Variability of energy density among mesozooplankton community: new insights in functional diversity to forage fish

Aurélie Dessier (1) , Christine Dupuy (1) , Anaïs Kerric (1) , Françoise Mornet (2) , Matthieu Authier (3) , Paco Bustamante (1) , Jérôme Spitz (3)

1 LIENSs - LIttoral ENvironnement et Sociétés
2 LRHLR - Laboratoire Ressources Halieutiques La Rochelle-L'Houmeau
3 PELAGIS - Observatoire pour la Conservation de la Mégafaune Marine

To assess one of the dimensions of mesozooplankton functional diversity, this study quantifies energy density during the springtime in the Bay of Biscay considering both taxonomic and size-classes diversity. Energy density among copepods species (Centropages typicus, Anomalocera patersoni, Calanus helgolandicus, and Labidocera wollastoni), as well as anchovy eggs (Engraulis encrasicolus) ranges from 0.5 to 6.7 kJ/g on a taxonomic basis. Considering size-classes, energy density varies from 0.74 to 1.26 kJ/g. C. helgolandicus exhibits with average energy density estimates generally higher in the plume of the Gironde estuary. In contrast, no spatial coherence is found in the variability of mesozooplankton energy density by size-classes. Our results show that the mesozooplanktonic resource is not homogeneous in terms of quality in the Bay of Biscay. During spring, some species and some geographical areas seems thus to be more profitable to predators than others. We argue that the energy density is a key functional trait of mesozooplankton, but the assessment of mesozooplankton quality should be preferentially based on taxonomy rather than on size-classes. We conclude that interspecific and spatial variability of energy density among the mesozooplankton community can have important implications on fish population dynamics.

Mots clés: Bay of Biscay; profitability; copepods; prey-predator relationship; fisheries

Domaines: Biodiversité et Ecologie; Océanographie

Aurélie Dessier, Christine Dupuy, Anaïs Kerric, Françoise Mornet, Matthieu Authier, et al.. Variability of energy density among mesozooplankton community: new insights in functional diversity to forage fish. Progress in Oceanography, 2018, 166, pp.121-128. ⟨10.1016/j.pocean.2017.10.009⟩. ⟨hal-01675022⟩