Population biology of an endangered species: the common guitarfish Rhinobatos rhinobatos in Lebanese marine waters of the eastern Mediterranean Sea
Résumé
This study focuses on the population biology of the common guitarfish Rhinobatos rhinobatos, a cartilaginous
fish listed as Endangered in the International Union for the Conservation of Nature (IUCN)
Red List. Between December 2012 and January 2014, 67 individuals were collected by bottom longlining
in coastal Lebanese marine waters at different ports at depths ranging from 10 to 110 m. The total
length (LT) of the specimens ranged from 50 to 143 cm, and the mean±s.d. was 76⋅2±19⋅7 cm. The
most common LT classes were between 60 and 70 cm. The total mass of the specimens ranged from
410 to 10 000 g, and the mean±s.d. was 1841±1987 g. A total of 34 males and 33 females were
collected, and the sex ratio was not significantly different from 1:1. The mass and LT relationship
showed positive allometric growth (b=3⋅096 and r2 =0⋅99), and the mean±s.d. LT at which 50% of
the individuals were sexually mature was 84⋅73±5⋅81 cm for females and 78⋅57±4⋅88 cm for males.
The gonado-somatic and hepato-somatic indices were determined along with a condition factor, and
parturition appeared to occur in winter. The primary prey items found in the fish stomachs during the
autumn and winter seasons were Penaeidae. The results of this study will help to parameterize models
of the population dynamics for this exploited fish stock to ensure the long-term sustainability of its
fishery.