In it, because the fish can talk to each other, a school of fish trapped in a fishing net manage to all swim together in one direction —down. The combined force of their swimming eventually snap the wooden arm on the fishing boat that holds the net, allowing them all to go free.
My question: If fish were capable of coordinating their action this way, would it be possible for them to similarly escape a fishing boat’s net? Or is the physics wrong, regardless of the cartoon zoology at work?
(Note: I don’t really mind if it’s impossible; this is a movie about talking fish. I’m fine with it if this couldn’t work, but I’m curious about the physics.)
I can’t imagine that it would be possible. Surely the combined added force from the fish is no more than twice their weight, and I imagine that the arm of the crane is plenty strong enough to handle the added load.
In terms of the physics, though, the fish swimming downward would exert more force on the crane arm. This works because the net can let the water pushed upward by the fishes’ fins pass through the top of the net and therefore out of the system. If the net were impermeable to water, the fish swimming downward would have no effect at all because the forces would balance.
The fact that they’re all bunched together quite tightly in the gathering net is going to significantly hamper the effectiveness of their efforts anyway - a fish that’s surrounded on all sides by other fish - not water - isn’t going to be very able to swim at all.
I’m sure an experienced line fisherman could give you some real numbers about how much force a fish can exert in the water individually - you certainly want your pole and line to be able to support more weight than the fish itself because of the force it exerts while swimming.
But… I see I’m ninja’d when it comes to pointing out that what one fish can do while hooked on a line in the open water is not going to compare well to what ten thousand fish can do while smashed together in a net.
If they could exert enough force to damage the winch, they’d be exerting enough force to kill all the fish at the bottom of the pile, and probably cut them into cubes against the net.
The fish at the top of the pile would push themselves into the fish at the bottom of the pile making the lower fishes’ ability to ‘swim’ useless. Or, from the point of the view of the fish at the bottom, they’re creating thrust pushing them down by pushing water backwards… right into the face of the fish above them, canceling out their attempt to swim downwards.
Being too heavy and capsizing a boat? That happens for sure. Even a story in the Gospels about that almost happening.
It seems more likely that, if something like this happened in the real world, it was just because they tried to winch up a net loaded beyond the safe lifting capacity, and the boat winched itself over, rather than the fish actively pulling it.
The way it has been shown? No, it would not. The fish would have to push against the net, and pull it to the bottom. Like another poster said, unless the strongest fish have their noses pressed against the net, they will end up crushing the ones ahead of them.
Heh, no. In the spirit of mad scientific inquiry, Madame Pepperwinkle and I rowed out to sea and caught a blind mass of a few hundred various piscatorial entities. Back in the lab, I bonded them using the usual hypergenetic bioadhesives (Mme. Pepperwinkle prefers ZooGoop), creating a megafish monster, which I slaved to a double entropy board for safety. Then Mme. Pepperwinkle and I rowed back out and set Big Tyke out in the path of a fisherman’s net.
Once netted, Big Tyke performed as desired, attempting to get out by pushing down, but, alas, current fishing technology proved more than sufficient, and they quickly brought him up to the deck. Mme. Pepperwinkle and I rowed away, sadly, as the crew were screaming and wildly harpooning it. I think it only ate two of them.