Larval life history traits and larval growth of Gnathodentex aurolineatus Lethrinidae before and after settlement in a sandy bay of Reunion Island SW Indian Ocean Traits de vie et croissance larvaire de Gnathodentex aurolineatus Lethrinidae avant et apres installation dans une baie de Iile de La Reunion SO ocean Indien

Pothin, K.; Tessier, E.; Chabanet, P.; Lecomte-Finiger, R.

Cybium 31 mars; 301: 27-33

2006


ISSN/ISBN: 0399-0974
Accession: 038371055

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Abstract
Larval life history traits and larval growth of Gnathodentex aurolineatus (Lethrinidae) before and after settlment in a sandy bay of Reunion Island (SW Indian Ocean). The larval history of Gnathodentex aurolineatus (Lethrinidae), a widespread species of the coral reefs in Reunion Island (SW Indian Ocean), was revealed by otolith analysis. Pairs of otoliths from 108 fishes were collected during a peak settlement in Saint-Paul Bay. Standard length (SL) ranged from 62.5 to 70.7 mm and total length from 73.7 to 85.5 mm. Morphometric analysis of both all fishes and their otoliths, suggested that the.-samples came from a single cohort. Transverse sections of sagitta (embedded in thermoplastic glue (Crystal Bond) and polished) were analysed. Daily periodicity of increments formation in otoliths was validated by alizarin red labelling. Daily increments were observed under a light microscope and counted to estimate age, age at settlement, larval life duration and laying, hatching and settlement dates. A settlement mark was visible on otolith sections. Fish age ranged between 55.2 and 59.4 days. The pelagic larval stage was estimated to 40.0 plus or minus 2.5 days. Laying dates were estimated to occur in December 2002, between the 23rd and the 27th, a few days before the new moon period. Hatching dates were estimated to occur between December 24 and 28, and the first feeding dates between December 26 and 30. Colonization took place in January 2003, between the 15th and the 19th, during the full moon period. The back-calculated laying size was comprised between 0.83 and 2.41 mm SL. The back-calculated settlement size found in this study in the bay (between 44.60 and 50.44 min SL) was lower than the settlement size found in the lagoon zone (80 min). Width increments on otolith sections were measured to establish otolith growth. Otolith growth (mean: 1.1 plus or minus 0.1 mm.d-1) was divided in two parts, showing significantly different growth rates. A first phase of rapid growth 1.4 plus or minus 0.1 mm.d-1 during the pelagic stage, followed by a slowed down growth 0.7 plus or minus 0.2 mm.d-1 after settlement. The analysis of larval life events in relation to the current context in Indian Ocean Suggests that recruits (i) come from Reunion Island or Mauritius Island and (ii) colonize the sandy and protected bay of Saint-Paul as an intermediate zone, before their resettlement on coral reef.