DAHLBERG: ECOLOGICAL STUDY OF GEORGIA COASTAL FISHES 



quite similar in diversity and location but some 

 interesting differences exist. The canal is more 

 open to high-salinity water and to the marsh. 

 Larger individuals of some species, such as the 

 striped mullet, silver perch, and spot, entered 

 the canal but not the more isolated pools. The 

 pools contained small species and small individu- 

 als of large species. Species characteristic of 

 both habitats include the ladyfish, tarpon, sheeps- 

 head minnow, mummichog, mosquitofish, sailfin 

 molly, snook, striped mullet, white mullet, and 

 spot. Species that were restricted to the pools 

 include the marsh killifish, fat sleeper, and fresh- 

 water goby. 



The greater diversity (37) of the high-salinity 

 tidal pools, compared to the low-salinity pools, 

 is probably related to their higher salinity and 

 greater accessibility from habitats of high di- 

 versity (beach and lower reach) . As noted pre- 

 viously, salinities and temperatures were similar 

 in the two series of high-salinity pools on the 

 east and west sides of the road to the Sapelo 

 Island lighthouse. Conspicuous faunal differ- 

 ences in the two series of pools may be related 

 to water depth. In the shallow pools of the east 

 side there were large numbers of cyprinodonti- 

 form fishes (including the sailfin molly, mum- 

 michog, sheepshead minnow, mosquitofish, and 

 striped killifish) and spotfin mojarra. These 

 were all found in much smaller numbers in the 

 deep pool on the west side of the road. The 

 deep pool produced larger numbers of young 

 silver perch, young spot, and gobies. The sharp- 

 tail goby, emerald goby, and green goby were 

 not found in the shallow pool. Large numbers 

 of striped mullet, white mullet, ladyfish, and bay 

 anchovy were found in the shallow and deep 

 pools. 



These semi-isolated tidal pools of estuaries 

 have 'received little attention in ichthyological 

 studies although they are nursery grounds for 

 many species. Kilby (1955) compared "inner 

 pools" and "outer pools" for two regions on the 

 Florida Gulf coast. He found a higher diversity 

 (36 and 26 species) in the outer pools than in 

 the lower salinity inner pools (19 and 28 spe- 

 cies) . He did not find significantly more species 

 in open water as I have, because of differences 

 in collecting methods. 



The ecological stability of a habitat is gener- 

 ally related to its species diversity. Therefore, 

 it would appear that the low-salinity habitats, 

 tidal pools, and tidal canals would be more vul- 

 nerable to pollution than the other habitats. This 

 suggests that locating factories or developments 

 on lower reach or beach habitats would be less 

 likely to damage the fish populations. However, 

 other factors must be considered. For example, 

 the beaches are especially sensitive to develop- 

 ment because removal of the stabilizing beach 

 plants results in rapid erosion. 



ADDITIONAL COASTAL HABITATS 



I consider the oyster habitat to include the 

 oyster reefs of the lower reach and smaller 

 patches of oysters in tidal creeks. The oyster 

 habitat was located near the low tide level and 

 was sampled by hand. Fishes that remain with- 

 in the interstices between oysters at low tide I 

 consider characteristic. In general order of de- 

 creasing abundance, these are: naked goby, 

 feather blenny, skilletfish, seaboard goby, striped 

 blenny, oyster toadfish, and crested blenny. The 

 mummichog was often observed swimming in 

 the vicinity of oysters. At high tide a number 

 of sciaenids migrate to submerged oyster reefs 

 where they provide good fishing. The naked 

 goby, feather blenny, mummichog, and oyster 

 toadfish (one specimen) were also associated 

 with the fouling community on the underside 

 of floating docks in the lower reach. 



Few species occur in strictly freshwater hab- 

 itat on Sapelo Island. Collections were made 

 in a pond at the Marine Institute and ditches 

 at artesian wells. The largemouth bass and blue- 

 gill were introduced and are well established in 

 ponds. There are specimens in the University 

 of Georgia Fish Collection of the yellow bullhead 

 and warmouth that were collected on Sapelo 

 Island. These species probably were introduced. 

 Five species that were common in a ditch at an 

 artesian well, locally called Flora Bottom, are 

 the mosquitofish, sailfin molly, marsh killifish, 

 least killifish, and bluefin killifish (Lucania good- 

 ei). Of these, the first three are euryhaline. 

 The least killifish and bluefin killifish may be 

 native to Sapelo Island, or they could have dis- 



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