Based on the options provided and the common patterns of population dynamics, the statement that most accurately describes the change in the population of Species A would typically be:
Its numbers grow rapidly then level off
This is a common pattern seen in ecological studies where a population experiences exponential growth when resources are abundant but eventually levels off as it reaches the carrying capacity of the environment due to limiting factors. Without specific data on Species A, this response aligns with observed trends in fish populations when new species are introduced or environmental conditions change.