Abstract
A marking method for Kuruma prawn Penaeus japonicus, through recovery of the colored pigment area in uropods, was developed. The method was tested by cutting the uropods of 75 prawns ranging from 21 to 73mm in body length (BL) in the laboratory and 3, 733 prawns from 35 to 75mm in BL in the sea off Kyoto Prefecture.
After cutting uropods, the recolored pigment area was visibly reduced though uropods length regrew nearly equal to that of uncut uropods. The degree of pigment reduction increased with the increase in the BL of prawn used, and a 50% reduction in comparison with uncut uropods occurred for 60mm in BL. As it was suggested that a 30% reduction of the colored pigment area could be detected by the naked eye as marks, this method is suitable for prawns larger than 30mm in BL. The effective location of cutting uropods was just below the protopodite with no severe effects on survival and growth of marked prawns. From the test in the sea, the method proved successful for application as a long-lasting mark to a large field sample of prawns.
