Stock structure based on truss network analysis, length-weight relationship and condition factor of Decapterus macrosoma (Bleeker, 1851) from two fishing areas, Red Sea, Egypt

Abstract

The round scad, Decapterus macrosoma is an important pelagic carangid species distributed in the Indo-Pacific and the Southeast Atlantic including the Red Sea. Using the truss network based on images (TNA), the stock structure of D. macrosoma from two fishing grounds, Suez and Hurghada, was evaluated.Information on the length-weight relationship and condition factor of this species were provided. The b-values of LWR were 2.86 in Suez and 2.87 in Hurghada, with an R 2 estimate greater than 0.92, indicating a negative allometric growth type for both studied areas. A narrow distribution range of relative condition factor (Kn) was observed in the two fishing areas, recording a value of 0.95-1.075 with a mean of 1.013±0.038 for Hurghada and 0.911-1.098 with an average of 1.017±0.039 for Suez. No differences were detected in LWR and Kn values between the two stocks. The form factors of this species were calculated between 0.006 and 0.14, with 0.01 as a mean and median value. The truss network analysis based on 15 measurements between eight landmarks revealed that the stock of D. macrosoma in the two areas was identical. This may be due to the similarity of the ecological and physical conditions of the Suez Gulf and Hurghada, Red Sea. Within stock, distinctions were reported in the present study. Thus, the study would aid in the development and conservation arrangements of this species, as well as in properly taking the right decision for the management of both studied areas.