Blue Tilapia in Georgia 29 



was not known by the fisherman, who released most back into the 

 Skidaway River. Examination of dead specimens, discarded as bait, 

 established their identity as a species of cichlid. These specimens were 

 kept for more detailed examination, which led to the study reported 

 herein. 



METHODS AND MATERIALS 



To determine the extent of the distribution of blue tilapia in the 

 area, numerous collections were made with five minnow traps, which 

 were fished overnight in numerous places along the creek. Collections 

 were also made with a cast net (2.4-m diameter, 1.2-cm mesh) in deep 

 (>1 m) tidal pools. Daily collections with the cast net and minnow traps 

 were made from 21 July to 3 August 1989. Temperature and salinity 

 were recorded. All blue tilapia were placed immediately in 5% buffered 

 seawater formalin. The occurrence of other species and their life history 

 stages were noted; those specimens were then released alive. The tilapia 

 were taken to the lab for processing. 



All specimens were measured (total length, abbreviated as TL) on 

 a measuring board to the nearest mm and weighed on an electronic 

 balance to the nearest 0.1 g. An attempt was made to determine sex of 

 the fish from macroscopic examination of gonads. Otoliths and scales 

 were removed for possible age determination. Counts of dorsal fin rays 

 and spines were made to ascertain the identity of the species (Trewavas 

 1983). 



Voucher specimens have been placed in the collections of the 

 University of Georgia Museum of Natural History (Athens, Ga.) and 

 the Marine Extension Service Aquarium (Savannah, Ga.). 



RESULTS 



A total of 36 blue tilapia, ranging from 45 to 86 mm total length 

 (mean - 65) and weighing from 1.7 to 1 1.9 g, were collected. The largest 

 specimens were collected with cast net, but most specimens were 

 collected in minnow traps. The length frequency distribution for all 

 specimens is given in Fig. 2. All specimens exhibited the juvenile color 

 pattern, consisting of 8 to 10 dark vertical bars from head to tail with a 

 dark spot at the base of the soft portion of the dorsal fin. In most 

 specimens, the maxillary and opercle were flecked with a metallic blue 

 iridescence and the distal margin of the caudal fin was red. Counts of 

 dorsal fin spines and rays ranged from 14 to 16 (mean = 15.4) and 12 to 

 13 (mean = 12.5), respectively, indicative of T. aurea and not a hybrid of 

 T. aurea and T. nilotica (L.) (Trewavas 1983). 



It was not possible to determine the sex of any individual from 

 macroscopic examination. Gonads were barely visible to the naked eye. 



