Influence of food availability on the spatial distribution of juvenile fish within soft sediment nursery habitats
Résumé
Soft sediments in coastal shallow waters constitute nursery habitats for juveniles of several flatfishes. The quality of a nursery is defined by its capacity to optimize the growth and the survival of juvenile fish. The influence of biotic factors, such as food availability, is poorly studied at the scale of a nursery ground. Whether food availability limits juvenile survival is still uncertain. A spatial approach is used to understand the influence of food availability on the distribution of juvenile fish of various benthic and demersal species in the Bay of Vilaine (France), a productive nursery ground. We quantified the spatial overlap between benthic macro-invertebrates and their predators (juvenile fish) to assess if the latter were spatially covering the most productive areas of the Bay. Three scenarios describing the shapes of the predator prey spatial relationship were tested to quantify the strength of the relationship and consequently the importance of food availability in determining fish distribution. Our results underline that both.food availability and fish densities vary greatly over the nursery ground. When considering small organisational levels (e.g., a single fish species), the predator prey spatial relationship was not dear, likely because of additional environmental effects not identified here; but at larger organisational level (the whole juvenile fish community), a strong overlap between the fish predators and their prey was identified. The evidence that fish concentrate in sectors with high food availability suggests that either food is the limiting factor in that nursery or/and fish display behavioural responses by optimising their energetic expenditures associated with foraging. Further investigations are needed to test the two hypotheses and to assess the impact of benthic and demersal juvenile fish in the food web of coastal nurseries. (C) 2015 Elsevier B.V. All rights reserved.
Mots clés
sole solea-solea
Food limitation
plaice pleuronectes-platessa
Predator-prey relationship
Nursery habitat
Flatfish
Demersal fish
Benthic invertebrates
Spatial overlap
southern north-sea
cod
gadus-morhua
dutch wadden sea
epibenthic fauna
gironde estuary
benthic prey
bay
growth
Marine & Freshwater Biology
Oceanography
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