bacterial isolates at high concentrations (>105/ml) are pathogenic for 

 shellfish larvae, but only "true" pathogens kill at very high dilutions 

 (<10 3 /ml) , which suggests that true pathogens require larvae for growth. 

 Presence of higher concentrations, even of sterile nutritive broth, produces 

 a lethal effect, which suggests that food concentrations, dead or decaying 

 algal foods, or larvae, may aggravate the pathogenic effect of extrinsic and 

 intrinsic microbial concentration. At high concentrations of bacteria or 

 equivalent culture media, lethal effects are rapid and are not associated 

 with protozoan activity. At lower levels lethal effects are more gradual 

 and are associated with intense protozoan proliferation and activity. 

 Without knowledge of the presence of experimental bacterial inoculum 

 it could be concluded that protozoa are the primary pathogen. Results of 

 field studies tended to support these conclusions. Each hatchery was 

 different in techniques and methods of operation. The need to define 

 characteristics for optimum performance is apparent. - J.L.M. 



1062 



Leibovitz, Louis. 1978. 



Bacteriologic studies of Long Island shellfish hatcheries: An abstract. 

 Mar. Fish. Rev. 40(10): 8. 



A total of 1,279 cultures were taken from sick and healthy oyster and clam 

 larval cultures and their ingredients, and 710 pure bacterial isolates were 

 identified. Sixty-six percent of all bacteria isolated and identified from 

 intake water samples were gram negative, and 15.7 percent were gram positive. 

 Well water had a higher percentage of gram-positive organisms than bay water. 

 Dominant gram-negative isolates were Pseudomonas 33%, Flavobaoterium or 

 Cytophaga 10.4%, Aainetobaater 8.7%, Aeromonas 4.9%, Enterobaoteriacea 3.8%, 

 Vibrio 3.2%, and Aahromobacter spp. 1.5%. Well water counts were lower but 

 contained a higher percentage of Aeromonas , Vibrio, and Flavobaoterium or 

 Cytophaga, and less Enterobaoteriacea than bay water. Sick clam larval 

 cultures were associated with a drop in percentage of Flavobaoterium or 

 Cytophaga, Aeromonas, and Enterobaoteriacea spp. Each hatchery (of 5) larval 

 culture medium had its own distinctive bacterial flora. High bacterial 

 counts were associated with warm weather, increased storage and culture time, 

 and high organic content. - J.L.M. 



1063 



Leibovitz, Louis. 1978. 



A study of vibriosis at a Long Island shellfish hatchery. Natl. Shellf. 

 Assn., 70th Joint Ann. SINA-NSA Conv. & Meeting, 18-22 June 1978, Abstracts: 

 page not numbered. 



Summarizes results of a 5-yr study of bacterial flora of incoming well and 

 Bay water, stock and pooled algal cultures, and oyster larval cultures. 

 Water quality studies also were made of incoming Bay and well water for 

 3 yrs. Hard clam is not mentioned, but the results presumably are applicable 

 also to Mercenaria mercenaria. Vibrio spp. were present at low frequencies 

 throughout the shellfish growing season, but were the dominant bacterial 

 population in incoming Bay water during a single peak period each yr, which 

 was of variable duration and occurred in spring or summer. Ammonia levels 

 of incoming water dropped sharply during peak Vibrio periods. These peaks 

 also were associated with increased total bacterial counts and suspended 

 organic content of incoming Bay water. Although peaks occurred annually, 

 outbreaks of hatchery vibriosis, with high oyster larval mortality, did not 

 occur each yr. Hatchery vibriosis began during peak concentrations of 

 Vibrio spp. in incoming Bay water, but persisted in the hatchery after peak 

 periods had passed, when Vibrio could not be detected in incoming water. 

 - J.L.M. 



297 



