Bacterial Fluctuation In Differenti Systems Of Aquaculture

Abstract

Diseases of freshwater fish increased in its importance in both- wild and cultured systems. It lead to great economic losses in body gain, feed intake with increasiqg mortality level and decrease the productive efficiency of fish production farms as well as public health significance in certain circumstances

This study was carried-out for : examination of the degree of seasonal fluctuation of bacterial pathogens in intensive and semi-intensive system in relation to water quality, Identification of the most prevalent bacterial pathogens that spread under Egyptian conditions and Determination of the physiochemical parameters of water in intensive and semi-intensive fish ponds.

This study concluded that :

It is found that the number of bacterial isolates of A.hydrophila, P.jluorescens, and P.aerogenosa, isolated from liver was higher in semi-intensive system than intensive system.While V.anguillarum, and V.parahaemolyticus, isolates was higher in intensive system. F.columnaris isolates were high in both systems.

The number of bacterial isolates of A.hydrophila, and F.columnaris, Staphylococcus aureus and Streptococcus iniae, isolated from spleen was higher in semi-intensive system than intensive system. While P.jluorescens, P.aerogenosa, V.anguillarum and V.parahaemolyticus, were higher in intensive e system. The number of bacterial isolates of P.aerogenosa, isolated from kidney was higher in semi­ intensive system than intensive system. While other types of bacterial isolates were higher in intensive system, no detectable isolation of Staphylococcus aureus and Streptococcus iniae, in both semi­ intensive and intensive systems.

The number of bacterial isolates of P.jluorescens and Staphylococcus aureus isolated from gills was higher in semi-intensive system than intensive system. While other types of bacterial isolates were higher in intensive system, no detectable isolation of Streptococcus iniae, in both semi-intensive and intensive systems.

The isolation ofbacter1a from gall bladder occurred only in summer season.

The number of..bacterial isolates of P.jluorescens, isolated from water was higher in semi-• intensive system than intensive system. While other types of bacterial isolates were higher in intensive system, no detectable isolation for Streptococcus iniae, in both systems.

In general the number of bacterial isolates obtained from intensive fish farming system was higher than the number of bacterial isolates in semi-intensive fish farming system in all seasons except spring.

The maximum number of bacterial isolates obtained from gills, and the lowest from liver in both systems. The present study highlights the prevalence of opportunistic pathogens in the culture system. However, the stable nature of the physiochemical parameters in the system did not exert much stress on cultured animals and hence no noticeable disease outbreaks were observed during the period of investigation. It is found that any further alternation in the stability of the system could deteriorate the water quality, which may favor the growth and replicatiqn of opportunistic pathogens in the system. Furthermore, the MAR indices revealed the high risk nature of isolates from the system, suggesting that the unrestricted and often unnecessary use of antibiotics in aquaculture systems has to be checked.