DAHLBERG: ECOLOGICAL STUDY OF GEORGIA COASTAL FISHES 



ORDER SILURIFORMES 



Ictaluridae - freshwater catfishes 



Three species of freshwater catfishes were 

 collected. The yellow bullhead (Ictalurns na- 

 talis) was common in freshwater stations. A 

 16-mm tadpole madtom {Noturus gyrinus) 

 wandered downstream from its typical fresh- 

 water habitat to the Crossroads station where 

 the salinity was 1.9%c. The white catfish (/. 

 catus) ranged down the estuary to the middle 

 reach (trawl stations 10 and 11) when the sa- 

 linity was reduced to 11.7 and 9.2%o and temper- 

 atures were 11.1° and 10.8°C, in January and 

 February. White catfish were seined and 

 trawled (10-ft trawl) on nine occasions in the 

 oligohaline creek at salinities less than l%o and 

 at a temperature range of 7.4° to 28.4°C. Large 

 samples including specimens over a length range 

 of 40 to 300 mm, trawled in January and Feb- 

 ruary 1970, suggest that large numbers of white 

 catfish moved into the oligohaline creek when 

 temperatures were 8.6° and 10.0°C. The low 

 temperatures could also reduce their mobility 

 and ability to avoid the trawl. 



Ariidae - sea catfishes 



The sea catfish {Arius felis) and gafftopsail 

 (Bagre marinus) were most abundant in the 

 lower reach of the estuary but also occurred in 

 the middle reach and beach habitats. Most of 

 the sea catfish (Arius) migrated to the ocean 

 in the late autumn and winter and returned to 

 the estuary and beaches in the spring (Table 3) . 

 Males orally incubated the marble-sized eggs in 

 June and July. Young with and without yolk 

 sacs were incubated in August until they were 

 42 mm long or longer. Young lost the yolk sac 

 when they were 37 to 40 mm long. The gafftop- 

 sail also is an oral incubator, but none of the few 

 adults collected contained eggs or young. This 

 species is common in the warm months but scarce 

 in the winter. 



ORDER PERCOPSIFORMES 



Amblyopsidae - cavefishes 



The rare swampfish (Chologaster cornuta) 

 was collected at freshwater station 7. 



Table 3. — Length-frequency distribution of the sea cat- 

 fish, Arius felis, collected with a trawl, 1967. There was 

 no June collection. 



Aphredoderidae - pirate perches 



The pirate perch (Aphredoderus sayanus) 

 was collected at freshwater stations 3, 4, 5, and 7, 

 and one specimen was taken in fresh water in 

 the oligohaline creek. 



ORDER BATRACHOIDIFORMES 



Batrachoididae - toadfishes 



The oyster toadfish (Opsanus tau) was often 

 collected in small numbers in trawls in the lower 

 and middle reaches of the estuary throughout 

 the year. This toadfish is sometimes seen in 

 oyster reefs, and one specimen was found in a 

 fouling community on the underside of a floating 

 dock. The collection of only one specimen in 

 the beach habitat can be attributed to the lack 

 of cover. Salinity ranged from 12.4 to 32.0%o 

 and temperature, from 28.4° to 30.8 °C. 



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