impact of light intensity and algal-induced turbidity on first-feeding Seriola lalandi larvae

Feeding performance (intensity and incidence) of first-feeding yellowtail kingfish larvae was evaluated under a range of light intensities and algal-induced turbidities. Larvae were fed with varying degrees of success under all light intensities tested (0-17 micromol s-1 m-2), in both clearwater and greenwater (8 x 10(4) cells mL-1). There was a consistent trend for feeding performance to increase with larval age and light intensity in both clearwater and greenwater conditions, demonstrating that visual proficiency increases with larval age. Feeding intensity remained low over the first 3 days of first feeding across all light intensities tested. Days 6 and 7 post-hatch larvae showed considerably higher feeding intensities particularly at 8 and 17 micromol s-1 m-2. This improvement indicates an ontogenetic shift in sensory or locomotor competence. First-feeding larvae performed equally well in both clearwater and greenwater (8 x 10(4) cells mL-1) conditions, although at the lowest light intensity tested (0.1 micromol s-1 m-2) feeding performance was noticeably reduced. Feeding performance was severely diminished across all larval ages at an algal cell density of 32 x 10(4) cells mL-1, demonstrating that for this species algal-induced turbidities >16 x 10(4) cells mL-1 adversely affect the ability to capture free-swimming prey during the first-feeding window.