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The article presents a study which investigates the notion that separating mechanisms of shoreward transport and estuarine ingress might enable identification of vital transport mechanism through eliminating interactions between tide-driven and wind-driven mechanisms. The authors revealed that there was an apparent relationship between the peak months of estuarine ingress in October and November and assert that there is a conceptual model being proposed describing the environmental conditions of the estuaries. It relates that the transport of postlarvae is thought to occur by a combination of physical and behavioral mechanisms.

Female blue crabs (Callinectes sapidus Rathbun) with mature embryos have a spawning migration in which they: (1) undergo ebb-tide transport for movement seaward from estuaries, (2) release their larvae, and (3) reverse direction by undergoing flood-tide transport for up-estuary movement. The study determined whether ebb-tide transport during the spawning migration is based upon an endogenous rhythm in vertical migration. Under constant conditions in a rectangular container, which limited horizontal and vertical movements, females with young and mature embryos had circatidal rhythms (periods=12.11–12.95 h) in migratory restlessness (swimming activity) and egg maintenance behavior (abdominal pumping). However, the rhythms were out of phase, as migratory restlessness occurred during the expected time of ebb tide in the field, and egg maintenance behavior, during the time of flood tide. Under constant conditions in vertical columns (1.32 m high), crabs with mature embryos had a circatidal rhythm (periods=12.2–13.7 h) in which they had frequent bouts of swimming to the surface of the column during the expected time of ebb tide in the field and remained on the bottom during the time of flood tide. This rhythm was not present in crabs with young embryos and disappeared after larval release. Thus, an endogenous rhythm in vertical migration does underlie the ebb-tide transport behavior of ovigerous blue crabs with mature embryos during their spawning migration. [ABSTRACT FROM AUTHOR]

Examines the behavior of the blue crab Callinectes sapidus postlarvae (megalopae) under simultaneous variations in salinity and turbulence to simulate flood tide. Role of salinity in initiating swimming in megalopae; Materials and methods used; Results and discussion.

Most marine organisms have a highly specialized larval settlement stage. A major function of the settlement stage is response to environmental input that results in deposition of the larvae in a location which confers probability of survival and successful reproduction. The settlement stage is a prime target for management strategies because it is a key and vulnerable step in the colonization process. Published and unpublished work will be synthesized to provide an overview of responses of a variety of settlement stage larvae to chemical and physical cues. It is maintained that due to tiny larval brains and poor memories, it is environmental cues rather than larval choice that determines where larvae settle. Larval examples include ascidians, brachyurans, bryozoans, cirripedes, hydroids and polychaetes. Chemical cues include inorganic and organic compounds, including stimulatory peptides and odors. Physical cues include surface energy, vibration and light. The aims of this review are to find common ground with others in the field and to add to the theoretical context the consideration of environmental input for larval settlement. [ABSTRACT FROM AUTHOR]