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Abstract: Light can have significant impacts on larval growth and survival of many marine fish species. Here, we study the effect of photoperiod on larvae from captive populations of two marine finfish species, California yellowtail (CYT; Seriola lalandi) and white seabass (WSB; Atractoscion nobilis). Two photoperiod treatments were tested: 12h light and 12h dark (12-L), and 24h light and 0h dark (24-L). CYT larvae were significantly heavier (240±16μg dry weight) in the 24-L treatment group than the 12-L group (155±25μg dry weight) at 10dph. Similarly, WSB were significantly heavier (685±77μg dry weight) in the 24-L treatment group than the 12-L group (455±44μg dry weight) at 18dph. CYT larvae also had significantly greater survival (16.6±6.2%) in the 24-L treatment over the 12-L conditions (7.6±4.9%). In contrast, WSB larvae showed no significant difference in survival between treatments. Food consumption was significantly greater in the 24-L treatment for both species up until 6dph, after which time no difference was observed. Swim bladder inflation rates were not significantly affected by the photoperiod treatments. These results indicate that photoperiod is a significant factor in early larval performance for both CYT and WSB, although it is unknown if continuous light becomes detrimental as larvae develop. [Copyright &y& Elsevier]