Fish Movement Patterns

Food web structure is substantially influenced by the movement of organisms at variety of spatial and temporal scales. In both of my focus food webs, I am currently examining fish movement patterns and how these movements drive food web structure and dynamics. For example, in the Cinaruco River (Venezuela), large-scale movements of critical species occur on a seasonal time scale. The important migratory algivore/detritivore Semaprochilodus kneri moves into the river during the falling water period, providing an important “spatial subsidy” to many predators in the system. Peacock bass (Cichla spp.) may move long distances to take advantage of this productive prey species. We have tagged over 2300 peacock bass, using plastic dart tags (each with a unique number), to study large-scale movement patterns. We are currently extending this tagging work to other Venezuelan rivers.

In Bahamian estuarine tidal creeks, tidal water fluctuations can drive daily patterns of movement. For example, snapper species (see photo) move into abundant mangrove habitat with the rising tide to exploit productive intertidal food resources. Ontogenetic movements are also common in some species. For example, Nassau grouper (see photo) settle into tidal creeks as juveniles following widespread dispersal as pelagic larvae. After a period of rapid growth, individuals migrate to nearshore coral reef habitats.

In both Venezuelan floodplain rivers and Bahamian estuaries, I am initiating various radio telemetry techniques to provide more detailed data on these and other fish movement patterns.

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