Rachel carson wrote about the delicate balance of organisms in a food web. snakeheads, a freshwater fish that is not normally found in the united states, was accidentally introduced to the lake eugene. as an adult, the snakehead would feed on crustaceans, small fish, reptiles, and even small mammals. it would not have any predators in this environment. considering the food web below how would this affect the ecosystem?

The snakehead could unreservedly eat little fish and scavangers, so that would evacuate/diminish the predator for zooplankton and phytoplankton. So zooplankton and phytoplankton populace would increment while little fish and scavanger populace would diminish. Presently if little fish and shellfish populace diminishes, their predators would have bring down sustenance, so vast fish pop. would diminish. On the off chance that vast fish pop. diminishes, their predators will have less nourishment thus the number of inhabitants in well evolved creatures will somewhat drop, however not by much, since they can feast upon zooplankton. 
So at last, just the phytoplankton populace would increment while everything else diminishes.