Models of fish recruitment must include a realistic description of the underlying prey population dynamics. In the example presented here a model for the growth of haddock larvae (Melanogrammus aeglefinus) and recruitment to the population of juvenile fish is coupled to an excitable medium representation of the planktonic ecosystem. The results elucidate and quantify non-trivial interactions between the larval and planktonic populations. Fish spawning can act to influence the date of onset of the spring phytoplankton bloom, and to increase bloom duration. Simulations show the effects of different reproductive strategies in a stochastic and evolving environment.