Publication Abstract

Disinfection Techniques for Amberjack (Seriola rivoliana) and Pacific Threadfin (Polydactylus sexfilis) eggs

D.W. Verner - Jeffreys, I. Nakamura, J. Kobashigawa, C.W. Laidley and R.J. Shields.

Farmers rearing warm water marine fish species, such as amberjack and Pacific threadfin, require practical, effective, egg disinfection procedures. Egg disinfection helps to prevent the transfer of potentially pathogenic microorganisms from the broodstock facility to the hatchery. The U.S. Food and Drug Administration (FDA) currently approves the use of three chemicals [hydrogen peroxide, povidone iodine (betadine) and formalin] for aquacultured species. Hydrogen peroxide offers significant advantages to the aquaculturist due to its increased level of safety.

The effectiveness of a range of concentrations of hydrogen peroxide in disinfecting amberjack and Pacific threadfin eggs was assessed in a model petri dish rearing system. Treatments were examined for effects on hatch rate and sterilization efficiency. Sterilization efficiency was assessed by transferring treated eggs to culture tubes containing 1ml sterile marine broth. The adherent, Marine agar culturable, microbial flora of control (untreated) eggs was examined using PCR-RFLP (polymerase chain reaction -restriction fragment length polymorphism), followed by partial sequencing of the16S rRNA genes of selected isolates.

Data from seven separate experiments showed that eggs of both species could be exposed to up to 1% hydrogen peroxide (20 x the FDA limit of 0.05%) for 5 min. At this level, sterilization efficiency was high, with no significant reduction in hatch rate, compared to untreated controls. Similar results were also obtained for flame angelfish (Centropyge loriculus) and bluefin trevally (Caranx melampygus) eggs. Further experiments showed that Pacific threadfin eggs could be effectively sterilized by exposure to 0.1% povidone iodine for up to 10 min (10x FDA limit). Independent of treatment, and reflecting problems seen in the hatchery at a production scale, our model system showed high inter-batch variation in hatch rate for all species tested.

The results of the characterization showed that the adherent flora for both aquaculture species varied considerably from batch to batch, both quantitatively and qualitatively. Members of the following genera were isolated from the eggs of both species: Pseudoalteromonas, Vibrio and Cytophaga.

Reference:

D.W. Verner - Jeffreys, I. Nakamura, J. Kobashigawa, C.W. Laidley and R.J. Shields. 2004. Disinfection Techniques for Amberjack (Seriola rivoliana ) and Pacific Threadfin (Polydactylus sexfilis) eggs.World Aquaculture Society Meeting, 1-5 March 2004, Honolulu, Hawaii, USA