Here is the first ever video of a fish using a tool. Specifically, an orange-dotted tuskfish using a rock to crack open a clam. But it might not be long before fish are using clams to crack open our skulls.

That's the completely reasonable conclusion I've decided to draw from new research in the Journal of Applied Animal Welfare Science. Researchers found that fish stored in small to mid-sized aquariums - basically anything 100 gallons or less, which is the size of many household aquariums - show significant violent and aggressive tendencies. It's all far in excess of their counterparts who enjoy roomier accommodations.

This is the first concrete evidence that captivity - particularly in cramped conditions - does indeed affect the mental health of fish. The fish were more likely to attack their peers when living in small aquariums, and their entire demeanor indicated they were in a pretty much constant state of aggression, with lots of flaring of fins and attempts to bite those around them.

This news comes hot on the heels of this video of a tool-using fish. This is the fourth time such behavior has been observed - we reported on the first photo of such behavior a few months ago - but now we have video evidence, thanks to Giacomo Bernardi of UC Santa Cruz, who recorded this video in the shallow waters off the Pacific island nation of Palau. The fish picked up a clam, used a rock like an anvil to open it up, and then repeated the process three more times over the next twenty minutes, all of which is very sophisticated behavior for a fish.

So then, we know that fish are getting more aggressive because of how we're treating them, and we know that they're learning to use tools to violently crack things open. Hmm...after careful consideration, I'd just like to say that I, for one, welcome our new fish overlords. I'd like to remind them that as a somewhat trusted science blogger, I can be helpful in rounding up others to toil in their undersea oyster hatcheries.

...Or, you know, we could just try putting more plants in aquariums. The researchers found that the more complex environment gives the fish more things to interact with, and this markedly reduces their aggression. It's worth a shot before we completely surrender to the fish, I guess.

Via Discoblog and Scientific American.