Storm-Induced Spawning by the Atlantic Menhaden

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Prior research led to the hypothesis that the Atlantic menhaden, >Brevoortia tyrannus>, spawns during storms in water upwelled near the western wall of the Gulf Stream. This hypothesis is based on inference from the sizes and birth dates of surviving larvae. A rigorous test of this hypothesis, and investigation of its adpative significance, requires studies of recently spawned eggs and the resultant larvae. Methods must be developed to facilitate such studies. In particular, the ability of an optical particle counter to distinguish and count eggs needs to be evaluated. The optical counter may also distinguish yolk sac larvae of the Atlantic menhaden in natural assemblages of the zooplankton. Tests will be done in the larboratory, with live eggs and larvae of the Atlantic menhaden from a captive spawning stock, and at sea during a seven day cruise, deploying the optical counter with a CTD on a towed body. The ability of a radio tracked, surface drifter to follow a patch of Atlantic menhaden eggs and larvae will also be tested. A small group of scientists with expertise in meteorology, physical, chemical and biological oceanogaphy, and theory will meet to plan a rigorous investigation of weather effects on the spawning and egg and larval ecology of the Atlantic menhaden. The work will provide results valuable for the Atlantic menhaden and also other organisms with pelagic eggs and/or larvae. Such organisms typically exhibit large variation in recruitment. %%%