Spatial and temporal dynamics of ichthyoplankton in a temperate estuary: identifying essential habitats for early life stages

• Published in: Journal of plankton research 2024-12
• Main Authors: Arevalo, Elorri, Villeneuve, Bertrand, Possémé, Carl, Lançon, Kévin, François, Baptiste, Jan, Gwilherm, Quinton, Eric, Cabral, Henrique N, Lepage, Mario
• Format: Article
• Language: English
• ISSN: 0142-7873; 1464-3774
• DOI: 10.1093/plankt/fbae070

Estuaries are important nursery habitats for the early life stages of fishes. Fish populations in the Gironde Estuary (South-Western France) have collapsed in recent decades, due to massive habitat destruction and poor water quality. In this context, we sampled the ichthyoplankton in the Gironde Estuary for one year to understand the spatio-temporal dynamics of fish larvae and identify key habitats. Total density of larvae was analyzed in relation to season (summer, winter, spring), area (oligo, meso, polyhaline), habitat type (confluences, mudflats) and depth (shallow, intermediate, deep). In total, 32 499 fish larvae were identified and divided into 14 taxa. Larval densities were largely dominated by an estuarine resident taxon, but marine estuarine-opportunist and diadromous species were also present. Summer was characterized by few taxa, including Engraulis encrasicolus, Dicentrarchus spp. or Pomatoschistus spp., in low density (0.16 ± 0.53 larvae m-3 on average). Larval densities were higher in winter (0.30 ± 2.13) and spring (29.50 ± 291.00). Diadromous species were particularly present in winter, and gobies (Pomatoschistus spp.) dominated the spring assemblage. The oligohaline area and intertidal mudflats appeared to be key habitats in terms of larval density and diversity and should be target locations of conservation/restoration measures.