DAHLBERG: ECOLOGICAL STUDY OF GEORGIA COASTAL FISHES 



life cycle, but many normally complete their life 

 cycle in the estuary. Some species that typically 

 pass their complete life cycle in the estuary, at 

 least in Georgia estuaries, include those species 

 I later consider to be characteristic of the oyster 

 reefs and certain cyprinodontid fishes such as 

 the marsh killifish, spotfin killifish, and mum- 

 michog. The spotted seatrout possibly belongs 

 to this category but adults are common along 

 the beach at times and northern populations mi- 

 grate offshore in the winter (Tabb, 1966). 



There are species that typically complete 

 their life cycle in the ocean or fresh water that 

 are either regular or accidental visitors to the 

 estuary. Another life cycle pattern is exhibited 

 by the anadromous shads (Alosa) which "spawn 

 in Georgia rivers, including the Altamaha River 

 (Godwin and Adams, 1969). The American eel 

 is the only catadromous species in the estu- 

 ary. 



DIVERSITY OF COASTAL HABITATS 



Diversity of habitats is considered here in 

 order to determine the importance of the var- 

 ious habitats to the fish community and also to 

 explore the possible relationship of diversity and 

 stability. A simple index, number of species, 

 is used here in a comparison of habitats (Table 

 9) . To be objective, I define stragglers as those 

 species that are represented by only one collec- 

 tion in a habitat. Further studies would be 



Table 9. — Number of species recorded for nine Georgia 

 coastal habitats. To eliminate the influence of strag- 

 glers, species recorded (collected or seen) once in the 

 estuary are subtracted from total. 



Habitat 



Number of 

 species 



Species 

 recorded once 



Species 



recorded 



more than once 



needed to confidently ascertain which species are 

 naturally rare in their preferred habitats. Dis- 

 counting stragglers removes a large percentage 



of the accidental species and makes diversity 

 comparison more meaningful. These diversity 

 values are only roughly comparable because of 

 the differences in sampling effort and gear. 



The beach habitat produced the highest diver- 

 sity — 114 or 95 species if stragglers are dis- 

 counted. A high diversity of clupeids, carangids, 

 sciaenids, and bothids accounted for 36 species. 

 Tagatz and Dudley (1961) recorded only 40 fish 

 species from a Beaufort, N.C., beach. Gunter 

 (1958) recorded 44 species from Texas beach 

 station, and Springer and Woodburn (1960) re- 

 corded 48 from a beach near Tampa Bay. The 

 latter consider the beach notable for harboring 

 few species compared to other coastal habitats. 

 A low diversity would be expected because the 

 beach offers little niche variety or cover. The 

 higher diversity I report may be attributed to 

 several factors. A large number of species that 

 are typical of other marine and estuarine habi- 

 tats are occasionally found along the beach. An- 

 other factor is the inclusion of eight shark spe- 

 cies that were caught while fishing from the 

 beach. A third factor is that Miller and Jorgen- 

 son (1969) sampled more extensively than in 

 other studies noted herein. They found 98 spe- 

 cies at St. Simons Beach; this total includes 38 

 species which did not occur at Sapelo Beach. 



Species that I consider to be eurj^thermal in 

 the estuary were collected in both winter and 

 summer and usually in all four seasons, but not 

 necessarily every month. Species that are eury- 

 thermal in the beach habitat include the rough 

 silverside (Miller and Jorgenson, 1969), Atlantic 

 silverside, striped killifish, bay anchovy, and 

 striped mullet. Some species that were abun- 

 dant only in the warm months include the bump- 

 er, pompano, white mullet, southern kingfish, 

 and gulf kingfish. Numbers of species and indi- 

 viduals were considerably reduced during the 

 cold months. 



The lower reach ranked high in diversity. 

 Most of its 100 species were caught in trawls 

 but seven shark records are based on Dahlberg 

 and Heard (1969). Since only four species are 

 ranked as stragglers, diversity of the charac- 

 teristic species is similar to the beach habitat. 

 Trawl collections in the region of Cedar Key, 

 Fla., yielded only 63 species (Reid, 1954). This 



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