Abstract

We are investigating transport mechanisms and connectivity among life history stages of the pink shrimp (Farfantepenaeus duorarum) to test hypotheses of transport in South Florida and to improve management of this commercially important species. Pink shrimp spawns offshore near Dry Tortugas and larvae migrate to the nursery grounds in western Florida Bay, about 150 km to the east-northeast. During the first phase of our study we identified pathways and potential transport mechanisms. Results of four years of sampling indicated that the vast majority of postlarvae enter Florida Bay through its NW border, which connects the Bay with the SW Florida Shelf of the Gulf of Mexico. A relatively small number of postlarvae enter through the tidal channels of the Middle Florida Keys, previously the most widely recognized path in terms of favorable physical conditions for onshore larval transport. A Lagrangian trajectory model (horizontal) coupled with larval behaviors was developed to explore transport mechanisms across the SW Florida Shelf. Simulations of transport indicated that planktonic stages could travel up to 200 km eastward in 30 days (planktonic time of development of pink shrimp) with a flood-tide transport known as Selective Tidal Stream Transport (STST). This mechanism assumes that postlarvae ascend in the water column on dark flood tides and descend to the bottom during ebb tides. The behavioral assumption of the model has not yet been demonstrated for early larval stages, in which only simpler vertical migrations cued by light has been observed. An oceanographic cruise was conducted in summer 2004 across the SW Florida Shelf with the aim of clarifying hydrodynamics and larval behavior. Results of this study will be discussed in terms of our transport model and previous mechanisms and behaviors proposed for penaeid shrimps.

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