Fish Hatchery Management - fisheries & aquaculture

FISH HA'I'CHERY MANAGEMEN'IImmunilation of FishesIn the past few years there has been rapid development in the technologyof fish vaccination, primarily for salmonids. In the 1977 Proceedings oJ' theInternational symposium on Diseases of cultured salmonids, produced by Tavolek,Inc., T. P. T. Evelyn thoroughly reviewed the status of fish immunization;excerpts of his report are presented in this section.Pressures conspiring to make vaccination an attractive and almost inevitableadjunct approach to fish health were probably most acutely felt in theUnited States where it was becoming increasingly clear that reliance on theuse of antimicrobial drugs in fish culture might have to be reduced. First,the list of antibacterial drugs that could legally be used is extremelysmall...and the prospects for enlarging the list were dim. Second, the effectivenessof the few available antibacterial drugs was rapidly being diminishedbecause of the development of antibiotic resistance among thebacterial fish pathoeens. Third, there was the danger that this antibioticresistance might be transmissible to micro-organisms of public health concern,and because of this there was the very real possibility that drugs nowapproved for use in fish culture would have their approval revoked.Finally, viral infections in fish could not be treated with any of the antibioticsavailable.Faced with the foregoing situation, American fish culturists were forcedto consider other measures that might help to ensure the health of theircharges. one obvious approach was immunization. Advantages of immunizationwere several. First, immunization did not generate antibiotic resistantmicro-organisms; second, it could be applied to control viral as well asbacterial diseases; third, it appeared that fish may be vaccinated economicallyand conveniently while still very small; and fourth, protection conferredby vaccination was more durable than that resulting from chemotherapy,and could be expected to persist for considerable periods followingvaccination. Finally, with killed vaccines, at least, the requirements forlicensing the vaccines were less stringent than those required for the registrationof antimicrobial drugs.Unfortunately, the biggest single factor working against the widespreaduse of fish vaccination was the lack of a safe, economical and convenienttechnique for vaccinating large numbers of fish. Recent advances in salmonid immunization are very promising.Vaccination MethodsAttempts at oral vaccination have been unsuccessful, and alternative procedureshave been devised: mass inoculation; infiltration; and spray vaccination.