FISHERY BULLETIN: VOL. 74, NO. 2 



ity were noted among river-dominated and East 

 Bay stations (1, 2, 4, 5, 5A); outer bay stations 

 (lA, IB, IC) also w^ere somew^hat alike according 

 to the Cx similarity analysis. Station 6, as a 

 grass-bed area, differed from most of the other 

 collections. Station IB, v^ith consistently higher 

 salinity than the other stations, differed in terms 

 of invertebrate species composition. These data 

 indicate that fishes are more widespread in their 

 distribution throughout the bay system than the 

 invertebrates, which were more habitat-specific 

 with respect to substrate, salinity, etc. 



Seasonal Fluctuations of 

 Dominant Species 



Comparative dominance figures for the 10 most 

 numerous fish and invertebrate species are given 

 in Table 2. Relative dominance is high in both 

 groups with the top three species of fishes and 

 invertebrates constituting 77.0 and 80.7% of the 

 respective combined totals. Some species such 

 as H. pensacolae, B. patronus, and Atlantic 

 threadfin, Polydactylus octonemus, were found 

 during limited periods (April 1973, April 1974, 

 and May-August 1973, respectively). Seasonal 

 variations in the six dominant species are shown 

 in Figure 2. The most conspicuous species was A. 

 mitchilli, which was particularly abundant dur- 

 ing the first year of study. Peaks of numbers 

 usually occurred during fall or early winter 

 (October-January). With M. undulatus, peak 

 levels usually were noted during late winter or 

 early spring (February-March) whereas C. 

 arenarius reached abundance during late spring 

 and summer months (usually around August). 

 The sea catfish, Arius felis, usually peaked by 

 midsummer (July) while Atlantic bumper, 

 Chloroscombrus chrysurus, and southern king- 

 fish, Menticirrhus americanus, were prevalent 



Table 2. — The lO dominant species of fishes and inverte- 

 brates taken in the Apalachicola Bay system from March 1972 

 to February 1975. Figures are expressed in percentages of 

 total numbers of individuals. 



3000- 



< 



D 

 Q 



> 



Q 



tr 

 lij 



CO 



D 



£ 

 E 



X 



o 



z 



Ui 



" I I I 



MJ S D M J S DMJ S DM 



MJ S DM J S DM J S DM 



TIME-MONTHS 



Figure 2. — Seasonal changes of numbers of individuals and 

 mean size of six dominant species of fishes taken in the 

 Apalachicola Bay system from March 1972 to February 1975. 



during late summer or early fall (August- 

 October). The spot, Leiostomus xanthurus, usu- 

 ally peaked during winter and spring months; 

 silver perch, Bairdiella chrysura, had a variable 

 abundance curve. Overall, there was considerable 

 regularity in the appearance of the dominant bay 

 fishes even though there was often a marked 

 within-species variation in total numbers from 

 year to year. 



Annual fluctuations of the dominant inverte- 

 brate species are shown in Figure 3. The white 

 shrimp, Penaeus setiferus, was prevalent from 

 August to November with autumn peaks of 

 abundance; the other penaeids usually reached 

 high numbers in the late spring (P. aztecus) or 

 late summer (P. duorarum). Palaemonetes pugio 

 was usually found in the bay during spring 

 months (March-May) while P. vulgaris reached 

 high numbers in November. The blue crab peaked 

 during summer and winter periods. Early sum- 

 mer and fall peaks were noted for Lolliguncula 



314 



