Abstract

Recruitment dynamics of marine fishes are largely driven by processes operating during the early life history (ELH) stages. Yet, for billfishes, the early stages have been only cursorily studied, in part due to the large spatial extent of potential larval and juvenile habitat, difficulties in collecting sufficient numbers of young, and adequately resolving the taxonomic identity of specimens. Early work solved some of the identification issues based on morphological characters, at least for the Pacific, but sufficient resolution was still hampered. Nonetheless, opportunistic sampling, and some targeted efforts, have helped identify potential areas where spawning may be occurring, and provided some idea of the temporal pattern of spawning activity. With the onset of more definitive molecular identification techniques, and advanced sampling systems, more extensive studies into the dynamics of the ELH of billfish are now possible. Here I discuss one such program that was developed to address several aspects of the ELH of billfish within the Western Central Atlantic, with a focus on the Straits of Florida (SOF). Specifically, this study is directed at providing a seasonally-resolved understanding of billfish spawning, larval growth, feeding, and transport within the oceanographic context of the SOF. The work includes measures of the temporal qualities of cross-strait features (i.e., water mass distribution, larval billfish patches, and zooplankton community structure) via monthly sampling (ichthyoplankton, zooplankton, CTD, fluorometry, and ADCP measurements) linked, via otolith aging studies and circulation patterns, to estimates of spawning locations. Otolith work on larval growth rates will be coupled to zooplankton work on community composition and dynamics to identify trophodynamic differences among patches. Ultimately, information on the flux of larvae through this system combined with knowledge of the reproductive output of billfish, may provide estimates of spawning production, and hence, stock size within this region

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