Vladimir, I’m not sure about the orientation bit. Imagine constructing a sphere of fish around the lightning strike, so that the fish tile the sphere and are flat against the sphere (actually, hemisphere). Necessarily, all the electricity flows through the fish, because they completely tile the hemisphere. Now re-orient the fish without otherwise changing their location. Now, because the fish are thin, they no longer cover the sphere, and between them is a lot of seawater. So only a small fraction, now, of the electricity flows through the fish, and the rest passes by them in the seawater.
Meanwhile, of course, that small fraction of electricity is staying in the fish for much longer, because each unit of power is flowing the entire length of the fish, from head to tail, whereas when the fish are placed sideways relative to the flow of electricity, each unit of power is only flowing from one side to the other.
At first glance, it seems to cancel out.
Imagine the following: each fish is made out ten unit cubes placed next to each other. They can either be placed perpendicular to the flow of energy, so that each cube gets the energy that flows through one unit square. Or, they can be placed parallel to the flow of energy, so that they all share the energy from a single unit square, which flows through all of them one after the other.
It seems to come to the same thing.
But here’s one further complication: if the fish is a better conductor than the seawater, then the energy will tend to re-direct to seek out the fish (more electricity will flow through the better conductor, cet.par.), so that placing the fish parallel to the flow of energy rather than perpendicular to it will not entirely protect it from the neighboring energy. In short, if the fish is a better conductor than the seawater, then it is better for the fish to be oriented perpendicular to the flow of energy.
But, without going into details, I hastily extrapolate that if the fish is a poorer conductor than the seawater, then it is better for the fish to be oriented parallel to the flow of energy (i.e. facing the lighting strike point, or facing away).
But, without going into details, I hastily extrapolate that if the fish is a poorer conductor than the seawater, then it is better for the fish to be oriented parallel to the flow of energy (i.e. facing the lighting strike point, or facing away).
You are correct! I hastily analogized from the human step potential, ignoring the fact that fish, unlike humans, may well be much poorer conductors than the surrounding (or, in the human case, underlying) medium. Sadly, it seems the electrical engineering courses I took long ago haven’t left many surviving correct intuitions.
After a bit of googling about this question, I’m intrigued to find out that the problem of electrocuting fish has attracted considerable research attention. A prominent reference appears to be a paper titled Electrical stunning of fish: the relationship between the electrical field strength and water conductivity by two gentlemen named J. Lines and S. Kestin (available ungated here, and with a gruesome experimental section). Alas, the paper says, “No publications appear to be available which identify conductivity measurements of fish tissue at the frequencies being used.” It does however say that we might expect something in the hundreds or low thousands of uS/cm, whereas Wikipedia informs us that the conductivity of seawater is around 4.8 S/m, i.e. as much as 48,000 uS/cm.
So, yes, this was definitely a blunder on my part.
Vladimir, I’m not sure about the orientation bit. Imagine constructing a sphere of fish around the lightning strike, so that the fish tile the sphere and are flat against the sphere (actually, hemisphere). Necessarily, all the electricity flows through the fish, because they completely tile the hemisphere. Now re-orient the fish without otherwise changing their location. Now, because the fish are thin, they no longer cover the sphere, and between them is a lot of seawater. So only a small fraction, now, of the electricity flows through the fish, and the rest passes by them in the seawater.
Meanwhile, of course, that small fraction of electricity is staying in the fish for much longer, because each unit of power is flowing the entire length of the fish, from head to tail, whereas when the fish are placed sideways relative to the flow of electricity, each unit of power is only flowing from one side to the other.
At first glance, it seems to cancel out.
Imagine the following: each fish is made out ten unit cubes placed next to each other. They can either be placed perpendicular to the flow of energy, so that each cube gets the energy that flows through one unit square. Or, they can be placed parallel to the flow of energy, so that they all share the energy from a single unit square, which flows through all of them one after the other.
It seems to come to the same thing.
But here’s one further complication: if the fish is a better conductor than the seawater, then the energy will tend to re-direct to seek out the fish (more electricity will flow through the better conductor, cet.par.), so that placing the fish parallel to the flow of energy rather than perpendicular to it will not entirely protect it from the neighboring energy. In short, if the fish is a better conductor than the seawater, then it is better for the fish to be oriented perpendicular to the flow of energy.
But, without going into details, I hastily extrapolate that if the fish is a poorer conductor than the seawater, then it is better for the fish to be oriented parallel to the flow of energy (i.e. facing the lighting strike point, or facing away).
Constant:
You are correct! I hastily analogized from the human step potential, ignoring the fact that fish, unlike humans, may well be much poorer conductors than the surrounding (or, in the human case, underlying) medium. Sadly, it seems the electrical engineering courses I took long ago haven’t left many surviving correct intuitions.
After a bit of googling about this question, I’m intrigued to find out that the problem of electrocuting fish has attracted considerable research attention. A prominent reference appears to be a paper titled Electrical stunning of fish: the relationship between the electrical field strength and water conductivity by two gentlemen named J. Lines and S. Kestin (available ungated here, and with a gruesome experimental section). Alas, the paper says, “No publications appear to be available which identify conductivity measurements of fish tissue at the frequencies being used.” It does however say that we might expect something in the hundreds or low thousands of uS/cm, whereas Wikipedia informs us that the conductivity of seawater is around 4.8 S/m, i.e. as much as 48,000 uS/cm.
So, yes, this was definitely a blunder on my part.