Démarche pour identifier les poissons récifaux capturés dans les baies de Toliara et de Ranobe, sudouest de Madagascar

Abstract

Reef fish are the main target of the small-scale fishery in southwest Madagascar. Despite the
diversity of research on the monitoring of catches of small-scale fishermen on this island, no
study on the identification of precise names of the species of fish caught by the different gears
in the region had been carried out. Thus, from February 2020 to August 2021, a study that aims
to establish an identification approach of the reef fish caught in the bay of Toliara and Ranobe,
is carried out. It is based on the description of the anatomical characters and the DNA barcoding
analysis of the samples collected by the GEOFIA project in 2018 and 2019, added by those of
Ranobe Bay in 2020. These samples are derived from the catches of the five main fishing gears
used in this region, including gillnet, handline, speargun, beach seine, and trawl net. The
approach consists of (1) the collection of images and pieces of caudal fins, (2) the grouping by
morpho-species of individuals of the same family from the images, (3) the identification based
on the external morphology of each morpho-species, (4) the selection of individuals to be
barcoded and (5) the analysis by barcoding. Even if the latter is not carried out, from 2193
individuals, the study was able to identify 64 families, 530 morpho-species, and 452
hypothetical species (EH), with the dominance of Labridae. Beach seine and gillnet had the
most common families (4), while gillnet and handline had the most common EH (23). Of the
five gears, gillnets are the most diverse in families (49), morpho-species (202), and TE (182).
The beach seine has the least number of morpho-species (132) and EH (118), while the speargun
catches have the lowest number of families (29). A sample collection effort is still needed to
estimate the maximum family and species diversity of reef fish caught by the different gears in
this area, especially for beach seine and gillnet.
Keywords: identification, reef fishes, morphology.