Disease investigation of transported Chanos chanos stocked in Laguna Lake, Philippines

Abstract

Milkfish,Chanos chanos fingerlings transported by boat (petuya) for seven to eight hours were observed for stress-inducing factors during transport, daily for 10 days after stocking in pens in Laguna Lake, Philippines. Handling, hauling, and crowding of fish contributed to stressful conditions. Likewise, the transport procedure of the clising the water entry hole at the bottom of the boat to block water exchange was associated with decreased dissolved oxygen and increase tubidity, with respective values of 2.4 mg/l and 79 Formalin Turbidity Units when water change was possible. In addition , marked and abrupy fluctuations in salinity from 15 to 30 ppt then 0 ppt within 1 to 3 hr were observed during transport. Although moralities during transport were minimal, subseqeunt deaths after stocking in pens mounted to not less than 2.4%. Reddish snout, scale loss and hemorrhagic areas along the lateral body surface wwere observed. Bacterial counts of water increased significantly during trasnport when water exchange was stopped. Kidney and skin/muscle specimens yielded significantly higher bacterial counts on days 2, 3, 5 and 8 poststocking predominated by Aeromonas hydrophila biovar hydrophila and two species of gram-negative bacilli phenotypically resembling Pseudomonas sp.