Jaonalison H. auteur aut IRD Ponton Dominique auteur aut IRD Léopold Marc auteur aut IRD Raharinaivo R. L. auteur aut IRD Nomenisoa A. L. D. auteur aut IRD Frédérich B. auteur aut IRD Durand Jean-Dominique auteur aut IRD Mahafina J. auteur aut IRD text journalArticle eng text/pdf born digital access Mosquito net trawling in seagrass meadows is a widespread but illegal fishing practice in southwestern Madagascar, with poorly documented ecological impacts. This study assessed fish assemblages in trawl catches across two warm seasons (2016-2018) using both morphological and molecular-based identification, focusing on species composition, ontogenetic structure, and spatial and temporal variation in fish assemblages. A total of 201 species from 50 families were recorded across 72 hauls, with an average catch density of 2465 +/- 2166 individuals ha(-)1 and a mean size of 4.7 +/- 2.8 cm. Juveniles comprised 51.6% of total individuals, with an average of 58 +/- 26 juvenile species per sample and a density of 1193 +/- 1040 individuals ha(-)1. The foremost dominant juvenile species was Siganus sutor (43% of juvenile catch, with a mean body size of 3.3 +/- 1.5 cm), followed by Stethojulis strigiventer, Lethrinus borbonicus, and Fistularia commersonii. Moreover, trawls captured juveniles of two threatened species-Lethrinus mahsena (endangered, 2% of juvenile catch) and Hippocampus kuda (vulnerable, less than 0.1%). While juvenile assemblages showed no significant interannual variation, spatial differences among substrate types were significant with ANOSIM R = 0.47. These findings confirm that mosquito net trawling contributes to high juvenile mortality, including for long-lived and conservation-priority species. Protecting seagrass meadows as nursery habitats is essential to ensure sustainable recruitment and preserve the fish diversity and production. Effective small-scale fisheries management will require urgent restrictions on destructive gear and expanded community-based conservation initiatives. specialized DNA barcoding Fish assemblages Fish density Juvenile proportion Interannual variability MADAGASCAR 082 034 040 109 3 102 [16 p.] 2026 0378-1909 https://www.documentation.ird.fr/hor/fdi:010097522 10.1007/s10641-026-01873-1 0378-1909 [F B010097522] https://www.documentation.ird.fr/hor/fdi:010097522 https://www.documentation.ird.fr/intranet/publi/2026-08/010097522.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2026-08-06 2026-08-06 fdi:010097522 fre