Fecundity and condition of successful invaders: Siganus rivulatus and S. luridus (Actinopterygii: Perciformes: Siganidae) in the eastern Mediterranean Sea

Abstract

Background. Rabbitfishes, Siganus rivulatus and S. luridus, are among the most successful invaders in the Mediterranean Sea but population parameters in their new environment are barely known. Fecundity and condition are key parameters of fish populations and their assessment is very important for exotic species; this information is needed to properly evaluate their reproductive and invasive potential. The current is study contributes to fill this gap by exploring fecundity and condition of those two fish species. Materials and methods. About 1000 individuals of Siganus rivulatus and S. luridus were processed from off the Lebanese coasts over a 20-month period. Fecundity and condition index were estimated and compared. Regression analyses tested the dependence of fecundity on fish length, mass, and gonad mass. Results. Fecundity values were assessed for S. rivulatus and for S. luridus: Fabs = 272 043 ± 144 666 (SD), Frel = 2123 ± 808 oocytes · g-1 for S. rivulatus and Fabs = 245 273 ± 164 211, Frel = 1584 ± 627 oocytes · g-1 for S. luridus. The relation between Fabs and gonad mass [g] was y = 14 339x + 59 297 for S. rivulatus and y = 9245x + 62 140 for S. luridus. Condition exhibited a clear seasonal trend for the two rabbitfishes. It increased in spring prior to the reproduction period and again in autumn before the decrease of seawater temperature, and remained low during the cold period. Its values were significantly higher for S. luridus than to S. rivulatus. Conclusion. S. rivulatus displayed a higher fecundity while S. luridus showed a better condition in the Eastern Mediterranean. Gonad mass was the best predictor of fecundity for both species while condition exhibited a clear seasonal trend in both rabbitfishes.

Keywords

• rabbitfish
• Siganus rivulatus
• Siganus luridus
• ma