First Observations of Shortfinned Anguilla Bicolor Bicolor and Longfinned Anguilla Marmorata Silver Eels in the Reunion Island.

Abstract

Silver stage specimens of Anguilla bicolor bicolor and A. marmorata were fished with a keep net in an estuary of the Reunion island (Indian ocean). Such silver anguillids eels have not been pointed out since the years 1957-1958 in South Africa. This short note gives the first morphometric observations of these specimens, before starting histological, endocrinological and otolithometrical analysis, that should contribute to a have a better undestanding of these tropical eels species biological cycle. PREMIÈRES OBSERVATIONS D'ANGUILLES ARGENTÉES ANGUILLA BICOLOR BICOLOR ET ANGUILLA MARMORATA DANS L'ÎLE DE LA RÉUNION. RÉSUMÉDes anguilles Anguilla bicolor bicolor et A. marmorata au stade argenté ont été pêchées à la nasse dans un estuaire de l'île de la Réunion (océan Indien). De telles anguilles argentées n'avaient pas été signalées depuis les années 1957-58 en Afrique du Sud. Cette courte note présente les premières observations morphométriques de ces spécimens, avant d'entreprendre des analyses histologiques, endocrinologiques et otolithométriques, qui devraient contribuer à une meilleure connaissance du cycle biologique de ces espèces tropicales.

Morphological and physiological changes of female tropical eels, Anguilla celebesensis and Anguilla marmorata, in relation to downstream migration

“…No S2 eels of A. marmorata were found in this study, and the A. marmorata caught in an estuary area of Réunion Island, south-west Indian Ocean, seems to have been an S1 eel (Robinet & Feunteun, 2002). Recently, adult eels of A. japonica and A. marmorata were caught in their spawning area, and the adult eels of both species were silvery black in colour all over their bodies (Chow et al, 2009;Tsukamoto et al, 2011) similar to that of the S2 stage eels of A. celebesensis in this study.…”

Eel community structure, fluvial recruitment of Anguilla marmorata and indication for a weak local production of spawners from rivers of Réunion and Mauritius islands

“…Local lack of future spawners and the regional panmixia hypothesis Sexual maturation in A. marmorata, is thought to be slow (Sugeha 2003), the single maturing male captured in Ré union Island was 10 years old and 708 mm long (Robinet and Feunteun 2002;Robinet et al 2003c). Therefore, due to the lack of such large eels in Ré union and Mauritius rivers, the local reproductive turnover is uncertain.…”

Advanced sexual maturation before marine migration of Anguilla bicolor bicolor and Anguilla marmorata at Réunion Island

“…None of these specimens were subjected to histological or physiological analysis. In Réunion Island, Indian Ocean, a silver female of A. bicolor bicolor and a silver male of A. marmorata were collected (Robinet & Feunteun, 2002). The former was the first maturing specimen collected in the Mascarene area since those reported by Jubb (1961), and the latter remained uncollected since Schmidt's (1927) investigations.…”

“…All morphometric details are presented in Robinet & Feunteun (2002). Vertical and horizontal eye diameters were measured to calculate the ocular index ( I O ) (Pankhurst, 1982).…”

“…The short‐finned eel was 744·0 mm total length ( L T ) and weighed 661·3 g; its anal‐dorsal ratio was 2·1%; the back was nonmarbled; I O were moderate (6·02 and 5·72); I G was 6·78; I D was low (0·97) (Robinet & Feunteun, 2002). The macroscopic appearance of the gonads indicated that the specimen was a maturing female.…”