Reproductive cycles and spawning periods of two Lessepsian siganid fishes on the Lebanese coast

A total of 1048 specimens of Siganus rivulatus and Siganus luridus were collected from the Batrun area of the Mediterranean Sea from January 1999 to August 2000. The sex-ratio in both species did not differ significantly from 1 : 1 between size classes or months. For S. rivulatus, the estimated mean length at first maturity (L-T50) was 132.5 mm for males and 136.5 mm for females, and 139.0 and 142.0 mm, respectively., for male and female S. luridus. Spawning occurred in June in S. rivulatus and from May to July in S. luridus. High temperature in summer appeared to be a limiting factor in the gonadal development of both siganid species, which have reduced their breeding seasons on the Lebanese coast compared to their native Red Sea. (C) 2003 The Fisheries Society of the British Isles.