Biométrie et éthologie alimentaire de deux Sparidae: Oblada melanura (Linnaeus, 1758) et Lithognathus mormyrus (Linnaeus,1758) du Golfe de Tunis.

Abstract

A study of the morphometry of two monospecific Sparidae, Oblada melanura (saddled bream) and Lithognathus mormyrus (striped seabream), has been conducted. The samples were collected from the Gulf of Tunis during the period from February to June 2014; their sizes were comprised between 14.1 to 32 cm for the saddled bream and 13 to 27.5 cm for the striped seabream. On the nineteen metric characters selected 57.89% of them presented an allometric growth for L. mormyrus and only 10.52% for O. melanura. The results show that the metric characters wich present a different growth rate are essentially measurements at the level of the head and fins what is related with the diet and the swimming. Indeed, it is known that the striped seabream is a demersal species whereas the saddled bream is often observed between two waters or on the surface; this has repercussions on the qualitative composition of their diet; results show that their alimentation is preferentially composed on benthic preys as mollusks (IRI = 81.8%) for the striped seabream, while it is on small zooplanctonic crustaceans (IRI = 64.04%) for the saddled bream.