MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14799

ABSTRACT: Prey selectivity, diel feeding patterns, and effects of light intensity on prey consumption, growth and survival of laboratory-reared yellowfin tuna (YFT) Thunnus albacares larvae were studied at the Inter-American Tropical Tuna Commission’s, Achotines Laboratory in the Republic of Panama. Prey selectivity analysis (Pearre’s c index) for first-feeding larvae (~3–4.5 mm standard length ‘SL’) indicated that, within mixed-prey assemblages containing wild-plankton (WP) (copepods), enriched rotifers, enriched Artemia nauplii, and yolk-sac larvae (YSL) of YFT, rotifers were the prey of preference until the onset of piscivory on YSL prey at ~6 mm SL, a period in which larvae exhibited an increase in caloric intake and exponential growth. Flexion and post-flexion larvae (~5–12.5 mm SL), when foraging under low food concentrations (30 WP l^-1), also selected rotifers and YSL. Under high food concentrations (300 WP l^-1) larvae preferentially selected Artemia nauplii and YSL. Minimum light levels at which foraging occurred decreased with larval growth, and post-flexion larvae were successfully feeding at light levels as low as 0.025 µmol s^-1 m^-2. Prey consumption of first-feeding larvae was significantly higher under higher light conditions (7–25 µmol s^-1 m^-2) while prey consumption of flexion larvae was not affected by lower light conditions (2 µmol s^-1 m^-2). Survival and standardized cohort biomass were significantly higher in treatments with higher light levels. Constructing knowledge of YFT larval feeding dynamics provides greater understanding of the early life history and underlying factors related to pre-recruit survival, providing scientific support for assessments of population fluctuations of adult YFT.