Epizotological and bacteriological investigations on Vibrio spp. isolated from some Red Sea fish larvae at Hurghada, Egypt

Fish larvae were captured seasonally (2018) using light trap from coral reef lagoon of the Marine Biological Station at Hurghada on the Egyptian Red Sea coast. A total of 182 larvae belonging to seven fish families were collected and identified based on the morphological characteristics.The diseased larvae were clinically examined and macerated tissues were injected onto Trypton Soy Agar (1.5% NaCl ) and incubated at 25.5 °C for 2-5 days. The obtained bacterial isolates were identified as V. harveyi, V. parahaemolyticus, V. alginolyticus, V. vulnifacus, non virulence V. cholerae and unidentified Vibrio species by the morphological and biochemical characterization. The prevalence ratio of bacterial infection of all infected larvae was 101 larvae (55.5%). The highest number of infected larvae was recorded in summer (45 larvae, 86.5%), while the lowest was recorded in winter (10 larvae, 25%). The most frequently encountered Vibrio sp. was V. harveyi which was isolated from 28 fish larvae followed by V. parahaemolyticus which was isolated from 25 fish larvae. The delicate round herring exhibit the highest prevalence of infection with different Vibrio spp. (58.3%) during different seasons.