Quantitative morphometric analysis of dorsal fin for species identification in sharks (Family: Carcharhinidae) from the Suez Gulf, Red Sea,Egypt

Shark fins are essential for distinguishing various shark species; however, they may be visually tough to differentiate. This study introduces an innovative method for measuring and comparing the dorsal fins of sharks in the Suez Coastal region of the Red Sea, Egypt. Thirty-four shark specimens, encompassing 9 distinct species s were acquired from two fish markets, and their dorsal fins were documented by photography. We used a software program called Image for the purpose of evaluating images. This program can compute the ratios of certain fin properties.  The species include Carcharhinus brevipinna, C. sorrah, C. melanopterus, C. albimarginatus, C. altimus, C. amblyrhynchoides, C. falciformis, C. plumbeus, and C. limbatus. Each species had differences in dorsal fin size, shape, and structure, with forms that ranged from triangular to falcate, with concave or convex anterior edges and concave posterior margins. The color varied from deep shades to lighter or reddish tones. Comprehensive measurements of the dorsal fin, including the free rear tip, fin base, and anterior and posterior edges, were examined. The ratios among these dimensions differed markedly between species, enabling categorization. Carcharhinus melanopterus had the largest M2/M4 ratio, signifying an elongated dorsal fin, but C. altimus possessed the best M15/M2 ratio, indicating an expanded fin base. Principal Component Analysis (PCA) and heat map studies elucidated morphological differences by grouping species according to fin measurements. The findings indicate that dorsal fin ratios may proficiently differentiate between species, establishing a foundation for shark categorization. This methodology, along with morphometric analysis, is essential for species identification and conservation initiatives.