First results on the diet of the European sturgeon, Acipenser sturio, in the Gironde estuary. Comparison with the benthic fauna.

Very little is known about the diet of the European sturgeon, Acipenser stu rio, in its natural environment. For the juveniles, a better understanding in this field is a step towards the assessment of this species' major feedi ng areas in the estuary with the aim of preserving and protecting them. Fro m May 1998 to March 1999, stomach contents were collected by stomach flushi ng in 61 juveniles (63-116 cm total length) during monthly trawling campaig ns to monitor sturgeon migration in the Gironde estuary. Specimens were mai nly caught during spring (n = 41) and summer (n = 15) in two areas of incre ased abundance located in mesohaline (n = 19) and polyhaline (n = 32) secto rs. Twelve taxa of preys were found. The highest proportion of preys identi fied consisted of polychaetes, mainly represented by Heteromastus filiformi s Clarapede, Polydora sp. and some nereides in lower proportions. Crustacea ns were the second most abundant group of preys. Preliminary work on the in vertebrate fauna repartition in the estuary and literature show that these preys are benthic and are considered as very abundant only in the tidal are as, along the lateral strands. Moreover, the major taxa in the strand is re presented by molluscs Macoma sp. and Hydrobia sp., which were absent from s tomach contents. These observations indicate that young European sturgeons in the Gironde estuary show a strong preference for polychaeta and suggest they have a strong selectivity for the choice of their major trophic areas which are still to identify.