Ecological and evolutionary implications of the larval transport and reproductive strategy of bluefish Pomatomus saltatrix

The current view of bluefish Pomatomus saltatrixliie history holds that there are 2 distinct spawning events along the east coast of the United States which result in the recruitment of 2 juvenile cohorts to estuaries of the Middle Atlantic Bight. This two-spawning hypothesis is examined through an analysis of gonosomatic indices, larval abundances and larval distributions from both the South Atlantic and Middle Atlantic Bights. These data suggest that bluefish spawn continuously from about March to at least September, rather than in 2 distinct episodes. This continuous-spawning hypothesis raises the problem of which processes could act between spawning and estuarine recruitment to create the appearance of 2 juvenile cohorts. A model is developed which is based on large-scale circulation features of the east coast of the United States and on the hypothesis that bluefish spawn continuously as they migrate northward along the coast. The model predicts that offspring spawned in the middle of the spawning season will have a lower probability of recruitment, thereby creating a bimodal pattern of offspring survival. These results are discussed both in terms of variations in the large-scale circulation which may be responsible for creating intra- and interannual variation in recruitment, and in terms of the apparent non-adaptive nature of bluefish reproductive strategy.