Abundance and distribution of delphinids in the Red Sea (Egypt)

Abstract

Knowledge about cetaceans in the Red Sea is limited with only a handful of sporadic or spatially-limited studies carried out to date. Funded by the Italian Cooperation through a Debt-for-Nature Swap programme and carried out in collaboration with the Egyptian NGO HEPCA, this thesis presents the results from the first ever systematic vessel-based surveys conducted in the southern Egyptian Red Sea from 2010 to 2013 using linetransect methodology. The main aims of the thesis were (a) to estimate cetacean abundance, (b) to determine distribution patterns and habitat use of the cetacean species, (c) to investigate movement patterns for species for which individual recognition techniques were suitable and (d) to identify areas of conservation concern for cetaceans with a particular focus on existing protected areas. Eight species were identified, of which five were commonly encountered (Stenella longirostris, S. attenuata, Tursiops truncatus, T. aduncus, and Grampus griseus) and three were rare (Pseudorca crassidens, Sousa plumbea, Balaenoptera edeni). Estimates of abundance using design-based line transect sampling techniques were obtained for five species: S. attenuata 10,268 (CV=0.26); S. longirostris 6,961 (CV=0.26); T. aduncus 659 (CV=0.69); T. truncatus 509 (CV=0.33), and G. griseus 367 (CV=0.37). Habitat modelling revealed that the two Stenella species were widely distributed across the study area. In contrast, T. truncatus was concentrated in waters around Ras Banas peninsula (in particular Satayah offshore reef), and T. aduncus was mainly found along the coast with possibly separate sub-populations in the northern and southern study area. G. griseus was only encountered in the southern part. The information provided in this study will allow the development of a conservation strategy for the protected areas and will serve as baseline information to carry out future survey work in the Red Sea.