DAHLBERG and CONYERS: ECOLOGICAL STUDY OF GOBIOSOMA 



We collected G. bosci at temperatures of 12.7° 

 to 31.3°C. It is known to occur at temperatures 

 of 1.5° (Hoese, see footnote 3) to 33.2°C (Gunt- 

 er, 1945). 



G. bosci is euryhaline and is common in low 

 to moderate salinities. Dawson (1966) sug-g-est- 

 ed that G. bosci apparently departs from the 

 size-salinity relationship described by Gunter 

 (1945) wherein the youngest individuals pre- 

 dominate in the low salinities. Our data gen- 

 erally support Gunter's observations as our three 

 low-salinity (0-1.9/^() collections contained only 

 14- to 22-mm specimens. However, Dawson 

 (1966) found most 9.5 to 11.0-mm G. bosci to 

 occur at 14.8 to 24.7^f salinities. G. bosci spawns 

 in moderate to high-salinity waters and the 4- to 

 15-mm pelagic larvae move upriver by an un- 

 know^n mechanism (Massmann, Norcross, and 

 Joseph, 1963). Since the smallest specimens 

 reported by Dawson (1966) apparently were 

 recently spawned, his observation does not dis- 

 prove the size-salinity hypothesis. 



Habitats of G. ginsburgi and G. bosci overlap 

 to some degree. G. ginsburgi was commonly 

 found in oyster shells at Big Hole. It was rare 

 in the marsh creek; here only a single 16-mm 

 G. ginsbiirgi was collected, along with 44 G. 

 bosci, on 12 February 1968. G. ginsburgi was 

 more abundant than G. bosci in burrows in the 

 eroding clay banks on the beach as noted above 

 and in deepwater stations in the estuary. There 



Table 1. — List of fishes and common macroinvertebrates 

 that were associated with the subtidal patches of oyster 

 shells in Georgia. 



Polychaete worm 

 Nereis suecinea 



Snails 



Urosalpinx cinerea 

 Terebra dislocata 

 Odostomia sp. 



Bivalves 



Petricola pholadijormis 

 Brachidontes exustus 



Isopods 



Sphaeroma quadridentatum 

 Cassidinidea lunijrons 



Amphipods 

 Gammarus sp. 

 Melita nitida 



Shrimps 



Palaemonetes vulgaris 

 Palaemonetes pugio 



Crabs 



Callinectes sapidus 

 Menippe mercenaria 

 Rhithropanopeus harrisi 

 Neopanope ttxana sayi 

 Eurypanopeus depressus 

 Panopeus herbstii 

 Pagurus longicarpus 



Fishes 



Gohiosoma bosci 

 Gobiosoma ginsburgi 

 Gobiesox strumosus 

 Opsanus tau 

 Hypsoblennius hentzi 

 Chasmodes bosquianus 

 Hypleurochilus geminatus 



were nine dredge and trawl collections of G. 

 ginsburgi (13 specimens) in the estuary com- 

 pared with four of G. bosci (4 specimens). In 

 contrast to G. bosci, these collections of G. gins- 

 burgi were all taken in shell areas. G. ginsburgi 

 ranges offshore to a depth of 45 m (Dawson, 

 1966) . Apparently it spawns in deep water, and 

 its young do not migrate into low-salinity water. 

 G. ginsburgi occurred in three dredge collections 

 from 1.6 to 12.9 km (about 10 m depth) off the 

 Georgia coast. G. ginsburgi was not found in 

 shallow marsh pools, fouling communities, or in 

 low salinities. We collected it at salinities of 

 24.9 to 34.i;^r in the estuary, and de Sylva, Kal- 

 ber, and Shuster (1962) collected it at 22 to SOf/r. 



ASSOCIATED SPECIES IN 

 OYSTER PATCHES 



Other fishes and conspicuous invertebrates 

 were collected with the gobies for the purpose of 

 characterizing the small oyster shell patches and 

 to allow comparison with the larger, typical 

 oyster reefs. The larger reefs are primarily in- 

 tertidal in sounds and high-salinity rivers. The 

 small reef patches are mostly subtidal and are 

 subjected to a stronger ebb tide current and 

 probably more erosion than the larger reefs in 

 the mud flats. 



Most of the invertebrates and all the fishes 

 collected (Table 1) were reported for North 

 Carolina oyster reefs by Wells ( 1961 ) . The only 

 records we add are the amphipod Melita nitida 

 and the auger Terebra dislocata. Some species 

 that we consider to be common in the subtidal 

 reef patches were considered to occur in less 

 than 20 ^r of the collections in North Carolina 

 (Wells, 1961). These include Palaemonetes 

 pugio, P. vulgaris, Callinectes sapidus, Menippe 

 mercenaria, Rhithropanopeus harrisi, Pagurus 

 longicarpus, and Cassidinidea lunifrons. 



The seven species of fishes (Table 1) are char- 

 acteristic oyster reef species. They are inti- 

 mately associated with the reefs. They remain 

 within the interstices of the reef throughout the 

 tidal cycle during the warmest months and all 

 nest there to some degree. However, they be- 

 come scarce or absent on the reefs in winter. 

 Other fishes collected with oysters (Wells, 1961) 



281 



