by myself and others that a box of crab packed for airshipping and dropped from waist height can result in excess of 50% mortalities within a few hours. It appears that those large sinuses leave so much space for movement that, when dropped, the internal organs move to such a degree that connective tissue is irreparably damaged. Fishermen have known of this fragile nature for along time.
Those in the know have constructed slides or shoots to soften the landing insituations where crabs must be transferred with potentially damaging vertical drops such as from the deck into a hold.
Even small mechanical shocks can have damaging effects. The simple transfer from one container to another and even into water can have serious consequences. The impact of “tossing” crab into a tank can result in mortalities. If not while in your possession then in your customers. Years ago I observed an extreme example of what I’m talking about.
It was in the very early days of live shipping to the east coast markets. I had begun shipping to a new customer who had never bought Dungeness before and who constantly reported excessive next day (after arrival at his facility) mortalities. Even though he seemed to be a nice enough fellow I started to suspect him to be one of those credit junkies who are only satisfied if they are getting their credit fix. It happened that I had an opportunity to fly to his area for a trade show so we timed a shipment to coincide with my arrival. Before the shipment arrived we ran some tests on his system water to rule out problems in that area. Everything looked fine and the crab leftover from the previous shipment looked healthy enough though they were the survivors of a 55% next day mortality. When the shipment arrived at his facility we inspected the outer boxes for evidence of dropping. It all looked good so, scratching my head, I followed him toward his office while the workers prepared to load the crab into the tanks. As we were leaving his warehouse I heard a thump, splash, thump, splash, sound. I turned and watched in horror as the workers were tossing the crab from floor height into the top tank of a triple-stack system using the wall behind as a “backboard” to bounce the crab off! Needless to say we had found the cause of hisnext day mortality problem.
Later on that same trip I visited a number of large lobster holding facilities and observed similar if not identical practices being used in handling lobster from crate to tank and tank to tank. Obviously I had my work cut out for me as far as education of the new east coast markets were concerned.
ACTION TO TAKE: HANDLE DUNGENESS LIKE YOU ARE DOING YOUR MOTHERS HEIRLOOM DISHES AFTER THANKSGIVING DINNER. SET THE CRAB INTO WATER NEVER THROW THEM OR DROP THEM. WHEN BOXED NEVER DROP THE BOX, SET IT DOWN. CONSPICUOUSLY MARK SHIPPING CONTAINERS AS “FRAGILE” AND SPEND SOME TIME EDUCATING YOUR SHIPPERS TO THE FRAGILE NATURE OF YOUR SHIPMENTS.
I believe, these people pretty much have it figured out. If you want to read the whole article, it is here:
http://ari1.com/live-crab-handling/
If you take live Dungeness crab, put them on fresh water ice and keep them there until they die - you will probably be disappointed in the taste and quality of the meat. The taste becomes quite bland, quickly. I agree with cooking them alive! To the point, since my trips last up to a week I realistically can’t keep them alive within that 15 hour timeframe … The answer for me; if I know I can’t keep them alive – I cook them, right on the boat! Leave them whole, stick in ZipLock freezerbags, and put on ice. If you think, you’re going to cook them, then vacuum pack whole to keep them fresh? Save some money and buy ZipLock freezerbags. You will only have to vacuum pack one, to see what I am talking about! The vacuum will suck the “butter” right out of them.
Just my 2 cents on transporting crab!