en aquaculture aquaculture پژوهشي Orginal research papers In this study, S-type rotifer <em>Brachionus plicatilis</em> were enriched with 10 levels (0, 0.001, 0.01, 0.1, 1, 10, 100, 500, 1000 and 1500 mg L-carnitine per L) of L-carnitine supplements dissolved in <em>Chlorella</em> <em>vulgaris </em>culture medium in a 10 mL individual culture trial for 7 days. The initial rotifer density was 1 individual mL^-1. The trials were conducted to 200&times;0⁶cell mL^-1at food density at 25&plusmn;1&ordm;C under an axenic condition in the laboratory. L-carnitine enrichment has shown considerable influence on the population growth of rotifer<em> Brachionus plicatilis</em>. As a result, the maximum number of individuals was determined as 1560 &plusmn; 10.00 rot./mL in the group enriched with 100 mg/L L-carnitine supplement and the lowest number of individuals was determined 376.67&plusmn;25.17 rot./mL in the group enriched with 1500 mg/L L-carnitine addition (<em>p</em><0.05). The maximum growth rate was found to be 0.63&plusmn;0.02 rot/ day in the group enriched with 100 mg/L L-carnitine addition (<em>p</em><0.05). The maximum doubling time was 1.31&plusmn;0.02 rot./ day for the group enriched with 1000 mg/L L-carnitine (<em>p</em><0.05). The results suggested that L-carnitine could be a positive factor to enhance reproduction and population growth on enriched <em>Brachionus plicatilis</em> under the optimum concentration.<br> &nbsp; Rotifer, Brachionus plicatilis, L-carnitine, Population growth 1684 1690 http://jifro.ir/browse.php?a_code=A-10-3342-1&slc_lang=en&sid=1 H.B.E. Ozdogan hasanozdogan@isparta.edu.tr 100319475328460042761 100319475328460042761 Yes Isparta University of Applied Sciences, Egirdir Faculty of Fisheries, Department of Aquaculture, Isparta-Turkey S. Savas sevgisavas@isparta.edu.tr 100319475328460042762 100319475328460042762 No Isparta University of Applied Sciences, Egirdir Faculty of Fisheries, Department of Aquaculture, Isparta-Turkey