Feeding of juvenile twaite shad (Alosa fallax Lacepede, 1803) in the Elbe estuary.

Seasonal, diurnal and size-dependent trends of food composition, prey selection and daily ration of juvenile twaite shad were investigated in the! Elbe estuary. Juvenile twaite shad were caught for diet analysis with framed gape stow nets in the mesohaline region of the Elbe estuary in April, July and August 1991 Copepods, mysids and fish were identified as main food items of juvenile twaite shad. In August, the importance of mysids and fish as main prey organisms increased with increasing total length of twaite shad, whereas the proportion of copepods decreased. During night fishes were consumed to a lesser extent than during day. Insects were mainly eaten during night. In the early morning copepods were main food items. Juvenile twaite shad preferred the mysidacean Mesopodopsis slabbed and the sprat Sprattus sprattus. Cladocerans were ingested corresponding to their availability, whereas all other food items were avoided. Daily,ration according to WINBERG (1956) showed peak values in spring and summer and decreased during the following season. The maximum daily ration of about 45% of body wet weight was calculated in May. Daily ration decreased with increasing age of juvenile twaite shad.