species. Various microhabitat phenomena 

 such as salinity, bottom type, currents, 

 and the availability of detritus and food 

 are important. Thus, no single parameter 

 Drevails in the determination of the 

 community structure of the estuary, which 

 itself undergoes predictable seasonal 

 changes as part of a physically forced 

 system. 



Although there are appreciable short- 

 term fluctuations in the numbers of 

 individuals of different populations, the 

 system maintains a temporal constancy 

 which, according to a traditional view of 

 such phenomena, could be termed stability. 

 This does not mean that the system is not 

 in a constantly transient state. On the 

 contrary, through natural and unnatural 

 mechanisms such as habitat alteration and 

 destruction, hurricanes, cold winters, and 

 periodic flooding, the various population 

 equilibria continuously shift. Each 

 population fluctuates around a specific 

 point of equilibrium, and the fluctuations 

 reflect the adaptive response to the 

 specific aspects of the estuarine 

 environment. 



The 

 physically 



Apalachicola 

 unstable in 



estuary 

 time but 



IS 



is 



characterized by epibenthic populations 

 which maintain relatively stable temporal 

 interspecific relationships. The dominant 

 fishes and invertebrates are temporarily 

 partitioned in time. Particular groups of 

 fishes tend to co-occur (Figure 43). 

 Generally, three main clusters were 

 arranged around the top dominants, Anchoa 

 mitchilli (I), Micropogonias undulatus 

 (II), and Cynoscion arenarius ( IV) . The 

 anchovy group is abundant during the fall. 

 The Micropogonias group predominates 

 during winter and early spring periods, 

 and the Cynoscion group prevails during 

 the summer and early fall. 



Studies are currently being 

 undertaken to model the response of the 

 major groups of fish with respect to 

 physical stress, abundance of prey 

 (Mahoney and Livingston 1982; Livingston 

 et al. 1983), long-term changes of 

 concurrent populations, and experimental 

 manipulations of a variety of associations 

 within the estuary (Livingston et al. 

 1983; Livingston, unpubl.; Appendices A, 

 B, C). These studies will be based on 

 occurrence patterns over a 1?- to 13-year 

 period. 



97 



