Black Gill Disease
Black gill disease is due to chemical contaminants, heavy siltation and ammo-nia or nitrite in rearing water; high organic load due to residual feed, debris, and fecal matter on pond bottom (i.e. black soil).
The gills of affected shrimps show reddish, brownish to black discoloration and, in advanced cases, gill filaments become totally black (Fig. 6-8).
EFFECTS ON HOST:
Histological observations show that blackening of the gills may be due to the deposition of melanin at sites of tissue necrosis and heavy hemocyte activity.
PREVENTION AND CONTROL:
• Avoid heavy metal discharges of nearby factories from getting into the rear-ing facilities
• Remove black soil by scraping after each harvest and by draining pond wa-ter from the bottom during the culture period