A Biodiversity Study on Coral Reef Structure and             Fish Family Diversity in the Red Sea

Coral reefs are biodiversity rich ecosystems that provide shelter for a quarter of marine species and constitute a nursery for many fish species, playing a crucial role in coastal economy. Its biodiversity provides regulating services, ecotourism and constitutes a national treasure of cultural value. Consequently, some studies such as Gratwicke and Speight 2005 and Macdonald et al. 2016 have attempted to understand the patterns of reef biodiversity and found that diversity of coral growth forms, coral rugosity and depth were good predictors of biodiversity. In our study, we investigate whether these variables played an important role in predicting fish abundance and family diversity in one of the largest bay of the Red Sea - Mangrove Bay. We simplified Gratwicke and Speight 2005 methodology and developed a coral complexity score system based on structural complexity and on the number of growth forms and we expected to see a rise in biodiversity with an increase in coral growth forms, structural complexity and a shallower depth. Data was sampled between the 4th and 19th of October 2021 by our team, consisting of two buddy team divers. We surveyed two to four transects in randomly selected locations, without ever replicating them and covered 3 depth ranges, being the shallow (6.5-7.5m), the medium (9-10m) and the deep (14.5-15.5m). In total we performed 26 transects, of which 23 were included in the analyses and depth used as random factors due to lack of samples. We ran GLMER analyses and found fish abundance and the number of fish families to not be significantly correlated to reef complexity, although we still observed a positive trend. Our findings thus support the null hypothesis in both scenarios. Our study could be further improved by investigating other variables at play and adjusting our methods.