megalops 



Figure 28. Life cycle of the blue crab 

 along the gulf coast of Florida. 

 Ovigerous females move toward the 

 Apalachicola estuary. It is hypothesized 

 that developing stages move back down the 

 gulf coast of Florida with offshore 

 currents (after Oesterling and Evink 

 1P77). 



croaker spawn near passes during fall and 

 early winter; the iuveniles occupy the 

 estuary in peak numbers during late winter 

 and early spring when salinities are 

 usually less than 10-15 opt. Spot also 

 spawn near passes, and peaks of abundance 

 in the estuary generally coincide with 

 those of the Atlantic croaker. Sand 

 seatrout are usually most abundant during 

 summer months after spawning offshore 

 during the spring. This species is taken 

 at various salinities, but temperature 

 appears to be limiting; high catches are 

 generally taken in ?0O-350-C water. 



White shrimp are dominant from August 

 to November, with spring spawning and 

 recruitment. Other penaeids usually reach 

 peak numbers during late spring (brown 

 shrimp: Penaeus aztecus ) or late summer 

 (pink shrimp: P_. duorarum ) . The blue 

 crab shows a bimodal annual peak of 

 recruitment; numbers peak during winter 

 and summer periods. Oeoth and specific 

 microhabitat conditions are the principal 

 determinants of blue crab distribution at 



any given time (Laughlin 1<570; Livingston 

 unpubl.). The brief sguid (Lol liguncula 

 brevis ), is limited in spatial/temporal 

 distribution by salinitv ('O-'^O ppt) and 

 other habitat characteristics and complex 

 trophic relationshios (Laughlin and 

 Livingston 1P8?). In summary, these 

 species-specific responses to multifactor 

 complexes demonstrate the difficulty of 

 trying to design linear models to explain 

 and oredict spatial/temporal patterns of 

 occurrence. 



The spatial distributions of nektonic 

 fishes and invertebrates in the 

 Apalachicola estuary (Table 20) tend to be 

 associated with freshwater runoff into the 

 system. Relative dominance at a given 

 station varied according to salinity 

 gradients and habitat type. Regular 

 seasonal changes in distributions are 

 evident for most of the dominant nektonic 

 species. For example, anchovies are 

 relatively uniformly distributed within 

 the estuarv during January and February 

 (Figure 7°). By the spring, anchovies ^re 

 concentrated in upper portions of East 

 Ray. Huring the early summer, there are 

 minor population peaks with orimary 

 concentrations in eastern portions of East 

 Bay. Bv the fall, the anchovies 

 concentrate around the mouth of the 

 Apalachicola River as well as in portions 

 of East Bay, and during early winter, the 

 anchovies become uniformly distributed 

 throughout East Bay and Apalachicola Bay. 



In January, Atlantic croaker tend to 

 conqregate at the mouth of the 

 Apalachicola River and upper oortions o*" 

 East Bay (Figure ?0). Bv February, this 

 distribution is more uniform throughout 

 East Bav and northern Apalachicola Bay, a 

 situation that appears to hold during 

 ensuing winter and spring months until, 

 by May or June, the croakers move out of 

 the bay. 



The spatial distribution of sand 

 seatrout through a given seasonal cycle is 

 guite regular (Figure 31). As the young 

 seatrout move into the bay svstem in May, 

 thev concentrate in upper portions o^^ East 

 Bay and just off the mouth of the 

 Apalachicola River. Secondary concentra- 

 tions are found throuqhout East Bay and 

 northern oortions of Apalachicola Bav. 

 The distribution changes little in June, 



65 



