BUCK: BACTERIOLOGY OF ELASMOBRANCH FISH 



Enterobacteria are found frequently on os- 

 teichthyan fish, but there are no reports in the 

 literature on their occurrence in (on) elasmo- 

 branchs. If waters contain domestic wastes, then 

 the fish will almost certainly be contaminated also 

 (Shewan 1971; Horsley 1977). Coliform counts in 

 Sarasota Bay are generally low, although counts of 

 1,800/100 ml have been recorded in one bayou re- 

 ceiving treated sewage effluent (Buck, unpubl. 

 data 5 ). Areas north (Tamplin et al. 1982) and south 

 (Peterson and Yokel 1983) of Sarasota Bay have 

 shown the presence of potentially pathogenic en- 

 teric bacteria. Consequently, the elasmobranch 

 fish studied here may well have been in contact 

 with sources of enterobacteria. The enteric bac- 

 teria encountered on the teeth and in the intes- 

 tines of several elasmobranchs probably reflected 

 feeding habits and originated on smaller prey 

 which had passed through waters receiving 

 human and/or animal excretions. Enteric bacteria 

 do not multiply in passage through rainbow trout 

 but temperature may be an important factor 

 (Lesel and Peringer 1981; Lesel and LeGac 1983). 

 The internal temperature of some sharks (Lam- 

 nidae) (Carey et al. 1981; Smigh and Rhodes 1983) 

 is significantly warmer than the surrounding 

 water. In subtropical areas, increased water tem- 



5 J. D. Buck. University of Connecticut Marine Research 

 Laboratory. Noank, Conn., unpubl. data, 1982. 



TABLE 3. — Enterobactenaceae isolated from elasmobranch fish. 



Taxon 



Bacteria 



Nurse shark. Ginglymostoma cirratum^ 



Intestine 

 Shovelhead shark. Sphyrna tiburo 



Intestine 



Teeth 



Sandbar shark. Carcharhmus plumbeus 

 Intestine 

 Teeth 



Blacktip shark. Carcharhmus limbalus 

 Intestine 



Teeth 



Sand tiger shark. Odontaspis taurus ] 

 Intestine 



Cownose ray. Rhinoptera bonasus 



Intestine 



Teeth 

 Clearnose skate. Ra/a eglantera'' 



Intestine 



Proteus vulgaris 

 Escherichia coli 



Enterobacter agglomerans 

 Escherichia coli 

 Shigella sp. 

 Citrobacter Ireundii 

 Providencia rettgen 

 Providencia sp. 



Shigella sp 

 Proteus vulgaris 

 Providencia rettgeri 



Escherichia coli 

 Providencia alcalifaciens 

 Shigella sp 



Escherichia coli 

 Proteus vulgaris 



Citrobacter freundu 

 Morganella morgann 

 Proteus vulgaris 



Shigella sp. 

 Serratia liquetaciens 



Escherichia coli 



'Tank held. 



perature and that of the interior tissues of elasmo- 

 branchs might provide an environment that 

 encourages bacterial multiplication, including 

 potential pathogens. While none of the entero- 

 bacteria, except perhaps Shigella species, recov- 

 ered from intestines and teeth of elasmobranchs 

 represent primary pathogens, members of the 

 other genera are commonly found as secondary or 

 opportunistic pathogens in humans. Thus, 

 caution should be exercised when handling 

 dead shark material, particularly internal organs 

 such as the digestive tract. 



The genera Vibrio and Pseudomonas were pre- 

 dominant bacteria in combined data for all elas- 

 mobranch samples (Table 2). When isolates for 

 tank-held and open-water fish were compared, 

 these two genera were the most common in each 

 group. The occurrence of other microbes did not 

 vary more than 69c for any genus of bacteria be- 

 tween tank-held and freshly caught elasmo- 

 branchs, except for Photobacterium species which 

 represented 119c of the isolates from the former 

 and 39c of the latter. 



The bacterial flora of osteichthyan fish and sea- 

 water consisted largely of Gram negative bacte- 

 ria (829c and 949c, respectively), with Vibrio and 

 Pseudomonas predominating. No substantial dif- 

 ferences in generic composition were noted be- 

 tween Sarasota Bay water and fish holding tanks. 

 Fewer numbers of several other Gram negative 

 forms were found; these results agree with those of 

 others (e.g., Shewan 1961). Small populations of 

 Gram positive bacteria (Arthrobacter, Bacillus, 

 cocci) were noted and probably represented ter- 

 restrial influence because the fish were taken from 

 nearshore waters. This assumption may require 

 reevaluation because there may be a widespread 

 distribution of Gram positive bacteria in seawater 

 (Gunnetal. 1982). 



The microflora of spoiling shark muscle (no 

 species indicated) from Australia have been 

 studied, and the genus Corynebacterium was the 

 dominant organism; Pseudomonas species and 

 Gram positive cocci were also found in large num- 

 bers (Wood 1950). Few coryneforms were isolated 

 in the present study, although Pseudomonas and 

 Gram positive organisms were commonly recov- 

 ered. In the brief study here of nurse shark flesh, 

 the dominant bacteria found initially were species 

 of Vibrio and Pseudomonas. After 7 d of incuba- 

 tion at 5°C, the flora were composed principally of 

 Pseudomonas, Vibrio, and Micrococcus. When 

 flesh was held at room temperature (24°-26°C), 

 Gram positive cocci and Proteus vulgaris were 



379 



