輸送中あるいは輸送後飼育中に起きる魚の斃死に関する細菌学的研究-I

斃死の一原因について

抄録

In the previous repor¹⁾, YONE inferred that the death of fish during transportation or while keeping after transportation is mainly attributable to infection. The present study was carried out to demonstrate that the inference is correct.
The present paper deals with the isolation of bacteria from the liver of red sea bream (Chrysophyrys major) which died during keeping after the “keep on closed system” and the pathogenicity of the isolates.
The results obtained can be summarized as follows:
1) The adding of chlortetracycline (CTC) and nitrofuran derivatives suppressed the increase of bacterial count and the consumption of dissolved oxygen by bacteria in the sea water in polyethylene cases.
2) The mortality in the CTC group was lower than that in the non-added group.
3) Numerous bacteria existed in the liver of dead fish in the non-added group, but bacteria was not detected in those in the CTC group.
4) Of the isolates distinguished into thirteen groups, those belonging to groups V, IX, and X showed pathogenicity.
5) Organisms belonging to group X were isolated from the majority of livers of dead fish in the non-added group and accounted for 87 percent of the total isolates from the liver. On the other hand, group V was isolated from only one. Organisms belonging to groups V and X were also isolated from the sea water in polyethylene cases of the non-added group.
6) The conclusion that the death of fish during the keeping after the “keep on closed system” is caused by the infection of pathogens is led from the above results.