Stomach Histological Decay of Milkfish, Chanos Chanos (Forsskal, 1775): Ontogeny, Environmental Stress, Shifting Food Composition, And Disease Infection

Abstract

Monitoring of a traditional tambak (brackish-water pond) for milkfish culture was held in Sidoarjo, East Java, Indonesia from January to May 2012. The tambak was stocked with 14-days old fry at density of 0.5 fish m^-2. Pond owner decided to harvest the tambak after 98 days of culture period, 22 days earlier than the normal grow-out period in the region. Three heavy metals, Pb, Hg, and Cd were detected in the pond water system. High concentration of ammonia may result in the formation of free NH3-N that toxic to fish. Histological examination of digestive tract showed abnormalities the caused by changes in the availability of natural food composition, dominated by cyanophyta toward the end of culture period. Also, the presence of parasite, Myxobolus, was observed inside stomach and intestine wall. Combination of all these factors resulted in slower growth, high mortality and lower biomass production of traditional milkfish culture of East Java in the last decade.

Key words: milkfish, histopathology, environmental stress, natural food, diseases