EFFECTS OF LIGHT-INTENSITY, TANK COLOR AND PHOTOPERIOD ON SWIMBLADDERINFLATION SUCCESS IN LARVAL STRIPED BASS, MORONE-SAXATILIS (WALBAUM)

Striped bass, Morone saxatilis (Walbaum), larvae, although physoclisto us as adults, initially need to innate their swimbladders by passing i ngested air through a pneumatic duct to the swimbladder. Failure to in flate the swimbladder results in swimbladder atrophy, dysfunctional bu oyancy control, deformities, and poor larval survival and growth. The present investigation studied the effects of light intensity, tank col our and photoperiod on the initial swimbladder inflation success of st riped bass. In the first experiment, newly hatched larvae were reared for 2 weeks in black or white 350-L circular tanks exposed to incandes cent lighting at 163 or 10 lux. Larvae were fed Artemia from 6 days po st-hatching (dph). The standard length, and oil globule and yolk areas were measured. Swimbladder condition and evidence of feeding were rec orded. To study the effects of photoperiod on inflation, larvae were r eared in black tanks exposed to either 8 h:16 h or 16 h:8 h light:dark photoperiods at 139 lux. Striped bass inflated their swimbladders bet ween 6 and 9 dph at 17 degrees C, Inflation success was significantly higher in black tanks (65%) compared with white tanks (42%), but light intensity did not significantly affect swimbladder inflation. Larval growth and food consumption were better in black tanks, primarily beca use this treatment resulted in more larvae with inflated swimbladders, although larvae with uninflated swimbladders in black tanks were long er at 12 dph than larvae with inflated swimbladders in white tanks. La rvae that successfully inflated their swimbladders fed earlier and exh ibited better growth than larvae with noninflated swimbladders. Larvae reared at higher light intensities used up yolk reserves faster. Expo sing striped bass larvae to 8 h:16 h light:dark photoperiods resulted in higher inflation rates (55%) compared to larvae reared at 16 h:8 h light:dark photoperiods (30%). Therefore, black tanks and short photop eriods are preferable for early rearing of striped bass larvae to maxi mize swimbladder inflation success.