Population structure of Octopus defilippi (Verany, 1851) from the Gulf of Suez, Red Sea, Egypt.

Abstract

Octopuses are relatively abundant in the trawl landings of the Gulf of Suez;though they were considered discarded species till 1990's, but currently they have a commercial importance. The population structure and level ofexploitation of the Octopus defilippi were studied using the length frequency distribution of samples collected from the Gulf of Suez. Some morphometric relationships were estimated where the mantel length, total weight potentialequation was found to be W = 0.7087 L 2.646 for males and W = 0.9118 L 2.3629 for females. The length distribution pattern showed that females reach larger lengths than males. The population appeared to be structured in two cohorts formales and three for females. Growth of both sexes was fast and could be described well by the von Bertalanffy growth formula. The estimated asymptotic length for combined sexes was ML∞ = 9.0 cm and the growth coefficient was K= 0.94 y-1. The overall sex ratio of males to females was 1: 0.5. The total and natural mortality rates were high for both sexes, where the estimated values were Z = 3.341 y-1 and M = 1.43 y-1. The current exploitation ratio (E = 0.57) indicates that the Octopus population in the Gulf of Suez is overexploited.