SIZE-STRUCTURED PISCIVORY - ADVECTION AND THE LINKAGE BETWEEN PREDATOR AND PREY RECRUITMENT IN YOUNG-OF-THE-YEAR BLUEFISH

The interaction of size-structured predator and prey populations can a ffect the recruitment success of both predators and prey. Here, we exa mine how the timing and location of spawning, advective processes, and size-structured predator-prey interactions may influence the ecology and life history of an offshore-spawning, estuarine-dependent marine f ish. Bluefish Pomatomus saltatrix recruit to mid-Atlantic Eight estuar ies as 2 distinct cohorts. The predominant spring-spawned cohort resul ts from: (1) spawning in the South Atlantic Eight in March and April, (2) advection northward along the edges of the Gulf Stream, and (3) an active migration into New York/New Jersey (USA) estuaries in June and July. A second less abundant cohort resulting from summer-spawning in the mid-Atlantic Eight recruits to inshore areas in August. This insh ore recruitment entails a dramatic habitat shift that coincides with a feeding shift from planktivory to piscivory and a large increase in g rowth rates. We hypothesized that the migration of spring-spawned youn g-of-the-year (YOY) bluefish into northern estuaries at an advanced si ze facilitates piscivory on the local inshore fishes that become their principal prey. We tested this hypothesis by determining the annual r ecruitment date of YOY bluefish and their prey, and by examining the d iet and prey size selectivities, and predator size-prey size relations hips of YOY bluefish in Great South Bay (GSB), New York. Our results s howed that: (1) the date of juvenile recruitment into GSB coincides wi th the appearance of their main prey item, Atlantic silversides Menidi a menidia; (2) YOY bluefish feed primarily on the most abundant prey a vailable in GSB; and (3) bluefish are size selective, consistently ing esting small prey sizes. These results suggest that advection into hig h latitudes permits spring-spawned bluefish to exploit habitats at an earlier time and at a larger size than would otherwise be possible. Th is unique strategy also allows bluefish to accelerate the onset of pis civory by timing their estuarine entry with the appearance of small co astal fishes. The relationships between bluefish and their prey are de termined by a complex interplay between recruitment timing of both pre dator and prey, relative prey (size and type) abundances and predator selectivities. The observed pattern of spawning, advection and recruit ment to nursery areas, which is common to other bluefish populations, may represent a reproductive strategy that maximizes growth and surviv al.