Pengaruh sari kedelai sebagai krioprotektan alami terhadap kualitas sperma dan persentase fertilitas ikan kancra (Tor soro Valenciennes, 1842) 48 jam pascakriopreservasi = The effect of soybean milk as a natural cryoprotectant on sperm quality and fertility percentage of kancra fish (Tor soro Valenciennes, 1842) 48 hours postcryopreservation