How might a shark benefit from the ability to detect weak electrical fields and sound vibrations in the water?

Answer 1

It is the basis on how many species hunt.

There are species who from time to time hunt in poor conditions (dark, cloudy water, rockey areas, etc) and through using the electric currents that fish give off the sharks are able to better find their prey. So much so to the fact that have found that the sharks can find food hiding under the sand that is 100% hidden.

Answer 2

It helps in the search for food. Movement in the water or the electric field of a fish is an indication to the shark of a potential meal.

Answer 3

it helps to track their prey