Dead Crabs

One of the things that they repeatedly say on The Deadliest Catch is that it is absolutely catastrophic to have a dead crab in the tanks because, in fairly short order, it will start killing off the other crabs and start a chain reaction.

Is this true? If so why?

Sorry if this has been asked before.

I don’t know if it’s true for sure, but it makes sense.

It starts off at the reason you don’t want to over-feed fish in an aquarium: as the food decomposes, additional waste products are produced that have to be processed by the filters in the aquarium. It’s easy to have toxic levels of chemicals like ammonia build up. A dead crab is producing a lot more chemical waste than a live one.

A dead crab also gives bacteria a place to breed, and those might cause infections in other crab.

IIRC during the first season a greenhorn (who failed miserably at the job and was a screwup in many aspects) threw a dead fish into the crab tank, “as a joke.” When they unloaded, a significant amount of the catch had been killed. The kid was escorted off the docks by police, presumably for his own protection.

Wouldn’t think a bottom feeder/detritus eater would be so sensitive to dead things.

There is a good reason why crabs and lobsters are cooked alive or very soon after they die.

I haven’t seen the show, but this doesn’t make sense. Crabs eat dead fish, including dead crabs. If these are tanks in a boat, or on the docks, they can readily cycle fresh sea water in and there’d be no concern about the buildup of waste products. I don’t know how long the crabs are kept in water, they can survive quite a while out of the water, but if a lot of crabs are tightly crammed into a tank and they aren’t cycling the water I suppose a dead crab could slightly speed up something that would happen anyway.

I wonder how it is that they can stand on the bio-mass in the tanks and not kill a bunch of them while trying to stuff more in or off-load them.

And, I’ll add, there ain’t nothin’ stinkyer than dead crabs!

My understanding is that king crab and snow crab are cooked and frozen on board quite soon after they’re caught. It doesn’t make sense to me that the crabs would spend much time in a tank, and certainly not long enough to make it to shore. Am I mistaken?

In the show, you can see them offloading the crabs from the holding tanks after they return to shore and the crabs are still alive: video clip. Certainly not cooked or frozen.

Ammonia is a byproduct of the decomposition of seafood, and crabs ammoniate very quickly once they are dead. And this ammonia is what kills the other crabs.

I live on the coast where the local crab is Dungeness mostly. You buy them live or cooked. If you caught them yourself and one is not alive when you get ready to cook it, it is garbage and should be tossed out. Even if it has only died in the short time between catch and getting it home. Seriously, even a hour.

When you are buying seafood, particularly shellfish and you smell even a whiff of ammonia, do not buy it, it is starting to turn bad.

That’s largely what I was thinking. That and that the tank should hold enough water that the products of decomposition should be seriously diffuse.

Again, this is what I would have thought.

I think you may be onto something here.

According to this site - if I understand correctly though I’m no scientician - ammonia can remain as ammonia in water and can also form ammonium.

According to the site as temperature decreases (Bering Sea water is very cold) and Ph increases the toxicity also increases.

So if one crab dies it might give off enough ammonia to whack the crab(s) next to it before the ammonia can disperse. Those crabs give off more ammonia which in turn kills of more crabs and the chain reaction continues.

So we now have one possible mechanism (I think). This satisfies the “detritus feeder” question in that the cause of death would not be ingested pathogens or toxins but rather an increasingly toxic environment.

This leaves the question of flushing the tanks with new water. I’m sure that they cycle the water - not 100% sure granted - so how could ammonia build up to noticeably toxic levels?

Thanks Dallas.


After looking at dofe’s video I think those crabs are in bad shape anyway. There’s way too many packed into the hold of that ship and the oxygen levels will be low, and I suspect they aren’t cycling the water. In addition any dead crab they pull up had probably been dead for a while and already beginning to rot. If they’re out there for days the crabs must be in pretty bad shape by the time they’re unloaded.