Effect of lactic acid bacteria and the potential probiotic Hafnia alvei on growth and survival rates of narrow clawed crayfish (Astacus leptodactylus Esch., 1823) stage II juveniles

The aim of this study was to screen potential probiotic bacteria against Aeromonas hydrophila and determine the effects of antagonistic bacteria and a commercial product containing lactic acid bacteria on the survival and growth of stage II Astacus leptodactylus juveniles. For this purpose, a total of 110 bacterial strains were isolated from adult, stage II crayfish juveniles and rearing water screened for antagonistic activities against A. hydrophila with well diffusion agar assay. Hafnia alvei strain from stage II crayfish juveniles displayed the inhibition zone (10mm) against A. hydrophila. The experiment was conducted in a completely randomized design with four treatments for 60 days: (I) crayfish fed with live food without probiotics (control group); (II) crayfish fed with live food enriched with lactic acid bacteria (0.015 gL^-1); (III) crayfish fed with live food enriched with Hafnia alvei (10^6 CFU mL^−1); (IV) crayfish fed with control diet and H. alvei added to rearing water (10^6 CFU mL^−1). As a result of this study, lactic acid bacteria and Hafnia alvei applications did not positively affect growth and survival of stage II A. leptodactylus juveniles. In the future, studies on screening potential probiotic bacteria should be used in vitro and in vivo tests. In addition, it will be useful to investigate the lactic acid bacteria and Bacillus spp. from indigenous microflora of crayfish