SWIMMING ABILITY OF BASTARD HALIBUT PARAL ICHTHYS-OLIVACEUS AT THE BOTTOM OF NET CAGE

Swimming speed-fatigue tests were conducted to understand the performa nce ability of bastard halibut Paralichthys olivaceus. In a small circ ular tank, a polyethylene net was set on a slant and the fish was put onto the net with its blind side facing a water current. Fish of 4.6 t o 36.3 cm in total length (L) were classified into 5 size groups and f atigue time was measured at 5 water temperature ranges. Fatigue time, defined as the length of time for a caudal fin to touch the metal grat ing at the downstream end of the working section of the tank, was meas ured by the changes in the current velocity (V). Swimming ability inde x (SAI=integral(0)(3600)V . L(-1)dt x 10(-4)) was calculated. Far comp arison, a fatigue test was also done on barfin flounder Verasper moser i. For bastard halibut, fatigue time was longer in higher temperatures with smaller fish having a higher performance in SAI at the same temp erature. At 17 degrees C, fatigue time was estimated over 3 hours in 1 L/s; and a few minutes in 2 L/s. Barfin flounder showed a higher perf ormance than bastard halibut.