How could a decrease in the number of herring cause an decrease in the number of sand eels?

A decrease in the number of herring could lead to a decrease in sand eels because herring are a key predator of sand eels in the marine food web. With fewer herring, the population dynamics may shift, potentially allowing other predators, such as larger fish or seabirds, to thrive and increase their predation on sand eels. Additionally, the loss of herring could disrupt the overall ecosystem balance, affecting prey availability and habitat conditions that sand eels rely on for survival.