Ichthyofaunal diversity of the SS Orestes shipwreck, Unawatuna, Sri Lanka

Abstract

Artificial reefs, including shipwrecks, play a crucial role in enhancing marine biodiversity. The Unawatuna region has witnessed numerous shipwrecks over time, enriching the area’s maritime narrative. The SS Orestes shipwreck, located 4 km off the Unawatuna shore at a depth of 24 meters, provides a unique artificial reef environment. The present study was conducted to determine the ichthyofaunal diversity and species richness at the SS Orestes shipwreck, assessing the role of the shipwreck as a habitat for the fish community. The study was conducted once a month, between 9 a.m. to 12 p.m., from January 2024 to March 2024. Data on fish species were collected by using video surveys conducted by SCUBA diving. A GoPro hero 10 camera was used to collect relevant data. Fish species were identified to the lowest possible taxonomic level using standard keys and guides and then counted using video transects. Further, diversity indices (Shannon-Wiener diversity index and Simpson’s index of diversity) were calculated to determine the ichthyofaunal diversity at the study site. A total of 31 fish species belonging to 18 families were recorded at the SS Orestes shipwreck, indicating a rich and diverse marine ecosystem. The Shannon-Wiener diversity index was 2.79, and the Simpson’s index of diversity was 0.91, with an evenness value of 0.53. Family Pomacentridae (six species - Chrysiptera parasema, Neopomacentrus filamentosus, Amphiprion polymnus, Dascyllus trimaculatus, Chromis xanthochira, Neopomacentrus azysron) had the highest species richness among the ichthyofauna families. Family Lutjanidae (Lutjanus fulviflamma, Lutjanus kasmira, Lutjanus carponotatus, Lutjanus fulvus) had the highest individual fish count during the survey at a species level. Therefore, it can be concluded that SS Orestes shipwreck acts as an important artificial reef, fostering a diverse fish community and enhancing marine biodiversity. Further, the study site is important for fisheries, tourism, and scientific research.