LIVINGSTON ET AL.: LONG-TERM FLUCTUATIONS OF POPULATIONS 



data had skewed distributions, logarithmic trans- 

 formations were used for such variables to ap- 

 proximate normality. 



RESULTS 



Physicochemical Parameters 



Depths of the various stations ranged from 1 to 

 2.5 m. With the exception of shallow areas, such 

 as station 6, which are characterized by periodi- 

 cally moderate concentrations of widgeon grass, 

 Ruppia maritima, East Bay has a silty-sand bot- 

 tom with little benthic macrophyte development. 

 Stations proximal to river drainage (stations 2-4) 

 are marked by strong currents and seasonally 

 high deposits of allochthonous detritus (leaf lit- 

 ter, branches, etc.). Except for shallow fringing 

 areas, Apalachiocola Bay (stations 1, lA-lC) has 

 little benthic macrophyte development; it is 

 dominated by silty-sand bottom with interspersed 

 oyster bars. 



The Apalachicola River is a major determinant 

 of the physical environment of the bay system. 

 There is a seasonal fluctuation in flow with peak 

 levels occurring during winter and spring 

 months. Local rainfall, with peaks during late 

 summer and early fall, is out of phase with this 

 pattern. During the present period of study, river 

 flow determined salinity throughout the bay. 

 Mean salinity in East Bay was lower than that in 

 Apalachicola Bay; oligohaline areas (stations 5A, 

 6) were without measureable salinity from mid- 

 winter to early summer. Outer bay stations had 

 higher salinities; at station IB, the salinity did 

 not go below lb"L during the 3-yr study. During 

 periods of increased salinity, the shallow bay sys- 

 tem was vertically stratified (Estabrook 1973; 

 Livingston et al. 1974). However, there was little 



horizontal or vertical variability in water tem- 

 perature at any given time. Low temperatures oc- 

 curred during the winter months. Turbidity 

 levels were relatively high throughout the bay, 

 and were directly related to river flow rates. Color 

 levels reflected both river flow and proximity to 

 land runoff, with elevated levels in East Bay 

 areas during the summer. Although there were 

 various complex physical changes in different 

 areas of the bay due to basin physiography, local 

 runoff, tidal currents, depth, etc., the major 

 habitat features of the Apalachicola Bay system 

 were determined by river conditions. 



Distribution of Fishes 

 and Invertebrates 



Similarity coefficients (cumulative, by station) 

 are shown in Table 1. Species such as bay an- 

 chovy, Anchoa mitchilli; Atlantic croaker, Mic- 

 ropogon undulatus; and sand seatrout, Cynoscion 

 arenarius, were dominant throughout the sam- 

 pling area. Others such as scaled sardine, Haren- 

 gula pensacolae, and Gulf menhaden, Brevoortia 

 patronus, were taken primarily in East Bay. High 

 interstation similarity of species assemblages of 

 fishes was noted, although grass bed areas such 

 as station 6 were characterized by higher num- 

 bers of species than other (mud-flat) stations. 

 There was increased spatial variability among 

 the invertebrate assemblages. Species such as the 

 blue crab and the penaeid shrimps (Penaeus 

 setiferus , P. duorarum ) were more evenly distri- 

 buted throughout the system than others. Grass 

 shrimps (Falaemonetes pugio, P. vulgaris, P. in- 

 termedius) were more frequently taken in the 

 grass beds of East Bay while the brief squid, Lo/- 

 liguncula brevis, was a dominant species in 

 Apalachicola Bay. High levels of species similar- 



TabLE 1. — C\ values (by station) for invertebrates and fishes taken in the Apalachicola Bay system 



(March 1972-February 1975). 



313 



